概述: 用Go读取0x Protocol智能合约事件日志的教程

读取0x Protocol事件日志

要读取0x Protocol事件日志，我们必须首先将solidity智能合约编译为一个Go包。

安装solc版本0.4.11

npm i -g solc@0.4.11

为例如Exchange.sol的事件日志创建0x Protocol交易所智能合约接口:

Create the 0x protocol exchange smart contract interface for event logs as Exchange.sol:

pragma solidity 0.4.11;
contract Exchange {
    event LogFill(
        address indexed maker,
        address taker,
        address indexed feeRecipient,
        address makerToken,
        address takerToken,
        uint filledMakerTokenAmount,
        uint filledTakerTokenAmount,
        uint paidMakerFee,
        uint paidTakerFee,
        bytes32 indexed tokens, // keccak256(makerToken, takerToken), allows subscribing to a token pair
        bytes32 orderHash
    );
    event LogCancel(
        address indexed maker,
        address indexed feeRecipient,
        address makerToken,
        address takerToken,
        uint cancelledMakerTokenAmount,
        uint cancelledTakerTokenAmount,
        bytes32 indexed tokens,
        bytes32 orderHash
    );
    event LogError(uint8 indexed errorId, bytes32 indexed orderHash);
}

接着给定abi，使用abigen来创建Goexchange包：

Then use abigen to create the Go exchange package given the abi:

solc --abi Exchange.sol
abigen --abi="Exchange.sol:Exchange.abi" --pkg=exchange --out=Exchange.go

现在在我们的Go应用程序中，让我们创建与0xProtocol事件日志签名类型匹配的结构体类型：

type LogFill struct {
    Maker                  common.Address
    Taker                  common.Address
    FeeRecipient           common.Address
    MakerToken             common.Address
    TakerToken             common.Address
    FilledMakerTokenAmount *big.Int
    FilledTakerTokenAmount *big.Int
    PaidMakerFee           *big.Int
    PaidTakerFee           *big.Int
    Tokens                 [32]byte
    OrderHash              [32]byte
}
type LogCancel struct {
    Maker                     common.Address
    FeeRecipient              common.Address
    MakerToken                common.Address
    TakerToken                common.Address
    CancelledMakerTokenAmount *big.Int
    CancelledTakerTokenAmount *big.Int
    Tokens                    [32]byte
    OrderHash                 [32]byte
}
type LogError struct {
    ErrorID   uint8
    OrderHash [32]byte
}

初始化以太坊客户端：

client, err := ethclient.Dial("https://mainnet.infura.io")
if err != nil {
  log.Fatal(err)
}

创建一个FilterQuery，并为其传递0x Protocol智能合约地址和所需的区块范围：

// 0x Protocol Exchange smart contract address
contractAddress := common.HexToAddress("0x12459C951127e0c374FF9105DdA097662A027093")
query := ethereum.FilterQuery{
  FromBlock: big.NewInt(6383482),
  ToBlock:   big.NewInt(6383488),
  Addresses: []common.Address{
    contractAddress,
  },
}

用FilterLogs查询日志：

logs, err := client.FilterLogs(context.Background(), query)
if err != nil {
  log.Fatal(err)
}

接下来我们将解析JSON abi，我们后续将使用解压缩原始日志数据：

contractAbi, err := abi.JSON(strings.NewReader(string(exchange.ExchangeABI)))
if err != nil {
  log.Fatal(err)
}

为了按某种日志类型过滤，我们需要知晓每个事件日志函数签名的keccak256摘要。正如我们很快所见到的那样，事件日志函数签名摘要总是topic[0]：

// NOTE: keccak256("LogFill(address,address,address,address,address,uint256,uint256,uint256,uint256,bytes32,bytes32)")
logFillEvent := common.HexToHash("0d0b9391970d9a25552f37d436d2aae2925e2bfe1b2a923754bada030c498cb3")
// NOTE: keccak256("LogCancel(address,address,address,address,uint256,uint256,bytes32,bytes32)")
logCancelEvent := common.HexToHash("67d66f160bc93d925d05dae1794c90d2d6d6688b29b84ff069398a9b04587131")
// NOTE: keccak256("LogError(uint8,bytes32)")
logErrorEvent := common.HexToHash("36d86c59e00bd73dc19ba3adfe068e4b64ac7e92be35546adeddf1b956a87e90")

现在我们迭代所有的日志并设置一个switch语句来按事件日志类型过滤：

for _, vLog := range logs {
  fmt.Printf("Log Block Number: %d\n", vLog.BlockNumber)
  fmt.Printf("Log Index: %d\n", vLog.Index)
  switch vLog.Topics[0].Hex() {
  case logFillEvent.Hex():
    //
  case logCancelEvent.Hex():
    //
  case logErrorEvent.Hex():
    //
  }
}

