pragma solidity ^0.4.24;

// File: contracts/token/interfaces/IERC20Token.sol

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {}
    function symbol() public view returns (string) {}
    function decimals() public view returns (uint8) {}
    function totalSupply() public view returns (uint256) {}
    function balanceOf(address _owner) public view returns (uint256) { _owner; }
    function allowance(address _owner, address _spender) public view returns (uint256) { _owner; _spender; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

// File: contracts/utility/interfaces/IWhitelist.sol

/*
    Whitelist interface
*/
contract IWhitelist {
    function isWhitelisted(address _address) public view returns (bool);
}

// File: contracts/converter/interfaces/IBancorConverter.sol

/*
    Bancor Converter interface
*/
contract IBancorConverter {
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256);
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function conversionWhitelist() public view returns (IWhitelist) {}
    function conversionFee() public view returns (uint32) {}
    function connectors(address _address) public view returns (uint256, uint32, bool, bool, bool) { _address; }
    function getConnectorBalance(IERC20Token _connectorToken) public view returns (uint256);
    function claimTokens(address _from, uint256 _amount) public;
    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
}

// File: contracts/converter/interfaces/IBancorConverterUpgrader.sol

/*
    Bancor Converter Upgrader interface
*/
contract IBancorConverterUpgrader {
    function upgrade(bytes32 _version) public;
    function upgrade(uint16 _version) public;
}

// File: contracts/converter/interfaces/IBancorFormula.sol

/*
    Bancor Formula interface
*/
contract IBancorFormula {
    function calculatePurchaseReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _depositAmount) public view returns (uint256);
    function calculateSaleReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _sellAmount) public view returns (uint256);
    function calculateCrossConnectorReturn(uint256 _fromConnectorBalance, uint32 _fromConnectorWeight, uint256 _toConnectorBalance, uint32 _toConnectorWeight, uint256 _amount) public view returns (uint256);
}

// File: contracts/IBancorNetwork.sol

/*
    Bancor Network interface
*/
contract IBancorNetwork {
    function convert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public payable returns (uint256);
    function convertFor(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _for) public payable returns (uint256);
    
    function convertForPrioritized3(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _customVal,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);
    
    // deprecated, backward compatibility
    function convertForPrioritized2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function convertForPrioritized(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint256 _nonce,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);
}

// File: contracts/ContractIds.sol

/**
    Id definitions for bancor contracts

    Can be used in conjunction with the contract registry to get contract addresses
*/
contract ContractIds {
    // generic
    bytes32 public constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 public constant CONTRACT_REGISTRY = "ContractRegistry";

    // bancor logic
    bytes32 public constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 public constant BANCOR_FORMULA = "BancorFormula";
    bytes32 public constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 public constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 public constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";

    // BNT core
    bytes32 public constant BNT_TOKEN = "BNTToken";
    bytes32 public constant BNT_CONVERTER = "BNTConverter";

    // BancorX
    bytes32 public constant BANCOR_X = "BancorX";
    bytes32 public constant BANCOR_X_UPGRADER = "BancorXUpgrader";
}

// File: contracts/FeatureIds.sol

/**
    Id definitions for bancor contract features

    Can be used to query the ContractFeatures contract to check whether a certain feature is supported by a contract
*/
contract FeatureIds {
    // converter features
    uint256 public constant CONVERTER_CONVERSION_WHITELIST = 1 << 0;
}

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Managed.sol

/*
    Provides support and utilities for contract management
    Note that a managed contract must also have an owner
*/
contract Managed is Owned {
    address public manager;
    address public newManager;

    event ManagerUpdate(address indexed _prevManager, address indexed _newManager);

    /**
        @dev constructor
    */
    constructor() public {
        manager = msg.sender;
    }

    // allows execution by the manager only
    modifier managerOnly {
        assert(msg.sender == manager);
        _;
    }

    // allows execution by either the owner or the manager only
    modifier ownerOrManagerOnly {
        require(msg.sender == owner || msg.sender == manager);
        _;
    }

    /**
        @dev allows transferring the contract management
        the new manager still needs to accept the transfer
        can only be called by the contract manager

        @param _newManager    new contract manager
    */
    function transferManagement(address _newManager) public ownerOrManagerOnly {
        require(_newManager != manager);
        newManager = _newManager;
    }

    /**
        @dev used by a new manager to accept a management transfer
    */
    function acceptManagement() public {
        require(msg.sender == newManager);
        emit ManagerUpdate(manager, newManager);
        manager = newManager;
        newManager = address(0);
    }
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

}

// File: contracts/utility/SafeMath.sol

/*
    Library for basic math operations with overflow/underflow protection
*/
library SafeMath {
    /**
        @dev returns the sum of _x and _y, reverts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function add(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        require(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, reverts if the calculation underflows

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function sub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, reverts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function mul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        // gas optimization
        if (_x == 0)
            return 0;

        uint256 z = _x * _y;
        require(z / _x == _y);
        return z;
    }

      /**
        @dev Integer division of two numbers truncating the quotient, reverts on division by zero.

        @param _x   dividend
        @param _y   divisor

        @return quotient
    */
    function div(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_y > 0);
        uint256 c = _x / _y;

        return c;
    }
}

// File: contracts/utility/interfaces/IContractRegistry.sol

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/utility/interfaces/IContractFeatures.sol

/*
    Contract Features interface
*/
contract IContractFeatures {
    function isSupported(address _contract, uint256 _features) public view returns (bool);
    function enableFeatures(uint256 _features, bool _enable) public;
}

// File: contracts/token/interfaces/ISmartToken.sol

/*
    Smart Token interface
*/
contract ISmartToken is IOwned, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

// File: contracts/utility/interfaces/ITokenHolder.sol

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

// File: contracts/utility/TokenHolder.sol

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
        @dev constructor
    */
    constructor() public {
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

// File: contracts/token/SmartTokenController.sol

/*
    The smart token controller is an upgradable part of the smart token that allows
    more functionality as well as fixes for bugs/exploits.
    Once it accepts ownership of the token, it becomes the token's sole controller
    that can execute any of its functions.

    To upgrade the controller, ownership must be transferred to a new controller, along with
    any relevant data.

    The smart token must be set on construction and cannot be changed afterwards.
    Wrappers are provided (as opposed to a single 'execute' function) for each of the token's functions, for easier access.

    Note that the controller can transfer token ownership to a new controller that
    doesn't allow executing any function on the token, for a trustless solution.
    Doing that will also remove the owner's ability to upgrade the controller.
*/
contract SmartTokenController is TokenHolder {
    ISmartToken public token;   // smart token

    /**
        @dev constructor
    */
    constructor(ISmartToken _token)
        public
        validAddress(_token)
    {
        token = _token;
    }

    // ensures that the controller is the token's owner
    modifier active() {
        require(token.owner() == address(this));
        _;
    }

    // ensures that the controller is not the token's owner
    modifier inactive() {
        require(token.owner() != address(this));
        _;
    }

    /**
        @dev allows transferring the token ownership
        the new owner needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new token owner
    */
    function transferTokenOwnership(address _newOwner) public ownerOnly {
        token.transferOwnership(_newOwner);
    }

    /**
        @dev used by a new owner to accept a token ownership transfer
        can only be called by the contract owner
    */
    function acceptTokenOwnership() public ownerOnly {
        token.acceptOwnership();
    }

    /**
        @dev disables/enables token transfers
        can only be called by the contract owner

        @param _disable    true to disable transfers, false to enable them
    */
    function disableTokenTransfers(bool _disable) public ownerOnly {
        token.disableTransfers(_disable);
    }

    /**
        @dev withdraws tokens held by the controller and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawFromToken(IERC20Token _token, address _to, uint256 _amount) public ownerOnly {
        ITokenHolder(token).withdrawTokens(_token, _to, _amount);
    }
}

// File: contracts/token/interfaces/IEtherToken.sol

/*
    Ether Token interface
*/
contract IEtherToken is ITokenHolder, IERC20Token {
    function deposit() public payable;
    function withdraw(uint256 _amount) public;
    function withdrawTo(address _to, uint256 _amount) public;
}

// File: contracts/bancorx/interfaces/IBancorX.sol

contract IBancorX {
    function xTransfer(bytes32 _toBlockchain, bytes32 _to, uint256 _amount, uint256 _id) public;
    function getXTransferAmount(uint256 _xTransferId, address _for) public view returns (uint256);
}

// File: contracts/converter/BancorConverter.sol

/*
    Bancor Converter v12

    The Bancor version of the token converter, allows conversion between a smart token and other ERC20 tokens and between different ERC20 tokens and themselves.

    ERC20 connector balance can be virtual, meaning that the calculations are based on the virtual balance instead of relying on
    the actual connector balance. This is a security mechanism that prevents the need to keep a very large (and valuable) balance in a single contract.

    The converter is upgradable (just like any SmartTokenController).

    WARNING: It is NOT RECOMMENDED to use the converter with Smart Tokens that have less than 8 decimal digits
             or with very small numbers because of precision loss

    Open issues:
    - Front-running attacks are currently mitigated by the following mechanisms:
        - minimum return argument for each conversion provides a way to define a minimum/maximum price for the transaction
        - gas price limit prevents users from having control over the order of execution
        - gas price limit check can be skipped if the transaction comes from a trusted, whitelisted signer
      Other potential solutions might include a commit/reveal based schemes
    - Possibly add getters for the connector fields so that the client won't need to rely on the order in the struct
*/
contract BancorConverter is IBancorConverter, SmartTokenController, Managed, ContractIds, FeatureIds {
    using SafeMath for uint256;

    
    uint32 private constant MAX_WEIGHT = 1000000;
    uint64 private constant MAX_CONVERSION_FEE = 1000000;

    struct Connector {
        uint256 virtualBalance;         // connector virtual balance
        uint32 weight;                  // connector weight, represented in ppm, 1-1000000
        bool isVirtualBalanceEnabled;   // true if virtual balance is enabled, false if not
        bool isSaleEnabled;             // is sale of the connector token enabled, can be set by the owner
        bool isSet;                     // used to tell if the mapping element is defined
    }

    uint16 public version = 12;
    string public converterType = 'bancor';

    bool public allowRegistryUpdate = true;             // allows the owner to prevent/allow the registry to be updated
    bool public claimTokensEnabled = false;             // allows BancorX contract to claim tokens without allowance (one transaction instread of two)
    IContractRegistry public prevRegistry;              // address of previous registry as security mechanism
    IContractRegistry public registry;                  // contract registry contract
    IWhitelist public conversionWhitelist;              // whitelist contract with list of addresses that are allowed to use the converter
    IERC20Token[] public connectorTokens;               // ERC20 standard token addresses
    mapping (address => Connector) public connectors;   // connector token addresses -> connector data
    uint32 private totalConnectorWeight = 0;            // used to efficiently prevent increasing the total connector weight above 100%
    uint32 public maxConversionFee = 0;                 // maximum conversion fee for the lifetime of the contract,
                                                        // represented in ppm, 0...1000000 (0 = no fee, 100 = 0.01%, 1000000 = 100%)
    uint32 public conversionFee = 0;                    // current conversion fee, represented in ppm, 0...maxConversionFee
    bool public conversionsEnabled = true;              // true if token conversions is enabled, false if not
    IERC20Token[] private convertPath;

    // triggered when a conversion between two tokens occurs
    event Conversion(
        address indexed _fromToken,
        address indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );
    // triggered after a conversion with new price data
    event PriceDataUpdate(
        address indexed _connectorToken,
        uint256 _tokenSupply,
        uint256 _connectorBalance,
        uint32 _connectorWeight
    );
    // triggered when the conversion fee is updated
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);

    // triggered when conversions are enabled/disabled
    event ConversionsEnable(bool _conversionsEnabled);

    /**
        @dev constructor

        @param  _token              smart token governed by the converter
        @param  _registry           address of a contract registry contract
        @param  _maxConversionFee   maximum conversion fee, represented in ppm
        @param  _connectorToken     optional, initial connector, allows defining the first connector at deployment time
        @param  _connectorWeight    optional, weight for the initial connector
    */
    constructor(
        ISmartToken _token,
        IContractRegistry _registry,
        uint32 _maxConversionFee,
        IERC20Token _connectorToken,
        uint32 _connectorWeight
    )
        public
        SmartTokenController(_token)
        validAddress(_registry)
        validMaxConversionFee(_maxConversionFee)
    {
        registry = _registry;
        prevRegistry = _registry;
        IContractFeatures features = IContractFeatures(registry.addressOf(ContractIds.CONTRACT_FEATURES));

        // initialize supported features
        if (features != address(0))
            features.enableFeatures(FeatureIds.CONVERTER_CONVERSION_WHITELIST, true);

        maxConversionFee = _maxConversionFee;

        if (_connectorToken != address(0))
            addConnector(_connectorToken, _connectorWeight, false);
    }

    // validates a connector token address - verifies that the address belongs to one of the connector tokens
    modifier validConnector(IERC20Token _address) {
        require(connectors[_address].isSet);
        _;
    }

    // validates a token address - verifies that the address belongs to one of the convertible tokens
    modifier validToken(IERC20Token _address) {
        require(_address == token || connectors[_address].isSet);
        _;
    }

    // validates maximum conversion fee
    modifier validMaxConversionFee(uint32 _conversionFee) {
        require(_conversionFee >= 0 && _conversionFee <= MAX_CONVERSION_FEE);
        _;
    }

    // validates conversion fee
    modifier validConversionFee(uint32 _conversionFee) {
        require(_conversionFee >= 0 && _conversionFee <= maxConversionFee);
        _;
    }

    // validates connector weight range
    modifier validConnectorWeight(uint32 _weight) {
        require(_weight > 0 && _weight <= MAX_WEIGHT);
        _;
    }

    // validates a conversion path - verifies that the number of elements is odd and that maximum number of 'hops' is 10
    modifier validConversionPath(IERC20Token[] _path) {
        require(_path.length > 2 && _path.length <= (1 + 2 * 10) && _path.length % 2 == 1);
        _;
    }

    // allows execution only when the total weight is 100%
    modifier maxTotalWeightOnly() {
        require(totalConnectorWeight == MAX_WEIGHT);
        _;
    }

    // allows execution only when conversions aren't disabled
    modifier conversionsAllowed {
        assert(conversionsEnabled);
        _;
    }

    // allows execution by the BancorNetwork contract only
    modifier bancorNetworkOnly {
        IBancorNetwork bancorNetwork = IBancorNetwork(registry.addressOf(ContractIds.BANCOR_NETWORK));
        require(msg.sender == address(bancorNetwork));
        _;
    }

    // allows execution by the converter upgrader contract only
    modifier converterUpgraderOnly {
        address converterUpgrader = registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER);
        require(owner == converterUpgrader);
        _;
    }

    // allows execution only when claim tokens is enabled
    modifier whenClaimTokensEnabled {
        require(claimTokensEnabled);
        _;
    }

    /**
        @dev sets the contract registry to whichever address the current registry is pointing to
     */
    function updateRegistry() public {
        // require that upgrading is allowed or that the caller is the owner
        require(allowRegistryUpdate || msg.sender == owner);

        // get the address of whichever registry the current registry is pointing to
        address newRegistry = registry.addressOf(ContractIds.CONTRACT_REGISTRY);

        // if the new registry hasn't changed or is the zero address, revert
        require(newRegistry != address(registry) && newRegistry != address(0));

        // set the previous registry as current registry and current registry as newRegistry
        prevRegistry = registry;
        registry = IContractRegistry(newRegistry);
    }

    /**
        @dev security mechanism allowing the converter owner to revert to the previous registry,
        to be used in emergency scenario
    */
    function restoreRegistry() public ownerOrManagerOnly {
        // set the registry as previous registry
        registry = prevRegistry;

        // after a previous registry is restored, only the owner can allow future updates
        allowRegistryUpdate = false;
    }

    /**
        @dev disables the registry update functionality
        this is a safety mechanism in case of a emergency
        can only be called by the manager or owner

        @param _disable    true to disable registry updates, false to re-enable them
    */
    function disableRegistryUpdate(bool _disable) public ownerOrManagerOnly {
        allowRegistryUpdate = !_disable;
    }

    /**
        @dev disables/enables the claim tokens functionality

        @param _enable    true to enable claiming of tokens, false to disable
     */
    function enableClaimTokens(bool _enable) public ownerOnly {
        claimTokensEnabled = _enable;
    }

    /**
        @dev returns the number of connector tokens defined

        @return number of connector tokens
    */
    function connectorTokenCount() public view returns (uint16) {
        return uint16(connectorTokens.length);
    }

    /**
        @dev allows the owner to update & enable the conversion whitelist contract address
        when set, only addresses that are whitelisted are actually allowed to use the converter
        note that the whitelist check is actually done by the BancorNetwork contract

        @param _whitelist    address of a whitelist contract
    */
    function setConversionWhitelist(IWhitelist _whitelist)
        public
        ownerOnly
        notThis(_whitelist)
    {
        conversionWhitelist = _whitelist;
    }

    /**
        @dev disables the entire conversion functionality
        this is a safety mechanism in case of a emergency
        can only be called by the manager

        @param _disable true to disable conversions, false to re-enable them
    */
    function disableConversions(bool _disable) public ownerOrManagerOnly {
        if (conversionsEnabled == _disable) {
            conversionsEnabled = !_disable;
            emit ConversionsEnable(conversionsEnabled);
        }
    }

    /**
        @dev allows transferring the token ownership
        the new owner needs to accept the transfer
        can only be called by the contract owner
        note that token ownership can only be transferred while the owner is the converter upgrader contract

        @param _newOwner    new token owner
    */
    function transferTokenOwnership(address _newOwner)
        public
        ownerOnly
        converterUpgraderOnly
    {
        super.transferTokenOwnership(_newOwner);
    }

    /**
        @dev updates the current conversion fee
        can only be called by the manager

        @param _conversionFee new conversion fee, represented in ppm
    */
    function setConversionFee(uint32 _conversionFee)
        public
        ownerOrManagerOnly
        validConversionFee(_conversionFee)
    {
        emit ConversionFeeUpdate(conversionFee, _conversionFee);
        conversionFee = _conversionFee;
    }

    /**
        @dev given a return amount, returns the amount minus the conversion fee

        @param _amount      return amount
        @param _magnitude   1 for standard conversion, 2 for cross connector conversion

        @return return amount minus conversion fee
    */
    function getFinalAmount(uint256 _amount, uint8 _magnitude) public view returns (uint256) {
        return _amount.mul((MAX_CONVERSION_FEE - conversionFee) ** _magnitude).div(MAX_CONVERSION_FEE ** _magnitude);
    }

    /**
        @dev withdraws tokens held by the converter and sends them to an account
        can only be called by the owner
        note that connector tokens can only be withdrawn by the owner while the converter is inactive
        unless the owner is the converter upgrader contract

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public {
        address converterUpgrader = registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER);

        // if the token is not a connector token, allow withdrawal
        // otherwise verify that the converter is inactive or that the owner is the upgrader contract
        require(!connectors[_token].isSet || token.owner() != address(this) || owner == converterUpgrader);
        super.withdrawTokens(_token, _to, _amount);
    }

    /**
        @dev allows the BancorX contract to claim BNT from any address (so that users
        dont have to first give allowance when calling BancorX)

        @param _from      address to claim the BNT from
        @param _amount    the amount to claim
     */
    function claimTokens(address _from, uint256 _amount) public whenClaimTokensEnabled {
        address bancorX = registry.addressOf(ContractIds.BANCOR_X);

        // only the bancorX contract may call this method
        require(msg.sender == bancorX);

        // destroy the tokens belonging to _from, and issue the same amount to bancorX contract
        token.destroy(_from, _amount);
        token.issue(msg.sender, _amount);
    }

    /**
        @dev upgrades the converter to the latest version
        can only be called by the owner
        note that the owner needs to call acceptOwnership/acceptManagement on the new converter after the upgrade
    */
    function upgrade() public ownerOnly {
        IBancorConverterUpgrader converterUpgrader = IBancorConverterUpgrader(registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER));

        transferOwnership(converterUpgrader);
        converterUpgrader.upgrade(version);
        acceptOwnership();
    }

    /**
        @dev defines a new connector for the token
        can only be called by the owner while the converter is inactive

        @param _token                  address of the connector token
        @param _weight                 constant connector weight, represented in ppm, 1-1000000
        @param _enableVirtualBalance   true to enable virtual balance for the connector, false to disable it
    */
    function addConnector(IERC20Token _token, uint32 _weight, bool _enableVirtualBalance)
        public
        ownerOnly
        inactive
        validAddress(_token)
        notThis(_token)
        validConnectorWeight(_weight)
    {
        require(_token != token && !connectors[_token].isSet && totalConnectorWeight + _weight <= MAX_WEIGHT); // validate input

        connectors[_token].virtualBalance = 0;
        connectors[_token].weight = _weight;
        connectors[_token].isVirtualBalanceEnabled = _enableVirtualBalance;
        connectors[_token].isSaleEnabled = true;
        connectors[_token].isSet = true;
        connectorTokens.push(_token);
        totalConnectorWeight += _weight;
    }

    /**
        @dev updates one of the token connectors
        can only be called by the owner

        @param _connectorToken         address of the connector token
        @param _weight                 constant connector weight, represented in ppm, 1-1000000
        @param _enableVirtualBalance   true to enable virtual balance for the connector, false to disable it
        @param _virtualBalance         new connector's virtual balance
    */
    function updateConnector(IERC20Token _connectorToken, uint32 _weight, bool _enableVirtualBalance, uint256 _virtualBalance)
        public
        ownerOnly
        validConnector(_connectorToken)
        validConnectorWeight(_weight)
    {
        Connector storage connector = connectors[_connectorToken];
        require(totalConnectorWeight - connector.weight + _weight <= MAX_WEIGHT); // validate input

        totalConnectorWeight = totalConnectorWeight - connector.weight + _weight;
        connector.weight = _weight;
        connector.isVirtualBalanceEnabled = _enableVirtualBalance;
        connector.virtualBalance = _virtualBalance;
    }

    /**
        @dev disables converting from the given connector token in case the connector token got compromised
        can only be called by the owner
        note that converting to the token is still enabled regardless of this flag and it cannot be disabled by the owner

        @param _connectorToken  connector token contract address
        @param _disable         true to disable the token, false to re-enable it
    */
    function disableConnectorSale(IERC20Token _connectorToken, bool _disable)
        public
        ownerOnly
        validConnector(_connectorToken)
    {
        connectors[_connectorToken].isSaleEnabled = !_disable;
    }

    /**
        @dev returns the connector's virtual balance if one is defined, otherwise returns the actual balance

        @param _connectorToken  connector token contract address

        @return connector balance
    */
    function getConnectorBalance(IERC20Token _connectorToken)
        public
        view
        validConnector(_connectorToken)
        returns (uint256)
    {
        Connector storage connector = connectors[_connectorToken];
        return connector.isVirtualBalanceEnabled ? connector.virtualBalance : _connectorToken.balanceOf(this);
    }

    /**
        @dev returns the expected return for converting a specific amount of _fromToken to _toToken

        @param _fromToken  ERC20 token to convert from
        @param _toToken    ERC20 token to convert to
        @param _amount     amount to convert, in fromToken

        @return expected conversion return amount and conversion fee
    */
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256) {
        require(_fromToken != _toToken); // validate input

        // conversion between the token and one of its connectors
        if (_toToken == token)
            return getPurchaseReturn(_fromToken, _amount);
        else if (_fromToken == token)
            return getSaleReturn(_toToken, _amount);

        // conversion between 2 connectors
        return getCrossConnectorReturn(_fromToken, _toToken, _amount);
    }

    /**
        @dev returns the expected return for buying the token for a connector token

