區塊鏈持久化--golang實現區塊鏈系列之三
摘要：
本篇使用boltdb的簡易資料庫將區塊鏈的資料持久化到一個檔案中。boltdb是kv形式儲存的。
下面程式碼：
package main
import (
"github.com/boltdb/bolt"
"os"
...
本篇使用boltdb的簡易資料庫將區塊鏈的資料持久化到一個檔案中。boltdb是kv形式儲存的。
下面程式碼：
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 {
//讀取lasthash
lasthash = bucket.Get([]byte(lastHashKey))
} else {
// 1.建立bucket
// 2. 創世區塊
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形式的資料庫， 所以，區塊鏈儲存hash當做key, 區塊鏈的內容當做value進行儲存。
上面有一個特殊不變的key儲存最後一個區塊的hash。
先獲取最後區塊的hash，就可以獲取到區塊的資料，獲取資料就可以獲取前一個區塊的hash，以此遞推，可以獲取所有區塊的資料。
命令列工具：
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 {
// 取回當前hash指定的block，並且將當前的hash指向上一個區塊的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
}
}
}
終端執行效果：
