Contract Source Code:

pragma solidity 0.4.26;

// 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) {this;}
    function symbol() public view returns (string) {this;}
    function decimals() public view returns (uint8) {this;}
    function totalSupply() public view returns (uint256) {this;}
    function balanceOf(address _owner) public view returns (uint256) {_owner; this;}
    function allowance(address _owner, address _spender) public view returns (uint256) {_owner; _spender; this;}

    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 convert2(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn, address _affiliateAccount, uint256 _affiliateFee) public returns (uint256);
    function quickConvert2(IERC20Token[] _path, uint256 _amount, uint256 _minReturn, address _affiliateAccount, uint256 _affiliateFee) public payable returns (uint256);
    function conversionWhitelist() public view returns (IWhitelist) {this;}
    function conversionFee() public view returns (uint32) {this;}
    function reserves(address _address) public view returns (uint256, uint32, bool, bool, bool) {_address; this;}
    function getReserveBalance(IERC20Token _reserveToken) public view returns (uint256);
    function reserveTokens(uint256 _index) public view returns (IERC20Token) {_index; this;}
    // deprecated, backward compatibility
    function change(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function convert(IERC20Token _fromToken, IERC20Token _toToken, uint256 _amount, uint256 _minReturn) public returns (uint256);
    function quickConvert(IERC20Token[] _path, uint256 _amount, uint256 _minReturn) public payable returns (uint256);
    function connectors(address _address) public view returns (uint256, uint32, bool, bool, bool);
    function getConnectorBalance(IERC20Token _connectorToken) public view returns (uint256);
    function connectorTokens(uint256 _index) public view returns (IERC20Token);
}

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

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

// 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) {this;}

    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/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/converter/interfaces/IBancorConverterFactory.sol

/*
    Bancor Converter Factory interface
*/
contract IBancorConverterFactory {
    function createConverter(
        ISmartToken _token,
        IContractRegistry _registry,
        uint32 _maxConversionFee,
        IERC20Token _reserveToken,
        uint32 _reserveRatio
    )
    public returns (address);
}

// File: contracts/utility/Owned.sol

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

    /**
      * @dev triggered when the owner is updated
      * 
      * @param _prevOwner previous owner
      * @param _newOwner  new owner
    */
    event OwnerUpdate(address indexed _prevOwner, address indexed _newOwner);

    /**
      * @dev initializes a new Owned instance
    */
    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/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/ContractIds.sol

/**
  * @dev 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

/**
  * @dev 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/converter/BancorConverterUpgrader.sol

/*
    Bancor converter dedicated interface
*/
contract IBancorConverterExtended is IBancorConverter, IOwned {
    function token() public view returns (ISmartToken) {this;}
    function maxConversionFee() public view returns (uint32) {this;}
    function conversionFee() public view returns (uint32) {this;}
    function connectorTokenCount() public view returns (uint16);
    function reserveTokenCount() public view returns (uint16);
    function connectorTokens(uint256 _index) public view returns (IERC20Token) {_index; this;}
    function reserveTokens(uint256 _index) public view returns (IERC20Token) {_index; this;}
    function setConversionWhitelist(IWhitelist _whitelist) public;
    function transferTokenOwnership(address _newOwner) public;
    function withdrawTokens(IERC20Token _token, address _to, uint256 _amount) public;
    function acceptTokenOwnership() public;
    function transferManagement(address _newManager) public;
    function acceptManagement() public;
    function setConversionFee(uint32 _conversionFee) public;
    function addConnector(IERC20Token _token, uint32 _weight, bool _enableVirtualBalance) public;
    function updateConnector(IERC20Token _connectorToken, uint32 _weight, bool _enableVirtualBalance, uint256 _virtualBalance) public;
}

/**
  * @dev Bancor Converter Upgrader
  * 
  * The Bancor converter upgrader contract allows upgrading an older Bancor converter contract (0.4 and up)
  * to the latest version.
  * To begin the upgrade process, simply execute the 'upgrade' function.
  * At the end of the process, the ownership of the newly upgraded converter will be transferred
  * back to the original owner and the original owner will need to execute the 'acceptOwnership' function.
  * 
  * The address of the new converter is available in the ConverterUpgrade event.
  * 
  * Note that for older converters that don't yet have the 'upgrade' function, ownership should first
  * be transferred manually to the ConverterUpgrader contract using the 'transferOwnership' function
  * and then the upgrader 'upgrade' function should be executed directly.
*/
contract BancorConverterUpgrader is IBancorConverterUpgrader, Owned, ContractIds, FeatureIds {
    string public version = '0.3';