现在要解析LogFill，我们将使用abi.Unpack将原始数据类型解析为我们自定义的日志类型结构体。Unpack不会解析indexed事件类型，因为这些它们存储在topics下，所以对于那些我们必须单独解析，如下例所示：

fmt.Printf("Log Name: LogFill\n")
var fillEvent LogFill
err := contractAbi.Unpack(&fillEvent, "LogFill", vLog.Data)
if err != nil {
  log.Fatal(err)
}
fillEvent.Maker = common.HexToAddress(vLog.Topics[1].Hex())
fillEvent.FeeRecipient = common.HexToAddress(vLog.Topics[2].Hex())
fillEvent.Tokens = vLog.Topics[3]
fmt.Printf("Maker: %s\n", fillEvent.Maker.Hex())
fmt.Printf("Taker: %s\n", fillEvent.Taker.Hex())
fmt.Printf("Fee Recipient: %s\n", fillEvent.FeeRecipient.Hex())
fmt.Printf("Maker Token: %s\n", fillEvent.MakerToken.Hex())
fmt.Printf("Taker Token: %s\n", fillEvent.TakerToken.Hex())
fmt.Printf("Filled Maker Token Amount: %s\n", fillEvent.FilledMakerTokenAmount.String())
fmt.Printf("Filled Taker Token Amount: %s\n", fillEvent.FilledTakerTokenAmount.String())
fmt.Printf("Paid Maker Fee: %s\n", fillEvent.PaidMakerFee.String())
fmt.Printf("Paid Taker Fee: %s\n", fillEvent.PaidTakerFee.String())
fmt.Printf("Tokens: %s\n", hexutil.Encode(fillEvent.Tokens[:]))
fmt.Printf("Order Hash: %s\n", hexutil.Encode(fillEvent.OrderHash[:]))

对于LogCancel类似：

fmt.Printf("Log Name: LogCancel\n")
var cancelEvent LogCancel
err := contractAbi.Unpack(&cancelEvent, "LogCancel", vLog.Data)
if err != nil {
  log.Fatal(err)
}
cancelEvent.Maker = common.HexToAddress(vLog.Topics[1].Hex())
cancelEvent.FeeRecipient = common.HexToAddress(vLog.Topics[2].Hex())
cancelEvent.Tokens = vLog.Topics[3]
fmt.Printf("Maker: %s\n", cancelEvent.Maker.Hex())
fmt.Printf("Fee Recipient: %s\n", cancelEvent.FeeRecipient.Hex())
fmt.Printf("Maker Token: %s\n", cancelEvent.MakerToken.Hex())
fmt.Printf("Taker Token: %s\n", cancelEvent.TakerToken.Hex())
fmt.Printf("Cancelled Maker Token Amount: %s\n", cancelEvent.CancelledMakerTokenAmount.String())
fmt.Printf("Cancelled Taker Token Amount: %s\n", cancelEvent.CancelledTakerTokenAmount.String())
fmt.Printf("Tokens: %s\n", hexutil.Encode(cancelEvent.Tokens[:]))
fmt.Printf("Order Hash: %s\n", hexutil.Encode(cancelEvent.OrderHash[:]))

最后是LogError：

fmt.Printf("Log Name: LogError\n")
errorID, err := strconv.ParseInt(vLog.Topics[1].Hex(), 16, 64)
if err != nil {
  log.Fatal(err)
}
errorEvent := &LogError{
  ErrorID:   uint8(errorID),
  OrderHash: vLog.Topics[2],
}
fmt.Printf("Error ID: %d\n", errorEvent.ErrorID)
fmt.Printf("Order Hash: %s\n", hexutil.Encode(errorEvent.OrderHash[:]))