        @param _connectorToken  connector token contract address
        @param _depositAmount   amount to deposit (in the connector token)

        @return expected purchase return amount and conversion fee
    */
    function getPurchaseReturn(IERC20Token _connectorToken, uint256 _depositAmount)
        public
        view
        active
        validConnector(_connectorToken)
        returns (uint256, uint256)
    {
        Connector storage connector = connectors[_connectorToken];
        require(connector.isSaleEnabled); // validate input

        uint256 tokenSupply = token.totalSupply();
        uint256 connectorBalance = getConnectorBalance(_connectorToken);
        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculatePurchaseReturn(tokenSupply, connectorBalance, connector.weight, _depositAmount);
        uint256 finalAmount = getFinalAmount(amount, 1);

        // return the amount minus the conversion fee and the conversion fee
        return (finalAmount, amount - finalAmount);
    }

    /**
        @dev returns the expected return for selling the token for one of its connector tokens

        @param _connectorToken  connector token contract address
        @param _sellAmount      amount to sell (in the smart token)

        @return expected sale return amount and conversion fee
    */
    function getSaleReturn(IERC20Token _connectorToken, uint256 _sellAmount)
        public
        view
        active
        validConnector(_connectorToken)
        returns (uint256, uint256)
    {
        Connector storage connector = connectors[_connectorToken];
        uint256 tokenSupply = token.totalSupply();
        uint256 connectorBalance = getConnectorBalance(_connectorToken);
        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculateSaleReturn(tokenSupply, connectorBalance, connector.weight, _sellAmount);
        uint256 finalAmount = getFinalAmount(amount, 1);

        // return the amount minus the conversion fee and the conversion fee
        return (finalAmount, amount - finalAmount);
    }

    /**
        @dev returns the expected return for selling one of the connector tokens for another connector token

        @param _fromConnectorToken  contract address of the connector token to convert from
        @param _toConnectorToken    contract address of the connector token to convert to
        @param _sellAmount          amount to sell (in the from connector token)

        @return expected sale return amount and conversion fee (in the to connector token)
    */
    function getCrossConnectorReturn(IERC20Token _fromConnectorToken, IERC20Token _toConnectorToken, uint256 _sellAmount)
        public
        view
        active
        validConnector(_fromConnectorToken)
        validConnector(_toConnectorToken)
        returns (uint256, uint256)
    {
        Connector storage fromConnector = connectors[_fromConnectorToken];
        Connector storage toConnector = connectors[_toConnectorToken];
        require(fromConnector.isSaleEnabled); // validate input

        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculateCrossConnectorReturn(
            getConnectorBalance(_fromConnectorToken), 
            fromConnector.weight, 
            getConnectorBalance(_toConnectorToken), 
            toConnector.weight, 
            _sellAmount);
        uint256 finalAmount = getFinalAmount(amount, 2);

        // return the amount minus the conversion fee and the conversion fee
        // the fee is higher (magnitude = 2) since cross connector conversion equals 2 conversions (from / to the smart token)
        return (finalAmount, amount - finalAmount);
    }

    /**
        @dev converts a specific amount of _fromToken to _toToken

        @param _fromToken  ERC20 token to convert from
        @param _toToken    ERC20 token to convert to
        @param _amount     amount to convert, in fromToken
        @param _minReturn  if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return conversion return amount
    */
    function convertInternal(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn)
        public
        bancorNetworkOnly
        conversionsAllowed
        greaterThanZero(_minReturn)
        returns (uint256)
    {
        require(_fromToken != _toToken); // validate input

        // conversion between the token and one of its connectors
        if (_toToken == token)
            return buy(_fromToken, _amount, _minReturn);
        else if (_fromToken == token)
            return sell(_toToken, _amount, _minReturn);

        uint256 amount;
        uint256 feeAmount;

        // conversion between 2 connectors
        (amount, feeAmount) = getCrossConnectorReturn(_fromToken, _toToken, _amount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // update the source token virtual balance if relevant
        Connector storage fromConnector = connectors[_fromToken];
        if (fromConnector.isVirtualBalanceEnabled)
            fromConnector.virtualBalance = fromConnector.virtualBalance.add(_amount);

        // update the target token virtual balance if relevant
        Connector storage toConnector = connectors[_toToken];
        if (toConnector.isVirtualBalanceEnabled)
            toConnector.virtualBalance = toConnector.virtualBalance.sub(amount);

        // ensure that the trade won't deplete the connector balance
        uint256 toConnectorBalance = getConnectorBalance(_toToken);
        assert(amount < toConnectorBalance);

        // transfer funds from the caller in the from connector token
        assert(_fromToken.transferFrom(msg.sender, this, _amount));
        // transfer funds to the caller in the to connector token
        // the transfer might fail if the actual connector balance is smaller than the virtual balance
        assert(_toToken.transfer(msg.sender, amount));

        // dispatch the conversion event
        // the fee is higher (magnitude = 2) since cross connector conversion equals 2 conversions (from / to the smart token)
        dispatchConversionEvent(_fromToken, _toToken, _amount, amount, feeAmount);

        // dispatch price data updates for the smart token / both connectors
        emit PriceDataUpdate(_fromToken, token.totalSupply(), getConnectorBalance(_fromToken), fromConnector.weight);
        emit PriceDataUpdate(_toToken, token.totalSupply(), getConnectorBalance(_toToken), toConnector.weight);
        return amount;
    }

    /**
        @dev converts a specific amount of _fromToken to _toToken

        @param _fromToken  ERC20 token to convert from
        @param _toToken    ERC20 token to convert to
        @param _amount     amount to convert, in fromToken
        @param _minReturn  if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return conversion return amount
    */
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256) {
        convertPath = [_fromToken, token, _toToken];
        return quickConvert(convertPath, _amount, _minReturn);
    }

    /**
        @dev buys the token by depositing one of its connector tokens

        @param _connectorToken  connector token contract address
        @param _depositAmount   amount to deposit (in the connector token)
        @param _minReturn       if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return buy return amount
    */
    function buy(IERC20Token _connectorToken, uint256 _depositAmount, uint256 _minReturn) internal returns (uint256) {
        uint256 amount;
        uint256 feeAmount;
        (amount, feeAmount) = getPurchaseReturn(_connectorToken, _depositAmount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // update virtual balance if relevant
        Connector storage connector = connectors[_connectorToken];
        if (connector.isVirtualBalanceEnabled)
            connector.virtualBalance = connector.virtualBalance.add(_depositAmount);

        // transfer funds from the caller in the connector token
        assert(_connectorToken.transferFrom(msg.sender, this, _depositAmount));
        // issue new funds to the caller in the smart token
        token.issue(msg.sender, amount);

        // dispatch the conversion event
        dispatchConversionEvent(_connectorToken, token, _depositAmount, amount, feeAmount);

        // dispatch price data update for the smart token/connector
        emit PriceDataUpdate(_connectorToken, token.totalSupply(), getConnectorBalance(_connectorToken), connector.weight);
        return amount;
    }

    /**
        @dev sells the token by withdrawing from one of its connector tokens

        @param _connectorToken  connector token contract address
        @param _sellAmount      amount to sell (in the smart token)
        @param _minReturn       if the conversion results in an amount smaller the minimum return - it is cancelled, must be nonzero

        @return sell return amount
    */
    function sell(IERC20Token _connectorToken, uint256 _sellAmount, uint256 _minReturn) internal returns (uint256) {
        require(_sellAmount <= token.balanceOf(msg.sender)); // validate input
        uint256 amount;
        uint256 feeAmount;
        (amount, feeAmount) = getSaleReturn(_connectorToken, _sellAmount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // ensure that the trade will only deplete the connector balance if the total supply is depleted as well
        uint256 tokenSupply = token.totalSupply();
        uint256 connectorBalance = getConnectorBalance(_connectorToken);
        assert(amount < connectorBalance || (amount == connectorBalance && _sellAmount == tokenSupply));

        // update virtual balance if relevant
        Connector storage connector = connectors[_connectorToken];
        if (connector.isVirtualBalanceEnabled)
            connector.virtualBalance = connector.virtualBalance.sub(amount);

        // destroy _sellAmount from the caller's balance in the smart token
        token.destroy(msg.sender, _sellAmount);
        // transfer funds to the caller in the connector token
        // the transfer might fail if the actual connector balance is smaller than the virtual balance
        assert(_connectorToken.transfer(msg.sender, amount));

        // dispatch the conversion event
        dispatchConversionEvent(token, _connectorToken, _sellAmount, amount, feeAmount);

        // dispatch price data update for the smart token/connector
        emit PriceDataUpdate(_connectorToken, token.totalSupply(), getConnectorBalance(_connectorToken), connector.weight);
        return amount;
    }

    /**
        @dev converts the token to any other token in the bancor network by following a predefined conversion path
        note that when converting from an ERC20 token (as opposed to a smart token), allowance must be set beforehand

        @param _path        conversion path, see conversion path format in the BancorNetwork contract
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return tokens issued in return
    */
    function quickConvert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn)
        public
        payable
        returns (uint256)
    {
        return quickConvertPrioritized(_path, _amount, _minReturn, 0x0, 0x0, 0x0, 0x0);
    }

    /**
        @dev converts the token to any other token in the bancor network by following a predefined conversion path
        note that when converting from an ERC20 token (as opposed to a smart token), allowance must be set beforehand

        @param _path        conversion path, see conversion path format in the BancorNetwork contract
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _block       if the current block exceeded the given parameter - it is cancelled
        @param _v           (signature[128:130]) associated with the signer address and helps validating if the signature is legit
        @param _r           (signature[0:64]) associated with the signer address and helps validating if the signature is legit
        @param _s           (signature[64:128]) associated with the signer address and helps validating if the signature is legit

        @return tokens issued in return
    */
    function quickConvertPrioritized(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, uint256 _block, uint8 _v, bytes32 _r, bytes32 _s)
        public
        payable
        returns (uint256)
    {
        IERC20Token fromToken = _path[0];
        IBancorNetwork bancorNetwork = IBancorNetwork(registry.addressOf(ContractIds.BANCOR_NETWORK));

        // we need to transfer the source tokens from the caller to the BancorNetwork contract,
        // so it can execute the conversion on behalf of the caller
        if (msg.value == 0) {
            // not ETH, send the source tokens to the BancorNetwork contract
            // if the token is the smart token, no allowance is required - destroy the tokens
            // from the caller and issue them to the BancorNetwork contract
            if (fromToken == token) {
                token.destroy(msg.sender, _amount); // destroy _amount tokens from the caller's balance in the smart token
                token.issue(bancorNetwork, _amount); // issue _amount new tokens to the BancorNetwork contract
            } else {
                // otherwise, we assume we already have allowance, transfer the tokens directly to the BancorNetwork contract
                assert(fromToken.transferFrom(msg.sender, bancorNetwork, _amount));
            }
        }

        // execute the conversion and pass on the ETH with the call
        return bancorNetwork.convertForPrioritized3.value(msg.value)(_path, _amount, _minReturn, msg.sender, _amount, _block, _v, _r, _s);
    }

    /**
        @dev allows a user to convert BNT that was sent from another blockchain into any other
        token on the BancorNetwork without specifying the amount of BNT to be converted, but
        rather by providing the xTransferId which allows us to get the amount from BancorX.

        @param _path             conversion path, see conversion path format in the BancorNetwork contract
        @param _minReturn        if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _conversionId     pre-determined unique (if non zero) id which refers to this transaction 
        @param _block            if the current block exceeded the given parameter - it is cancelled
        @param _v                (signature[128:130]) associated with the signer address and helps to validate if the signature is legit
        @param _r                (signature[0:64]) associated with the signer address and helps to validate if the signature is legit
        @param _s                (signature[64:128]) associated with the signer address and helps to validate if the signature is legit

        @return tokens issued in return
    */
    function completeXConversion(
        IERC20Token[] _path,
        uint256 _minReturn,
        uint256 _conversionId,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    )
        public
        returns (uint256)
    {
        IBancorX bancorX = IBancorX(registry.addressOf(ContractIds.BANCOR_X));
        IBancorNetwork bancorNetwork = IBancorNetwork(registry.addressOf(ContractIds.BANCOR_NETWORK));

        // verify that the first token in the path is BNT
        require(_path[0] == registry.addressOf(ContractIds.BNT_TOKEN));

        // get conversion amount from BancorX contract
        uint256 amount = bancorX.getXTransferAmount(_conversionId, msg.sender);

        // send BNT from msg.sender to the BancorNetwork contract
        token.destroy(msg.sender, amount);
        token.issue(bancorNetwork, amount);

        return bancorNetwork.convertForPrioritized3(_path, amount, _minReturn, msg.sender, _conversionId, _block, _v, _r, _s);
    }

    /**
        @dev buys the token with all connector tokens using the same percentage
        i.e. if the caller increases the supply by 10%, it will cost an amount equal to
        10% of each connector token balance
        can only be called if the max total weight is exactly 100% and while conversions are enabled

        @param _amount  amount to increase the supply by (in the smart token)
    */
    function fund(uint256 _amount)
        public
        maxTotalWeightOnly
        conversionsAllowed
    {
        uint256 supply = token.totalSupply();

        // iterate through the connector tokens and transfer a percentage equal to the ratio between _amount
        // and the total supply in each connector from the caller to the converter
        IERC20Token connectorToken;
        uint256 connectorBalance;
        uint256 connectorAmount;
        for (uint16 i = 0; i < connectorTokens.length; i++) {
            connectorToken = connectorTokens[i];
            connectorBalance = getConnectorBalance(connectorToken);
            connectorAmount = _amount.mul(connectorBalance).div(supply);

            // update virtual balance if relevant
            Connector storage connector = connectors[connectorToken];
            if (connector.isVirtualBalanceEnabled)
                connector.virtualBalance = connector.virtualBalance.add(connectorAmount);

            // transfer funds from the caller in the connector token
            assert(connectorToken.transferFrom(msg.sender, this, connectorAmount));

            // dispatch price data update for the smart token/connector
            emit PriceDataUpdate(connectorToken, supply + _amount, connectorBalance + connectorAmount, connector.weight);
        }

        // issue new funds to the caller in the smart token
        token.issue(msg.sender, _amount);
    }

    /**
        @dev sells the token for all connector tokens using the same percentage
        i.e. if the holder sells 10% of the supply, they will receive 10% of each
        connector token balance in return
        can only be called if the max total weight is exactly 100%
        note that the function can also be called if conversions are disabled

        @param _amount  amount to liquidate (in the smart token)
    */
    function liquidate(uint256 _amount) public maxTotalWeightOnly {
        uint256 supply = token.totalSupply();

        // destroy _amount from the caller's balance in the smart token
        token.destroy(msg.sender, _amount);

        // iterate through the connector tokens and send a percentage equal to the ratio between _amount
        // and the total supply from each connector balance to the caller
        IERC20Token connectorToken;
        uint256 connectorBalance;
        uint256 connectorAmount;
        for (uint16 i = 0; i < connectorTokens.length; i++) {
            connectorToken = connectorTokens[i];
            connectorBalance = getConnectorBalance(connectorToken);
            connectorAmount = _amount.mul(connectorBalance).div(supply);

            // update virtual balance if relevant
            Connector storage connector = connectors[connectorToken];
            if (connector.isVirtualBalanceEnabled)
                connector.virtualBalance = connector.virtualBalance.sub(connectorAmount);

            // transfer funds to the caller in the connector token
            // the transfer might fail if the actual connector balance is smaller than the virtual balance
            assert(connectorToken.transfer(msg.sender, connectorAmount));

            // dispatch price data update for the smart token/connector
            emit PriceDataUpdate(connectorToken, supply - _amount, connectorBalance - connectorAmount, connector.weight);
        }
    }

    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256) {
        return convertInternal(_fromToken, _toToken, _amount, _minReturn);
    }

    /**
        @dev helper, dispatches the Conversion event

        @param _fromToken       ERC20 token to convert from
        @param _toToken         ERC20 token to convert to
        @param _amount          amount purchased/sold (in the source token)
        @param _returnAmount    amount returned (in the target token)
    */
    function dispatchConversionEvent(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _returnAmount, uint256 _feeAmount) private {
        // fee amount is converted to 255 bits -
        // negative amount means the fee is taken from the source token, positive amount means its taken from the target token
        // currently the fee is always taken from the target token
        // since we convert it to a signed number, we first ensure that it's capped at 255 bits to prevent overflow
        assert(_feeAmount <= 2 ** 255);
        emit Conversion(_fromToken, _toToken, msg.sender, _amount, _returnAmount, int256(_feeAmount));
    }
}

pragma solidity ^0.4.11;

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    function Utils() {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != 0x0);
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public constant returns (address owner) { owner; }

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address _prevOwner, address _newOwner);

    /**
        @dev constructor
    */
    function Owned() {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        assert(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = 0x0;
    }
}

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
        @dev constructor
    */
    function TokenHolder() {
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public constant returns (string name) { name; }
    function symbol() public constant returns (string symbol) { symbol; }
    function decimals() public constant returns (uint8 decimals) { decimals; }
    function totalSupply() public constant returns (uint256 totalSupply) { totalSupply; }
    function balanceOf(address _owner) public constant returns (uint256 balance) { _owner; balance; }
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) { _owner; _spender; remaining; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

/**
    ERC20 Standard Token implementation
*/
contract ERC20Token is IERC20Token, Utils {
    string public standard = 'Token 0.1';
    string public name = '';
    string public symbol = '';
    uint8 public decimals = 0;
    uint256 public totalSupply = 0;
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /**
        @dev constructor

        @param _name        token name
        @param _symbol      token symbol
        @param _decimals    decimal points, for display purposes
    */
    function ERC20Token(string _name, string _symbol, uint8 _decimals) {
        require(bytes(_name).length > 0 && bytes(_symbol).length > 0); // validate input

        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        validAddress(_to)
        returns (bool success)
    {
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        validAddress(_from)
        validAddress(_to)
        returns (bool success)
    {
        allowance[_from][msg.sender] = safeSub(allowance[_from][msg.sender], _value);
        balanceOf[_from] = safeSub(balanceOf[_from], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        Transfer(_from, _to, _value);
        return true;
    }

    /**
        @dev allow another account/contract to spend some tokens on your behalf
        throws on any error rather then return a false flag to minimize user errors

        also, to minimize the risk of the approve/transferFrom attack vector
        (see https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/), approve has to be called twice
        in 2 separate transactions - once to change the allowance to 0 and secondly to change it to the new allowance value

        @param _spender approved address
        @param _value   allowance amount

        @return true if the approval was successful, false if it wasn't
    */
    function approve(address _spender, uint256 _value)
        public
        validAddress(_spender)
        returns (bool success)
    {
        // if the allowance isn't 0, it can only be updated to 0 to prevent an allowance change immediately after withdrawal
        require(_value == 0 || allowance[msg.sender][_spender] == 0);

        allowance[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
}

/*
    Ether Token interface
*/
contract IEtherToken is ITokenHolder, IERC20Token {
    function deposit() public payable;
    function withdraw(uint256 _amount) public;
    function withdrawTo(address _to, uint256 _amount);
}

/**
    Ether tokenization contract

    'Owned' is specified here for readability reasons
*/
contract EtherToken is IEtherToken, Owned, ERC20Token, TokenHolder {
    // triggered when the total supply is increased
    event Issuance(uint256 _amount);
    // triggered when the total supply is decreased
    event Destruction(uint256 _amount);

    /**
        @dev constructor
    */
    function EtherToken()
        ERC20Token('Ether Token', 'ETH', 18) {
    }

    /**
        @dev deposit ether in the account
    */
    function deposit() public payable {
        balanceOf[msg.sender] = safeAdd(balanceOf[msg.sender], msg.value); // add the value to the account balance
        totalSupply = safeAdd(totalSupply, msg.value); // increase the total supply

        Issuance(msg.value);
        Transfer(this, msg.sender, msg.value);
    }

    /**
        @dev withdraw ether from the account

        @param _amount  amount of ether to withdraw
    */
    function withdraw(uint256 _amount) public {
        withdrawTo(msg.sender, _amount);
    }

    /**
        @dev withdraw ether from the account to a target account

        @param _to      account to receive the ether
        @param _amount  amount of ether to withdraw
    */
    function withdrawTo(address _to, uint256 _amount)
        public
        notThis(_to)
    {
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _amount); // deduct the amount from the account balance
        totalSupply = safeSub(totalSupply, _amount); // decrease the total supply
        _to.transfer(_amount); // send the amount to the target account

        Transfer(msg.sender, this, _amount);
        Destruction(_amount);
    }

    // ERC20 standard method overrides with some extra protection

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        notThis(_to)
        returns (bool success)
    {
        assert(super.transfer(_to, _value));
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        notThis(_to)
        returns (bool success)
    {
        assert(super.transferFrom(_from, _to, _value));
        return true;
    }

    /**
        @dev deposit ether in the account
    */
    function() public payable {
        deposit();
    }
}

pragma solidity ^0.4.24;

// File: contracts/token/interfaces/IERC20Token.sol

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {}
    function symbol() public view returns (string) {}
    function decimals() public view returns (uint8) {}
    function totalSupply() public view returns (uint256) {}
    function balanceOf(address _owner) public view returns (uint256) { _owner; }
    function allowance(address _owner, address _spender) public view returns (uint256) { _owner; _spender; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

// File: contracts/IBancorNetwork.sol

/*
    Bancor Network interface
*/
contract IBancorNetwork {
    function convert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public payable returns (uint256);
    function convertFor(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _for) public payable returns (uint256);
    
    function convertForPrioritized3(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _customVal,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);
    
    // deprecated, backward compatibility
    function convertForPrioritized2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);

    // deprecated, backward compatibility
    function convertForPrioritized(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint256 _nonce,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) public payable returns (uint256);
}

// File: contracts/ContractIds.sol

/**
    Id definitions for bancor contracts

    Can be used in conjunction with the contract registry to get contract addresses
*/
contract ContractIds {
    // generic
    bytes32 public constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 public constant CONTRACT_REGISTRY = "ContractRegistry";
    bytes32 public constant NON_STANDARD_TOKEN_REGISTRY = "NonStandardTokenRegistry";

    // bancor logic
    bytes32 public constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 public constant BANCOR_FORMULA = "BancorFormula";
    bytes32 public constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 public constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 public constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";

    // BNT core
    bytes32 public constant BNT_TOKEN = "BNTToken";
    bytes32 public constant BNT_CONVERTER = "BNTConverter";

    // BancorX
    bytes32 public constant BANCOR_X = "BancorX";
    bytes32 public constant BANCOR_X_UPGRADER = "BancorXUpgrader";
}

// File: contracts/FeatureIds.sol

/**
    Id definitions for bancor contract features

    Can be used to query the ContractFeatures contract to check whether a certain feature is supported by a contract
*/
contract FeatureIds {
    // converter features
    uint256 public constant CONVERTER_CONVERSION_WHITELIST = 1 << 0;
}

// File: contracts/utility/interfaces/IWhitelist.sol

/*
    Whitelist interface
*/
contract IWhitelist {
    function isWhitelisted(address _address) public view returns (bool);
}

// File: contracts/converter/interfaces/IBancorConverter.sol

/*
    Bancor Converter interface
*/
contract IBancorConverter {
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256);
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function conversionWhitelist() public view returns (IWhitelist) {}
    function conversionFee() public view returns (uint32) {}
    function connectors(address _address) public view returns (uint256, uint32, bool, bool, bool) { _address; }
    function getConnectorBalance(IERC20Token _connectorToken) public view returns (uint256);
    function claimTokens(address _from, uint256 _amount) public;
    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
}

// File: contracts/converter/interfaces/IBancorFormula.sol

/*
    Bancor Formula interface
*/
contract IBancorFormula {
    function calculatePurchaseReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _depositAmount) public view returns (uint256);
    function calculateSaleReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _sellAmount) public view returns (uint256);
    function calculateCrossConnectorReturn(uint256 _fromConnectorBalance, uint32 _fromConnectorWeight, uint256 _toConnectorBalance, uint32 _toConnectorWeight, uint256 _amount) public view returns (uint256);
}

// File: contracts/converter/interfaces/IBancorGasPriceLimit.sol

/*
    Bancor Gas Price Limit interface
*/
contract IBancorGasPriceLimit {
    function gasPrice() public view returns (uint256) {}
    function validateGasPrice(uint256) public view;
}

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

}

// File: contracts/utility/interfaces/ITokenHolder.sol

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

// File: contracts/token/interfaces/INonStandardERC20.sol

/*
    ERC20 Standard Token interface which doesn't return true/false for transfer, transferFrom and approve
*/
contract INonStandardERC20 {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {}
    function symbol() public view returns (string) {}
    function decimals() public view returns (uint8) {}
    function totalSupply() public view returns (uint256) {}
    function balanceOf(address _owner) public view returns (uint256) { _owner; }
    function allowance(address _owner, address _spender) public view returns (uint256) { _owner; _spender; }

    function transfer(address _to, uint256 _value) public;
    function transferFrom(address _from, address _to, uint256 _value) public;
    function approve(address _spender, uint256 _value) public;
}

// File: contracts/utility/TokenHolder.sol

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.

