​​区块链持久化--golang实现区块链系列之三

本篇使用boltdb的简易数据库将区块链的数据持久化到一个文件中。boltdb是kv形式保存的。
下面代码：

package main

import (
    "github.com/boltdb/bolt"
    "os"
)

const dbfile  = "blockchain.db"
const blockBucket  = "block_demo"
const lastHashKey  = "genesis"

type BlockChian struct {
    //blocks []*Block
    db *bolt.DB
    lastHash []byte
}

func NewBlockChain() *BlockChian {
    //return &Blo ckChian{[]*Block{NewGenesisBlock()}}
    //func Open(path string, mode os.FileMode, options *Options) (*DB, error) {
    //  var db = &DB{opened: true}

    db, err := bolt.Open(dbfile, 7777, nil)
    CheckErr(err)
    var lasthash []byte
    //db.View()
    db.Update(func(tx *bolt.Tx) error {
        bucket := tx.Bucket([]byte(blockBucket))

        if bucket != nil {
            //读取lasthash
            lasthash = bucket.Get([]byte(lastHashKey))
        } else {
            // 1.创建bucket
            // 2. 创世区块
            genesis := NewGenesisBlock()
            bucket, err := tx.CreateBucket([]byte(blockBucket))
            CheckErr(err)

            err = bucket.Put(genesis.Hash, genesis.Serialize())
            CheckErr(err)
            lasthash = genesis.Hash
            err = bucket.Put([]byte(lastHashKey), genesis.Hash)
            CheckErr(err)
        }
        return nil
    })

    return &BlockChian{db:db, lastHash:lasthash}

}


func (bc *BlockChian)AddBlock(data string) {
    //var prevBlockHash  []byte
    /*err := bc.db.View(func(tx *bolt.Tx) error {
        bucket := tx.Bucket([]byte(blockBucket))
        lasthash := bucket.Get([]byte(lastHashKey))
        prevBlockHash = lasthash
        return nil
    })*/


    block := NewBlock(data, bc.lastHash)

    err := bc.db.Update(func(tx *bolt.Tx) error {
        bucket := tx.Bucket([]byte(blockBucket))
        err := bucket.Put(block.Hash, block.Serialize())
        CheckErr(err)

        err = bucket.Put([]byte(lastHashKey), block.Hash)
        CheckErr(err)
        return nil
    })

    CheckErr(err)
}

type BlockChainIterator struct {
    db *bolt.DB
    currentHash []byte
}


func (bc *BlockChian)Iterator() *BlockChainIterator {
    return &BlockChainIterator{bc.db, bc.lastHash}
}

func (it *BlockChainIterator)Next() *Block  {
    var block *Block


    err := it.db.View(func(tx *bolt.Tx) error {
        bucket := tx.Bucket([]byte(blockBucket))
        if bucket == nil {
            os.Exit(1)
        }

        blockTmp := bucket.Get(it.currentHash)
        block = Deserialize(blockTmp)

        it.currentHash = block.PrevBlockHash
        return nil

    })

    CheckErr(err)
    return block
}

boltdb是key-value形式的数据库， 所以，区块链保存hash当做key, 区块链的内容当做value进行保存。

上面有一个特殊不变的key保存最后一个区块的hash。

先获取最后区块的hash，就可以获取到区块的数据，获取数据就可以获取前一个区块的hash，以此递推，可以获取所有区块的数据。

命令行工具：

package main

import (
    "flag"
    "fmt"
    "os"
)

const Usage  = `
    addBlock --data DATA  "add a block to block chain"
    printChain            "print all blocks"
`

type CLI struct {
    bc *BlockChian
}

func (cli *CLI)Run()  {
    if len(os.Args) < 2 {
        fmt.Println("too few parameters!\n", Usage)
        os.Exit(1)
    }
    
    addBlockCmd := flag.NewFlagSet("addBlock", flag.ExitOnError)
    printChainCmd := flag.NewFlagSet("printChain", flag.ExitOnError)
    
    addBlockCmdPara := addBlockCmd.String("data", "", "block info")

    switch os.Args[1] {
    case "addBlock":
        err := addBlockCmd.Parse(os.Args[2:])
        CheckErr(err)
        if addBlockCmd.Parsed() {
            if *addBlockCmdPara == "" {
                fmt.Println("data is empty")
                os.Exit(1)
            }
            cli.AddBlock(*addBlockCmdPara)
        }
    case "printChain":
        err := printChainCmd.Parse(os.Args[2:])
        CheckErr(err)
        if printChainCmd.Parsed() {
            cli.PrintChain()
        }
    default:
        fmt.Println("invalid cmd\n", Usage)
        os.Exit(1)

    
    }
    
}

package main

import "fmt"

func (cli *CLI)AddBlock(data string)  {
    cli.bc.AddBlock(data)
}


func (cli *CLI)PrintChain()  {
    bc := cli.bc
    it := bc.Iterator()
    for {
        // 取回当前hash指定的block，并且将当前的hash指向上一个区块的hash
        block := it.Next()

        fmt.Println("data:", string(block.Data))
        fmt.Println("Version:", block.Version)
        fmt.Printf("Hash:%x\n", block.Hash)
        fmt.Printf("TimeStamp:%d\n", block.TimeStamp)
        fmt.Printf("MerkeRoot:%x\n", block.MerkeRoot)
        fmt.Printf("Nonce:%d\n", block.Nonce)
        fmt.Printf("preblock Hash:%x\n", block.PrevBlockHash)
        println("  ")

        pow := NewProofOfWork(block)
        fmt.Println("Vaild:", pow.IsVaild())

        if len(block.PrevBlockHash) == 0 {
            break
        }


    }
}

终端执行效果：