ERC677transferAndCall_Improve.sol

contract Sender {
    
    function contractFallbackHack(address _to, uint value, bytes _data)
        private
        returns(bool)
    {
        return _to.call(abi.encodeWithSignature("onTokenTransfer(address,uint256,bytes)",  msg.sender, value, _data));
    }
    
    function transferAndCallHack(address _to, uint value, bytes _data)
        external returns (bool)
    {
        if(isContract(_to)){
            return contractFallbackHack(_to, value, _data);
        }
        
        return true;
    }
    
    function isContract(address _addr)
        private
        view
        returns (bool)
    {
        uint length;
        assembly { length := extcodesize(_addr) }
        return length > 0;
    }
}

contract Recipient {
    
    address public who;
    uint public value;
    bytes public data;
    
    function () payable {
        revert();
    }
    
    function onTokenTransfer(address _who, uint256 _value, bytes _data) returns(bool) {
        who = _who;
        value = _value;
        data = _data;
        return true;
    }
    
}

contract Recipient2 {
    
    address public who;
    
    function () payable {
        revert();
    }
}

contract Recipient3 {
    
    address public who;

}