以太坊event log查询与解析

查询event log

从ethereum json-rpc文档的文档中找到一个同时指定多个事件以 OR 或者 AND 查询的方法.以下是查询 Approval 或 Transfer 事件的方法：

{
    "jsonrpc":"2.0",
    "method":"eth_getLogs",
    "params":[{
        "topics":[["0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925","0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"]],
        "address": "0xa7f6c9a5052a08a14ff0e3349094b6efbc591ea4",
        "fromBlock": "0x499a",
        "toBlock": "0x18999"
        
    }],
    "id":74
}

topics字段中指定查询条件的语法参考上面链接。

ERC20代币交易详情解析

通过getTransactionReceipt在ropsten测试网上查询到交易号为0x7e9eaf019928b7f8cf6f5fafa626a58d477f4800054f7101ffe941fda353abcb的交易详情

{
    "jsonrpc": "2.0",
    "id": 74,
    "result": {
        "blockHash": "0xbc4dfb56410f28476ac6dbdaf68513a4b01ac0084fb21cc81b6803bd956d6365",
        "blockNumber": "0x81b4",
        "contractAddress": null,
        "cumulativeGasUsed": "0xca9d",
        "from": "0xdb33dfd3d61308c33c63209845dad3e6bfb2c674",
        "gasUsed": "0xca9d",
        "logs": [
            {
                "address": "0xa7f6c9a5052a08a14ff0e3349094b6efbc591ea4",
                "topics": [
                    "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
                    "0x000000000000000000000000db33dfd3d61308c33c63209845dad3e6bfb2c674",
                    "0x0000000000000000000000006f2a8ee9452ba7d336b3fba03cac27f7818aead6"
                ],
                "data": "0x0000000000000000000000000000000000000000000000056bc75e2d63100000",
                "blockNumber": "0x81b4",
                "transactionHash": "0x7e9eaf019928b7f8cf6f5fafa626a58d477f4800054f7101ffe941fda353abcb",
                "transactionIndex": "0x0",
                "blockHash": "0xbc4dfb56410f28476ac6dbdaf68513a4b01ac0084fb21cc81b6803bd956d6365",
                "logIndex": "0x0",
                "removed": false
            }
        ],
        "logsBloom": "0x0000000000000000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000008c000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000010000000000000000000001000000200000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000020002000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000",
        "root": "0xb6824b5b1ff9cab405435d9735dfe3971755b78b955c957b96adfe96a0552217",
        "to": "0xa7f6c9a5052a08a14ff0e3349094b6efbc591ea4",
        "transactionHash": "0x7e9eaf019928b7f8cf6f5fafa626a58d477f4800054f7101ffe941fda353abcb",
        "transactionIndex": "0x0"
    }
}

这个交易从"from": "0xdb33dfd3d61308c33c63209845dad3e6bfb2c674"发送到合约地址"to": "0xa7f6c9a5052a08a14ff0e3349094b6efbc591ea4".这个合约为ERC20代币合约.从topics的第一个元素可以看出合约中产生了Transfer事件(topics第一个元素一定是事件的keccak哈希). topics的第二个字段是转出代币的地址，第三个字段是接收者地址.ERC20代币Transfer事件的签名为

event Transfer(address indexed from, address indexed to, uint tokens);

我们注意到Transfer事件的第一个和第二个参数被标记为indexed, 因此他们的值被放在 topics array 中. 由于tokens参数没有标记为indexed, 所以他的值被放在data字段. 如果事件中有多个字段未标记为indexed， 那么他们的值都会被记录在data字段中。

参考链接

• What does the indexed keyword do?
• a note on specifying topic filters