220723

• blockchain

package main

import (
	"crypto/sha256"
	"fmt"
)

type block struct {
	data     string
	hash     string
	prevHash string
}

type blockchain struct {
	blocks []block
}

func (b *blockchain) getLastHash() string {
	if len(b.blocks) > 0 {
		return b.blocks[len(b.blocks)-1].hash
	}
	return ""
}

func (b *blockchain) addBlock(data string) {
	newBlock := block{data, "", b.getLastHash()}
	hash := sha256.Sum256([]byte(newBlock.data + newBlock.prevHash))
	newBlock.hash = fmt.Sprintf("%x", hash)
	b.blocks = append(b.blocks, newBlock)
}

func (b *blockchain) listBlocks() {
	for _, block := range b.blocks {
		fmt.Printf("Data: %s\n", block.data)
		fmt.Printf("Hash: %s\n", block.hash)
		fmt.Printf("PrevHash: %s\n", block.prevHash)
	}
}

func main() {
	chain := blockchain{}
	chain.addBlock("Genesis Block")
	chain.addBlock("Second Block")
	chain.addBlock("Third Block")
	chain.listBlocks()
}

• refactoring

package main

import (
	"fmt"

	"github.com/nomadcoders/nomadcoin/blockchain"
)

func main() {
	chain := blockchain.GetBlockchain()
	chain.AddBlock("Second Block")
	chain.AddBlock("Third Block")

	chain.AllBlocks()
	for _, block := range chain.AllBlocks() {
		fmt.Printf("%s\n", block.Data)
		fmt.Printf("%s\n", block.Hash)
		fmt.Printf("%s\n", block.PrevHash)
	}
}

package blockchain

import (
	"crypto/sha256"
	"fmt"
	"sync"
)

type block struct {
	Data     string
	Hash     string
	PrevHash string
}

type blockchain struct {
	blocks []*block
}

var b *blockchain
var once sync.Once

func (b *block) calculateHash() {
	hash := sha256.Sum256([]byte(b.Data + b.PrevHash))
	b.Hash = fmt.Sprintf("%x", hash)
}

func getLastHash() string {
	totalBlocks := len(GetBlockchain().blocks)
	if totalBlocks == 0 {
		return ""
	}
	return GetBlockchain().blocks[totalBlocks-1].Hash
}

func createBlock(data string) *block {
	newBlock := block{data, "", getLastHash()}
	newBlock.calculateHash()
	return &newBlock
}

func (b *blockchain) AddBlock(data string) {
	b.blocks = append(b.blocks, createBlock(""))
}

func GetBlockchain() *blockchain {
	if b == nil {
		once.Do(func() {
			b = &blockchain{}
			b.blocks = append(b.blocks, createBlock("Genesis Block"))
			b.AddBlock("Genesis")
		})
	}
	return b
}

func (b *blockchain) AllBlocks() []*block {
	return b.blocks
}