    Note that we use the non standard ERC-20 interface which has no return value for transfer
    in order to support both non standard as well as standard token contracts.
    see https://github.com/ethereum/solidity/issues/4116
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
        @dev constructor
    */
    constructor() public {
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        INonStandardERC20(_token).transfer(_to, _amount);
    }
}

// File: contracts/utility/SafeMath.sol

/*
    Library for basic math operations with overflow/underflow protection
*/
library SafeMath {
    /**
        @dev returns the sum of _x and _y, reverts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function add(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        require(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, reverts if the calculation underflows

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function sub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, reverts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function mul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        // gas optimization
        if (_x == 0)
            return 0;

        uint256 z = _x * _y;
        require(z / _x == _y);
        return z;
    }

      /**
        @dev Integer division of two numbers truncating the quotient, reverts on division by zero.

        @param _x   dividend
        @param _y   divisor

        @return quotient
    */
    function div(uint256 _x, uint256 _y) internal pure returns (uint256) {
        require(_y > 0);
        uint256 c = _x / _y;

        return c;
    }
}

// File: contracts/utility/interfaces/IContractRegistry.sol

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/utility/interfaces/IContractFeatures.sol

/*
    Contract Features interface
*/
contract IContractFeatures {
    function isSupported(address _contract, uint256 _features) public view returns (bool);
    function enableFeatures(uint256 _features, bool _enable) public;
}

// File: contracts/utility/interfaces/IAddressList.sol

/*
    Address list interface
*/
contract IAddressList {
    mapping (address => bool) public listedAddresses;
}

// File: contracts/token/interfaces/IEtherToken.sol

/*
    Ether Token interface
*/
contract IEtherToken is ITokenHolder, IERC20Token {
    function deposit() public payable;
    function withdraw(uint256 _amount) public;
    function withdrawTo(address _to, uint256 _amount) public;
}

// File: contracts/token/interfaces/ISmartToken.sol

/*
    Smart Token interface
*/
contract ISmartToken is IOwned, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

// File: contracts/bancorx/interfaces/IBancorX.sol

contract IBancorX {
    function xTransfer(bytes32 _toBlockchain, bytes32 _to, uint256 _amount, uint256 _id) public;
    function getXTransferAmount(uint256 _xTransferId, address _for) public view returns (uint256);
}

// File: contracts/BancorNetwork.sol

/*
    The BancorNetwork contract is the main entry point for bancor token conversions.
    It also allows converting between any token in the bancor network to any other token
    in a single transaction by providing a conversion path.

    A note on conversion path -
    Conversion path is a data structure that's used when converting a token to another token in the bancor network
    when the conversion cannot necessarily be done by single converter and might require multiple 'hops'.
    The path defines which converters should be used and what kind of conversion should be done in each step.

    The path format doesn't include complex structure and instead, it is represented by a single array
    in which each 'hop' is represented by a 2-tuple - smart token & to token.
    In addition, the first element is always the source token.
    The smart token is only used as a pointer to a converter (since converter addresses are more likely to change).

    Format:
    [source token, smart token, to token, smart token, to token...]
*/
contract BancorNetwork is IBancorNetwork, TokenHolder, ContractIds, FeatureIds {
    using SafeMath for uint256;

    
    uint64 private constant MAX_CONVERSION_FEE = 1000000;

    address public signerAddress = 0x0;         // verified address that allows conversions with higher gas price
    IContractRegistry public registry;          // contract registry contract address

    mapping (address => bool) public etherTokens;       // list of all supported ether tokens
    mapping (bytes32 => bool) public conversionHashes;  // list of conversion hashes, to prevent re-use of the same hash

    /**
        @dev constructor

        @param _registry    address of a contract registry contract
    */
    constructor(IContractRegistry _registry) public validAddress(_registry) {
        registry = _registry;
    }

    // validates a conversion path - verifies that the number of elements is odd and that maximum number of 'hops' is 10
    modifier validConversionPath(IERC20Token[] _path) {
        require(_path.length > 2 && _path.length <= (1 + 2 * 10) && _path.length % 2 == 1);
        _;
    }

    /*
        @dev allows the owner to update the contract registry contract address

        @param _registry   address of a contract registry contract
    */
    function setRegistry(IContractRegistry _registry)
        public
        ownerOnly
        validAddress(_registry)
        notThis(_registry)
    {
        registry = _registry;
    }

    /*
        @dev allows the owner to update the signer address

        @param _signerAddress    new signer address
    */
    function setSignerAddress(address _signerAddress)
        public
        ownerOnly
        validAddress(_signerAddress)
        notThis(_signerAddress)
    {
        signerAddress = _signerAddress;
    }

    /**
        @dev allows the owner to register/unregister ether tokens

        @param _token       ether token contract address
        @param _register    true to register, false to unregister
    */
    function registerEtherToken(IEtherToken _token, bool _register)
        public
        ownerOnly
        validAddress(_token)
        notThis(_token)
    {
        etherTokens[_token] = _register;
    }

    /**
        @dev verifies that the signer address is trusted by recovering 
        the address associated with the public key from elliptic 
        curve signature, returns zero on error.
        notice that the signature is valid only for one conversion
        and expires after the give block.

        @return true if the signer is verified
    */
    function verifyTrustedSender(IERC20Token[] _path, uint256 _customVal, uint256 _block, address _addr, uint8 _v, bytes32 _r, bytes32 _s) private returns(bool) {
        bytes32 hash = keccak256(_block, tx.gasprice, _addr, msg.sender, _customVal, _path);

        // checking that it is the first conversion with the given signature
        // and that the current block number doesn't exceeded the maximum block
        // number that's allowed with the current signature
        require(!conversionHashes[hash] && block.number <= _block);

        // recovering the signing address and comparing it to the trusted signer
        // address that was set in the contract
        bytes32 prefixedHash = keccak256("\x19Ethereum Signed Message:\n32", hash);
        bool verified = ecrecover(prefixedHash, _v, _r, _s) == signerAddress;

        // if the signer is the trusted signer - mark the hash so that it can't
        // be used multiple times
        if (verified)
            conversionHashes[hash] = true;
        return verified;
    }

    /**
        @dev validates xConvert call by verifying the path format, claiming the callers tokens (if not ETH),
        and verifying the gas price limit

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _block       if the current block exceeded the given parameter - it is cancelled
        @param _v           (signature[128:130]) associated with the signer address and helps to validate if the signature is legit
        @param _r           (signature[0:64]) associated with the signer address and helps to validate if the signature is legit
        @param _s           (signature[64:128]) associated with the signer address and helps to validate if the signature is legit
    */
    function validateXConversion(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    ) 
        private 
        validConversionPath(_path)    
    {
        // if ETH is provided, ensure that the amount is identical to _amount and verify that the source token is an ether token
        IERC20Token fromToken = _path[0];
        require(msg.value == 0 || (_amount == msg.value && etherTokens[fromToken]));

        // require that the dest token is BNT
        require(_path[_path.length - 1] == registry.addressOf(ContractIds.BNT_TOKEN));

        // if ETH was sent with the call, the source is an ether token - deposit the ETH in it
        // otherwise, we claim the tokens from the sender
        if (msg.value > 0) {
            IEtherToken(fromToken).deposit.value(msg.value)();
        } else {
            ensureTransferFrom(fromToken, msg.sender, this, _amount);
        }

        // verify gas price limit
        if (_v == 0x0 && _r == 0x0 && _s == 0x0) {
            IBancorGasPriceLimit gasPriceLimit = IBancorGasPriceLimit(registry.addressOf(ContractIds.BANCOR_GAS_PRICE_LIMIT));
            gasPriceLimit.validateGasPrice(tx.gasprice);
        } else {
            require(verifyTrustedSender(_path, _amount, _block, msg.sender, _v, _r, _s));
        }
    }

    /**
        @dev converts the token to any other token in the bancor network by following
        a predefined conversion path and transfers the result tokens to a target account
        note that the converter should already own the source tokens

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _for         account that will receive the conversion result

        @return tokens issued in return
    */
    function convertFor(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _for) public payable returns (uint256) {
        return convertForPrioritized3(_path, _amount, _minReturn, _for, _amount, 0x0, 0x0, 0x0, 0x0);
    }

    /**
        @dev converts the token to any other token in the bancor network
        by following a predefined conversion path and transfers the result
        tokens to a target account.
        this version of the function also allows the verified signer
        to bypass the universal gas price limit.
        note that the converter should already own the source tokens

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _for         account that will receive the conversion result
        @param _customVal   custom value that was signed for prioritized conversion
        @param _block       if the current block exceeded the given parameter - it is cancelled
        @param _v           (signature[128:130]) associated with the signer address and helps to validate if the signature is legit
        @param _r           (signature[0:64]) associated with the signer address and helps to validate if the signature is legit
        @param _s           (signature[64:128]) associated with the signer address and helps to validate if the signature is legit

        @return tokens issued in return
    */
    function convertForPrioritized3(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _customVal,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    )
        public
        payable
        returns (uint256)
    {
        // if ETH is provided, ensure that the amount is identical to _amount and verify that the source token is an ether token
        IERC20Token fromToken = _path[0];
        require(msg.value == 0 || (_amount == msg.value && etherTokens[fromToken]));

        // if ETH was sent with the call, the source is an ether token - deposit the ETH in it
        // otherwise, we assume we already have the tokens
        if (msg.value > 0)
            IEtherToken(fromToken).deposit.value(msg.value)();

        return convertForInternal(_path, _amount, _minReturn, _for, _customVal, _block, _v, _r, _s);
    }

    /**
        @dev converts any other token to BNT in the bancor network
        by following a predefined conversion path and transfers the resulting
        tokens to BancorX.
        note that the network should already have been given allowance of the source token (if not ETH)

        @param _path             conversion path, see conversion path format above
        @param _amount           amount to convert from (in the initial source token)
        @param _minReturn        if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _toBlockchain     blockchain BNT will be issued on
        @param _to               address/account on _toBlockchain to send the BNT to
        @param _conversionId     pre-determined unique (if non zero) id which refers to this transaction 

        @return the amount of BNT received from this conversion
    */
    function xConvert(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        bytes32 _toBlockchain,
        bytes32 _to,
        uint256 _conversionId
    )
        public
        payable
        returns (uint256)
    {
        return xConvertPrioritized(_path, _amount, _minReturn, _toBlockchain, _to, _conversionId, 0x0, 0x0, 0x0, 0x0);
    }

    /**
        @dev converts any other token to BNT in the bancor network
        by following a predefined conversion path and transfers the resulting
        tokens to BancorX.
        this version of the function also allows the verified signer
        to bypass the universal gas price limit.
        note that the network should already have been given allowance of the source token (if not ETH)

        @param _path            conversion path, see conversion path format above
        @param _amount          amount to convert from (in the initial source token)
        @param _minReturn       if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _toBlockchain    blockchain BNT will be issued on
        @param _to              address/account on _toBlockchain to send the BNT to
        @param _conversionId    pre-determined unique (if non zero) id which refers to this transaction 
        @param _block           if the current block exceeded the given parameter - it is cancelled
        @param _v               (signature[128:130]) associated with the signer address and helps to validate if the signature is legit
        @param _r               (signature[0:64]) associated with the signer address and helps to validate if the signature is legit
        @param _s               (signature[64:128]) associated with the signer address and helps to validate if the signature is legit

        @return the amount of BNT received from this conversion
    */
    function xConvertPrioritized(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        bytes32 _toBlockchain,
        bytes32 _to,
        uint256 _conversionId,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    )
        public
        payable
        returns (uint256)
    {
        // do a lot of validation and transfers in separate function to work around 16 variable limit
        validateXConversion(_path, _amount, _block, _v, _r, _s);

        // convert to BNT and get the resulting amount
        (, uint256 retAmount) = convertByPath(_path, _amount, _minReturn, _path[0], this);

        // transfer the resulting amount to BancorX, and return the amount
        IBancorX(registry.addressOf(ContractIds.BANCOR_X)).xTransfer(_toBlockchain, _to, retAmount, _conversionId);

        return retAmount;
    }

    /**
        @dev converts token to any other token in the bancor network
        by following a predefined conversion paths and transfers the result
        tokens to a target account.

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _for         account that will receive the conversion result
        @param _block       if the current block exceeded the given parameter - it is cancelled
        @param _v           (signature[128:130]) associated with the signer address and helps to validate if the signature is legit
        @param _r           (signature[0:64]) associated with the signer address and helps to validate if the signature is legit
        @param _s           (signature[64:128]) associated with the signer address and helps to validate if the signature is legit

        @return tokens issued in return
    */
    function convertForInternal(
        IERC20Token[] _path, 
        uint256 _amount, 
        uint256 _minReturn, 
        address _for, 
        uint256 _customVal,
        uint256 _block,
        uint8 _v, 
        bytes32 _r, 
        bytes32 _s
    )
        private
        validConversionPath(_path)
        returns (uint256)
    {
        if (_v == 0x0 && _r == 0x0 && _s == 0x0) {
            IBancorGasPriceLimit gasPriceLimit = IBancorGasPriceLimit(registry.addressOf(ContractIds.BANCOR_GAS_PRICE_LIMIT));
            gasPriceLimit.validateGasPrice(tx.gasprice);
        }
        else {
            require(verifyTrustedSender(_path, _customVal, _block, _for, _v, _r, _s));
        }

        // if ETH is provided, ensure that the amount is identical to _amount and verify that the source token is an ether token
        IERC20Token fromToken = _path[0];

        IERC20Token toToken;
        
        (toToken, _amount) = convertByPath(_path, _amount, _minReturn, fromToken, _for);

        // finished the conversion, transfer the funds to the target account
        // if the target token is an ether token, withdraw the tokens and send them as ETH
        // otherwise, transfer the tokens as is
        if (etherTokens[toToken])
            IEtherToken(toToken).withdrawTo(_for, _amount);
        else
            ensureTransfer(toToken, _for, _amount);

        return _amount;
    }

    /**
        @dev executes the actual conversion by following the conversion path

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _fromToken   ERC20 token to convert from (the first element in the path)
        @param _for         account that will receive the conversion result

        @return ERC20 token to convert to (the last element in the path) & tokens issued in return
    */
    function convertByPath(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        IERC20Token _fromToken,
        address _for
    ) private returns (IERC20Token, uint256) {
        ISmartToken smartToken;
        IERC20Token toToken;
        IBancorConverter converter;

        // get the contract features address from the registry
        IContractFeatures features = IContractFeatures(registry.addressOf(ContractIds.CONTRACT_FEATURES));

        // iterate over the conversion path
        uint256 pathLength = _path.length;
        for (uint256 i = 1; i < pathLength; i += 2) {
            smartToken = ISmartToken(_path[i]);
            toToken = _path[i + 1];
            converter = IBancorConverter(smartToken.owner());
            checkWhitelist(converter, _for, features);

            // if the smart token isn't the source (from token), the converter doesn't have control over it and thus we need to approve the request
            if (smartToken != _fromToken)
                ensureAllowance(_fromToken, converter, _amount);

            // make the conversion - if it's the last one, also provide the minimum return value
            _amount = converter.change(_fromToken, toToken, _amount, i == pathLength - 2 ? _minReturn : 1);
            _fromToken = toToken;
        }
        return (toToken, _amount);
    }

    /**
        @dev returns the expected return amount for converting a specific amount by following
        a given conversion path.
        notice that there is no support for circular paths.

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)

        @return expected conversion return amount and conversion fee
    */
    function getReturnByPath(IERC20Token[] _path, uint256 _amount) public view returns (uint256, uint256) {
        IERC20Token fromToken;
        ISmartToken smartToken; 
        IERC20Token toToken;
        IBancorConverter converter;
        uint256 amount;
        uint256 fee;
        uint256 supply;
        uint256 balance;
        uint32 weight;
        ISmartToken prevSmartToken;
        IBancorFormula formula = IBancorFormula(registry.getAddress(ContractIds.BANCOR_FORMULA));

        amount = _amount;
        fromToken = _path[0];

        // iterate over the conversion path
        for (uint256 i = 1; i < _path.length; i += 2) {
            smartToken = ISmartToken(_path[i]);
            toToken = _path[i + 1];
            converter = IBancorConverter(smartToken.owner());

            if (toToken == smartToken) { // buy the smart token
                // check if the current smart token supply was changed in the previous iteration
                supply = smartToken == prevSmartToken ? supply : smartToken.totalSupply();

                // validate input
                require(getConnectorSaleEnabled(converter, fromToken));

                // calculate the amount & the conversion fee
                balance = converter.getConnectorBalance(fromToken);
                weight = getConnectorWeight(converter, fromToken);
                amount = formula.calculatePurchaseReturn(supply, balance, weight, amount);
                fee = amount.mul(converter.conversionFee()).div(MAX_CONVERSION_FEE);
                amount -= fee;

                // update the smart token supply for the next iteration
                supply = smartToken.totalSupply() + amount;
            }
            else if (fromToken == smartToken) { // sell the smart token
                // check if the current smart token supply was changed in the previous iteration
                supply = smartToken == prevSmartToken ? supply : smartToken.totalSupply();

                // calculate the amount & the conversion fee
                balance = converter.getConnectorBalance(toToken);
                weight = getConnectorWeight(converter, toToken);
                amount = formula.calculateSaleReturn(supply, balance, weight, amount);
                fee = amount.mul(converter.conversionFee()).div(MAX_CONVERSION_FEE);
                amount -= fee;

                // update the smart token supply for the next iteration
                supply = smartToken.totalSupply() - amount;
            }
            else { // cross connector conversion
                (amount, fee) = converter.getReturn(fromToken, toToken, amount);
            }

            prevSmartToken = smartToken;
            fromToken = toToken;
        }

        return (amount, fee);
    }

    /**
        @dev checks whether the given converter supports a whitelist and if so, ensures that
        the account that should receive the conversion result is actually whitelisted

        @param _converter   converter to check for whitelist
        @param _for         account that will receive the conversion result
        @param _features    contract features contract address
    */
    function checkWhitelist(IBancorConverter _converter, address _for, IContractFeatures _features) private view {
        IWhitelist whitelist;

        // check if the converter supports the conversion whitelist feature
        if (!_features.isSupported(_converter, FeatureIds.CONVERTER_CONVERSION_WHITELIST))
            return;

        // get the whitelist contract from the converter
        whitelist = _converter.conversionWhitelist();
        if (whitelist == address(0))
            return;

        // check if the account that should receive the conversion result is actually whitelisted
        require(whitelist.isWhitelisted(_for));
    }

    /**
        @dev claims the caller's tokens, converts them to any other token in the bancor network
        by following a predefined conversion path and transfers the result tokens to a target account
        note that allowance must be set beforehand

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _for         account that will receive the conversion result

        @return tokens issued in return
    */
    function claimAndConvertFor(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _for) public returns (uint256) {
        // we need to transfer the tokens from the caller to the converter before we follow
        // the conversion path, to allow it to execute the conversion on behalf of the caller
        // note: we assume we already have allowance
        IERC20Token fromToken = _path[0];
        ensureTransferFrom(fromToken, msg.sender, this, _amount);
        return convertFor(_path, _amount, _minReturn, _for);
    }

    /**
        @dev converts the token to any other token in the bancor network by following
        a predefined conversion path and transfers the result tokens back to the sender
        note that the converter should already own the source tokens

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return tokens issued in return
    */
    function convert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public payable returns (uint256) {
        return convertFor(_path, _amount, _minReturn, msg.sender);
    }

    /**
        @dev claims the caller's tokens, converts them to any other token in the bancor network
        by following a predefined conversion path and transfers the result tokens back to the sender
        note that allowance must be set beforehand

        @param _path        conversion path, see conversion path format above
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return tokens issued in return
    */
    function claimAndConvert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public returns (uint256) {
        return claimAndConvertFor(_path, _amount, _minReturn, msg.sender);
    }

    /**
        @dev ensures transfer of tokens, taking into account that some ERC-20 implementations don't return
        true on success but revert on failure instead

        @param _token     the token to transfer
        @param _to        the address to transfer the tokens to
        @param _amount    the amount to transfer
    */
    function ensureTransfer(IERC20Token _token, address _to, uint256 _amount) private {
        IAddressList addressList = IAddressList(registry.addressOf(ContractIds.NON_STANDARD_TOKEN_REGISTRY));

        if (addressList.listedAddresses(_token)) {
            uint256 prevBalance = _token.balanceOf(_to);
            // we have to cast the token contract in an interface which has no return value
            INonStandardERC20(_token).transfer(_to, _amount);
            uint256 postBalance = _token.balanceOf(_to);
            assert(postBalance > prevBalance);
        } else {
            // if the token isn't whitelisted, we assert on transfer
            assert(_token.transfer(_to, _amount));
        }
    }

    /**
        @dev ensures transfer of tokens, taking into account that some ERC-20 implementations don't return
        true on success but revert on failure instead

        @param _token     the token to transfer
        @param _from      the address to transfer the tokens from
        @param _to        the address to transfer the tokens to
        @param _amount    the amount to transfer
    */
    function ensureTransferFrom(IERC20Token _token, address _from, address _to, uint256 _amount) private {
        IAddressList addressList = IAddressList(registry.addressOf(ContractIds.NON_STANDARD_TOKEN_REGISTRY));

        if (addressList.listedAddresses(_token)) {
            uint256 prevBalance = _token.balanceOf(_to);
            // we have to cast the token contract in an interface which has no return value
            INonStandardERC20(_token).transferFrom(_from, _to, _amount);
            uint256 postBalance = _token.balanceOf(_to);
            assert(postBalance > prevBalance);
        } else {
            // if the token isn't whitelisted, we assert on transfer
            assert(_token.transferFrom(_from, _to, _amount));
        }
    }

    /**
        @dev utility, checks whether allowance for the given spender exists and approves one if it doesn't.
        Note that we use the non standard erc-20 interface in which `approve` has no return value so that
        this function will work for both standard and non standard tokens

        @param _token   token to check the allowance in
        @param _spender approved address
        @param _value   allowance amount
    */
    function ensureAllowance(IERC20Token _token, address _spender, uint256 _value) private {
        // check if allowance for the given amount already exists
        if (_token.allowance(this, _spender) >= _value)
            return;

        // if the allowance is nonzero, must reset it to 0 first
        if (_token.allowance(this, _spender) != 0)
            INonStandardERC20(_token).approve(_spender, 0);

