200行代码实现blockchain 区块链实例详解

class Block {   constructor(index, previousHash, timestamp, data, hash) {     this.index = index;     this.previousHash = previousHash.toString();     this.timestamp = timestamp;     this.data = data;     this.hash = hash.toString();   } }

var calculateHash = (index, previousHash, timestamp, data) => {   return CryptoJS.SHA256(index + previousHash + timestamp + data).toString(); }; 

var generateNextBlock = (blockData) => {   var previousBlock = getLatestBlock();   var nextIndex = previousBlock.index + 1;   var nextTimestamp = new Date().getTime() / 1000;   var nextHash = calculateHash(nextIndex, previousBlock.hash, nextTimestamp, blockData);   return new Block(nextIndex, previousBlock.hash, nextTimestamp, blockData, nextHash); }; 

var getGenesisBlock = () => {   return new Block(0, "0", 1465154705, "my genesis block!!", "816534932c2b7154836da6afc367695e6337db8a921823784c14378abed4f7d7"); }; var blockchain = [getGenesisBlock()]; 

var isValidNewBlock = (newBlock, previousBlock) => {   if (previousBlock.index + 1 !== newBlock.index) {     console.log('invalid index');     return false;   } else if (previousBlock.hash !== newBlock.previousHash) {     console.log('invalid previoushash');     return false;   } else if (calculateHashForBlock(newBlock) !== newBlock.hash) {     console.log(typeof (newBlock.hash) + ' ' + typeof calculateHashForBlock(newBlock));     console.log('invalid hash: ' + calculateHashForBlock(newBlock) + ' ' + newBlock.hash);     return false;   }   return true; }; 

var replaceChain = (newBlocks) => {   if (isValidChain(newBlocks) && newBlocks.length > blockchain.length) {     console.log('Received blockchain is valid. Replacing current blockchain with received blockchain');     blockchain = newBlocks;     broadcast(responseLatestMsg());   } else {     console.log('Received blockchain invalid');   } }; 

