ERC777ERC20BaseToken.sol

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
pragma solidity ^0.4.24;


import { ERC20Token } from "./ERC20Token.sol";
import { ERC777BaseToken } from "./ERC777BaseToken.sol";


contract ERC777ERC20BaseToken is ERC20Token, ERC777BaseToken {
    bool internal mErc20compatible;

    mapping(address => mapping(address => uint256)) internal mAllowed;

    constructor(
        string _name,
        string _symbol,
        uint256 _granularity,
        address[] _defaultOperators
    )
        internal ERC777BaseToken(_name, _symbol, _granularity, _defaultOperators)
    {
        mErc20compatible = true;
        setInterfaceImplementation("ERC20Token", this);
    }

    /// @notice This modifier is applied to erc20 obsolete methods that are
    ///  implemented only to maintain backwards compatibility. When the erc20
    ///  compatibility is disabled, this methods will fail.
    modifier erc20 () {
        require(mErc20compatible, "ERC20 is disabled");
        _;
    }

    /// @notice For Backwards compatibility
    /// @return The decimls of the token. Forced to 18 in ERC777.
    function decimals() public erc20 view returns (uint8) { return uint8(18); }

    /// @notice ERC20 backwards compatible transfer.
    /// @param _to The address of the recipient
    /// @param _amount The number of tokens to be transferred
    /// @return `true`, if the transfer can't be done, it should fail.
    function transfer(address _to, uint256 _amount) public erc20 returns (bool success) {
        doSend(msg.sender, msg.sender, _to, _amount, "", "", false);
        return true;
    }

    /// @notice ERC20 backwards compatible transferFrom.
    /// @param _from The address holding the tokens being transferred
    /// @param _to The address of the recipient
    /// @param _amount The number of tokens to be transferred
    /// @return `true`, if the transfer can't be done, it should fail.
    function transferFrom(address _from, address _to, uint256 _amount) public erc20 returns (bool success) {
        require(_amount <= mAllowed[_from][msg.sender], "Not enough funds allowed");

        // Cannot be after doSend because of tokensReceived re-entry
        mAllowed[_from][msg.sender] = mAllowed[_from][msg.sender].sub(_amount);
        doSend(msg.sender, _from, _to, _amount, "", "", false);
        return true;
    }

    /// @notice ERC20 backwards compatible approve.
    ///  `msg.sender` approves `_spender` to spend `_amount` tokens on its behalf.
    /// @param _spender The address of the account able to transfer the tokens
    /// @param _amount The number of tokens to be approved for transfer
    /// @return `true`, if the approve can't be done, it should fail.
    function approve(address _spender, uint256 _amount) public erc20 returns (bool success) {
        mAllowed[msg.sender][_spender] = _amount;
        emit Approval(msg.sender, _spender, _amount);
        return true;
    }

    /// @notice ERC20 backwards compatible allowance.
    ///  This function makes it easy to read the `allowed[]` map
    /// @param _owner The address of the account that owns the token
    /// @param _spender The address of the account able to transfer the tokens
    /// @return Amount of remaining tokens of _owner that _spender is allowed
    ///  to spend
    function allowance(address _owner, address _spender) public erc20 view returns (uint256 remaining) {
        return mAllowed[_owner][_spender];
    }

    function doSend(
        address _operator,
        address _from,
        address _to,
        uint256 _amount,
        bytes _data,
        bytes _operatorData,
        bool _preventLocking
    )
        internal
    {
        super.doSend(_operator, _from, _to, _amount, _data, _operatorData, _preventLocking);
        if (mErc20compatible) { emit Transfer(_from, _to, _amount); }
    }

    function doBurn(address _operator, address _tokenHolder, uint256 _amount, bytes _data, bytes _operatorData)
        internal
    {
        super.doBurn(_operator, _tokenHolder, _amount, _data, _operatorData);
        if (mErc20compatible) { emit Transfer(_tokenHolder, 0x0, _amount); }
    }
}