        // approve the new allowance
        INonStandardERC20(_token).approve(_spender, _value);
    }

    /**
        @dev returns the connector weight

        @param _converter       converter contract address
        @param _connector       connector's address to read from

        @return connector's weight
    */
    function getConnectorWeight(IBancorConverter _converter, IERC20Token _connector) 
        private
        view
        returns(uint32)
    {
        uint256 virtualBalance;
        uint32 weight;
        bool isVirtualBalanceEnabled;
        bool isSaleEnabled;
        bool isSet;
        (virtualBalance, weight, isVirtualBalanceEnabled, isSaleEnabled, isSet) = _converter.connectors(_connector);
        return weight;
    }

    /**
        @dev returns true if connector sale is enabled

        @param _converter       converter contract address
        @param _connector       connector's address to read from

        @return true if connector sale is enabled, otherwise - false
    */
    function getConnectorSaleEnabled(IBancorConverter _converter, IERC20Token _connector) 
        private
        view
        returns(bool)
    {
        uint256 virtualBalance;
        uint32 weight;
        bool isVirtualBalanceEnabled;
        bool isSaleEnabled;
        bool isSet;
        (virtualBalance, weight, isVirtualBalanceEnabled, isSaleEnabled, isSet) = _converter.connectors(_connector);
        return isSaleEnabled;
    }

    // deprecated, backward compatibility
    function convertForPrioritized2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s
    )
        public
        payable
        returns (uint256)
    {
        return convertForPrioritized3(_path, _amount, _minReturn, _for, _amount, _block, _v, _r, _s);
    }

    // deprecated, backward compatibility
    function convertForPrioritized(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint256 _nonce,
        uint8 _v,
        bytes32 _r,
        bytes32 _s)
        public payable returns (uint256)
    {
        _nonce;
        return convertForPrioritized3(_path, _amount, _minReturn, _for, _amount, _block, _v, _r, _s);
    }
}

pragma solidity ^0.4.11;

/*
    Overflow protected math functions
*/
contract SafeMath {
    /**
        constructor
    */
    function SafeMath() {
    }

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
} 

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public constant returns (address owner) { owner; }

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address _prevOwner, address _newOwner);

    /**
        @dev constructor
    */
    function Owned() {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        assert(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still need to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = 0x0;
    }
}

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned {
    /**
        @dev constructor
    */
    function TokenHolder() {
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != 0x0);
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public constant returns (string name) { name; }
    function symbol() public constant returns (string symbol) { symbol; }
    function decimals() public constant returns (uint8 decimals) { decimals; }
    function totalSupply() public constant returns (uint256 totalSupply) { totalSupply; }
    function balanceOf(address _owner) public constant returns (uint256 balance) { _owner; balance; }
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining) { _owner; _spender; remaining; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

/**
    ERC20 Standard Token implementation
*/
contract ERC20Token is IERC20Token, SafeMath {
    string public standard = 'Token 0.1';
    string public name = '';
    string public symbol = '';
    uint8 public decimals = 0;
    uint256 public totalSupply = 0;
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /**
        @dev constructor

        @param _name        token name
        @param _symbol      token symbol
        @param _decimals    decimal points, for display purposes
    */
    function ERC20Token(string _name, string _symbol, uint8 _decimals) {
        require(bytes(_name).length > 0 && bytes(_symbol).length > 0); // validate input

        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != 0x0);
        _;
    }

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        validAddress(_to)
        returns (bool success)
    {
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        validAddress(_from)
        validAddress(_to)
        returns (bool success)
    {
        allowance[_from][msg.sender] = safeSub(allowance[_from][msg.sender], _value);
        balanceOf[_from] = safeSub(balanceOf[_from], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        Transfer(_from, _to, _value);
        return true;
    }

    /**
        @dev allow another account/contract to spend some tokens on your behalf
        throws on any error rather then return a false flag to minimize user errors

        also, to minimize the risk of the approve/transferFrom attack vector
        (see https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/), approve has to be called twice
        in 2 separate transactions - once to change the allowance to 0 and secondly to change it to the new allowance value

        @param _spender approved address
        @param _value   allowance amount

        @return true if the approval was successful, false if it wasn't
    */
    function approve(address _spender, uint256 _value)
        public
        validAddress(_spender)
        returns (bool success)
    {
        // if the allowance isn't 0, it can only be updated to 0 to prevent an allowance change immediately after withdrawal
        require(_value == 0 || allowance[msg.sender][_spender] == 0);

        allowance[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }
}

/*
    Smart Token interface
*/
contract ISmartToken is ITokenHolder, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

/*
    Smart Token v0.2

    'Owned' is specified here for readability reasons
*/
contract SmartToken is ISmartToken, ERC20Token, Owned, TokenHolder {
    string public version = '0.2';

    bool public transfersEnabled = true;    // true if transfer/transferFrom are enabled, false if not

    // triggered when a smart token is deployed - the _token address is defined for forward compatibility, in case we want to trigger the event from a factory
    event NewSmartToken(address _token);
    // triggered when the total supply is increased
    event Issuance(uint256 _amount);
    // triggered when the total supply is decreased
    event Destruction(uint256 _amount);

    /**
        @dev constructor

        @param _name       token name
        @param _symbol     token short symbol, 1-6 characters
        @param _decimals   for display purposes only
    */
    function SmartToken(string _name, string _symbol, uint8 _decimals)
        ERC20Token(_name, _symbol, _decimals)
    {
        require(bytes(_symbol).length <= 6); // validate input
        NewSmartToken(address(this));
    }

    // allows execution only when transfers aren't disabled
    modifier transfersAllowed {
        assert(transfersEnabled);
        _;
    }

    /**
        @dev disables/enables transfers
        can only be called by the contract owner

        @param _disable    true to disable transfers, false to enable them
    */
    function disableTransfers(bool _disable) public ownerOnly {
        transfersEnabled = !_disable;
    }

    /**
        @dev increases the token supply and sends the new tokens to an account
        can only be called by the contract owner

        @param _to         account to receive the new amount
        @param _amount     amount to increase the supply by
    */
    function issue(address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_to)
        notThis(_to)
    {
        totalSupply = safeAdd(totalSupply, _amount);
        balanceOf[_to] = safeAdd(balanceOf[_to], _amount);

        Issuance(_amount);
        Transfer(this, _to, _amount);
    }

    /**
        @dev removes tokens from an account and decreases the token supply
        can only be called by the contract owner

        @param _from       account to remove the amount from
        @param _amount     amount to decrease the supply by
    */
    function destroy(address _from, uint256 _amount)
        public
        ownerOnly
    {
        balanceOf[_from] = safeSub(balanceOf[_from], _amount);
        totalSupply = safeSub(totalSupply, _amount);

        Transfer(_from, this, _amount);
        Destruction(_amount);
    }

    // ERC20 standard method overrides with some extra functionality

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors
        note that when transferring to the smart token's address, the coins are actually destroyed

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transfer(_to, _value));

        // transferring to the contract address destroys tokens
        if (_to == address(this)) {
            balanceOf[_to] -= _value;
            totalSupply -= _value;
            Destruction(_value);
        }

        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors
        note that when transferring to the smart token's address, the coins are actually destroyed

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transferFrom(_from, _to, _value));

        // transferring to the contract address destroys tokens
        if (_to == address(this)) {
            balanceOf[_to] -= _value;
            totalSupply -= _value;
            Destruction(_value);
        }

        return true;
    }
}

pragma solidity ^0.4.24;

// File: contracts/token/interfaces/IERC20Token.sol

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {}
    function symbol() public view returns (string) {}
    function decimals() public view returns (uint8) {}
    function totalSupply() public view returns (uint256) {}
    function balanceOf(address _owner) public view returns (uint256) { _owner; }
    function allowance(address _owner, address _spender) public view returns (uint256) { _owner; _spender; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

// File: contracts/utility/interfaces/IWhitelist.sol

/*
    Whitelist interface
*/
contract IWhitelist {
    function isWhitelisted(address _address) public view returns (bool);
}

// File: contracts/converter/interfaces/IBancorConverter.sol

/*
    Bancor Converter interface
*/
contract IBancorConverter {
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256);
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function conversionWhitelist() public view returns (IWhitelist) {}
    function conversionFee() public view returns (uint32) {}
    function connectors(address _address) public view returns (uint256, uint32, bool, bool, bool) { _address; }
    function getConnectorBalance(IERC20Token _connectorToken) public view returns (uint256);
    function claimTokens(address _from, uint256 _amount) public;
    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
}

// File: contracts/converter/interfaces/IBancorConverterUpgrader.sol

/*
    Bancor Converter Upgrader interface
*/
contract IBancorConverterUpgrader {
    function upgrade(bytes32 _version) public;
}

// File: contracts/converter/interfaces/IBancorFormula.sol

/*
    Bancor Formula interface
*/
contract IBancorFormula {
    function calculatePurchaseReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _depositAmount) public view returns (uint256);
    function calculateSaleReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _sellAmount) public view returns (uint256);
    function calculateCrossConnectorReturn(uint256 _fromConnectorBalance, uint32 _fromConnectorWeight, uint256 _toConnectorBalance, uint32 _toConnectorWeight, uint256 _amount) public view returns (uint256);
}

// File: contracts/IBancorNetwork.sol

/*
    Bancor Network interface
*/
contract IBancorNetwork {
    function convert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public payable returns (uint256);
    function convertFor(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _for) public payable returns (uint256);
    function convertForPrioritized2(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint8 _v,
        bytes32 _r,
        bytes32 _s)
        public payable returns (uint256);

    // deprecated, backward compatibility
    function convertForPrioritized(
        IERC20Token[] _path,
        uint256 _amount,
        uint256 _minReturn,
        address _for,
        uint256 _block,
        uint256 _nonce,
        uint8 _v,
        bytes32 _r,
        bytes32 _s)
        public payable returns (uint256);
}

// File: contracts/ContractIds.sol

/**
    Id definitions for bancor contracts

    Can be used in conjunction with the contract registry to get contract addresses
*/
contract ContractIds {
    // generic
    bytes32 public constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 public constant CONTRACT_REGISTRY = "ContractRegistry";

    // bancor logic
    bytes32 public constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 public constant BANCOR_FORMULA = "BancorFormula";
    bytes32 public constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 public constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 public constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";

    // Ids of BNT converter and BNT token
    bytes32 public constant BNT_TOKEN = "BNTToken";
    bytes32 public constant BNT_CONVERTER = "BNTConverter";

    // Id of BancorX contract
    bytes32 public constant BANCOR_X = "BancorX";
}

// File: contracts/FeatureIds.sol

/**
    Id definitions for bancor contract features

    Can be used to query the ContractFeatures contract to check whether a certain feature is supported by a contract
*/
contract FeatureIds {
    // converter features
    uint256 public constant CONVERTER_CONVERSION_WHITELIST = 1 << 0;
}

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Managed.sol

/*
    Provides support and utilities for contract management
    Note that a managed contract must also have an owner
*/
contract Managed is Owned {
    address public manager;
    address public newManager;

    event ManagerUpdate(address indexed _prevManager, address indexed _newManager);

    /**
        @dev constructor
    */
    constructor() public {
        manager = msg.sender;
    }

    // allows execution by the manager only
    modifier managerOnly {
        assert(msg.sender == manager);
        _;
    }

    // allows execution by either the owner or the manager only
    modifier ownerOrManagerOnly {
        require(msg.sender == owner || msg.sender == manager);
        _;
    }

    /**
        @dev allows transferring the contract management
        the new manager still needs to accept the transfer
        can only be called by the contract manager

        @param _newManager    new contract manager
    */
    function transferManagement(address _newManager) public ownerOrManagerOnly {
        require(_newManager != manager);
        newManager = _newManager;
    }

    /**
        @dev used by a new manager to accept a management transfer
    */
    function acceptManagement() public {
        require(msg.sender == newManager);
        emit ManagerUpdate(manager, newManager);
        manager = newManager;
        newManager = address(0);
    }
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

// File: contracts/utility/interfaces/IContractRegistry.sol

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/utility/interfaces/IContractFeatures.sol

/*
    Contract Features interface
*/
contract IContractFeatures {
    function isSupported(address _contract, uint256 _features) public view returns (bool);
    function enableFeatures(uint256 _features, bool _enable) public;
}

// File: contracts/token/interfaces/ISmartToken.sol

/*
    Smart Token interface
*/
contract ISmartToken is IOwned, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

// File: contracts/utility/interfaces/ITokenHolder.sol

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

// File: contracts/utility/TokenHolder.sol

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
        @dev constructor
    */
    constructor() public {
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

// File: contracts/token/SmartTokenController.sol

/*
    The smart token controller is an upgradable part of the smart token that allows
    more functionality as well as fixes for bugs/exploits.
    Once it accepts ownership of the token, it becomes the token's sole controller
    that can execute any of its functions.

    To upgrade the controller, ownership must be transferred to a new controller, along with
    any relevant data.

    The smart token must be set on construction and cannot be changed afterwards.
    Wrappers are provided (as opposed to a single 'execute' function) for each of the token's functions, for easier access.

    Note that the controller can transfer token ownership to a new controller that
    doesn't allow executing any function on the token, for a trustless solution.
    Doing that will also remove the owner's ability to upgrade the controller.
*/
contract SmartTokenController is TokenHolder {
    ISmartToken public token;   // smart token

    /**
        @dev constructor
    */
    constructor(ISmartToken _token)
        public
        validAddress(_token)
    {
        token = _token;
    }

    // ensures that the controller is the token's owner
    modifier active() {
        require(token.owner() == address(this));
        _;
    }

    // ensures that the controller is not the token's owner
    modifier inactive() {
        require(token.owner() != address(this));
        _;
    }

    /**
        @dev allows transferring the token ownership
        the new owner needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new token owner
    */
    function transferTokenOwnership(address _newOwner) public ownerOnly {
        token.transferOwnership(_newOwner);
    }

    /**
        @dev used by a new owner to accept a token ownership transfer
        can only be called by the contract owner
    */
    function acceptTokenOwnership() public ownerOnly {
        token.acceptOwnership();
    }

    /**
        @dev disables/enables token transfers
        can only be called by the contract owner

        @param _disable    true to disable transfers, false to enable them
    */
    function disableTokenTransfers(bool _disable) public ownerOnly {
        token.disableTransfers(_disable);
    }

    /**
        @dev withdraws tokens held by the controller and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawFromToken(IERC20Token _token, address _to, uint256 _amount) public ownerOnly {
        ITokenHolder(token).withdrawTokens(_token, _to, _amount);
    }
}

// File: contracts/token/interfaces/IEtherToken.sol

/*
    Ether Token interface
*/
contract IEtherToken is ITokenHolder, IERC20Token {
    function deposit() public payable;
    function withdraw(uint256 _amount) public;
    function withdrawTo(address _to, uint256 _amount) public;
}

// File: contracts/converter/BancorConverter.sol

/*
    Bancor Converter v0.11

    The Bancor version of the token converter, allows conversion between a smart token and other ERC20 tokens and between different ERC20 tokens and themselves.

    ERC20 connector balance can be virtual, meaning that the calculations are based on the virtual balance instead of relying on
    the actual connector balance. This is a security mechanism that prevents the need to keep a very large (and valuable) balance in a single contract.

    The converter is upgradable (just like any SmartTokenController).

    WARNING: It is NOT RECOMMENDED to use the converter with Smart Tokens that have less than 8 decimal digits
             or with very small numbers because of precision loss

    Open issues:
    - Front-running attacks are currently mitigated by the following mechanisms:
        - minimum return argument for each conversion provides a way to define a minimum/maximum price for the transaction
        - gas price limit prevents users from having control over the order of execution
        - gas price limit check can be skipped if the transaction comes from a trusted, whitelisted signer
      Other potential solutions might include a commit/reveal based schemes
    - Possibly add getters for the connector fields so that the client won't need to rely on the order in the struct
*/
contract BancorConverter is IBancorConverter, SmartTokenController, Managed, ContractIds, FeatureIds {
    uint32 private constant MAX_WEIGHT = 1000000;
    uint64 private constant MAX_CONVERSION_FEE = 1000000;

    struct Connector {
        uint256 virtualBalance;         // connector virtual balance
        uint32 weight;                  // connector weight, represented in ppm, 1-1000000
        bool isVirtualBalanceEnabled;   // true if virtual balance is enabled, false if not
        bool isPurchaseEnabled;         // is purchase of the smart token enabled with the connector, can be set by the owner
        bool isSet;                     // used to tell if the mapping element is defined
    }

    bytes32 public version = '0.11';
    string public converterType = 'bancor';

    bool public allowRegistryUpdate = true;             // allows the owner to prevent/allow the registry to be updated
    bool public claimTokensEnabled = false;             // allows BancorX contract to claim tokens without allowance (one transaction instread of two)
    IContractRegistry public prevRegistry;              // address of previous registry as security mechanism
    IContractRegistry public registry;                  // contract registry contract
    IWhitelist public conversionWhitelist;              // whitelist contract with list of addresses that are allowed to use the converter
    IERC20Token[] public connectorTokens;               // ERC20 standard token addresses
    mapping (address => Connector) public connectors;   // connector token addresses -> connector data
    uint32 private totalConnectorWeight = 0;            // used to efficiently prevent increasing the total connector weight above 100%
    uint32 public maxConversionFee = 0;                 // maximum conversion fee for the lifetime of the contract,
                                                        // represented in ppm, 0...1000000 (0 = no fee, 100 = 0.01%, 1000000 = 100%)
    uint32 public conversionFee = 0;                    // current conversion fee, represented in ppm, 0...maxConversionFee
    bool public conversionsEnabled = true;              // true if token conversions is enabled, false if not
    IERC20Token[] private convertPath;

    // triggered when a conversion between two tokens occurs
    event Conversion(
        address indexed _fromToken,
        address indexed _toToken,
        address indexed _trader,
        uint256 _amount,
        uint256 _return,
        int256 _conversionFee
    );
    // triggered after a conversion with new price data
    event PriceDataUpdate(
        address indexed _connectorToken,
        uint256 _tokenSupply,
        uint256 _connectorBalance,
        uint32 _connectorWeight
    );
    // triggered when the conversion fee is updated
    event ConversionFeeUpdate(uint32 _prevFee, uint32 _newFee);

    // triggered when conversions are enabled/disabled
    event ConversionsEnable(bool _conversionsEnabled);

    /**
        @dev constructor

        @param  _token              smart token governed by the converter
        @param  _registry           address of a contract registry contract
        @param  _maxConversionFee   maximum conversion fee, represented in ppm
        @param  _connectorToken     optional, initial connector, allows defining the first connector at deployment time
        @param  _connectorWeight    optional, weight for the initial connector
    */
    constructor(
        ISmartToken _token,
        IContractRegistry _registry,
        uint32 _maxConversionFee,
        IERC20Token _connectorToken,
        uint32 _connectorWeight
    )
        public
        SmartTokenController(_token)
        validAddress(_registry)
        validMaxConversionFee(_maxConversionFee)
    {
        registry = _registry;
        prevRegistry = _registry;
        IContractFeatures features = IContractFeatures(registry.addressOf(ContractIds.CONTRACT_FEATURES));

        // initialize supported features
        if (features != address(0))
            features.enableFeatures(FeatureIds.CONVERTER_CONVERSION_WHITELIST, true);

        maxConversionFee = _maxConversionFee;

        if (_connectorToken != address(0))
            addConnector(_connectorToken, _connectorWeight, false);
    }

    // validates a connector token address - verifies that the address belongs to one of the connector tokens
    modifier validConnector(IERC20Token _address) {
        require(connectors[_address].isSet);
        _;
    }

    // validates a token address - verifies that the address belongs to one of the convertible tokens
    modifier validToken(IERC20Token _address) {
        require(_address == token || connectors[_address].isSet);
        _;
    }

    // validates maximum conversion fee
    modifier validMaxConversionFee(uint32 _conversionFee) {
        require(_conversionFee >= 0 && _conversionFee <= MAX_CONVERSION_FEE);
        _;
    }

    // validates conversion fee
    modifier validConversionFee(uint32 _conversionFee) {
        require(_conversionFee >= 0 && _conversionFee <= maxConversionFee);
        _;
    }

    // validates connector weight range
    modifier validConnectorWeight(uint32 _weight) {
        require(_weight > 0 && _weight <= MAX_WEIGHT);
        _;
    }

    // validates a conversion path - verifies that the number of elements is odd and that maximum number of 'hops' is 10
    modifier validConversionPath(IERC20Token[] _path) {
        require(_path.length > 2 && _path.length <= (1 + 2 * 10) && _path.length % 2 == 1);
        _;
    }

    // allows execution only when the total weight is 100%
    modifier maxTotalWeightOnly() {
        require(totalConnectorWeight == MAX_WEIGHT);
        _;
    }

    // allows execution only when conversions aren't disabled
    modifier conversionsAllowed {
        assert(conversionsEnabled);
        _;
    }

    // allows execution by the BancorNetwork contract only
    modifier bancorNetworkOnly {
        IBancorNetwork bancorNetwork = IBancorNetwork(registry.addressOf(ContractIds.BANCOR_NETWORK));
        require(msg.sender == address(bancorNetwork));
        _;
    }

    // allows execution by the converter upgrader contract only
    modifier converterUpgraderOnly {
        address converterUpgrader = registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER);
        require(owner == converterUpgrader);
        _;
    }

    // allows execution only when claim tokens is enabled
    modifier whenClaimTokensEnabled {
        require(claimTokensEnabled);
        _;
    }

    /**
        @dev sets the contract registry to whichever address the current registry is pointing to
     */
    function updateRegistry() public {
        // require that upgrading is allowed or that the caller is the owner
        require(allowRegistryUpdate || msg.sender == owner);

        // get the address of whichever registry the current registry is pointing to
        address newRegistry = registry.addressOf(ContractIds.CONTRACT_REGISTRY);

        // if the new registry hasn't changed or is the zero address, revert
        require(newRegistry != address(registry) && newRegistry != address(0));

        // set the previous registry as current registry and current registry as newRegistry
        prevRegistry = registry;
        registry = IContractRegistry(newRegistry);
    }

    /**
        @dev security mechanism allowing the converter owner to revert to the previous registry,
        to be used in emergency scenario
    */
    function restoreRegistry() public ownerOrManagerOnly {
        // set the registry as previous registry
        registry = prevRegistry;

        // after a previous registry is restored, only the owner can allow future updates
        allowRegistryUpdate = false;
    }

    /**
        @dev disables the registry update functionality
        this is a safety mechanism in case of a emergency
        can only be called by the manager or owner

        @param _disable    true to disable registry updates, false to re-enable them
    */
    function disableRegistryUpdate(bool _disable) public ownerOrManagerOnly {
        allowRegistryUpdate = !_disable;
    }

    /**
        @dev disables/enables the claim tokens functionality

        @param _enable    true to enable claiming of tokens, false to disable
     */
    function enableClaimTokens(bool _enable) public ownerOnly {
        claimTokensEnabled = _enable;
    }

    /**
        @dev returns the number of connector tokens defined

        @return number of connector tokens
    */
    function connectorTokenCount() public view returns (uint16) {
        return uint16(connectorTokens.length);
    }

    /**
        @dev allows the owner to update & enable the conversion whitelist contract address
        when set, only addresses that are whitelisted are actually allowed to use the converter
        note that the whitelist check is actually done by the BancorNetwork contract

        @param _whitelist    address of a whitelist contract
    */
    function setConversionWhitelist(IWhitelist _whitelist)
        public
        ownerOnly
        notThis(_whitelist)
    {
        conversionWhitelist = _whitelist;
    }