    IContractRegistry public registry;                      // contract registry contract address

    /**
      * @dev triggered when the contract accept a converter ownership
      * 
      * @param _converter   converter address
      * @param _owner       new owner - local upgrader address
    */
    event ConverterOwned(address indexed _converter, address indexed _owner);

    /**
      * @dev triggered when the upgrading process is done
      * 
      * @param _oldConverter    old converter address
      * @param _newConverter    new converter address
    */
    event ConverterUpgrade(address indexed _oldConverter, address indexed _newConverter);

    /**
      * @dev initializes a new BancorConverterUpgrader instance
    */
    constructor(IContractRegistry _registry) public {
        registry = _registry;
    }

    /**
      * @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 {
        registry = _registry;
    }

    /**
      * @dev upgrades an old converter to the latest version
      * will throw if ownership wasn't transferred to the upgrader before calling this function.
      * ownership of the new converter will be transferred back to the original owner.
      * fires the ConverterUpgrade event upon success.
      * can only be called by a converter
      * 
      * @param _version old converter version
    */
    function upgrade(bytes32 _version) public {
        upgradeOld(IBancorConverter(msg.sender), _version);
    }

    /**
      * @dev upgrades an old converter to the latest version
      * will throw if ownership wasn't transferred to the upgrader before calling this function.
      * ownership of the new converter will be transferred back to the original owner.
      * fires the ConverterUpgrade event upon success.
      * can only be called by a converter
      * 
      * @param _version old converter version
    */
    function upgrade(uint16 _version) public {
        upgradeOld(IBancorConverter(msg.sender), bytes32(_version));
    }

    /**
      * @dev upgrades an old converter to the latest version
      * will throw if ownership wasn't transferred to the upgrader before calling this function.
      * ownership of the new converter will be transferred back to the original owner.
      * fires the ConverterUpgrade event upon success.
      * 
      * @param _converter   old converter contract address
      * @param _version     old converter version
    */
    function upgradeOld(IBancorConverter _converter, bytes32 _version) public {
        bool formerVersions = false;
        if (_version == "0.4")
            formerVersions = true;
        IBancorConverterExtended converter = IBancorConverterExtended(_converter);
        address prevOwner = converter.owner();
        acceptConverterOwnership(converter);
        IBancorConverterExtended newConverter = createConverter(converter);
        copyConnectors(converter, newConverter, formerVersions);
        copyConversionFee(converter, newConverter);
        transferConnectorsBalances(converter, newConverter, formerVersions);                
        ISmartToken token = converter.token();

        if (token.owner() == address(converter)) {
            converter.transferTokenOwnership(newConverter);
            newConverter.acceptTokenOwnership();
        }

        converter.transferOwnership(prevOwner);
        newConverter.transferOwnership(prevOwner);
        newConverter.transferManagement(prevOwner);

        emit ConverterUpgrade(address(converter), address(newConverter));
    }

    /**
      * @dev the first step when upgrading a converter is to transfer the ownership to the local contract.
      * the upgrader contract then needs to accept the ownership transfer before initiating
      * the upgrade process.
      * fires the ConverterOwned event upon success
      * 
      * @param _oldConverter       converter to accept ownership of
    */
    function acceptConverterOwnership(IBancorConverterExtended _oldConverter) private {
        _oldConverter.acceptOwnership();
        emit ConverterOwned(_oldConverter, this);
    }

    /**
      * @dev creates a new converter with same basic data as the original old converter
      * the newly created converter will have no connectors at this step.
      * 
      * @param _oldConverter    old converter contract address
      * 
      * @return the new converter  new converter contract address
    */
    function createConverter(IBancorConverterExtended _oldConverter) private returns(IBancorConverterExtended) {
        IWhitelist whitelist;
        ISmartToken token = _oldConverter.token();
        uint32 maxConversionFee = _oldConverter.maxConversionFee();