<span style="font-family:Arial, Helvetica, sans-serif;">'use strict';</span> var CryptoJS = require("crypto-js"); var express = require("express"); var bodyParser = require('body-parser'); var WebSocket = require("ws"); var http_port = process.env.HTTP_PORT || 3001; var p2p_port = process.env.P2P_PORT || 6001; var initialPeers = process.env.PEERS ? process.env.PEERS.split(',') : []; class Block {   constructor(index, previousHash, timestamp, data, hash) {     this.index = index;     this.previousHash = previousHash.toString();     this.timestamp = timestamp;     this.data = data;     this.hash = hash.toString();   } } var sockets = []; var MessageType = {   QUERY_LATEST: 0,   QUERY_ALL: 1,   RESPONSE_BLOCKCHAIN: 2 }; var getGenesisBlock = () => {   return new Block(0, "0", 1465154705, "my genesis block!!", "816534932c2b7154836da6afc367695e6337db8a921823784c14378abed4f7d7"); }; var blockchain = [getGenesisBlock()]; var initHttpServer = () => {   var app = express();   app.use(bodyParser.json());   app.get('/blocks', (req, res) => res.send(JSON.stringify(blockchain)));   app.post('/mineBlock', (req, res) => {     var newBlock = generateNextBlock(req.body.data);     addBlock(newBlock);     broadcast(responseLatestMsg());     console.log('block added: ' + JSON.stringify(newBlock));     res.send();   });   app.get('/peers', (req, res) => {     res.send(sockets.map(s => s._socket.remoteAddress + ':' + s._socket.remotePort));   });   app.post('/addPeer', (req, res) => {     connectToPeers([req.body.peer]);     res.send();   });   app.listen(http_port, () => console.log('Listening http on port: ' + http_port)); }; var initP2PServer = () => {   var server = new WebSocket.Server({port: p2p_port});   server.on('connection', ws => initConnection(ws));   console.log('listening websocket p2p port on: ' + p2p_port); }; var initConnection = (ws) => {   sockets.push(ws);   initMessageHandler(ws);   initErrorHandler(ws);   write(ws, queryChainLengthMsg()); }; var initMessageHandler = (ws) => {   ws.on('message', (data) => {     var message = JSON.parse(data);     console.log('Received message' + JSON.stringify(message));     switch (message.type) {       case MessageType.QUERY_LATEST:         write(ws, responseLatestMsg());         break;       case MessageType.QUERY_ALL:         write(ws, responseChainMsg());         break;       case MessageType.RESPONSE_BLOCKCHAIN:         handleBlockchainResponse(message);         break;     }   }); }; var initErrorHandler = (ws) => {   var closeConnection = (ws) => {     console.log('connection failed to peer: ' + ws.url);     sockets.splice(sockets.indexOf(ws), 1);   };   ws.on('close', () => closeConnection(ws));   ws.on('error', () => closeConnection(ws)); }; var generateNextBlock = (blockData) => {   var previousBlock = getLatestBlock();   var nextIndex = previousBlock.index + 1;   var nextTimestamp = new Date().getTime() / 1000;   var nextHash = calculateHash(nextIndex, previousBlock.hash, nextTimestamp, blockData);   return new Block(nextIndex, previousBlock.hash, nextTimestamp, blockData, nextHash); }; var calculateHashForBlock = (block) => {   return calculateHash(block.index, block.previousHash, block.timestamp, block.data); }; var calculateHash = (index, previousHash, timestamp, data) => {   return CryptoJS.SHA256(index + previousHash + timestamp + data).toString(); }; var addBlock = (newBlock) => {   if (isValidNewBlock(newBlock, getLatestBlock())) {     blockchain.push(newBlock);   } }; var isValidNewBlock = (newBlock, previousBlock) => {   if (previousBlock.index + 1 !== newBlock.index) {     console.log('invalid index');     return false;   } else if (previousBlock.hash !== newBlock.previousHash) {     console.log('invalid previoushash');     return false;   } else if (calculateHashForBlock(newBlock) !== newBlock.hash) {     console.log(typeof (newBlock.hash) + ' ' + typeof calculateHashForBlock(newBlock));     console.log('invalid hash: ' + calculateHashForBlock(newBlock) + ' ' + newBlock.hash);     return false;   }   return true; }; var connectToPeers = (newPeers) => {   newPeers.forEach((peer) => {     var ws = new WebSocket(peer);     ws.on('open', () => initConnection(ws));     ws.on('error', () => {       console.log('connection failed')     });   }); }; var handleBlockchainResponse = (message) => {   var receivedBlocks = JSON.parse(message.data).sort((b1, b2) => (b1.index - b2.index));   var latestBlockReceived = receivedBlocks[receivedBlocks.length - 1];   var latestBlockHeld = getLatestBlock();   if (latestBlockReceived.index > latestBlockHeld.index) {     console.log('blockchain possibly behind. We got: ' + latestBlockHeld.index + ' Peer got: ' + latestBlockReceived.index);     if (latestBlockHeld.hash === latestBlockReceived.previousHash) {       console.log("We can append the received block to our chain");       blockchain.push(latestBlockReceived);       broadcast(responseLatestMsg());     } else if (receivedBlocks.length === 1) {       console.log("We have to query the chain from our peer");       broadcast(queryAllMsg());     } else {       console.log("Received blockchain is longer than current blockchain");       replaceChain(receivedBlocks);     }   } else {     console.log('received blockchain is not longer than received blockchain. Do nothing');   } }; var replaceChain = (newBlocks) => {   if (isValidChain(newBlocks) && newBlocks.length > blockchain.length) {     console.log('Received blockchain is valid. Replacing current blockchain with received blockchain');     blockchain = newBlocks;     broadcast(responseLatestMsg());   } else {     console.log('Received blockchain invalid');   } }; var isValidChain = (blockchainToValidate) => {   if (JSON.stringify(blockchainToValidate[0]) !== JSON.stringify(getGenesisBlock())) {     return false;   }   var tempBlocks = [blockchainToValidate[0]];   for (var i = 1; i < blockchainToValidate.length; i++) {     if (isValidNewBlock(blockchainToValidate[i], tempBlocks[i - 1])) {       tempBlocks.push(blockchainToValidate[i]);     } else {       return false;     }   }   return true; }; var getLatestBlock = () => blockchain[blockchain.length - 1]; var queryChainLengthMsg = () => ({'type': MessageType.QUERY_LATEST}); var queryAllMsg = () => ({'type': MessageType.QUERY_ALL}); var responseChainMsg = () =>({   'type': MessageType.RESPONSE_BLOCKCHAIN, 'data': JSON.stringify(blockchain) }); var responseLatestMsg = () => ({   'type': MessageType.RESPONSE_BLOCKCHAIN,   'data': JSON.stringify([getLatestBlock()]) }); var write = (ws, message) => ws.send(JSON.stringify(message)); var broadcast = (message) => sockets.forEach(socket => write(socket, message)); connectToPeers(initialPeers); initHttpServer(); initP2PServer();