    /**
        @dev disables the entire conversion functionality
        this is a safety mechanism in case of a emergency
        can only be called by the manager

        @param _disable true to disable conversions, false to re-enable them
    */
    function disableConversions(bool _disable) public ownerOrManagerOnly {
        if (conversionsEnabled == _disable) {
            conversionsEnabled = !_disable;
            emit ConversionsEnable(conversionsEnabled);
        }
    }

    /**
        @dev allows transferring the token ownership
        the new owner needs to accept the transfer
        can only be called by the contract owner
        note that token ownership can only be transferred while the owner is the converter upgrader contract

        @param _newOwner    new token owner
    */
    function transferTokenOwnership(address _newOwner)
        public
        ownerOnly
        converterUpgraderOnly
    {
        super.transferTokenOwnership(_newOwner);
    }

    /**
        @dev updates the current conversion fee
        can only be called by the manager

        @param _conversionFee new conversion fee, represented in ppm
    */
    function setConversionFee(uint32 _conversionFee)
        public
        ownerOrManagerOnly
        validConversionFee(_conversionFee)
    {
        emit ConversionFeeUpdate(conversionFee, _conversionFee);
        conversionFee = _conversionFee;
    }

    /**
        @dev given a return amount, returns the amount minus the conversion fee

        @param _amount      return amount
        @param _magnitude   1 for standard conversion, 2 for cross connector conversion

        @return return amount minus conversion fee
    */
    function getFinalAmount(uint256 _amount, uint8 _magnitude) public view returns (uint256) {
        return safeMul(_amount, (MAX_CONVERSION_FEE - conversionFee) ** _magnitude) / MAX_CONVERSION_FEE ** _magnitude;
    }

    /**
        @dev withdraws tokens held by the converter and sends them to an account
        can only be called by the owner
        note that connector tokens can only be withdrawn by the owner while the converter is inactive
        unless the owner is the converter upgrader contract

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public {
        address converterUpgrader = registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER);

        // if the token is not a connector token, allow withdrawal
        // otherwise verify that the converter is inactive or that the owner is the upgrader contract
        require(!connectors[_token].isSet || token.owner() != address(this) || owner == converterUpgrader);
        super.withdrawTokens(_token, _to, _amount);
    }

    /**
        @dev allows the BancorX contract to claim BNT from any address (so that users
        dont have to first give allowance when calling BancorX)

        @param _from      address to claim the BNT from
        @param _amount    the amount to claim
     */
    function claimTokens(address _from, uint256 _amount) public whenClaimTokensEnabled {
        address bancorX = registry.addressOf(ContractIds.BANCOR_X);

        // only the bancorX contract may call this method
        require(msg.sender == bancorX);

        // destroy the tokens belonging to _from, and issue the same amount to bancorX contract
        token.destroy(_from, _amount);
        token.issue(bancorX, _amount);
    }

    /**
        @dev upgrades the converter to the latest version
        can only be called by the owner
        note that the owner needs to call acceptOwnership on the new converter after the upgrade
    */
    function upgrade() public ownerOnly {
        IBancorConverterUpgrader converterUpgrader = IBancorConverterUpgrader(registry.addressOf(ContractIds.BANCOR_CONVERTER_UPGRADER));

        transferOwnership(converterUpgrader);
        converterUpgrader.upgrade(version);
        acceptOwnership();
    }

    /**
        @dev defines a new connector for the token
        can only be called by the owner while the converter is inactive

        @param _token                  address of the connector token
        @param _weight                 constant connector weight, represented in ppm, 1-1000000
        @param _enableVirtualBalance   true to enable virtual balance for the connector, false to disable it
    */
    function addConnector(IERC20Token _token, uint32 _weight, bool _enableVirtualBalance)
        public
        ownerOnly
        inactive
        validAddress(_token)
        notThis(_token)
        validConnectorWeight(_weight)
    {
        require(_token != token && !connectors[_token].isSet && totalConnectorWeight + _weight <= MAX_WEIGHT); // validate input

        connectors[_token].virtualBalance = 0;
        connectors[_token].weight = _weight;
        connectors[_token].isVirtualBalanceEnabled = _enableVirtualBalance;
        connectors[_token].isPurchaseEnabled = true;
        connectors[_token].isSet = true;
        connectorTokens.push(_token);
        totalConnectorWeight += _weight;
    }

    /**
        @dev updates one of the token connectors
        can only be called by the owner

        @param _connectorToken         address of the connector token
        @param _weight                 constant connector weight, represented in ppm, 1-1000000
        @param _enableVirtualBalance   true to enable virtual balance for the connector, false to disable it
        @param _virtualBalance         new connector's virtual balance
    */
    function updateConnector(IERC20Token _connectorToken, uint32 _weight, bool _enableVirtualBalance, uint256 _virtualBalance)
        public
        ownerOnly
        validConnector(_connectorToken)
        validConnectorWeight(_weight)
    {
        Connector storage connector = connectors[_connectorToken];
        require(totalConnectorWeight - connector.weight + _weight <= MAX_WEIGHT); // validate input

        totalConnectorWeight = totalConnectorWeight - connector.weight + _weight;
        connector.weight = _weight;
        connector.isVirtualBalanceEnabled = _enableVirtualBalance;
        connector.virtualBalance = _virtualBalance;
    }

    /**
        @dev disables purchasing with the given connector token in case the connector token got compromised
        can only be called by the owner
        note that selling is still enabled regardless of this flag and it cannot be disabled by the owner

        @param _connectorToken  connector token contract address
        @param _disable         true to disable the token, false to re-enable it
    */
    function disableConnectorPurchases(IERC20Token _connectorToken, bool _disable)
        public
        ownerOnly
        validConnector(_connectorToken)
    {
        connectors[_connectorToken].isPurchaseEnabled = !_disable;
    }

    /**
        @dev returns the connector's virtual balance if one is defined, otherwise returns the actual balance

        @param _connectorToken  connector token contract address

        @return connector balance
    */
    function getConnectorBalance(IERC20Token _connectorToken)
        public
        view
        validConnector(_connectorToken)
        returns (uint256)
    {
        Connector storage connector = connectors[_connectorToken];
        return connector.isVirtualBalanceEnabled ? connector.virtualBalance : _connectorToken.balanceOf(this);
    }

    /**
        @dev returns the expected return for converting a specific amount of _fromToken to _toToken

        @param _fromToken  ERC20 token to convert from
        @param _toToken    ERC20 token to convert to
        @param _amount     amount to convert, in fromToken

        @return expected conversion return amount and conversion fee
    */
    function getReturn(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount) public view returns (uint256, uint256) {
        require(_fromToken != _toToken); // validate input

        // conversion between the token and one of its connectors
        if (_toToken == token)
            return getPurchaseReturn(_fromToken, _amount);
        else if (_fromToken == token)
            return getSaleReturn(_toToken, _amount);

        // conversion between 2 connectors
        return getCrossConnectorReturn(_fromToken, _toToken, _amount);
    }

    /**
        @dev returns the expected return for buying the token for a connector token

        @param _connectorToken  connector token contract address
        @param _depositAmount   amount to deposit (in the connector token)

        @return expected purchase return amount and conversion fee
    */
    function getPurchaseReturn(IERC20Token _connectorToken, uint256 _depositAmount)
        public
        view
        active
        validConnector(_connectorToken)
        returns (uint256, uint256)
    {
        Connector storage connector = connectors[_connectorToken];
        require(connector.isPurchaseEnabled); // validate input

        uint256 tokenSupply = token.totalSupply();
        uint256 connectorBalance = getConnectorBalance(_connectorToken);
        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculatePurchaseReturn(tokenSupply, connectorBalance, connector.weight, _depositAmount);
        uint256 finalAmount = getFinalAmount(amount, 1);

        // return the amount minus the conversion fee and the conversion fee
        return (finalAmount, amount - finalAmount);
    }

    /**
        @dev returns the expected return for selling the token for one of its connector tokens

        @param _connectorToken  connector token contract address
        @param _sellAmount      amount to sell (in the smart token)

        @return expected sale return amount and conversion fee
    */
    function getSaleReturn(IERC20Token _connectorToken, uint256 _sellAmount)
        public
        view
        active
        validConnector(_connectorToken)
        returns (uint256, uint256)
    {
        Connector storage connector = connectors[_connectorToken];
        uint256 tokenSupply = token.totalSupply();
        uint256 connectorBalance = getConnectorBalance(_connectorToken);
        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculateSaleReturn(tokenSupply, connectorBalance, connector.weight, _sellAmount);
        uint256 finalAmount = getFinalAmount(amount, 1);

        // return the amount minus the conversion fee and the conversion fee
        return (finalAmount, amount - finalAmount);
    }

    /**
        @dev returns the expected return for selling one of the connector tokens for another connector token

        @param _fromConnectorToken  contract address of the connector token to convert from
        @param _toConnectorToken    contract address of the connector token to convert to
        @param _sellAmount          amount to sell (in the from connector token)

        @return expected sale return amount and conversion fee (in the to connector token)
    */
    function getCrossConnectorReturn(IERC20Token _fromConnectorToken, IERC20Token _toConnectorToken, uint256 _sellAmount)
        public
        view
        active
        validConnector(_fromConnectorToken)
        validConnector(_toConnectorToken)
        returns (uint256, uint256)
    {
        Connector storage fromConnector = connectors[_fromConnectorToken];
        Connector storage toConnector = connectors[_toConnectorToken];
        require(toConnector.isPurchaseEnabled); // validate input

        IBancorFormula formula = IBancorFormula(registry.addressOf(ContractIds.BANCOR_FORMULA));
        uint256 amount = formula.calculateCrossConnectorReturn(
            getConnectorBalance(_fromConnectorToken), 
            fromConnector.weight, 
            getConnectorBalance(_toConnectorToken), 
            toConnector.weight, 
            _sellAmount);
        uint256 finalAmount = getFinalAmount(amount, 2);

        // return the amount minus the conversion fee and the conversion fee
        // the fee is higher (magnitude = 2) since cross connector conversion equals 2 conversions (from / to the smart token)
        return (finalAmount, amount - finalAmount);
    }

    /**
        @dev converts a specific amount of _fromToken to _toToken

        @param _fromToken  ERC20 token to convert from
        @param _toToken    ERC20 token to convert to
        @param _amount     amount to convert, in fromToken
        @param _minReturn  if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return conversion return amount
    */
    function convertInternal(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn)
        public
        bancorNetworkOnly
        conversionsAllowed
        greaterThanZero(_minReturn)
        returns (uint256)
    {
        require(_fromToken != _toToken); // validate input

        // conversion between the token and one of its connectors
        if (_toToken == token)
            return buy(_fromToken, _amount, _minReturn);
        else if (_fromToken == token)
            return sell(_toToken, _amount, _minReturn);

        uint256 amount;
        uint256 feeAmount;

        // conversion between 2 connectors
        (amount, feeAmount) = getCrossConnectorReturn(_fromToken, _toToken, _amount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // update the source token virtual balance if relevant
        Connector storage fromConnector = connectors[_fromToken];
        if (fromConnector.isVirtualBalanceEnabled)
            fromConnector.virtualBalance = safeAdd(fromConnector.virtualBalance, _amount);

        // update the target token virtual balance if relevant
        Connector storage toConnector = connectors[_toToken];
        if (toConnector.isVirtualBalanceEnabled)
            toConnector.virtualBalance = safeSub(toConnector.virtualBalance, amount);

        // ensure that the trade won't deplete the connector balance
        uint256 toConnectorBalance = getConnectorBalance(_toToken);
        assert(amount < toConnectorBalance);

        // transfer funds from the caller in the from connector token
        assert(_fromToken.transferFrom(msg.sender, this, _amount));
        // transfer funds to the caller in the to connector token
        // the transfer might fail if the actual connector balance is smaller than the virtual balance
        assert(_toToken.transfer(msg.sender, amount));

        // dispatch the conversion event
        // the fee is higher (magnitude = 2) since cross connector conversion equals 2 conversions (from / to the smart token)
        dispatchConversionEvent(_fromToken, _toToken, _amount, amount, feeAmount);

        // dispatch price data updates for the smart token / both connectors
        emit PriceDataUpdate(_fromToken, token.totalSupply(), getConnectorBalance(_fromToken), fromConnector.weight);
        emit PriceDataUpdate(_toToken, token.totalSupply(), getConnectorBalance(_toToken), toConnector.weight);
        return amount;
    }

    /**
        @dev converts a specific amount of _fromToken to _toToken

        @param _fromToken  ERC20 token to convert from
        @param _toToken    ERC20 token to convert to
        @param _amount     amount to convert, in fromToken
        @param _minReturn  if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return conversion return amount
    */
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256) {
        convertPath = [_fromToken, token, _toToken];
        return quickConvert(convertPath, _amount, _minReturn);
    }

    /**
        @dev buys the token by depositing one of its connector tokens

        @param _connectorToken  connector token contract address
        @param _depositAmount   amount to deposit (in the connector token)
        @param _minReturn       if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return buy return amount
    */
    function buy(IERC20Token _connectorToken, uint256 _depositAmount, uint256 _minReturn) internal returns (uint256) {
        uint256 amount;
        uint256 feeAmount;
        (amount, feeAmount) = getPurchaseReturn(_connectorToken, _depositAmount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // update virtual balance if relevant
        Connector storage connector = connectors[_connectorToken];
        if (connector.isVirtualBalanceEnabled)
            connector.virtualBalance = safeAdd(connector.virtualBalance, _depositAmount);

        // transfer funds from the caller in the connector token
        assert(_connectorToken.transferFrom(msg.sender, this, _depositAmount));
        // issue new funds to the caller in the smart token
        token.issue(msg.sender, amount);

        // dispatch the conversion event
        dispatchConversionEvent(_connectorToken, token, _depositAmount, amount, feeAmount);

        // dispatch price data update for the smart token/connector
        emit PriceDataUpdate(_connectorToken, token.totalSupply(), getConnectorBalance(_connectorToken), connector.weight);
        return amount;
    }

    /**
        @dev sells the token by withdrawing from one of its connector tokens

        @param _connectorToken  connector token contract address
        @param _sellAmount      amount to sell (in the smart token)
        @param _minReturn       if the conversion results in an amount smaller the minimum return - it is cancelled, must be nonzero

        @return sell return amount
    */
    function sell(IERC20Token _connectorToken, uint256 _sellAmount, uint256 _minReturn) internal returns (uint256) {
        require(_sellAmount <= token.balanceOf(msg.sender)); // validate input
        uint256 amount;
        uint256 feeAmount;
        (amount, feeAmount) = getSaleReturn(_connectorToken, _sellAmount);
        // ensure the trade gives something in return and meets the minimum requested amount
        require(amount != 0 && amount >= _minReturn);

        // ensure that the trade will only deplete the connector balance if the total supply is depleted as well
        uint256 tokenSupply = token.totalSupply();
        uint256 connectorBalance = getConnectorBalance(_connectorToken);
        assert(amount < connectorBalance || (amount == connectorBalance && _sellAmount == tokenSupply));

        // update virtual balance if relevant
        Connector storage connector = connectors[_connectorToken];
        if (connector.isVirtualBalanceEnabled)
            connector.virtualBalance = safeSub(connector.virtualBalance, amount);

        // destroy _sellAmount from the caller's balance in the smart token
        token.destroy(msg.sender, _sellAmount);
        // transfer funds to the caller in the connector token
        // the transfer might fail if the actual connector balance is smaller than the virtual balance
        assert(_connectorToken.transfer(msg.sender, amount));

        // dispatch the conversion event
        dispatchConversionEvent(token, _connectorToken, _sellAmount, amount, feeAmount);

        // dispatch price data update for the smart token/connector
        emit PriceDataUpdate(_connectorToken, token.totalSupply(), getConnectorBalance(_connectorToken), connector.weight);
        return amount;
    }

    /**
        @dev converts the token to any other token in the bancor network by following a predefined conversion path
        note that when converting from an ERC20 token (as opposed to a smart token), allowance must be set beforehand

        @param _path        conversion path, see conversion path format in the BancorNetwork contract
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero

        @return tokens issued in return
    */
    function quickConvert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn)
        public
        payable
        validConversionPath(_path)
        returns (uint256)
    {
        return quickConvertPrioritized(_path, _amount, _minReturn, 0x0, 0x0, 0x0, 0x0);
    }

    /**
        @dev converts the token to any other token in the bancor network by following a predefined conversion path
        note that when converting from an ERC20 token (as opposed to a smart token), allowance must be set beforehand

        @param _path        conversion path, see conversion path format in the BancorNetwork contract
        @param _amount      amount to convert from (in the initial source token)
        @param _minReturn   if the conversion results in an amount smaller than the minimum return - it is cancelled, must be nonzero
        @param _block       if the current block exceeded the given parameter - it is cancelled
        @param _v           (signature[128:130]) associated with the signer address and helps validating if the signature is legit
        @param _r           (signature[0:64]) associated with the signer address and helps validating if the signature is legit
        @param _s           (signature[64:128]) associated with the signer address and helps validating if the signature is legit

        @return tokens issued in return
    */
    function quickConvertPrioritized(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, uint256 _block, uint8 _v, bytes32 _r, bytes32 _s)
        public
        payable
        validConversionPath(_path)
        returns (uint256)
    {
        IERC20Token fromToken = _path[0];
        IBancorNetwork bancorNetwork = IBancorNetwork(registry.addressOf(ContractIds.BANCOR_NETWORK));

        // we need to transfer the source tokens from the caller to the BancorNetwork contract,
        // so it can execute the conversion on behalf of the caller
        if (msg.value == 0) {
            // not ETH, send the source tokens to the BancorNetwork contract
            // if the token is the smart token, no allowance is required - destroy the tokens
            // from the caller and issue them to the BancorNetwork contract
            if (fromToken == token) {
                token.destroy(msg.sender, _amount); // destroy _amount tokens from the caller's balance in the smart token
                token.issue(bancorNetwork, _amount); // issue _amount new tokens to the BancorNetwork contract
            } else {
                // otherwise, we assume we already have allowance, transfer the tokens directly to the BancorNetwork contract
                assert(fromToken.transferFrom(msg.sender, bancorNetwork, _amount));
            }
        }

        // execute the conversion and pass on the ETH with the call
        return bancorNetwork.convertForPrioritized2.value(msg.value)(_path, _amount, _minReturn, msg.sender, _block, _v, _r, _s);
    }

    /**
        @dev buys the token with all connector tokens using the same percentage
        i.e. if the caller increases the supply by 10%, it will cost an amount equal to
        10% of each connector token balance
        can only be called if the max total weight is exactly 100% and while conversions are enabled

        @param _amount  amount to increase the supply by (in the smart token)
    */
    function fund(uint256 _amount)
        public
        maxTotalWeightOnly
        conversionsAllowed
    {
        uint256 supply = token.totalSupply();

        // iterate through the connector tokens and transfer a percentage equal to the ratio between _amount
        // and the total supply in each connector from the caller to the converter
        IERC20Token connectorToken;
        uint256 connectorBalance;
        uint256 connectorAmount;
        for (uint16 i = 0; i < connectorTokens.length; i++) {
            connectorToken = connectorTokens[i];
            connectorBalance = getConnectorBalance(connectorToken);
            connectorAmount = safeMul(_amount, connectorBalance) / supply;

            // update virtual balance if relevant
            Connector storage connector = connectors[connectorToken];
            if (connector.isVirtualBalanceEnabled)
                connector.virtualBalance = safeAdd(connector.virtualBalance, connectorAmount);

            // transfer funds from the caller in the connector token
            assert(connectorToken.transferFrom(msg.sender, this, connectorAmount));

            // dispatch price data update for the smart token/connector
            emit PriceDataUpdate(connectorToken, supply + _amount, connectorBalance + connectorAmount, connector.weight);
        }

        // issue new funds to the caller in the smart token
        token.issue(msg.sender, _amount);
    }

    /**
        @dev sells the token for all connector tokens using the same percentage
        i.e. if the holder sells 10% of the supply, they will receive 10% of each
        connector token balance in return
        can only be called if the max total weight is exactly 100%
        note that the function can also be called if conversions are disabled

        @param _amount  amount to liquidate (in the smart token)
    */
    function liquidate(uint256 _amount) public maxTotalWeightOnly {
        uint256 supply = token.totalSupply();

        // destroy _amount from the caller's balance in the smart token
        token.destroy(msg.sender, _amount);

        // iterate through the connector tokens and send a percentage equal to the ratio between _amount
        // and the total supply from each connector balance to the caller
        IERC20Token connectorToken;
        uint256 connectorBalance;
        uint256 connectorAmount;
        for (uint16 i = 0; i < connectorTokens.length; i++) {
            connectorToken = connectorTokens[i];
            connectorBalance = getConnectorBalance(connectorToken);
            connectorAmount = safeMul(_amount, connectorBalance) / supply;

            // update virtual balance if relevant
            Connector storage connector = connectors[connectorToken];
            if (connector.isVirtualBalanceEnabled)
                connector.virtualBalance = safeSub(connector.virtualBalance, connectorAmount);

            // transfer funds to the caller in the connector token
            // the transfer might fail if the actual connector balance is smaller than the virtual balance
            assert(connectorToken.transfer(msg.sender, connectorAmount));

            // dispatch price data update for the smart token/connector
            emit PriceDataUpdate(connectorToken, supply - _amount, connectorBalance - connectorAmount, connector.weight);
        }
    }

    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256) {
        return convertInternal(_fromToken, _toToken, _amount, _minReturn);
    }

    /**
        @dev helper, dispatches the Conversion event

        @param _fromToken       ERC20 token to convert from
        @param _toToken         ERC20 token to convert to
        @param _amount          amount purchased/sold (in the source token)
        @param _returnAmount    amount returned (in the target token)
    */
    function dispatchConversionEvent(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _returnAmount, uint256 _feeAmount) private {
        // fee amount is converted to 255 bits -
        // negative amount means the fee is taken from the source token, positive amount means its taken from the target token
        // currently the fee is always taken from the target token
        // since we convert it to a signed number, we first ensure that it's capped at 255 bits to prevent overflow
        assert(_feeAmount <= 2 ** 255);
        emit Conversion(_fromToken, _toToken, msg.sender, _amount, _returnAmount, int256(_feeAmount));
    }
}

pragma solidity ^0.4.17;

/// @title ERC223ReceivingContract - Standard contract implementation for compatibility with ERC223 tokens.
contract ERC223ReceivingContract {

    /// @dev Function that is called when a user or another contract wants to transfer funds.
    /// @param _from Transaction initiator, analogue of msg.sender
    /// @param _value Number of tokens to transfer.
    /// @param _data Data containig a function signature and/or parameters
    function tokenFallback(address _from, uint256 _value, bytes _data) public;
}

contract Token {
    /*
     * Implements ERC 20 standard.
     * https://github.com/ethereum/EIPs/blob/f90864a3d2b2b45c4decf95efd26b3f0c276051a/EIPS/eip-20-token-standard.md
     * https://github.com/ethereum/EIPs/issues/20
     *
     *  Added support for the ERC 223 "tokenFallback" method in a "transfer" function with a payload.
     *  https://github.com/ethereum/EIPs/issues/223
     */

    /*
     * This is a slight change to the ERC20 base standard.
     * function totalSupply() constant returns (uint256 supply);
     * is replaced with:
     * uint256 public totalSupply;
     * This automatically creates a getter function for the totalSupply.
     * This is moved to the base contract since public getter functions are not
     * currently recognised as an implementation of the matching abstract
     * function by the compiler.
     */
    uint256 public totalSupply;

    /*
     * ERC 20
     */
    function balanceOf(address _owner) public constant returns (uint256 balance);
    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
    function allowance(address _owner, address _spender) public constant returns (uint256 remaining);

