CKB/以太坊 RPC 接口使用

本文的目的是编写相关代码, 从以太坊节点获取我们感兴趣的链上数据. 鉴于目前同步一个以太坊节点过于耗时, 因此我将使用 Infura 提供的公共以太坊节点来完成这一切. 那么我们开始吧!

$ go get -u -v github.com/ethereum/go-ethereum/ethclient

查询转账记录

以太坊交易数据中并不包含发送者, 要从交易中恢复发送者的地址, 可参考以下两个网页. 简单来说, 我们须首先从交易的签名中恢复发送者的公钥, 然后通过发送者公钥计算发送者地址.

• https://github.com/ethereum/go-ethereum/issues/22918
• https://ethereum.stackexchange.com/questions/67449/given-a-raw-transaction-how-to-get-senders-address

package main

import (
    "context"
    "log"
    "math/big"

    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/ethclient"
    "github.com/ethereum/go-ethereum/rpc"
    "github.com/godump/doa"
)

func main() {
    // Site: https://www.infura.io/zh
    // Docs: https://docs.infura.io/networks/ethereum/json-rpc-methods
    rawClient := doa.Try(rpc.DialHTTP("https://mainnet.infura.io/v3/5c17ecf14e0d4756aa81b6a1154dc599"))
    ethClient := ethclient.NewClient(rawClient)
    blockNumber := doa.Try(ethClient.BlockNumber(context.Background()))
    block := doa.Try(ethClient.BlockByNumber(context.Background(), big.NewInt(int64(blockNumber))))
    for _, tx := range block.Transactions() {
        from := doa.Try(types.Sender(types.LatestSignerForChainID(tx.ChainId()), tx))
        value, _ := tx.Value().Float64()
        log.Printf("%s %s -> %s %10.6f eth", tx.Hash(), from, tx.To(), value/1e18)
    }
}

程序将获取以太坊最后一个交易区块, 并依次打印交易哈希, 交易发送者, 交易接收者和交易金额.

查询 USDT-ERC20 转账记录

Tether USD 在以太坊上是一个 ERC20 Token, 可以在 Etherscan 查询该合约的完整信息. 我们通过解析交易的 Log 来查询 USDT 转账记录, 代码如下.

package main

import (
    "context"
    "log"
    "math/big"

    "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/ethclient"
    "github.com/ethereum/go-ethereum/rpc"
    "github.com/godump/doa"
)

func main() {
    rawClient := doa.Try(rpc.DialHTTP("https://mainnet.infura.io/v3/5c17ecf14e0d4756aa81b6a1154dc599"))
    ethClient := ethclient.NewClient(rawClient)
    blockNumber := doa.Try(ethClient.BlockNumber(context.Background()))
    query := ethereum.FilterQuery{
        Addresses: []common.Address{common.HexToAddress("0xdac17f958d2ee523a2206206994597c13d831ec7")},
        Topics: [][]common.Hash{
            {common.HexToHash("0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef")},
        },
        FromBlock: big.NewInt(int64(blockNumber)),
        ToBlock:   big.NewInt(int64(blockNumber)),
    }
    txlog := doa.Try(ethClient.FilterLogs(context.Background(), query))
    for _, e := range txlog {
        amount := new(big.Int)
        amount.SetBytes(e.Data)
        valuef, _ := amount.Float64()
        log.Printf("%s %s -> %s %14.6f USDT",
            e.TxHash,
            common.HexToAddress(e.Topics[1].Hex()),
            common.HexToAddress(e.Topics[2].Hex()),
            valuef/1e6,
        )
    }
}

查询 USDT 余额

我们还是以 USDT 合约为例, 我们的目标是查询 F977814e90dA44bFA03b6295A0616a897441aceC 这个地址的余额. 通过 USDT 合约代码可知, 有一个 balanceOf(address) 函数可以取得任意地址的余额, 因此我们只需要想办法调用这个函数即可.

要调用函数, 首先要获取函数的签名. 以 balanceOf(address) 为例, 其函数签名为 70a08231, 签名计算方式为 sha3("balanceOf(address)") 的前 4 个 Byte 的 Hex 值. 之后构建函数调用, 其构造方式为函数签名 + 参数. 注意所有参数都需要以 uint256 表示, 因此结果为 70a08231000000000000000000000000F977814e90dA44bFA03b6295A0616a897441aceC.

package main

import (
    "context"
    "encoding/hex"
    "log"
    "math/big"

    "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/ethclient"
    "github.com/ethereum/go-ethereum/rpc"
    "github.com/godump/doa"
)

func main() {
    rawClient := doa.Try(rpc.DialHTTP("https://mainnet.infura.io/v3/5c17ecf14e0d4756aa81b6a1154dc599"))
    ethClient := ethclient.NewClient(rawClient)
    blockNumber := doa.Try(ethClient.BlockNumber(context.Background()))
    contract := common.HexToAddress("0xdAC17F958D2ee523a2206206994597C13D831ec7")
    ret := doa.Try(ethClient.CallContract(context.Background(), ethereum.CallMsg{
        To:   &contract,
        Data: doa.Try(hex.DecodeString("70a08231000000000000000000000000F977814e90dA44bFA03b6295A0616a897441aceC")),
    }, big.NewInt(int64(blockNumber))))
    balance := big.Int{}
    balance.SetBytes(ret)
    data, _ := balance.Float64()
    log.Println(data / 1e6)
}