solidity智能合约之将函数调用记录为事件

将函数调用记录为事件

通过note修饰符提供通用函数调用日志记录，该修饰符触发数据捕获作为LogNote事件包含：

• msg.sig（索引）
• msg.sender（索引）
• 第一个函数参数（索引）
• 第二个函数参数（索引）
• msg.value
• msg.data

使用修饰符修饰的函数note将在使用区块链客户端可查询的索引字段调用时记录此信息。这涵盖了事件的大多数用例，使它成为一种快速将事件日志记录添加到 dapp 的简单方法。

/// note.sol -- the `note' modifier, for logging calls as events

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

pragma solidity >=0.4.23;

contract DSNote {
    event LogNote(
        bytes4   indexed  sig,
        address  indexed  guy,
        bytes32  indexed  foo,
        bytes32  indexed  bar,
        uint256           wad,
        bytes             fax
    ) anonymous;

    modifier note {
        bytes32 foo;
        bytes32 bar;
        uint256 wad;

        assembly {
            foo := calldataload(4)
            bar := calldataload(36)
            wad := callvalue()
        }

        _;

        emit LogNote(msg.sig, msg.sender, foo, bar, wad, msg.data);
    }
}