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200行代碼實(shí)現(xiàn)blockchain 區(qū)塊鏈實(shí)例詳解

 更新時(shí)間：2018年03月14日 09:35:42   作者：曹紀(jì)乾  
這篇文章主要介紹了200行代碼實(shí)現(xiàn)blockchain 區(qū)塊鏈的相關(guān)知識(shí)，非常不錯(cuò)，具有參考借鑒價(jià)值，需要的朋友參考下吧

了解blockchain的概念很簡(jiǎn)單（區(qū)塊鏈，交易鏈塊）：它是分布式的（即不是放置在同一臺(tái)機(jī)器上，不同的網(wǎng)絡(luò)設(shè)備上的）數(shù)據(jù)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?cè)噲D幫他解決了目標(biāo) - 在人們心中的那一刻，這個(gè)詞是相當(dāng)強(qiáng)烈的交易，合同或智能cryptocurrency的概念有關(guān)。

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(shí)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(jiǎn)單模型。這個(gè)項(xiàng)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(biāo)準(zhǔn)的ECMAScript 6。
塊結(jié)構(gòu)

第一步 - 確定應(yīng)包含塊的元素。為簡(jiǎn)單起見，我們只包括最必要的：先前塊的指數(shù)（指數(shù)），時(shí)間標(biāo)記（時(shí)間戳），數(shù)據(jù)（數(shù)據(jù)），散列和散列，要錄制，以保持電路的結(jié)構(gòu)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?jǐn)?shù)據(jù)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(guān)的開采，因?yàn)樵谶@種情況下，我們并沒有用表現(xiàn)證明實(shí)施保護(hù)。

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

產(chǎn)生單元

要生成塊，我們需要知道前一個(gè)塊的哈希，使我們?cè)诮Y(jié)構(gòu)已經(jīng)確定了元素的其余部分。數(shù)據(jù)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(chǔ)單元

使用blockchain 存儲(chǔ)陣列。第一個(gè)塊總是硬編碼“創(chuàng)世紀(jì)塊”。

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

確認(rèn)塊的完整性

我們必須始終能夠確認(rèn)單元或電路的完整性。尤其是當(dāng)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(fā)生沖突的情況下（例如，兩個(gè)節(jié)點(diǎn)同時(shí)在同一生成的塊和相同數(shù)量），我們選擇電路，其中包含的塊的數(shù)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(wǎng)絡(luò)節(jié)點(diǎn)

該網(wǎng)站的一個(gè)組成部分 - 與其他節(jié)點(diǎn)的數(shù)據(jù)交換。下列規(guī)則用于維護(hù)網(wǎng)絡(luò)同步：
當(dāng)一個(gè)節(jié)點(diǎn)產(chǎn)生新的單元，它會(huì)報(bào)告給網(wǎng)絡(luò);
當(dāng)本機(jī)連接到新的盛宴，他要求有關(guān)最后生成的塊信息;
當(dāng)一個(gè)節(jié)點(diǎn)正面臨著一個(gè)塊，其中有一個(gè)指標(biāo)比他還大，他增加了一個(gè)塊到電路或請(qǐng)求的完整鏈條的信息。
自動(dòng)搜索同齡人不執(zhí)行，所有環(huán)節(jié)都手動(dòng)添加。

單元的控制

用戶應(yīng)該能夠以某種方式控制節(jié)點(diǎn)，通過將HTTP服務(wù)器解決。當(dāng)與節(jié)點(diǎn)相互作用有以下功能：
打印所有單元的列表;
創(chuàng)建用戶生成內(nèi)容的新單元;
打印列表，或添加的節(jié)日。
互動(dòng)的最直接的方式 - 通過卷曲：

一個(gè)節(jié)點(diǎn)上的所有塊＃名單

curl http://localhost:3001/blocks

架構(gòu)

值得注意的是，該網(wǎng)站是指兩個(gè)Web服務(wù)器：HTTP進(jìn)行用戶控制的裝置和向所述的WebSocket HTTP來安裝節(jié)點(diǎn)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(jié)

以上所述是小編給大家介紹的200行代碼實(shí)現(xiàn)blockchain 區(qū)塊鏈實(shí)例詳解，希望對(duì)大家有所幫助，如果大家有任何疑問請(qǐng)給我留言，小編會(huì)及時(shí)回復(fù)大家的。在此也非常感謝大家對(duì)腳本之家網(wǎng)站的支持！

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