golang學習筆記19 用Golang實現以太坊代幣轉賬

golang學習筆記19 用Golang實現以太坊代幣轉賬

• 在以太坊區塊鏈中，我們稱代幣為Token，是以太坊區塊鏈中每個人都可以任意發行的數字資產。並且它必須是遵循erc20標准的，至於erc20標准，大家可以參考這篇文章 https://theethereum.wiki/w/index.php/ERC20_Token_Standard
• 它實際上一段智能合約代碼，智能合約代碼中必須要有以下的一些function 和 event。

contract ERC20 {
      function totalSupply() constant returns (uint totalSupply);
      function balanceOf(address _owner) constant returns (uint balance);
      function transfer(address _to, uint _value) returns (bool success);
      function transferFrom(address _from, address _to, uint _value) returns (bool success);
      function approve(address _spender, uint _value) returns (bool success);
      function allowance(address _owner, address _spender) constant returns (uint remaining);
      event Transfer(address indexed _from, address indexed _to, uint _value);
      event Approval(address indexed _owner, address indexed _spender, uint _value);
 }

• 能合約代碼是運行在以太坊智能合約虛擬機中的。文檔：https://solidity.readthedocs.io/en/latest/installing-solidity.html#building-from-source

• 我們看到上面那段類似golang中interface的代碼，里面分別包含了總量、余額、轉賬等方法。我們今天重點講的其實就是用golang來實現transfer、transferFrom方法。

連接以太坊RPC節點

• 目前廣泛使用的是go-ethereum，他的客戶端名是geth。你可以通過編譯、安裝等方式把節點搭建在你的電腦或者服務器中，並開啟rpc服務。本文省略這一步驟，網上有很文章供你了解。
• 附上github：https://github.com/ethereum/go-ethereum
• geth默認的rpc端口是8545，我使用默認端口，后面我們都用http://127.0.0.1:8545作為我們的rpc連接。

首先獲取go-ethereum代碼

• go get github.com/ethereum/go-ethereum
• 然后我們go-ethereum目錄，如果你的golang環境沒有問題，那么應該是這個路徑。
• cd $GOPATH/src/github.com/ethereum/go-ethereum
• 當你進入目錄，看到代碼已經完整拉取下來，那么我們就可以進行下一步了。

連接RPC節點

import (
    "github.com/ethereum/go-ethereum/rpc"
    "github.com/ethereum/go-ethereum/ethclient"
)
rpcDial, err := rpc.Dial("http://127.0.0.1:8545")
if err != nil {
	panic(err);	
}
client := ethclient.NewClient(rpcDial)

　　如果沒有panic，那么我們已經成功連接了

創建測試賬戶

• 要進行轉賬測試，那么我們需要兩個以太坊賬戶。我們用golang來生成，我們知道以太坊的賬戶私鑰是放在keystore文件中的，是一段json，並且創建的時候可以設置密碼。跟比特幣的wallet.dat文件是一樣的意思，不見哪一樣，你的資產就永遠留在區塊鏈網絡中，再也無法找回。
• 下面我們用代碼創建兩個以太坊賬戶。

import (
    "github.com/ethereum/go-ethereum/accounts/keystore"
)
ks := keystore.NewKeyStore("/", keystore.StandardScryptN, keystore.StandardScryptP)
address, _ := ks.NewAccount("password")
account, err := ks.Export(address, "password", "password")
if err != nil {
    panic(err)
}

• 從上面的代碼我們可以看到，創建了一個以太坊的賬戶，並且密碼設置為password，並導出。最終account變量就是賬戶的私鑰，是一段json文本。
• 通過address變量，我們可以獲得賬戶的地址。如 address.Address.Hex()

生成代幣文件

• 打開 cd $GOPATH/src/github.com/ethereum/go-ethereum/cmd/abigen 你能看到main.go文件

• 執行 go build main.go，會在目錄下生成一個main的二進制文件。

• 將以下的json 保存為token.abi，並放在當前目錄下。

[{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"bytes32"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"stop","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"guy","type":"address"},{"name":"wad","type":"uint256"}],"name":"approve","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"owner_","type":"address"}],"name":"setOwner","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"src","type":"address"},{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transferFrom","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"dst","type":"address"},{"name":"wad","type":"uint128"}],"name":"push","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"name_","type":"bytes32"}],"name":"setName","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"wad","type":"uint128"}],"name":"mint","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"src","type":"address"}],"name":"balanceOf","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"stopped","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"authority_","type":"address"}],"name":"setAuthority","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"src","type":"address"},{"name":"wad","type":"uint128"}],"name":"pull","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"wad","type":"uint128"}],"name":"burn","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"bytes32"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"dst","type":"address"},{"name":"wad","type":"uint256"}],"name":"transfer","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"start","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"authority","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"src","type":"address"},{"name":"guy","type":"address"}],"name":"allowance","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"inputs":[{"name":"symbol_","type":"bytes32"}],"payable":false,"type":"constructor"},{"anonymous":true,"inputs":[{"indexed":true,"name":"sig","type":"bytes4"},{"indexed":true,"name":"guy","type":"address"},{"indexed":true,"name":"foo","type":"bytes32"},{"indexed":true,"name":"bar","type":"bytes32"},{"indexed":false,"name":"wad","type":"uint256"},{"indexed":false,"name":"fax","type":"bytes"}],"name":"LogNote","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"authority","type":"address"}],"name":"LogSetAuthority","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"owner","type":"address"}],"name":"LogSetOwner","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"from","type":"address"},{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"owner","type":"address"},{"indexed":true,"name":"spender","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Approval","type":"event"}]

　　

• 執行命令 ./main --abi token.abi --pkg main --type Token --out token.go

• 我們可以看到目錄下生成了一個token.go文件。大功告成。

開始轉賬

• 首先就把上一步生成的token.go拖入項目中。

import (
    "github.com/ethereum/go-ethereum/accounts/abi/bind"
)
//首先導入上面生成的賬戶密鑰（json）和密碼
auth, err := bind.NewTransactor(strings.NewReader("json"), "password")
//這句用的是生成的token.go里面的方法
//client變量是我們第一步連接以太坊rpc節點的時候創建的
//contractAddress 是代幣地址，比如eos 的地址是0x86fa049857e0209aa7d9e616f7eb3b3b78ecfdb0
//那么我們轉賬針對的就是賬戶里的eos代幣
//具體看這里 https://etherscan.io/token/0x86fa049857e0209aa7d9e616f7eb3b3b78ecfdb0
token, err := NewToken(common.HexToAddress("0x86fa049857e0209aa7d9e616f7eb3b3b78ecfdb0"), client)
if err != nil {
    panic(err)
}
//每個代幣都會有相應的位數，例如eos是18位，那么我們轉賬的時候，需要在金額后面加18個0
decimal, err := token.Decimals(nil)
if err != nil {
    panic(err)
}
//這是處理位數的代碼段
tenDecimal := big.NewFloat(math.Pow(10, float64(decimal)))
convertAmount, _ := new(big.Float).Mul(tenDecimal, amount).Int(&big.Int{})
//然后就可以轉賬到你需要接受的賬戶上了
//toAddress 是接受eos的賬戶地址
txs, err := token.Transfer(auth, common.HexToAddress(toAddress), convertAmount)

　　到此轉賬就成功了。

https://golang.org/src/go/token/token.go

里面還有很多其他的方法