将它们放在一起并运行我们将看到以下输出：

Log Block Number: 6383482
Log Index: 35
Log Name: LogFill
Maker: 0x8dd688660ec0BaBD0B8a2f2DE3232645F73cC5eb
Taker: 0xe269E891A2Ec8585a378882fFA531141205e92E9
Fee Recipient: 0xe269E891A2Ec8585a378882fFA531141205e92E9
Maker Token: 0xD7732e3783b0047aa251928960063f863AD022D8
Taker Token: 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2
Filled Maker Token Amount: 240000000000000000000000
Filled Taker Token Amount: 6930282000000000000
Paid Maker Fee: 0
Paid Taker Fee: 0
Tokens: 0xf08499c9e419ea8c08c4b991f88632593fb36baf4124c62758acb21898711088
Order Hash: 0x306a9a7ecbd9446559a2c650b4cfc16d1fb615aa2b3f4f63078da6d021268440
Log Block Number: 6383482
Log Index: 38
Log Name: LogFill
Maker: 0x04aa059b2e31B5898fAB5aB24761e67E8a196AB8
Taker: 0xe269E891A2Ec8585a378882fFA531141205e92E9
Fee Recipient: 0xe269E891A2Ec8585a378882fFA531141205e92E9
Maker Token: 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2
Taker Token: 0xD7732e3783b0047aa251928960063f863AD022D8
Filled Maker Token Amount: 6941718000000000000
Filled Taker Token Amount: 240000000000000000000000
Paid Maker Fee: 0
Paid Taker Fee: 0
Tokens: 0x97ef123f2b566f36ab1e6f5d462a8079fbe34fa667b4eae67194b3f9cce60f2a
Order Hash: 0xac270e88ce27b6bb78ee5b68ebaef666a77195020a6ab8922834f07bc9e0d524
Log Block Number: 6383488
Log Index: 43
Log Name: LogCancel
Maker: 0x0004E79C978B95974dCa16F56B516bE0c50CC652
Fee Recipient: 0xA258b39954ceF5cB142fd567A46cDdB31a670124
Maker Token: 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2
Taker Token: 0x89d24A6b4CcB1B6fAA2625fE562bDD9a23260359
Cancelled Maker Token Amount: 30000000000000000000
Cancelled Taker Token Amount: 7274848425000000000000
Tokens: 0x9dd48110dcc444fdc242510c09bbbbe21a5975cac061d82f7b843bce061ba391
Order Hash: 0xe43eff38dc27af046bfbd431926926c072bbc7a509d56f6f1a7ae1f5ad7efe4f

将解析后的日志输出与etherscan上的内容进行比较：https://etherscan.io/tx/0xb73a4492c5db1f67930b25ce3869c1e6b9bdbccb239a23b6454925a5bc0e03c5

完整代码

命令

solc --abi Exchange.sol
abigen --abi="Exchange.sol:Exchange.abi" --pkg=exchange --out=Exchange.go

Exchange.sol

pragma solidity 0.4.11;
contract Exchange {
    event LogFill(
        address indexed maker,
        address taker,
        address indexed feeRecipient,
        address makerToken,
        address takerToken,
        uint filledMakerTokenAmount,
        uint filledTakerTokenAmount,
        uint paidMakerFee,
        uint paidTakerFee,
        bytes32 indexed tokens, // keccak256(makerToken, takerToken), allows subscribing to a token pair
        bytes32 orderHash
    );
    event LogCancel(
        address indexed maker,
        address indexed feeRecipient,
        address makerToken,
        address takerToken,
        uint cancelledMakerTokenAmount,
        uint cancelledTakerTokenAmount,
        bytes32 indexed tokens,
        bytes32 orderHash
    );
    event LogError(uint8 indexed errorId, bytes32 indexed orderHash);
}