    /*
     * ERC 223
     */
    function transfer(address _to, uint256 _value, bytes _data) public returns (bool success);

    /*
     * Events
     */
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    // There is no ERC223 compatible Transfer event, with `_data` included.
}


/// @title Standard token contract - Standard token implementation.
contract StandardToken is Token {

    /*
     * Data structures
     */
    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;

    /*
     * Public functions
     */
    /// @notice Send `_value` tokens to `_to` from `msg.sender`.
    /// @dev Transfers sender's tokens to a given address. Returns success.
    /// @param _to Address of token receiver.
    /// @param _value Number of tokens to transfer.
    /// @return Returns success of function call.
    function transfer(address _to, uint256 _value) public returns (bool) {
        require(_to != 0x0);
        require(_to != address(this));
        require(balances[msg.sender] >= _value);
        require(balances[_to] + _value >= balances[_to]);

        balances[msg.sender] -= _value;
        balances[_to] += _value;

        Transfer(msg.sender, _to, _value);

        return true;
    }

    /// @notice Send `_value` tokens to `_to` from `msg.sender` and trigger
    /// tokenFallback if sender is a contract.
    /// @dev Function that is called when a user or another contract wants to transfer funds.
    /// @param _to Address of token receiver.
    /// @param _value Number of tokens to transfer.
    /// @param _data Data to be sent to tokenFallback
    /// @return Returns success of function call.
    function transfer(
        address _to,
        uint256 _value,
        bytes _data)
        public
        returns (bool)
    {
        require(transfer(_to, _value));

        uint codeLength;

        assembly {
            // Retrieve the size of the code on target address, this needs assembly.
            codeLength := extcodesize(_to)
        }

        if (codeLength > 0) {
            ERC223ReceivingContract receiver = ERC223ReceivingContract(_to);
            receiver.tokenFallback(msg.sender, _value, _data);
        }

        return true;
    }

    /// @notice Transfer `_value` tokens from `_from` to `_to` if `msg.sender` is allowed.
    /// @dev Allows for an approved third party to transfer tokens from one
    /// address to another. Returns success.
    /// @param _from Address from where tokens are withdrawn.
    /// @param _to Address to where tokens are sent.
    /// @param _value Number of tokens to transfer.
    /// @return Returns success of function call.
    function transferFrom(address _from, address _to, uint256 _value)
        public
        returns (bool)
    {
        require(_from != 0x0);
        require(_to != 0x0);
        require(_to != address(this));
        require(balances[_from] >= _value);
        require(allowed[_from][msg.sender] >= _value);
        require(balances[_to] + _value >= balances[_to]);

        balances[_to] += _value;
        balances[_from] -= _value;
        allowed[_from][msg.sender] -= _value;

        Transfer(_from, _to, _value);

        return true;
    }

    /// @notice Allows `_spender` to transfer `_value` tokens from `msg.sender` to any address.
    /// @dev Sets approved amount of tokens for spender. Returns success.
    /// @param _spender Address of allowed account.
    /// @param _value Number of approved tokens.
    /// @return Returns success of function call.
    function approve(address _spender, uint256 _value) public returns (bool) {
        require(_spender != 0x0);

        // To change the approve amount you first have to reduce the addresses`
        // allowance to zero by calling `approve(_spender, 0)` if it is not
        // already 0 to mitigate the race condition described here:
        // https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
        require(_value == 0 || allowed[msg.sender][_spender] == 0);

        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        return true;
    }

    /*
     * Read functions
     */
    /// @dev Returns number of allowed tokens that a spender can transfer on
    /// behalf of a token owner.
    /// @param _owner Address of token owner.
    /// @param _spender Address of token spender.
    /// @return Returns remaining allowance for spender.
    function allowance(address _owner, address _spender)
        constant
        public
        returns (uint256)
    {
        return allowed[_owner][_spender];
    }

    /// @dev Returns number of tokens owned by the given address.
    /// @param _owner Address of token owner.
    /// @return Returns balance of owner.
    function balanceOf(address _owner) constant public returns (uint256) {
        return balances[_owner];
    }
}


/// @title Raiden Token
contract RaidenToken is StandardToken {

    /*
     *  Terminology:
     *  1 token unit = Rei
     *  1 token = RDN = Rei * multiplier
     *  multiplier set from token's number of decimals (i.e. 10 ** decimals)
     */

    /*
     *  Token metadata
     */
    string constant public name = "Raiden Token";
    string constant public symbol = "RDN";
    uint8 constant public decimals = 18;
    uint constant multiplier = 10 ** uint(decimals);

    event Deployed(uint indexed _total_supply);
    event Burnt(
        address indexed _receiver,
        uint indexed _num,
        uint indexed _total_supply
    );

    /*
     *  Public functions
     */
    /// @dev Contract constructor function sets dutch auction contract address
    /// and assigns all tokens to dutch auction.
    /// @param auction_address Address of dutch auction contract.
    /// @param wallet_address Address of wallet.
    /// @param initial_supply Number of initially provided token units (Rei).
    function RaidenToken(
        address auction_address,
        address wallet_address,
        uint initial_supply)
        public
    {
        // Auction address should not be null.
        require(auction_address != 0x0);
        require(wallet_address != 0x0);

        // Initial supply is in Rei
        require(initial_supply > multiplier);

        // Total supply of Rei at deployment
        totalSupply = initial_supply;

        balances[auction_address] = initial_supply / 2;
        balances[wallet_address] = initial_supply / 2;

        Transfer(0x0, auction_address, balances[auction_address]);
        Transfer(0x0, wallet_address, balances[wallet_address]);

        Deployed(totalSupply);

        assert(totalSupply == balances[auction_address] + balances[wallet_address]);
    }

    /// @notice Allows `msg.sender` to simply destroy `num` token units (Rei). This means the total
    /// token supply will decrease.
    /// @dev Allows to destroy token units (Rei).
    /// @param num Number of token units (Rei) to burn.
    function burn(uint num) public {
        require(num > 0);
        require(balances[msg.sender] >= num);
        require(totalSupply >= num);

        uint pre_balance = balances[msg.sender];

        balances[msg.sender] -= num;
        totalSupply -= num;
        Burnt(msg.sender, num, totalSupply);
        Transfer(msg.sender, 0x0, num);

        assert(balances[msg.sender] == pre_balance - num);
    }

}


/// @title Dutch auction contract - distribution of a fixed number of tokens using an auction.
/// The contract code is inspired by the Gnosis auction contract. Main difference is that the
/// auction ends if a fixed number of tokens was sold.
contract DutchAuction {
    /*
     * Auction for the RDN Token.
     *
     * Terminology:
     * 1 token unit = Rei
     * 1 token = RDN = Rei * token_multiplier
     * token_multiplier set from token's number of decimals (i.e. 10 ** decimals)
     */

    // Wait 7 days after the end of the auction, before anyone can claim tokens
    uint constant public token_claim_waiting_period = 7 days;

    // Bid value over which the address has to be whitelisted
    // At deployment moment, less than 1k$
    uint constant public bid_threshold = 2.5 ether;

    /*
     * Storage
     */

    RaidenToken public token;
    address public owner_address;
    address public wallet_address;
    address public whitelister_address;

    // Price decay function parameters to be changed depending on the desired outcome

    // Starting price in WEI; e.g. 2 * 10 ** 18
    uint public price_start;

    // Divisor constant; e.g. 524880000
    uint public price_constant;

    // Divisor exponent; e.g. 3
    uint32 public price_exponent;

    // For calculating elapsed time for price
    uint public start_time;
    uint public end_time;
    uint public start_block;

    // Keep track of all ETH received in the bids
    uint public received_wei;

    // Keep track of cumulative ETH funds for which the tokens have been claimed
    uint public funds_claimed;

    uint public token_multiplier;

    // Total number of Rei (RDN * token_multiplier) that will be auctioned
    uint public num_tokens_auctioned;

    // Wei per RDN (Rei * token_multiplier)
    uint public final_price;

    // Bidder address => bid value
    mapping (address => uint) public bids;

    // Whitelist for addresses that want to bid more than bid_threshold
    mapping (address => bool) public whitelist;

    Stages public stage;

    /*
     * Enums
     */
    enum Stages {
        AuctionDeployed,
        AuctionSetUp,
        AuctionStarted,
        AuctionEnded,
        TokensDistributed
    }

    /*
     * Modifiers
     */
    modifier atStage(Stages _stage) {
        require(stage == _stage);
        _;
    }

    modifier isOwner() {
        require(msg.sender == owner_address);
        _;
    }

    modifier isWhitelister() {
        require(msg.sender == whitelister_address);
        _;
    }

    /*
     * Events
     */

    event Deployed(
        uint indexed _price_start,
        uint indexed _price_constant,
        uint32 indexed _price_exponent
    );
    event Setup();
    event AuctionStarted(uint indexed _start_time, uint indexed _block_number);
    event BidSubmission(
        address indexed _sender,
        uint _amount,
        uint _missing_funds
    );
    event ClaimedTokens(address indexed _recipient, uint _sent_amount);
    event AuctionEnded(uint _final_price);
    event TokensDistributed();

    /*
     * Public functions
     */

    /// @dev Contract constructor function sets the starting price, divisor constant and
    /// divisor exponent for calculating the Dutch Auction price.
    /// @param _wallet_address Wallet address to which all contributed ETH will be forwarded.
    /// @param _price_start High price in WEI at which the auction starts.
    /// @param _price_constant Auction price divisor constant.
    /// @param _price_exponent Auction price divisor exponent.
    function DutchAuction(
        address _wallet_address,
        address _whitelister_address,
        uint _price_start,
        uint _price_constant,
        uint32 _price_exponent)
        public
    {
        require(_wallet_address != 0x0);
        require(_whitelister_address != 0x0);
        wallet_address = _wallet_address;
        whitelister_address = _whitelister_address;

        owner_address = msg.sender;
        stage = Stages.AuctionDeployed;
        changeSettings(_price_start, _price_constant, _price_exponent);
        Deployed(_price_start, _price_constant, _price_exponent);
    }

    /// @dev Fallback function for the contract, which calls bid() if the auction has started.
    function () public payable atStage(Stages.AuctionStarted) {
        bid();
    }

    /// @notice Set `_token_address` as the token address to be used in the auction.
    /// @dev Setup function sets external contracts addresses.
    /// @param _token_address Token address.
    function setup(address _token_address) public isOwner atStage(Stages.AuctionDeployed) {
        require(_token_address != 0x0);
        token = RaidenToken(_token_address);

        // Get number of Rei (RDN * token_multiplier) to be auctioned from token auction balance
        num_tokens_auctioned = token.balanceOf(address(this));

        // Set the number of the token multiplier for its decimals
        token_multiplier = 10 ** uint(token.decimals());

        stage = Stages.AuctionSetUp;
        Setup();
    }

    /// @notice Set `_price_start`, `_price_constant` and `_price_exponent` as
    /// the new starting price, price divisor constant and price divisor exponent.
    /// @dev Changes auction price function parameters before auction is started.
    /// @param _price_start Updated start price.
    /// @param _price_constant Updated price divisor constant.
    /// @param _price_exponent Updated price divisor exponent.
    function changeSettings(
        uint _price_start,
        uint _price_constant,
        uint32 _price_exponent)
        internal
    {
        require(stage == Stages.AuctionDeployed || stage == Stages.AuctionSetUp);
        require(_price_start > 0);
        require(_price_constant > 0);

        price_start = _price_start;
        price_constant = _price_constant;
        price_exponent = _price_exponent;
    }

    /// @notice Adds account addresses to whitelist.
    /// @dev Adds account addresses to whitelist.
    /// @param _bidder_addresses Array of addresses.
    function addToWhitelist(address[] _bidder_addresses) public isWhitelister {
        for (uint32 i = 0; i < _bidder_addresses.length; i++) {
            whitelist[_bidder_addresses[i]] = true;
        }
    }

    /// @notice Removes account addresses from whitelist.
    /// @dev Removes account addresses from whitelist.
    /// @param _bidder_addresses Array of addresses.
    function removeFromWhitelist(address[] _bidder_addresses) public isWhitelister {
        for (uint32 i = 0; i < _bidder_addresses.length; i++) {
            whitelist[_bidder_addresses[i]] = false;
        }
    }

    /// @notice Start the auction.
    /// @dev Starts auction and sets start_time.
    function startAuction() public isOwner atStage(Stages.AuctionSetUp) {
        stage = Stages.AuctionStarted;
        start_time = now;
        start_block = block.number;
        AuctionStarted(start_time, start_block);
    }

    /// @notice Finalize the auction - sets the final RDN token price and changes the auction
    /// stage after no bids are allowed anymore.
    /// @dev Finalize auction and set the final RDN token price.
    function finalizeAuction() public atStage(Stages.AuctionStarted)
    {
        // Missing funds should be 0 at this point
        uint missing_funds = missingFundsToEndAuction();
        require(missing_funds == 0);

        // Calculate the final price = WEI / RDN = WEI / (Rei / token_multiplier)
        // Reminder: num_tokens_auctioned is the number of Rei (RDN * token_multiplier) that are auctioned
        final_price = token_multiplier * received_wei / num_tokens_auctioned;

        end_time = now;
        stage = Stages.AuctionEnded;
        AuctionEnded(final_price);

        assert(final_price > 0);
    }

    /// --------------------------------- Auction Functions ------------------


    /// @notice Send `msg.value` WEI to the auction from the `msg.sender` account.
    /// @dev Allows to send a bid to the auction.
    function bid()
        public
        payable
        atStage(Stages.AuctionStarted)
    {
        require(msg.value > 0);
        require(bids[msg.sender] + msg.value <= bid_threshold || whitelist[msg.sender]);
        assert(bids[msg.sender] + msg.value >= msg.value);

        // Missing funds without the current bid value
        uint missing_funds = missingFundsToEndAuction();

        // We require bid values to be less than the funds missing to end the auction
        // at the current price.
        require(msg.value <= missing_funds);

        bids[msg.sender] += msg.value;
        received_wei += msg.value;

        // Send bid amount to wallet
        wallet_address.transfer(msg.value);

        BidSubmission(msg.sender, msg.value, missing_funds);

        assert(received_wei >= msg.value);
    }

    /// @notice Claim auction tokens for `msg.sender` after the auction has ended.
    /// @dev Claims tokens for `msg.sender` after auction. To be used if tokens can
    /// be claimed by beneficiaries, individually.
    function claimTokens() public atStage(Stages.AuctionEnded) returns (bool) {
        return proxyClaimTokens(msg.sender);
    }

    /// @notice Claim auction tokens for `receiver_address` after the auction has ended.
    /// @dev Claims tokens for `receiver_address` after auction has ended.
    /// @param receiver_address Tokens will be assigned to this address if eligible.
    function proxyClaimTokens(address receiver_address)
        public
        atStage(Stages.AuctionEnded)
        returns (bool)
    {
        // Waiting period after the end of the auction, before anyone can claim tokens
        // Ensures enough time to check if auction was finalized correctly
        // before users start transacting tokens
        require(now > end_time + token_claim_waiting_period);
        require(receiver_address != 0x0);

        if (bids[receiver_address] == 0) {
            return false;
        }

        // Number of Rei = bid_wei / Rei = bid_wei / (wei_per_RDN * token_multiplier)
        uint num = (token_multiplier * bids[receiver_address]) / final_price;

        // Due to final_price floor rounding, the number of assigned tokens may be higher
        // than expected. Therefore, the number of remaining unassigned auction tokens
        // may be smaller than the number of tokens needed for the last claimTokens call
        uint auction_tokens_balance = token.balanceOf(address(this));
        if (num > auction_tokens_balance) {
            num = auction_tokens_balance;
        }

        // Update the total amount of funds for which tokens have been claimed
        funds_claimed += bids[receiver_address];

        // Set receiver bid to 0 before assigning tokens
        bids[receiver_address] = 0;

        require(token.transfer(receiver_address, num));

        ClaimedTokens(receiver_address, num);

        // After the last tokens are claimed, we change the auction stage
        // Due to the above logic, rounding errors will not be an issue
        if (funds_claimed == received_wei) {
            stage = Stages.TokensDistributed;
            TokensDistributed();
        }

        assert(token.balanceOf(receiver_address) >= num);
        assert(bids[receiver_address] == 0);
        return true;
    }

    /// @notice Get the RDN price in WEI during the auction, at the time of
    /// calling this function. Returns `0` if auction has ended.
    /// Returns `price_start` before auction has started.
    /// @dev Calculates the current RDN token price in WEI.
    /// @return Returns WEI per RDN (token_multiplier * Rei).
    function price() public constant returns (uint) {
        if (stage == Stages.AuctionEnded ||
            stage == Stages.TokensDistributed) {
            return 0;
        }
        return calcTokenPrice();
    }

    /// @notice Get the missing funds needed to end the auction,
    /// calculated at the current RDN price in WEI.
    /// @dev The missing funds amount necessary to end the auction at the current RDN price in WEI.
    /// @return Returns the missing funds amount in WEI.
    function missingFundsToEndAuction() constant public returns (uint) {

        // num_tokens_auctioned = total number of Rei (RDN * token_multiplier) that is auctioned
        uint required_wei_at_price = num_tokens_auctioned * price() / token_multiplier;
        if (required_wei_at_price <= received_wei) {
            return 0;
        }

        // assert(required_wei_at_price - received_wei > 0);
        return required_wei_at_price - received_wei;
    }

    /*
     *  Private functions
     */

    /// @dev Calculates the token price (WEI / RDN) at the current timestamp
    /// during the auction; elapsed time = 0 before auction starts.
    /// Based on the provided parameters, the price does not change in the first
    /// `price_constant^(1/price_exponent)` seconds due to rounding.
    /// Rounding in `decay_rate` also produces values that increase instead of decrease
    /// in the beginning; these spikes decrease over time and are noticeable
    /// only in first hours. This should be calculated before usage.
    /// @return Returns the token price - Wei per RDN.
    function calcTokenPrice() constant private returns (uint) {
        uint elapsed;
        if (stage == Stages.AuctionStarted) {
            elapsed = now - start_time;
        }

        uint decay_rate = elapsed ** price_exponent / price_constant;
        return price_start * (1 + elapsed) / (1 + elapsed + decay_rate);
    }
}

pragma solidity ^0.4.24;

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

// File: contracts/utility/interfaces/IContractRegistry.sol

/*
    Contract Registry interface
*/
contract IContractRegistry {
    function addressOf(bytes32 _contractName) public view returns (address);

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address);
}

// File: contracts/ContractIds.sol

/**
    Id definitions for bancor contracts

    Can be used in conjunction with the contract registry to get contract addresses
*/
contract ContractIds {
    // generic
    bytes32 public constant CONTRACT_FEATURES = "ContractFeatures";
    bytes32 public constant CONTRACT_REGISTRY = "ContractRegistry";

    // bancor logic
    bytes32 public constant BANCOR_NETWORK = "BancorNetwork";
    bytes32 public constant BANCOR_FORMULA = "BancorFormula";
    bytes32 public constant BANCOR_GAS_PRICE_LIMIT = "BancorGasPriceLimit";
    bytes32 public constant BANCOR_CONVERTER_UPGRADER = "BancorConverterUpgrader";
    bytes32 public constant BANCOR_CONVERTER_FACTORY = "BancorConverterFactory";

    // Ids of BNT converter and BNT token
    bytes32 public constant BNT_TOKEN = "BNTToken";
    bytes32 public constant BNT_CONVERTER = "BNTConverter";

    // Id of BancorX contract
    bytes32 public constant BANCOR_X = "BancorX";
}

// File: contracts/utility/ContractRegistry.sol

/**
    Contract Registry

    The contract registry keeps contract addresses by name.
    The owner can update contract addresses so that a contract name always points to the latest version
    of the given contract.
    Other contracts can query the registry to get updated addresses instead of depending on specific
    addresses.

    Note that contract names are limited to 32 bytes UTF8 encoded ASCII strings to optimize gas costs
*/
contract ContractRegistry is IContractRegistry, Owned, Utils, ContractIds {
    struct RegistryItem {
        address contractAddress;    // contract address
        uint256 nameIndex;          // index of the item in the list of contract names
        bool isSet;                 // used to tell if the mapping element is defined
    }

    mapping (bytes32 => RegistryItem) private items;    // name -> RegistryItem mapping
    string[] public contractNames;                      // list of all registered contract names

    // triggered when an address pointed to by a contract name is modified
    event AddressUpdate(bytes32 indexed _contractName, address _contractAddress);

    /**
        @dev constructor
    */
    constructor() public {
        registerAddress(ContractIds.CONTRACT_REGISTRY, address(this));
    }

    /**
        @dev returns the number of items in the registry

        @return number of items
    */
    function itemCount() public view returns (uint256) {
        return contractNames.length;
    }

    /**
        @dev returns the address associated with the given contract name

        @param _contractName    contract name

        @return contract address
    */
    function addressOf(bytes32 _contractName) public view returns (address) {
        return items[_contractName].contractAddress;
    }

    /**
        @dev registers a new address for the contract name in the registry

        @param _contractName     contract name
        @param _contractAddress  contract address
    */
    function registerAddress(bytes32 _contractName, address _contractAddress)
        public
        ownerOnly
        validAddress(_contractAddress)
    {
        require(_contractName.length > 0); // validate input

        // update the address in the registry
        items[_contractName].contractAddress = _contractAddress;

        if (!items[_contractName].isSet) {
            // mark the item as set
            items[_contractName].isSet = true;
            // add the contract name to the name list
            uint256 i = contractNames.push(bytes32ToString(_contractName));
            // update the item's index in the list
            items[_contractName].nameIndex = i - 1;
        }

        // dispatch the address update event
        emit AddressUpdate(_contractName, _contractAddress);
    }

    /**
        @dev removes an existing contract address from the registry

        @param _contractName contract name
    */
    function unregisterAddress(bytes32 _contractName) public ownerOnly {
        require(_contractName.length > 0); // validate input

        // remove the address from the registry
        items[_contractName].contractAddress = address(0);

        // if there are multiple items in the registry, move the last element to the deleted element's position
        // and modify last element's registryItem.nameIndex in the items collection to point to the right position in contractNames
        if (contractNames.length > 1) {
            string memory lastContractNameString = contractNames[contractNames.length - 1];
            uint256 unregisterIndex = items[_contractName].nameIndex;

            contractNames[unregisterIndex] = lastContractNameString;
            bytes32 lastContractName = stringToBytes32(lastContractNameString);
            RegistryItem storage registryItem = items[lastContractName];
            registryItem.nameIndex = unregisterIndex;
        }

        // remove the last element from the name list
        contractNames.length--;
        // zero the deleted element's index
        items[_contractName].nameIndex = 0;

        // dispatch the address update event
        emit AddressUpdate(_contractName, address(0));
    }

    /**
        @dev utility, converts bytes32 to a string
        note that the bytes32 argument is assumed to be UTF8 encoded ASCII string

        @return string representation of the given bytes32 argument
    */
    function bytes32ToString(bytes32 _bytes) private pure returns (string) {
        bytes memory byteArray = new bytes(32);
        for (uint256 i; i < 32; i++) {
            byteArray[i] = _bytes[i];
        }

        return string(byteArray);
    }

    // @dev utility, converts string to bytes32
    function stringToBytes32(string memory _string) private pure returns (bytes32) {
        bytes32 result;
        assembly {
            result := mload(add(_string,32))
        }
        return result;
    }

    // deprecated, backward compatibility
    function getAddress(bytes32 _contractName) public view returns (address) {
        return addressOf(_contractName);
    }
}

pragma solidity ^0.4.18;


contract Utils {
    /**
        constructor
    */
    function Utils() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    function Owned() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        assert(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}



contract IBancorGasPriceLimit {
    function gasPrice() public view returns (uint256) {}
    function validateGasPrice(uint256) public view;
}


contract BancorGasPriceLimit is IBancorGasPriceLimit, Owned, Utils {
    uint256 public gasPrice = 0 wei;    // maximum gas price for bancor transactions
    
    /**
        @dev constructor

        @param _gasPrice    gas price limit
    */
    function BancorGasPriceLimit(uint256 _gasPrice)
        public
        greaterThanZero(_gasPrice)
    {
        gasPrice = _gasPrice;
    }

    /*
        @dev gas price getter

        @return the current gas price
    */
    function gasPrice() public view returns (uint256) {
        return gasPrice;
    }

    /*
        @dev allows the owner to update the gas price limit

        @param _gasPrice    new gas price limit
    */
    function setGasPrice(uint256 _gasPrice)
        public
        ownerOnly
        greaterThanZero(_gasPrice)
    {
        gasPrice = _gasPrice;
    }

    /*
        @dev validate that the given gas price is equal to the current network gas price

        @param _gasPrice    tested gas price
    */
    function validateGasPrice(uint256 _gasPrice)
        public
        view
        greaterThanZero(_gasPrice)
    {
        require(_gasPrice <= gasPrice);
    }
}

pragma solidity ^0.4.21;

/*
    Contract Features interface
*/
contract IContractFeatures {
    function isSupported(address _contract, uint256 _features) public view returns (bool);
    function enableFeatures(uint256 _features, bool _enable) public;
}

/**
    Contract Features

    Generic contract that allows every contract on the blockchain to define which features it supports.
    Other contracts can query this contract to find out whether a given contract on the
    blockchain supports a certain feature.
    Each contract type can define its own list of feature flags.
    Features can be only enabled/disabled by the contract they are defined for.

