Building a blockchain with Javascript : Part 3
Part 3 : Miner Rewards & transaction - Blockchain in Javascript
해당 포스트는 Savjee youtube를 참고하여 작성하였다.
이번 포스트에서는 miner reward와 tranaction을 구현해보도록 하겠다.
Transaction
Block 클래스의 멤버 변수 data를 transaction으로 수정하고 멤버 변수 index는 불필요하므로 제거한다. Blockchain 클래스에서 Genesis Block을 생성하는 createGenesisBlock 함수에서도 멤버 변수 index에게 넘겨주는 값 0을 제거한다. 다음은 수정 후의 소스코드이다.
class Block {
constructor(timestamp, transactions, previousHash = '') {
this.timestamp = timestamp;
this.transactions = transactions;
this.previousHash = previousHash;
this.hash = this.calculateHash();
this.nonce = 0;
}
calculateHash() {
return SHA256(this.timestamp + JSON.stringify(this.transactions) + this.previousHash + this.nonce).toString();
}
mineBlock(difficulty) {
while(this.hash.substring(0, difficulty) != Array(difficulty + 1).join("0")) {
this.nonce++;
this.hash = this.calculateHash();
}
console.log("Block mined: " + this.hash);
}
}
class Blockchain {
constructor() {
this.chain = [this.createGenesisBlock()];
this.difficulty = 2;
}
createGenesisBlock() {
return new Block("2018/01/01", "Genesis Block", "0");
}
getLatestBlock() {
return this.chain[this.chain.length - 1];
}
addBlock(newBlock) {
newBlock.previousHash = this.getLatestBlock().hash;
newBlock.mineBlock(this.difficulty);
this.chain.push(newBlock);
}
isCoinValid() {
for(let i = 1; i < this.chain.length; i++) {
let currentBlock = this.chain[i];
let previousBlock = this.chain[i - 1];
if(currentBlock.hash != currentBlock.calculateHash()) {
return false;
}
if(currentBlock.previousHash != previousBlock.hash) {
return false;
}
}
return true;
}
}
Transaction 클래스를 생성한다. Transaction 클래스에는 보내는 주소(fromAddress), 받는 주소(toAddress), 금액(amount)가 존재한다.
class Transaction {
constructor(fromAddress, toAddress, amount) {
this.fromAddress = fromAddress;
this.toAddress = toAddress;
this.amount = amount;
}
}
Rewards
Blockchain 클래스에서는 트랜젝션을 저장하는 pendingTransactions과 마이너에게 제공되는 보상인 miningReward가 추가된다.
constructor() {
this.chain = [this.createGenesisBlock()];
this.difficulty = 2;
this.pendingTransactions = [];
this.miningReward = 100;
}
Blockchain 클래스에서 addBlock 함수를 제거하고 minePendingTransactions 함수로 대체한다. 기존 addBlock 함수에서 체인에 블록을 추가하는 기능에 마이너에게 제공되는 초기 보상이 포함된 트랜젝션을 추가하는 기능이 추가되었다.
minePendingTransactions(miningRewardAddress) {
this.pendingTransactions = [
new Transaction(null, miningRewardAddress, this.miningReward)
];
let block = new Block(Date.now(), this.pendingTransactions);
block.mineBlock(this.difficulty);
console.log("Block successfully mind!");
this.chain.push(block);
}
Blockchain 클래스에서 트랜젝션을 추가하는 함수와 잔돈을 계산하는 함수를 구현한다.
createTransaction(transaction) {
this.pendingTransactions.push(transaction);
}
getBalanceOfAddress(address) {
let balance = 0;
for(const block of this.chain) {
for(const trans of block.transactions) {
if(trans.fromAddress == address) {
balance -= trans.amount;
}
if(trans.toAddress == address) {
balance += trans.amount;
}
}
}
return balance;
}
지금까지 완성한 소스코드는 다음과 같다.
const SHA256 = require('crypto-js/sha256');
class Transaction {
constructor(fromAddress, toAddress, amount) {
this.fromAddress = fromAddress;
this.toAddress = toAddress;
this.amount = amount;
}
}
class Block {
constructor(timestamp, transactions, previousHash = '') {
this.timestamp = timestamp;
this.transactions = transactions;
this.previousHash = previousHash;
this.hash = this.calculateHash();
this.nonce = 0;
}
calculateHash() {
return SHA256(this.timestamp + JSON.stringify(this.transactions) + this.previousHash + this.nonce).toString();
}
mineBlock(difficulty) {
while(this.hash.substring(0, difficulty) != Array(difficulty + 1).join("0")) {
this.nonce++;
this.hash = this.calculateHash();
}
console.log("Block mined: " + this.hash);
}
}
class Blockchain {
constructor() {
this.chain = [this.createGenesisBlock()];
this.difficulty = 2;
this.pendingTransactions = [];
this.miningReward = 100;
}
createGenesisBlock() {
return new Block("2018/01/01", "Genesis Block", "0");
}
getLatestBlock() {
return this.chain[this.chain.length - 1];
}
minePendingTransactions(miningRewardAddress) {
this.pendingTransactions = [
new Transaction(null, miningRewardAddress, this.miningReward)
];
let block = new Block(Date.now(), this.pendingTransactions);
block.mineBlock(this.difficulty);
console.log("Block successfully mind!");
this.chain.push(block);
}
createTransaction(transaction) {
this.pendingTransactions.push(transaction);
}
getBalanceOfAddress(address) {
let balance = 0;
for(const block of this.chain) {
for(const trans of block.transactions) {
if(trans.fromAddress == address) {
balance -= trans.amount;
}
if(trans.toAddress == address) {
balance += trans.amount;
}
}
}
return balance;
}
isCoinValid() {
for(let i = 1; i < this.chain.length; i++) {
let currentBlock = this.chain[i];
let previousBlock = this.chain[i - 1];
if(currentBlock.hash != currentBlock.calculateHash()) {
return false;
}
if(currentBlock.previousHash != previousBlock.hash) {
return false;
}
}
return true;
}
}
Test
let coin = new Blockchain();
console.log("\n Start the miner...");
coin.minePendingTransactions('frodo-address');
console.log("Balance of frodo is " + coin.getBalanceOfAddress('frodo-address'));
console.log("\n Start the miner again...");
coin.minePendingTransactions('frodo-address');
console.log("Balance of frodo is " + coin.getBalanceOfAddress('frodo-address'));
console.log("\n Start the miner again...");
coin.minePendingTransactions('frodo-address');
console.log("Balance of frodo is " + coin.getBalanceOfAddress('frodo-address'));
console.log("\n Sending Transactions...");
coin.createTransaction(new Transaction("frodo-address", "anna-address", 100));
coin.createTransaction(new Transaction("anna-address", "bob-address", 50));
console.log("Balance of frodo is " + coin.getBalanceOfAddress('frodo-address'));
console.log("Balance of anna is " + coin.getBalanceOfAddress('anna-address'));
console.log("Balance of bob is " + coin.getBalanceOfAddress('bob-address'));
이번 포스트에서 구현한 전체 소스코드는 여기에서 확인할 수 있다.