blockchain.go

package main

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

const dbFile = "blockchain_demo.db"
const blocksBucket = "blocks"

type Blockchain struct {
	tip []byte
	db  *bolt.DB
}

func (bc *Blockchain) AddBlock(data string) {
	var lastHash []byte

	err := bc.db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(blocksBucket))
		lastHash = b.Get([]byte("l"))

		return nil
	})
	if err != nil {
		log.Panic(err)
	}

	newBlock := NewBlock(data, lastHash)

	err = bc.db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(blocksBucket))
		err := b.Put(newBlock.Hash, newBlock.Serialize())
		if err != nil {
			log.Panic(err)
		}

		err = b.Put([]byte("l"), newBlock.Hash)
		if err != nil {
			log.Panic(err)
		}

		bc.tip = newBlock.Hash

		return nil
	})
	if err != nil {
		log.Panic(err)
	}
}

func NewGenesisBlock() *Block {
	return NewBlock("Genesis Block", []byte{})
}

func NewBlockchain() *Blockchain {
	var tip []byte
	db, err := bolt.Open(dbFile, 0600, nil)
	if err != nil {
		log.Panic(err)
	}

	err = db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(blocksBucket))

		if b == nil {
			genesis := NewGenesisBlock()
			b, err := tx.CreateBucket([]byte(blocksBucket))
			if err != nil {
				log.Panic(err)
			}

			err = b.Put(genesis.Hash, genesis.Serialize())
			if err != nil {
				log.Panic(err)
			}

			err = b.Put([]byte("l"), genesis.Hash)
			if err != nil {
				log.Panic(err)
			}

			tip = genesis.Hash
		} else {
			tip = b.Get([]byte("l"))
		}

		return nil
	})

	bc := Blockchain{tip, db}

	return &bc
}

// blockchain.go in ex2.1~3

// package main

// type Blockchain struct {
// 	blocks []*Block
// }

// func (bc *Blockchain) AddBlock(data string) {
// 	//可能用到的函数：
// 	//	len(array)：获取数组长度
// 	//	append(array,b):将元素b添加至数组array末尾
// 	if(len(bc.blocks) == 0){
// 		bc.blocks = append(bc.blocks, NewGenesisBlock())
// 	} else {
// 		bc.blocks = append(bc.blocks, NewBlock(data, bc.blocks[len(bc.blocks)-1].Hash))
// 	}
// }

// func NewGenesisBlock() *Block {
// 	//创世区块前置哈希为空，Data为"Genesis Block"
// 	return NewBlock("Genesis Block", []byte{})
// }

// func NewBlockchain() *Blockchain {
// 	return &Blockchain{[]*Block{NewGenesisBlock()}}
// }