    Features should be defined by each contract type as bit flags, e.g. -
    uint256 public constant FEATURE1 = 1 << 0;
    uint256 public constant FEATURE2 = 1 << 1;
    uint256 public constant FEATURE3 = 1 << 2;
    ...
*/
contract ContractFeatures is IContractFeatures {
    mapping (address => uint256) private featureFlags;

    event FeaturesAddition(address indexed _address, uint256 _features);
    event FeaturesRemoval(address indexed _address, uint256 _features);

    /**
        @dev constructor
    */
    function ContractFeatures() public {
    }

    /**
        @dev returns true if a given contract supports the given feature(s), false if not

        @param _contract    contract address to check support for
        @param _features    feature(s) to check for

        @return true if the contract supports the feature(s), false if not
    */
    function isSupported(address _contract, uint256 _features) public view returns (bool) {
        return (featureFlags[_contract] & _features) == _features;
    }

    /**
        @dev allows a contract to enable/disable certain feature(s)

        @param _features    feature(s) to enable/disable
        @param _enable      true to enable the feature(s), false to disabled them
    */
    function enableFeatures(uint256 _features, bool _enable) public {
        if (_enable) {
            if (isSupported(msg.sender, _features))
                return;

            featureFlags[msg.sender] |= _features;

            emit FeaturesAddition(msg.sender, _features);
        } else {
            if (!isSupported(msg.sender, _features))
                return;

            featureFlags[msg.sender] &= ~_features;

            emit FeaturesRemoval(msg.sender, _features);
        }
    }
}

pragma solidity ^0.4.21;

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    function Utils() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

/*
    Bancor Formula interface
*/
contract IBancorFormula {
    function calculatePurchaseReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _depositAmount) public view returns (uint256);
    function calculateSaleReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _sellAmount) public view returns (uint256);
    function calculateCrossConnectorReturn(uint256 _fromConnectorBalance, uint32 _fromConnectorWeight, uint256 _toConnectorBalance, uint32 _toConnectorWeight, uint256 _amount) public view returns (uint256);
}

contract BancorFormula is IBancorFormula, Utils {
    string public version = '0.3';

    uint256 private constant ONE = 1;
    uint32 private constant MAX_WEIGHT = 1000000;
    uint8 private constant MIN_PRECISION = 32;
    uint8 private constant MAX_PRECISION = 127;

    /**
        Auto-generated via 'PrintIntScalingFactors.py'
    */
    uint256 private constant FIXED_1 = 0x080000000000000000000000000000000;
    uint256 private constant FIXED_2 = 0x100000000000000000000000000000000;
    uint256 private constant MAX_NUM = 0x200000000000000000000000000000000;

    /**
        Auto-generated via 'PrintLn2ScalingFactors.py'
    */
    uint256 private constant LN2_NUMERATOR   = 0x3f80fe03f80fe03f80fe03f80fe03f8;
    uint256 private constant LN2_DENOMINATOR = 0x5b9de1d10bf4103d647b0955897ba80;

    /**
        Auto-generated via 'PrintFunctionOptimalLog.py' and 'PrintFunctionOptimalExp.py'
    */
    uint256 private constant OPT_LOG_MAX_VAL = 0x15bf0a8b1457695355fb8ac404e7a79e3;
    uint256 private constant OPT_EXP_MAX_VAL = 0x800000000000000000000000000000000;

    /**
        Auto-generated via 'PrintFunctionBancorFormula.py'
    */
    uint256[128] private maxExpArray;
    function BancorFormula() public {
    //  maxExpArray[  0] = 0x6bffffffffffffffffffffffffffffffff;
    //  maxExpArray[  1] = 0x67ffffffffffffffffffffffffffffffff;
    //  maxExpArray[  2] = 0x637fffffffffffffffffffffffffffffff;
    //  maxExpArray[  3] = 0x5f6fffffffffffffffffffffffffffffff;
    //  maxExpArray[  4] = 0x5b77ffffffffffffffffffffffffffffff;
    //  maxExpArray[  5] = 0x57b3ffffffffffffffffffffffffffffff;
    //  maxExpArray[  6] = 0x5419ffffffffffffffffffffffffffffff;
    //  maxExpArray[  7] = 0x50a2ffffffffffffffffffffffffffffff;
    //  maxExpArray[  8] = 0x4d517fffffffffffffffffffffffffffff;
    //  maxExpArray[  9] = 0x4a233fffffffffffffffffffffffffffff;
    //  maxExpArray[ 10] = 0x47165fffffffffffffffffffffffffffff;
    //  maxExpArray[ 11] = 0x4429afffffffffffffffffffffffffffff;
    //  maxExpArray[ 12] = 0x415bc7ffffffffffffffffffffffffffff;
    //  maxExpArray[ 13] = 0x3eab73ffffffffffffffffffffffffffff;
    //  maxExpArray[ 14] = 0x3c1771ffffffffffffffffffffffffffff;
    //  maxExpArray[ 15] = 0x399e96ffffffffffffffffffffffffffff;
    //  maxExpArray[ 16] = 0x373fc47fffffffffffffffffffffffffff;
    //  maxExpArray[ 17] = 0x34f9e8ffffffffffffffffffffffffffff;
    //  maxExpArray[ 18] = 0x32cbfd5fffffffffffffffffffffffffff;
    //  maxExpArray[ 19] = 0x30b5057fffffffffffffffffffffffffff;
    //  maxExpArray[ 20] = 0x2eb40f9fffffffffffffffffffffffffff;
    //  maxExpArray[ 21] = 0x2cc8340fffffffffffffffffffffffffff;
    //  maxExpArray[ 22] = 0x2af09481ffffffffffffffffffffffffff;
    //  maxExpArray[ 23] = 0x292c5bddffffffffffffffffffffffffff;
    //  maxExpArray[ 24] = 0x277abdcdffffffffffffffffffffffffff;
    //  maxExpArray[ 25] = 0x25daf6657fffffffffffffffffffffffff;
    //  maxExpArray[ 26] = 0x244c49c65fffffffffffffffffffffffff;
    //  maxExpArray[ 27] = 0x22ce03cd5fffffffffffffffffffffffff;
    //  maxExpArray[ 28] = 0x215f77c047ffffffffffffffffffffffff;
    //  maxExpArray[ 29] = 0x1fffffffffffffffffffffffffffffffff;
    //  maxExpArray[ 30] = 0x1eaefdbdabffffffffffffffffffffffff;
    //  maxExpArray[ 31] = 0x1d6bd8b2ebffffffffffffffffffffffff;
        maxExpArray[ 32] = 0x1c35fedd14ffffffffffffffffffffffff;
        maxExpArray[ 33] = 0x1b0ce43b323fffffffffffffffffffffff;
        maxExpArray[ 34] = 0x19f0028ec1ffffffffffffffffffffffff;
        maxExpArray[ 35] = 0x18ded91f0e7fffffffffffffffffffffff;
        maxExpArray[ 36] = 0x17d8ec7f0417ffffffffffffffffffffff;
        maxExpArray[ 37] = 0x16ddc6556cdbffffffffffffffffffffff;
        maxExpArray[ 38] = 0x15ecf52776a1ffffffffffffffffffffff;
        maxExpArray[ 39] = 0x15060c256cb2ffffffffffffffffffffff;
        maxExpArray[ 40] = 0x1428a2f98d72ffffffffffffffffffffff;
        maxExpArray[ 41] = 0x13545598e5c23fffffffffffffffffffff;
        maxExpArray[ 42] = 0x1288c4161ce1dfffffffffffffffffffff;
        maxExpArray[ 43] = 0x11c592761c666fffffffffffffffffffff;
        maxExpArray[ 44] = 0x110a688680a757ffffffffffffffffffff;
        maxExpArray[ 45] = 0x1056f1b5bedf77ffffffffffffffffffff;
        maxExpArray[ 46] = 0x0faadceceeff8bffffffffffffffffffff;
        maxExpArray[ 47] = 0x0f05dc6b27edadffffffffffffffffffff;
        maxExpArray[ 48] = 0x0e67a5a25da4107fffffffffffffffffff;
        maxExpArray[ 49] = 0x0dcff115b14eedffffffffffffffffffff;
        maxExpArray[ 50] = 0x0d3e7a392431239fffffffffffffffffff;
        maxExpArray[ 51] = 0x0cb2ff529eb71e4fffffffffffffffffff;
        maxExpArray[ 52] = 0x0c2d415c3db974afffffffffffffffffff;
        maxExpArray[ 53] = 0x0bad03e7d883f69bffffffffffffffffff;
        maxExpArray[ 54] = 0x0b320d03b2c343d5ffffffffffffffffff;
        maxExpArray[ 55] = 0x0abc25204e02828dffffffffffffffffff;
        maxExpArray[ 56] = 0x0a4b16f74ee4bb207fffffffffffffffff;
        maxExpArray[ 57] = 0x09deaf736ac1f569ffffffffffffffffff;
        maxExpArray[ 58] = 0x0976bd9952c7aa957fffffffffffffffff;
        maxExpArray[ 59] = 0x09131271922eaa606fffffffffffffffff;
        maxExpArray[ 60] = 0x08b380f3558668c46fffffffffffffffff;
        maxExpArray[ 61] = 0x0857ddf0117efa215bffffffffffffffff;
        maxExpArray[ 62] = 0x07ffffffffffffffffffffffffffffffff;
        maxExpArray[ 63] = 0x07abbf6f6abb9d087fffffffffffffffff;
        maxExpArray[ 64] = 0x075af62cbac95f7dfa7fffffffffffffff;
        maxExpArray[ 65] = 0x070d7fb7452e187ac13fffffffffffffff;
        maxExpArray[ 66] = 0x06c3390ecc8af379295fffffffffffffff;
        maxExpArray[ 67] = 0x067c00a3b07ffc01fd6fffffffffffffff;
        maxExpArray[ 68] = 0x0637b647c39cbb9d3d27ffffffffffffff;
        maxExpArray[ 69] = 0x05f63b1fc104dbd39587ffffffffffffff;
        maxExpArray[ 70] = 0x05b771955b36e12f7235ffffffffffffff;
        maxExpArray[ 71] = 0x057b3d49dda84556d6f6ffffffffffffff;
        maxExpArray[ 72] = 0x054183095b2c8ececf30ffffffffffffff;
        maxExpArray[ 73] = 0x050a28be635ca2b888f77fffffffffffff;
        maxExpArray[ 74] = 0x04d5156639708c9db33c3fffffffffffff;
        maxExpArray[ 75] = 0x04a23105873875bd52dfdfffffffffffff;
        maxExpArray[ 76] = 0x0471649d87199aa990756fffffffffffff;
        maxExpArray[ 77] = 0x04429a21a029d4c1457cfbffffffffffff;
        maxExpArray[ 78] = 0x0415bc6d6fb7dd71af2cb3ffffffffffff;
        maxExpArray[ 79] = 0x03eab73b3bbfe282243ce1ffffffffffff;
        maxExpArray[ 80] = 0x03c1771ac9fb6b4c18e229ffffffffffff;
        maxExpArray[ 81] = 0x0399e96897690418f785257fffffffffff;
        maxExpArray[ 82] = 0x0373fc456c53bb779bf0ea9fffffffffff;
        maxExpArray[ 83] = 0x034f9e8e490c48e67e6ab8bfffffffffff;
        maxExpArray[ 84] = 0x032cbfd4a7adc790560b3337ffffffffff;
        maxExpArray[ 85] = 0x030b50570f6e5d2acca94613ffffffffff;
        maxExpArray[ 86] = 0x02eb40f9f620fda6b56c2861ffffffffff;
        maxExpArray[ 87] = 0x02cc8340ecb0d0f520a6af58ffffffffff;
        maxExpArray[ 88] = 0x02af09481380a0a35cf1ba02ffffffffff;
        maxExpArray[ 89] = 0x0292c5bdd3b92ec810287b1b3fffffffff;
        maxExpArray[ 90] = 0x0277abdcdab07d5a77ac6d6b9fffffffff;
        maxExpArray[ 91] = 0x025daf6654b1eaa55fd64df5efffffffff;
        maxExpArray[ 92] = 0x0244c49c648baa98192dce88b7ffffffff;
        maxExpArray[ 93] = 0x022ce03cd5619a311b2471268bffffffff;
        maxExpArray[ 94] = 0x0215f77c045fbe885654a44a0fffffffff;
        maxExpArray[ 95] = 0x01ffffffffffffffffffffffffffffffff;
        maxExpArray[ 96] = 0x01eaefdbdaaee7421fc4d3ede5ffffffff;
        maxExpArray[ 97] = 0x01d6bd8b2eb257df7e8ca57b09bfffffff;
        maxExpArray[ 98] = 0x01c35fedd14b861eb0443f7f133fffffff;
        maxExpArray[ 99] = 0x01b0ce43b322bcde4a56e8ada5afffffff;
        maxExpArray[100] = 0x019f0028ec1fff007f5a195a39dfffffff;
        maxExpArray[101] = 0x018ded91f0e72ee74f49b15ba527ffffff;
        maxExpArray[102] = 0x017d8ec7f04136f4e5615fd41a63ffffff;
        maxExpArray[103] = 0x016ddc6556cdb84bdc8d12d22e6fffffff;
        maxExpArray[104] = 0x015ecf52776a1155b5bd8395814f7fffff;
        maxExpArray[105] = 0x015060c256cb23b3b3cc3754cf40ffffff;
        maxExpArray[106] = 0x01428a2f98d728ae223ddab715be3fffff;
        maxExpArray[107] = 0x013545598e5c23276ccf0ede68034fffff;
        maxExpArray[108] = 0x01288c4161ce1d6f54b7f61081194fffff;
        maxExpArray[109] = 0x011c592761c666aa641d5a01a40f17ffff;
        maxExpArray[110] = 0x0110a688680a7530515f3e6e6cfdcdffff;
        maxExpArray[111] = 0x01056f1b5bedf75c6bcb2ce8aed428ffff;
        maxExpArray[112] = 0x00faadceceeff8a0890f3875f008277fff;
        maxExpArray[113] = 0x00f05dc6b27edad306388a600f6ba0bfff;
        maxExpArray[114] = 0x00e67a5a25da41063de1495d5b18cdbfff;
        maxExpArray[115] = 0x00dcff115b14eedde6fc3aa5353f2e4fff;
        maxExpArray[116] = 0x00d3e7a3924312399f9aae2e0f868f8fff;
        maxExpArray[117] = 0x00cb2ff529eb71e41582cccd5a1ee26fff;
        maxExpArray[118] = 0x00c2d415c3db974ab32a51840c0b67edff;
        maxExpArray[119] = 0x00bad03e7d883f69ad5b0a186184e06bff;
        maxExpArray[120] = 0x00b320d03b2c343d4829abd6075f0cc5ff;
        maxExpArray[121] = 0x00abc25204e02828d73c6e80bcdb1a95bf;
        maxExpArray[122] = 0x00a4b16f74ee4bb2040a1ec6c15fbbf2df;
        maxExpArray[123] = 0x009deaf736ac1f569deb1b5ae3f36c130f;
        maxExpArray[124] = 0x00976bd9952c7aa957f5937d790ef65037;
        maxExpArray[125] = 0x009131271922eaa6064b73a22d0bd4f2bf;
        maxExpArray[126] = 0x008b380f3558668c46c91c49a2f8e967b9;
        maxExpArray[127] = 0x00857ddf0117efa215952912839f6473e6;
    }

    /**
        @dev given a token supply, connector balance, weight and a deposit amount (in the connector token),
        calculates the return for a given conversion (in the main token)

        Formula:
        Return = _supply * ((1 + _depositAmount / _connectorBalance) ^ (_connectorWeight / 1000000) - 1)

        @param _supply              token total supply
        @param _connectorBalance    total connector balance
        @param _connectorWeight     connector weight, represented in ppm, 1-1000000
        @param _depositAmount       deposit amount, in connector token

        @return purchase return amount
    */
    function calculatePurchaseReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _depositAmount) public view returns (uint256) {
        // validate input
        require(_supply > 0 && _connectorBalance > 0 && _connectorWeight > 0 && _connectorWeight <= MAX_WEIGHT);

        // special case for 0 deposit amount
        if (_depositAmount == 0)
            return 0;

        // special case if the weight = 100%
        if (_connectorWeight == MAX_WEIGHT)
            return safeMul(_supply, _depositAmount) / _connectorBalance;

        uint256 result;
        uint8 precision;
        uint256 baseN = safeAdd(_depositAmount, _connectorBalance);
        (result, precision) = power(baseN, _connectorBalance, _connectorWeight, MAX_WEIGHT);
        uint256 temp = safeMul(_supply, result) >> precision;
        return temp - _supply;
    }

    /**
        @dev given a token supply, connector balance, weight and a sell amount (in the main token),
        calculates the return for a given conversion (in the connector token)

        Formula:
        Return = _connectorBalance * (1 - (1 - _sellAmount / _supply) ^ (1 / (_connectorWeight / 1000000)))

        @param _supply              token total supply
        @param _connectorBalance    total connector
        @param _connectorWeight     constant connector Weight, represented in ppm, 1-1000000
        @param _sellAmount          sell amount, in the token itself

        @return sale return amount
    */
    function calculateSaleReturn(uint256 _supply, uint256 _connectorBalance, uint32 _connectorWeight, uint256 _sellAmount) public view returns (uint256) {
        // validate input
        require(_supply > 0 && _connectorBalance > 0 && _connectorWeight > 0 && _connectorWeight <= MAX_WEIGHT && _sellAmount <= _supply);

        // special case for 0 sell amount
        if (_sellAmount == 0)
            return 0;

        // special case for selling the entire supply
        if (_sellAmount == _supply)
            return _connectorBalance;

        // special case if the weight = 100%
        if (_connectorWeight == MAX_WEIGHT)
            return safeMul(_connectorBalance, _sellAmount) / _supply;

        uint256 result;
        uint8 precision;
        uint256 baseD = _supply - _sellAmount;
        (result, precision) = power(_supply, baseD, MAX_WEIGHT, _connectorWeight);
        uint256 temp1 = safeMul(_connectorBalance, result);
        uint256 temp2 = _connectorBalance << precision;
        return (temp1 - temp2) / result;
    }

    /**
        @dev given two connector balances/weights and a sell amount (in the first connector token),
        calculates the return for a conversion from the first connector token to the second connector token (in the second connector token)

        Formula:
        Return = _toConnectorBalance * (1 - (_fromConnectorBalance / (_fromConnectorBalance + _amount)) ^ (_fromConnectorWeight / _toConnectorWeight))

        @param _fromConnectorBalance    input connector balance
        @param _fromConnectorWeight     input connector weight, represented in ppm, 1-1000000
        @param _toConnectorBalance      output connector balance
        @param _toConnectorWeight       output connector weight, represented in ppm, 1-1000000
        @param _amount                  input connector amount

        @return second connector amount
    */
    function calculateCrossConnectorReturn(uint256 _fromConnectorBalance, uint32 _fromConnectorWeight, uint256 _toConnectorBalance, uint32 _toConnectorWeight, uint256 _amount) public view returns (uint256) {
        // validate input
        require(_fromConnectorBalance > 0 && _fromConnectorWeight > 0 && _fromConnectorWeight <= MAX_WEIGHT && _toConnectorBalance > 0 && _toConnectorWeight > 0 && _toConnectorWeight <= MAX_WEIGHT);

        // special case for equal weights
        if (_fromConnectorWeight == _toConnectorWeight)
            return safeMul(_toConnectorBalance, _amount) / safeAdd(_fromConnectorBalance, _amount);

        uint256 result;
        uint8 precision;
        uint256 baseN = safeAdd(_fromConnectorBalance, _amount);
        (result, precision) = power(baseN, _fromConnectorBalance, _fromConnectorWeight, _toConnectorWeight);
        uint256 temp1 = safeMul(_toConnectorBalance, result);
        uint256 temp2 = _toConnectorBalance << precision;
        return (temp1 - temp2) / result;
    }

    /**
        General Description:
            Determine a value of precision.
            Calculate an integer approximation of (_baseN / _baseD) ^ (_expN / _expD) * 2 ^ precision.
            Return the result along with the precision used.