        IBancorConverterFactory converterFactory = IBancorConverterFactory(registry.addressOf(ContractIds.BANCOR_CONVERTER_FACTORY));
        address converterAddress  = converterFactory.createConverter(
            token,
            registry,
            maxConversionFee,
            IERC20Token(address(0)),
            0
        );

        IBancorConverterExtended converter = IBancorConverterExtended(converterAddress);
        converter.acceptOwnership();
        converter.acceptManagement();

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

        if (features.isSupported(_oldConverter, FeatureIds.CONVERTER_CONVERSION_WHITELIST)) {
            whitelist = _oldConverter.conversionWhitelist();
            if (whitelist != address(0))
                converter.setConversionWhitelist(whitelist);
        }

        return converter;
    }

    /**
      * @dev copies the connectors from the old converter to the new one.
      * note that this will not work for an unlimited number of connectors due to block gas limit constraints.
      * 
      * @param _oldConverter    old converter contract address
      * @param _newConverter    new converter contract address
      * @param _isLegacyVersion true if the converter version is under 0.5
    */
    function copyConnectors(IBancorConverterExtended _oldConverter, IBancorConverterExtended _newConverter, bool _isLegacyVersion)
        private
    {
        uint256 virtualBalance;
        uint32 weight;
        bool isVirtualBalanceEnabled;
        bool isSaleEnabled;
        bool isSet;
        uint16 connectorTokenCount = _isLegacyVersion ? _oldConverter.reserveTokenCount() : _oldConverter.connectorTokenCount();

        for (uint16 i = 0; i < connectorTokenCount; i++) {
            address connectorAddress = _isLegacyVersion ? _oldConverter.reserveTokens(i) : _oldConverter.connectorTokens(i);
            (virtualBalance, weight, isVirtualBalanceEnabled, isSaleEnabled, isSet) = readConnector(
                _oldConverter,
                connectorAddress,
                _isLegacyVersion
            );

            IERC20Token connectorToken = IERC20Token(connectorAddress);
            _newConverter.addConnector(connectorToken, weight, isVirtualBalanceEnabled);

            if (isVirtualBalanceEnabled)
                _newConverter.updateConnector(connectorToken, weight, isVirtualBalanceEnabled, virtualBalance);
        }
    }

    /**
      * @dev copies the conversion fee from the old converter to the new one
      * 
      * @param _oldConverter    old converter contract address
      * @param _newConverter    new converter contract address
    */
    function copyConversionFee(IBancorConverterExtended _oldConverter, IBancorConverterExtended _newConverter) private {
        uint32 conversionFee = _oldConverter.conversionFee();
        _newConverter.setConversionFee(conversionFee);
    }

    /**
      * @dev transfers the balance of each connector in the old converter to the new one.
      * note that the function assumes that the new converter already has the exact same number of
      * also, this will not work for an unlimited number of connectors due to block gas limit constraints.
      * 
      * @param _oldConverter    old converter contract address
      * @param _newConverter    new converter contract address
      * @param _isLegacyVersion true if the converter version is under 0.5
    */
    function transferConnectorsBalances(IBancorConverterExtended _oldConverter, IBancorConverterExtended _newConverter, bool _isLegacyVersion)
        private
    {
        uint256 connectorBalance;
        uint16 connectorTokenCount = _isLegacyVersion ? _oldConverter.reserveTokenCount() : _oldConverter.connectorTokenCount();

        for (uint16 i = 0; i < connectorTokenCount; i++) {
            address connectorAddress = _isLegacyVersion ? _oldConverter.reserveTokens(i) : _oldConverter.connectorTokens(i);
            IERC20Token connector = IERC20Token(connectorAddress);
            connectorBalance = connector.balanceOf(_oldConverter);
            _oldConverter.withdrawTokens(connector, address(_newConverter), connectorBalance);
        }
    }

    /**
      * @dev returns the connector settings
      * 
      * @param _converter       old converter contract address
      * @param _address         connector's address to read from
      * @param _isLegacyVersion true if the converter version is under 0.5
      * 
      * @return connector's settings
    */
    function readConnector(IBancorConverterExtended _converter, address _address, bool _isLegacyVersion) 
        private
        view
        returns(uint256 virtualBalance, uint32 weight, bool isVirtualBalanceEnabled, bool isSaleEnabled, bool isSet)
    {
        return _isLegacyVersion ? _converter.reserves(_address) : _converter.connectors(_address);
    }
}