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200行代碼實現blockchain 區塊鏈實例詳解

2019-11-19 14:10:31
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了解blockchain的概念很簡單(區塊鏈,交易鏈塊):它是分布式的(即不是放置在同一臺機器上,不同的網絡設備上的)數據庫支持主辦記錄日益增長的名單。但是,這也是容易混淆blockchain與我們試圖幫他解決了目標 - 在人們心中的那一刻,這個詞是相當強烈的交易,合同或智能cryptocurrency的概念有關。

只有在這里blockchain - 是不是一回事比特幣,并理解鏈塊的基本知識比它似乎更容易,尤其是在,它是基于源代碼的情況下。在本文中,我們提出了建立與在JavaScript中200行代碼的簡單模型。這個項目,我們稱之為NaiveChain的源代碼,可以在GitHub上找到。第1部分和第2部分:如果您需要刷上它的功能,使用我們的備忘單,我們將使用標準的ECMAScript 6。
塊結構

第一步 - 確定應包含塊的元素。為簡單起見,我們只包括最必要的:先前塊的指數(指數),時間標記(時間戳),數據(數據),散列和散列,要錄制,以保持電路的結構完整性。

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();   } }

 散列單元

哈希塊需要保持數據的完整性。在我們的例子,這適用于算法SHA-256。這種類型的散列是不相關的開采,因為在這種情況下,我們并沒有用表現證明實施保護。

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

產生單元

要生成塊,我們需要知道前一個塊的哈希,使我們在結構已經確定了元素的其余部分。數據由最終用戶提供。

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); }; 

存儲單元

使用blockchain 存儲陣列。第一個塊總是硬編碼“創世紀塊”。

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

確認塊的完整性

我們必須始終能夠確認單元或電路的完整性。尤其是當你從其他單位新的單位,必須決定是否接受它們。

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; }; 

選擇鏈最長的

在電路塊的順序必須被明確指定,但是在發生沖突的情況下(例如,兩個節點同時在同一生成的塊和相同數量),我們選擇電路,其中包含的塊的數量較多。

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');   } }; 

消息到其它網絡節點

該網站的一個組成部分 - 與其他節點的數據交換。下列規則用于維護網絡同步:
當一個節點產生新的單元,它會報告給網絡;
當本機連接到新的盛宴,他要求有關最后生成的塊信息;
當一個節點正面臨著一個塊,其中有一個指標比他還大,他增加了一個塊到電路或請求的完整鏈條的信息。
自動搜索同齡人不執行,所有環節都手動添加。

單元的控制

用戶應該能夠以某種方式控制節點,通過將HTTP服務器解決。當與節點相互作用有以下功能:
打印所有單元的列表;
創建用戶生成內容的新單元;
打印列表,或添加的節日。
互動的最直接的方式 - 通過卷曲:

一個節點上的所有塊#名單

curl http://localhost:3001/blocks

架構

值得注意的是,該網站是指兩個Web服務器:HTTP進行用戶控制的裝置和向所述的WebSocket HTTP來安裝節點之間的P2P連接。

如下為js 200行代碼

<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(); 

總結

以上所述是小編給大家介紹的200行代碼實現blockchain 區塊鏈實例詳解,希望對大家有所幫助,如果大家有任何疑問請給我留言,小編會及時回復大家的。在此也非常感謝大家對武林網網站的支持!

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