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 mainimport ( "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}

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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 mainimport ( "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 mainimport "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 } }}

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终端执行效果：