event_read_0xprotocol.go

package main
import (
    "context"
    "fmt"
    "log"
    "math/big"
    "strconv"
    "strings"
    exchange "./contracts_0xprotocol" // for demo
    "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/accounts/abi"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/common/hexutil"
    "github.com/ethereum/go-ethereum/ethclient"
)
// LogFill ...
type LogFill struct {
    Maker                  common.Address
    Taker                  common.Address
    FeeRecipient           common.Address
    MakerToken             common.Address
    TakerToken             common.Address
    FilledMakerTokenAmount *big.Int
    FilledTakerTokenAmount *big.Int
    PaidMakerFee           *big.Int
    PaidTakerFee           *big.Int
    Tokens                 [32]byte
    OrderHash              [32]byte
}
// LogCancel ...
type LogCancel struct {
    Maker                     common.Address
    FeeRecipient              common.Address
    MakerToken                common.Address
    TakerToken                common.Address
    CancelledMakerTokenAmount *big.Int
    CancelledTakerTokenAmount *big.Int
    Tokens                    [32]byte
    OrderHash                 [32]byte
}
// LogError ...
type LogError struct {
    ErrorID   uint8
    OrderHash [32]byte
}
func main() {
    client, err := ethclient.Dial("https://mainnet.infura.io")
    if err != nil {
        log.Fatal(err)
    }
    // 0x Protocol Exchange smart contract address
    contractAddress := common.HexToAddress("0x12459C951127e0c374FF9105DdA097662A027093")
    query := ethereum.FilterQuery{
        FromBlock: big.NewInt(6383482),
        ToBlock:   big.NewInt(6383488),
        Addresses: []common.Address{
            contractAddress,
        },
    }
    logs, err := client.FilterLogs(context.Background(), query)
    if err != nil {
        log.Fatal(err)
    }
    contractAbi, err := abi.JSON(strings.NewReader(string(exchange.ExchangeABI)))
    if err != nil {
        log.Fatal(err)
    }
    // NOTE: keccak256("LogFill(address,address,address,address,address,uint256,uint256,uint256,uint256,bytes32,bytes32)")
    logFillEvent := common.HexToHash("0d0b9391970d9a25552f37d436d2aae2925e2bfe1b2a923754bada030c498cb3")
    // NOTE: keccak256("LogCancel(address,address,address,address,uint256,uint256,bytes32,bytes32)")
    logCancelEvent := common.HexToHash("67d66f160bc93d925d05dae1794c90d2d6d6688b29b84ff069398a9b04587131")
    // NOTE: keccak256("LogError(uint8,bytes32)")
    logErrorEvent := common.HexToHash("36d86c59e00bd73dc19ba3adfe068e4b64ac7e92be35546adeddf1b956a87e90")
    for _, vLog := range logs {
        fmt.Printf("Log Block Number: %d\n", vLog.BlockNumber)
        fmt.Printf("Log Index: %d\n", vLog.Index)
        switch vLog.Topics[0].Hex() {
        case logFillEvent.Hex():
            fmt.Printf("Log Name: LogFill\n")
            var fillEvent LogFill
            err := contractAbi.Unpack(&fillEvent, "LogFill", vLog.Data)
            if err != nil {
                log.Fatal(err)
            }
            fillEvent.Maker = common.HexToAddress(vLog.Topics[1].Hex())
            fillEvent.FeeRecipient = common.HexToAddress(vLog.Topics[2].Hex())
            fillEvent.Tokens = vLog.Topics[3]
            fmt.Printf("Maker: %s\n", fillEvent.Maker.Hex())
            fmt.Printf("Taker: %s\n", fillEvent.Taker.Hex())
            fmt.Printf("Fee Recipient: %s\n", fillEvent.FeeRecipient.Hex())
            fmt.Printf("Maker Token: %s\n", fillEvent.MakerToken.Hex())
            fmt.Printf("Taker Token: %s\n", fillEvent.TakerToken.Hex())
            fmt.Printf("Filled Maker Token Amount: %s\n", fillEvent.FilledMakerTokenAmount.String())
            fmt.Printf("Filled Taker Token Amount: %s\n", fillEvent.FilledTakerTokenAmount.String())
            fmt.Printf("Paid Maker Fee: %s\n", fillEvent.PaidMakerFee.String())
            fmt.Printf("Paid Taker Fee: %s\n", fillEvent.PaidTakerFee.String())
            fmt.Printf("Tokens: %s\n", hexutil.Encode(fillEvent.Tokens[:]))
            fmt.Printf("Order Hash: %s\n", hexutil.Encode(fillEvent.OrderHash[:]))
        case logCancelEvent.Hex():
            fmt.Printf("Log Name: LogCancel\n")
            var cancelEvent LogCancel
            err := contractAbi.Unpack(&cancelEvent, "LogCancel", vLog.Data)
            if err != nil {
                log.Fatal(err)
            }
            cancelEvent.Maker = common.HexToAddress(vLog.Topics[1].Hex())
            cancelEvent.FeeRecipient = common.HexToAddress(vLog.Topics[2].Hex())
            cancelEvent.Tokens = vLog.Topics[3]
            fmt.Printf("Maker: %s\n", cancelEvent.Maker.Hex())
            fmt.Printf("Fee Recipient: %s\n", cancelEvent.FeeRecipient.Hex())
            fmt.Printf("Maker Token: %s\n", cancelEvent.MakerToken.Hex())
            fmt.Printf("Taker Token: %s\n", cancelEvent.TakerToken.Hex())
            fmt.Printf("Cancelled Maker Token Amount: %s\n", cancelEvent.CancelledMakerTokenAmount.String())
            fmt.Printf("Cancelled Taker Token Amount: %s\n", cancelEvent.CancelledTakerTokenAmount.String())
            fmt.Printf("Tokens: %s\n", hexutil.Encode(cancelEvent.Tokens[:]))
            fmt.Printf("Order Hash: %s\n", hexutil.Encode(cancelEvent.OrderHash[:]))
        case logErrorEvent.Hex():
            fmt.Printf("Log Name: LogError\n")
            errorID, err := strconv.ParseInt(vLog.Topics[1].Hex(), 16, 64)
            if err != nil {
                log.Fatal(err)
            }
            errorEvent := &LogError{
                ErrorID:   uint8(errorID),
                OrderHash: vLog.Topics[2],
            }
            fmt.Printf("Error ID: %d\n", errorEvent.ErrorID)
            fmt.Printf("Order Hash: %s\n", hexutil.Encode(errorEvent.OrderHash[:]))
        }
        fmt.Printf("\n\n")
    }
}

这些示例使用的solc版本

$ solc --version
0.4.11+commit.68ef5810.Emscripten.clang