        Detailed Description:
            Instead of calculating "base ^ exp", we calculate "e ^ (log(base) * exp)".
            The value of "log(base)" is represented with an integer slightly smaller than "log(base) * 2 ^ precision".
            The larger "precision" is, the more accurately this value represents the real value.
            However, the larger "precision" is, the more bits are required in order to store this value.
            And the exponentiation function, which takes "x" and calculates "e ^ x", is limited to a maximum exponent (maximum value of "x").
            This maximum exponent depends on the "precision" used, and it is given by "maxExpArray[precision] >> (MAX_PRECISION - precision)".
            Hence we need to determine the highest precision which can be used for the given input, before calling the exponentiation function.
            This allows us to compute "base ^ exp" with maximum accuracy and without exceeding 256 bits in any of the intermediate computations.
            This functions assumes that "_expN < 2 ^ 256 / log(MAX_NUM - 1)", otherwise the multiplication should be replaced with a "safeMul".
    */
    function power(uint256 _baseN, uint256 _baseD, uint32 _expN, uint32 _expD) internal view returns (uint256, uint8) {
        assert(_baseN < MAX_NUM);

        uint256 baseLog;
        uint256 base = _baseN * FIXED_1 / _baseD;
        if (base < OPT_LOG_MAX_VAL) {
            baseLog = optimalLog(base);
        }
        else {
            baseLog = generalLog(base);
        }

        uint256 baseLogTimesExp = baseLog * _expN / _expD;
        if (baseLogTimesExp < OPT_EXP_MAX_VAL) {
            return (optimalExp(baseLogTimesExp), MAX_PRECISION);
        }
        else {
            uint8 precision = findPositionInMaxExpArray(baseLogTimesExp);
            return (generalExp(baseLogTimesExp >> (MAX_PRECISION - precision), precision), precision);
        }
    }

    /**
        Compute log(x / FIXED_1) * FIXED_1.
        This functions assumes that "x >= FIXED_1", because the output would be negative otherwise.
    */
    function generalLog(uint256 x) internal pure returns (uint256) {
        uint256 res = 0;

        // If x >= 2, then we compute the integer part of log2(x), which is larger than 0.
        if (x >= FIXED_2) {
            uint8 count = floorLog2(x / FIXED_1);
            x >>= count; // now x < 2
            res = count * FIXED_1;
        }

        // If x > 1, then we compute the fraction part of log2(x), which is larger than 0.
        if (x > FIXED_1) {
            for (uint8 i = MAX_PRECISION; i > 0; --i) {
                x = (x * x) / FIXED_1; // now 1 < x < 4
                if (x >= FIXED_2) {
                    x >>= 1; // now 1 < x < 2
                    res += ONE << (i - 1);
                }
            }
        }

        return res * LN2_NUMERATOR / LN2_DENOMINATOR;
    }

    /**
        Compute the largest integer smaller than or equal to the binary logarithm of the input.
    */
    function floorLog2(uint256 _n) internal pure returns (uint8) {
        uint8 res = 0;

        if (_n < 256) {
            // At most 8 iterations
            while (_n > 1) {
                _n >>= 1;
                res += 1;
            }
        }
        else {
            // Exactly 8 iterations
            for (uint8 s = 128; s > 0; s >>= 1) {
                if (_n >= (ONE << s)) {
                    _n >>= s;
                    res |= s;
                }
            }
        }

        return res;
    }

    /**
        The global "maxExpArray" is sorted in descending order, and therefore the following statements are equivalent:
        - This function finds the position of [the smallest value in "maxExpArray" larger than or equal to "x"]
        - This function finds the highest position of [a value in "maxExpArray" larger than or equal to "x"]
    */
    function findPositionInMaxExpArray(uint256 _x) internal view returns (uint8) {
        uint8 lo = MIN_PRECISION;
        uint8 hi = MAX_PRECISION;

        while (lo + 1 < hi) {
            uint8 mid = (lo + hi) / 2;
            if (maxExpArray[mid] >= _x)
                lo = mid;
            else
                hi = mid;
        }

        if (maxExpArray[hi] >= _x)
            return hi;
        if (maxExpArray[lo] >= _x)
            return lo;

        assert(false);
        return 0;
    }

    /**
        This function can be auto-generated by the script 'PrintFunctionGeneralExp.py'.
        It approximates "e ^ x" via maclaurin summation: "(x^0)/0! + (x^1)/1! + ... + (x^n)/n!".
        It returns "e ^ (x / 2 ^ precision) * 2 ^ precision", that is, the result is upshifted for accuracy.
        The global "maxExpArray" maps each "precision" to "((maximumExponent + 1) << (MAX_PRECISION - precision)) - 1".
        The maximum permitted value for "x" is therefore given by "maxExpArray[precision] >> (MAX_PRECISION - precision)".
    */
    function generalExp(uint256 _x, uint8 _precision) internal pure returns (uint256) {
        uint256 xi = _x;
        uint256 res = 0;

        xi = (xi * _x) >> _precision; res += xi * 0x3442c4e6074a82f1797f72ac0000000; // add x^02 * (33! / 02!)
        xi = (xi * _x) >> _precision; res += xi * 0x116b96f757c380fb287fd0e40000000; // add x^03 * (33! / 03!)
        xi = (xi * _x) >> _precision; res += xi * 0x045ae5bdd5f0e03eca1ff4390000000; // add x^04 * (33! / 04!)
        xi = (xi * _x) >> _precision; res += xi * 0x00defabf91302cd95b9ffda50000000; // add x^05 * (33! / 05!)
        xi = (xi * _x) >> _precision; res += xi * 0x002529ca9832b22439efff9b8000000; // add x^06 * (33! / 06!)
        xi = (xi * _x) >> _precision; res += xi * 0x00054f1cf12bd04e516b6da88000000; // add x^07 * (33! / 07!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000a9e39e257a09ca2d6db51000000; // add x^08 * (33! / 08!)
        xi = (xi * _x) >> _precision; res += xi * 0x000012e066e7b839fa050c309000000; // add x^09 * (33! / 09!)
        xi = (xi * _x) >> _precision; res += xi * 0x000001e33d7d926c329a1ad1a800000; // add x^10 * (33! / 10!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000002bee513bdb4a6b19b5f800000; // add x^11 * (33! / 11!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000003a9316fa79b88eccf2a00000; // add x^12 * (33! / 12!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000048177ebe1fa812375200000; // add x^13 * (33! / 13!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000005263fe90242dcbacf00000; // add x^14 * (33! / 14!)
        xi = (xi * _x) >> _precision; res += xi * 0x000000000057e22099c030d94100000; // add x^15 * (33! / 15!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000057e22099c030d9410000; // add x^16 * (33! / 16!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000052b6b54569976310000; // add x^17 * (33! / 17!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000004985f67696bf748000; // add x^18 * (33! / 18!)
        xi = (xi * _x) >> _precision; res += xi * 0x000000000000003dea12ea99e498000; // add x^19 * (33! / 19!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000000031880f2214b6e000; // add x^20 * (33! / 20!)
        xi = (xi * _x) >> _precision; res += xi * 0x000000000000000025bcff56eb36000; // add x^21 * (33! / 21!)
        xi = (xi * _x) >> _precision; res += xi * 0x000000000000000001b722e10ab1000; // add x^22 * (33! / 22!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000000000001317c70077000; // add x^23 * (33! / 23!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000000000000cba84aafa00; // add x^24 * (33! / 24!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000000000000082573a0a00; // add x^25 * (33! / 25!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000000000000005035ad900; // add x^26 * (33! / 26!)
        xi = (xi * _x) >> _precision; res += xi * 0x000000000000000000000002f881b00; // add x^27 * (33! / 27!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000000000000000001b29340; // add x^28 * (33! / 28!)
        xi = (xi * _x) >> _precision; res += xi * 0x00000000000000000000000000efc40; // add x^29 * (33! / 29!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000000000000000000007fe0; // add x^30 * (33! / 30!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000000000000000000000420; // add x^31 * (33! / 31!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000000000000000000000021; // add x^32 * (33! / 32!)
        xi = (xi * _x) >> _precision; res += xi * 0x0000000000000000000000000000001; // add x^33 * (33! / 33!)

        return res / 0x688589cc0e9505e2f2fee5580000000 + _x + (ONE << _precision); // divide by 33! and then add x^1 / 1! + x^0 / 0!
    }

    /**
        Return log(x / FIXED_1) * FIXED_1
        Input range: FIXED_1 <= x <= LOG_EXP_MAX_VAL - 1
        Auto-generated via 'PrintFunctionOptimalLog.py'
    */
    function optimalLog(uint256 x) internal pure returns (uint256) {
        uint256 res = 0;

        uint256 y;
        uint256 z;
        uint256 w;

        if (x >= 0xd3094c70f034de4b96ff7d5b6f99fcd8) {res += 0x40000000000000000000000000000000; x = x * FIXED_1 / 0xd3094c70f034de4b96ff7d5b6f99fcd8;}
        if (x >= 0xa45af1e1f40c333b3de1db4dd55f29a7) {res += 0x20000000000000000000000000000000; x = x * FIXED_1 / 0xa45af1e1f40c333b3de1db4dd55f29a7;}
        if (x >= 0x910b022db7ae67ce76b441c27035c6a1) {res += 0x10000000000000000000000000000000; x = x * FIXED_1 / 0x910b022db7ae67ce76b441c27035c6a1;}
        if (x >= 0x88415abbe9a76bead8d00cf112e4d4a8) {res += 0x08000000000000000000000000000000; x = x * FIXED_1 / 0x88415abbe9a76bead8d00cf112e4d4a8;}
        if (x >= 0x84102b00893f64c705e841d5d4064bd3) {res += 0x04000000000000000000000000000000; x = x * FIXED_1 / 0x84102b00893f64c705e841d5d4064bd3;}
        if (x >= 0x8204055aaef1c8bd5c3259f4822735a2) {res += 0x02000000000000000000000000000000; x = x * FIXED_1 / 0x8204055aaef1c8bd5c3259f4822735a2;}
        if (x >= 0x810100ab00222d861931c15e39b44e99) {res += 0x01000000000000000000000000000000; x = x * FIXED_1 / 0x810100ab00222d861931c15e39b44e99;}
        if (x >= 0x808040155aabbbe9451521693554f733) {res += 0x00800000000000000000000000000000; x = x * FIXED_1 / 0x808040155aabbbe9451521693554f733;}

        z = y = x - FIXED_1;
        w = y * y / FIXED_1;
        res += z * (0x100000000000000000000000000000000 - y) / 0x100000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x0aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa - y) / 0x200000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x099999999999999999999999999999999 - y) / 0x300000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x092492492492492492492492492492492 - y) / 0x400000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x08e38e38e38e38e38e38e38e38e38e38e - y) / 0x500000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x08ba2e8ba2e8ba2e8ba2e8ba2e8ba2e8b - y) / 0x600000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x089d89d89d89d89d89d89d89d89d89d89 - y) / 0x700000000000000000000000000000000; z = z * w / FIXED_1;
        res += z * (0x088888888888888888888888888888888 - y) / 0x800000000000000000000000000000000;

        return res;
    }

    /**
        Return e ^ (x / FIXED_1) * FIXED_1
        Input range: 0 <= x <= OPT_EXP_MAX_VAL - 1
        Auto-generated via 'PrintFunctionOptimalExp.py'
    */
    function optimalExp(uint256 x) internal pure returns (uint256) {
        uint256 res = 0;

        uint256 y;
        uint256 z;

        z = y = x % 0x10000000000000000000000000000000;
        z = z * y / FIXED_1; res += z * 0x10e1b3be415a0000; // add y^02 * (20! / 02!)
        z = z * y / FIXED_1; res += z * 0x05a0913f6b1e0000; // add y^03 * (20! / 03!)
        z = z * y / FIXED_1; res += z * 0x0168244fdac78000; // add y^04 * (20! / 04!)
        z = z * y / FIXED_1; res += z * 0x004807432bc18000; // add y^05 * (20! / 05!)
        z = z * y / FIXED_1; res += z * 0x000c0135dca04000; // add y^06 * (20! / 06!)
        z = z * y / FIXED_1; res += z * 0x0001b707b1cdc000; // add y^07 * (20! / 07!)
        z = z * y / FIXED_1; res += z * 0x000036e0f639b800; // add y^08 * (20! / 08!)
        z = z * y / FIXED_1; res += z * 0x00000618fee9f800; // add y^09 * (20! / 09!)
        z = z * y / FIXED_1; res += z * 0x0000009c197dcc00; // add y^10 * (20! / 10!)
        z = z * y / FIXED_1; res += z * 0x0000000e30dce400; // add y^11 * (20! / 11!)
        z = z * y / FIXED_1; res += z * 0x000000012ebd1300; // add y^12 * (20! / 12!)
        z = z * y / FIXED_1; res += z * 0x0000000017499f00; // add y^13 * (20! / 13!)
        z = z * y / FIXED_1; res += z * 0x0000000001a9d480; // add y^14 * (20! / 14!)
        z = z * y / FIXED_1; res += z * 0x00000000001c6380; // add y^15 * (20! / 15!)
        z = z * y / FIXED_1; res += z * 0x000000000001c638; // add y^16 * (20! / 16!)
        z = z * y / FIXED_1; res += z * 0x0000000000001ab8; // add y^17 * (20! / 17!)
        z = z * y / FIXED_1; res += z * 0x000000000000017c; // add y^18 * (20! / 18!)
        z = z * y / FIXED_1; res += z * 0x0000000000000014; // add y^19 * (20! / 19!)
        z = z * y / FIXED_1; res += z * 0x0000000000000001; // add y^20 * (20! / 20!)
        res = res / 0x21c3677c82b40000 + y + FIXED_1; // divide by 20! and then add y^1 / 1! + y^0 / 0!

        if ((x & 0x010000000000000000000000000000000) != 0) res = res * 0x1c3d6a24ed82218787d624d3e5eba95f9 / 0x18ebef9eac820ae8682b9793ac6d1e776;
        if ((x & 0x020000000000000000000000000000000) != 0) res = res * 0x18ebef9eac820ae8682b9793ac6d1e778 / 0x1368b2fc6f9609fe7aceb46aa619baed4;
        if ((x & 0x040000000000000000000000000000000) != 0) res = res * 0x1368b2fc6f9609fe7aceb46aa619baed5 / 0x0bc5ab1b16779be3575bd8f0520a9f21f;
        if ((x & 0x080000000000000000000000000000000) != 0) res = res * 0x0bc5ab1b16779be3575bd8f0520a9f21e / 0x0454aaa8efe072e7f6ddbab84b40a55c9;
        if ((x & 0x100000000000000000000000000000000) != 0) res = res * 0x0454aaa8efe072e7f6ddbab84b40a55c5 / 0x00960aadc109e7a3bf4578099615711ea;
        if ((x & 0x200000000000000000000000000000000) != 0) res = res * 0x00960aadc109e7a3bf4578099615711d7 / 0x0002bf84208204f5977f9a8cf01fdce3d;
        if ((x & 0x400000000000000000000000000000000) != 0) res = res * 0x0002bf84208204f5977f9a8cf01fdc307 / 0x0000003c6ab775dd0b95b4cbee7e65d11;

        return res;
    }
}

pragma solidity ^0.4.24;

// File: contracts/token/interfaces/IERC20Token.sol

/*
    ERC20 Standard Token interface
*/
contract IERC20Token {
    // these functions aren't abstract since the compiler emits automatically generated getter functions as external
    function name() public view returns (string) {}
    function symbol() public view returns (string) {}
    function decimals() public view returns (uint8) {}
    function totalSupply() public view returns (uint256) {}
    function balanceOf(address _owner) public view returns (uint256) { _owner; }
    function allowance(address _owner, address _spender) public view returns (uint256) { _owner; _spender; }

    function transfer(address _to, uint256 _value) public returns (bool success);
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
    function approve(address _spender, uint256 _value) public returns (bool success);
}

// File: contracts/utility/Utils.sol

/*
    Utilities & Common Modifiers
*/
contract Utils {
    /**
        constructor
    */
    constructor() public {
    }

    // verifies that an amount is greater than zero
    modifier greaterThanZero(uint256 _amount) {
        require(_amount > 0);
        _;
    }

    // validates an address - currently only checks that it isn't null
    modifier validAddress(address _address) {
        require(_address != address(0));
        _;
    }

    // verifies that the address is different than this contract address
    modifier notThis(address _address) {
        require(_address != address(this));
        _;
    }

    // Overflow protected math functions

    /**
        @dev returns the sum of _x and _y, asserts if the calculation overflows

        @param _x   value 1
        @param _y   value 2

        @return sum
    */
    function safeAdd(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x + _y;
        assert(z >= _x);
        return z;
    }

    /**
        @dev returns the difference of _x minus _y, asserts if the subtraction results in a negative number

        @param _x   minuend
        @param _y   subtrahend

        @return difference
    */
    function safeSub(uint256 _x, uint256 _y) internal pure returns (uint256) {
        assert(_x >= _y);
        return _x - _y;
    }

    /**
        @dev returns the product of multiplying _x by _y, asserts if the calculation overflows

        @param _x   factor 1
        @param _y   factor 2

        @return product
    */
    function safeMul(uint256 _x, uint256 _y) internal pure returns (uint256) {
        uint256 z = _x * _y;
        assert(_x == 0 || z / _x == _y);
        return z;
    }
}

// File: contracts/token/ERC20Token.sol

/**
    ERC20 Standard Token implementation
*/
contract ERC20Token is IERC20Token, Utils {
    string public standard = 'Token 0.1';
    string public name = '';
    string public symbol = '';
    uint8 public decimals = 0;
    uint256 public totalSupply = 0;
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 _value);

    /**
        @dev constructor

        @param _name        token name
        @param _symbol      token symbol
        @param _decimals    decimal points, for display purposes
    */
    constructor(string _name, string _symbol, uint8 _decimals) public {
        require(bytes(_name).length > 0 && bytes(_symbol).length > 0); // validate input

        name = _name;
        symbol = _symbol;
        decimals = _decimals;
    }

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value)
        public
        validAddress(_to)
        returns (bool success)
    {
        balanceOf[msg.sender] = safeSub(balanceOf[msg.sender], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value)
        public
        validAddress(_from)
        validAddress(_to)
        returns (bool success)
    {
        allowance[_from][msg.sender] = safeSub(allowance[_from][msg.sender], _value);
        balanceOf[_from] = safeSub(balanceOf[_from], _value);
        balanceOf[_to] = safeAdd(balanceOf[_to], _value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
        @dev allow another account/contract to spend some tokens on your behalf
        throws on any error rather then return a false flag to minimize user errors

        also, to minimize the risk of the approve/transferFrom attack vector
        (see https://docs.google.com/document/d/1YLPtQxZu1UAvO9cZ1O2RPXBbT0mooh4DYKjA_jp-RLM/), approve has to be called twice
        in 2 separate transactions - once to change the allowance to 0 and secondly to change it to the new allowance value

        @param _spender approved address
        @param _value   allowance amount

        @return true if the approval was successful, false if it wasn't
    */
    function approve(address _spender, uint256 _value)
        public
        validAddress(_spender)
        returns (bool success)
    {
        // if the allowance isn't 0, it can only be updated to 0 to prevent an allowance change immediately after withdrawal
        require(_value == 0 || allowance[msg.sender][_spender] == 0);

        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
}

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/token/interfaces/ISmartToken.sol

/*
    Smart Token interface
*/
contract ISmartToken is IOwned, IERC20Token {
    function disableTransfers(bool _disable) public;
    function issue(address _to, uint256 _amount) public;
    function destroy(address _from, uint256 _amount) public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/interfaces/ITokenHolder.sol

/*
    Token Holder interface
*/
contract ITokenHolder is IOwned {
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
}

// File: contracts/utility/TokenHolder.sol

/*
    We consider every contract to be a 'token holder' since it's currently not possible
    for a contract to deny receiving tokens.

    The TokenHolder's contract sole purpose is to provide a safety mechanism that allows
    the owner to send tokens that were sent to the contract by mistake back to their sender.
*/
contract TokenHolder is ITokenHolder, Owned, Utils {
    /**
        @dev constructor
    */
    constructor() public {
    }

    /**
        @dev withdraws tokens held by the contract and sends them to an account
        can only be called by the owner

        @param _token   ERC20 token contract address
        @param _to      account to receive the new amount
        @param _amount  amount to withdraw
    */
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_token)
        validAddress(_to)
        notThis(_to)
    {
        assert(_token.transfer(_to, _amount));
    }
}

// File: contracts/token/SmartToken.sol

/*
    Smart Token v0.3

    'Owned' is specified here for readability reasons
*/
contract SmartToken is ISmartToken, Owned, ERC20Token, TokenHolder {
    string public version = '0.3';

    bool public transfersEnabled = true;    // true if transfer/transferFrom are enabled, false if not

    // triggered when a smart token is deployed - the _token address is defined for forward compatibility, in case we want to trigger the event from a factory
    event NewSmartToken(address _token);
    // triggered when the total supply is increased
    event Issuance(uint256 _amount);
    // triggered when the total supply is decreased
    event Destruction(uint256 _amount);

    /**
        @dev constructor

        @param _name       token name
        @param _symbol     token short symbol, minimum 1 character
        @param _decimals   for display purposes only
    */
    constructor(string _name, string _symbol, uint8 _decimals)
        public
        ERC20Token(_name, _symbol, _decimals)
    {
        emit NewSmartToken(address(this));
    }

    // allows execution only when transfers aren't disabled
    modifier transfersAllowed {
        assert(transfersEnabled);
        _;
    }

    /**
        @dev disables/enables transfers
        can only be called by the contract owner

        @param _disable    true to disable transfers, false to enable them
    */
    function disableTransfers(bool _disable) public ownerOnly {
        transfersEnabled = !_disable;
    }

    /**
        @dev increases the token supply and sends the new tokens to an account
        can only be called by the contract owner

        @param _to         account to receive the new amount
        @param _amount     amount to increase the supply by
    */
    function issue(address _to, uint256 _amount)
        public
        ownerOnly
        validAddress(_to)
        notThis(_to)
    {
        totalSupply = safeAdd(totalSupply, _amount);
        balanceOf[_to] = safeAdd(balanceOf[_to], _amount);

        emit Issuance(_amount);
        emit Transfer(this, _to, _amount);
    }

    /**
        @dev removes tokens from an account and decreases the token supply
        can be called by the contract owner to destroy tokens from any account or by any holder to destroy tokens from his/her own account

        @param _from       account to remove the amount from
        @param _amount     amount to decrease the supply by
    */
    function destroy(address _from, uint256 _amount) public {
        require(msg.sender == _from || msg.sender == owner); // validate input

        balanceOf[_from] = safeSub(balanceOf[_from], _amount);
        totalSupply = safeSub(totalSupply, _amount);

        emit Transfer(_from, this, _amount);
        emit Destruction(_amount);
    }

    // ERC20 standard method overrides with some extra functionality

    /**
        @dev send coins
        throws on any error rather then return a false flag to minimize user errors
        in addition to the standard checks, the function throws if transfers are disabled

        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transfer(address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transfer(_to, _value));
        return true;
    }

    /**
        @dev an account/contract attempts to get the coins
        throws on any error rather then return a false flag to minimize user errors
        in addition to the standard checks, the function throws if transfers are disabled

        @param _from    source address
        @param _to      target address
        @param _value   transfer amount

        @return true if the transfer was successful, false if it wasn't
    */
    function transferFrom(address _from, address _to, uint256 _value) public transfersAllowed returns (bool success) {
        assert(super.transferFrom(_from, _to, _value));
        return true;
    }
}

pragma solidity ^0.4.24;

// File: contracts/utility/interfaces/IOwned.sol

/*
    Owned contract interface
*/
contract IOwned {
    // this function isn't abstract since the compiler emits automatically generated getter functions as external
    function owner() public view returns (address) {}

    function transferOwnership(address _newOwner) public;
    function acceptOwnership() public;
}

// File: contracts/utility/Owned.sol

/*
    Provides support and utilities for contract ownership
*/
contract Owned is IOwned {
    address public owner;
    address public newOwner;

    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
        @dev constructor
    */
    constructor() public {
        owner = msg.sender;
    }

    // allows execution by the owner only
    modifier ownerOnly {
        require(msg.sender == owner);
        _;
    }

    /**
        @dev allows transferring the contract ownership
        the new owner still needs to accept the transfer
        can only be called by the contract owner

        @param _newOwner    new contract owner
    */
    function transferOwnership(address _newOwner) public ownerOnly {
        require(_newOwner != owner);
        newOwner = _newOwner;
    }

    /**
        @dev used by a new owner to accept an ownership transfer
    */
    function acceptOwnership() public {
        require(msg.sender == newOwner);
        emit OwnerUpdate(owner, newOwner);
        owner = newOwner;
        newOwner = address(0);
    }
}

// File: contracts/utility/interfaces/IAddressList.sol

/*
    Address list interface
*/
contract IAddressList {
    mapping (address => bool) public listedAddresses;
}

// File: contracts/utility/NonStandardTokenRegistry.sol

/*
    Non standard token registry

    manages tokens who don't return true/false on transfer/transferFrom/approve but revert on failure instead 
*/
contract NonStandardTokenRegistry is IAddressList, Owned {

    mapping (address => bool) public listedAddresses;

    /**
        @dev constructor
    */
    constructor() public {

    }

    function setAddress(address token, bool register) public ownerOnly {
        listedAddresses[token] = register;
    }
}