200行程式碼實現blockchain 區塊鏈例項詳解

200行程式碼實現blockchain 區塊鏈例項詳解
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瞭解blockchain的概念很簡單(區塊鏈,交易鏈塊):它是分散式的(即不是放置在同一臺機器上,不同的網路裝置上的)資料庫支援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,合同或智慧cryptocurrency的概念有關。

只有在這裡blockchain – 是不是一回事比特幣,並理解鏈塊的基本知識比它似乎更容易,尤其是在,它是基於原始碼的情況下。在本文中,我們提出了建立與在JavaScript中200行程式碼的簡單模型。這個專案,我們稱之為NaiveChain的原始碼,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),資料(資料),雜湊和雜湊,要錄製,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(); 
} 
}

 雜湊單元

雜湊塊需要保持資料的完整性。在我們的例子,這適用於演算法SHA-256。這種型別的雜湊是不相關的開採,因為在這種情況下,我們並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雜湊,使我們在結構已經確定了元素的其餘部分。資料由終端使用者提供。


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); 
}; 

儲存單元

使用blockchain 儲存陣列。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,但是在發生衝突的情況下(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'); 
} 
}; 

訊息到其它網路節點

該網站的一個組成部分 – 與其他節點的資料交換。下列規則用於維護網路同步:
當一個節點產生新的單元,它會報告給網路;
當本機連線到新的盛宴,他要求有關最後生成的塊資訊;
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資訊。
自動搜尋同齡人不執行,所有環節都手動新增。

單元的控制

使用者應該能夠以某種方式控制節點,通過將HTTP伺服器解決。當與節點相互作用有以下功能:
列印所有單元的列表;
建立使用者生成內容的新單元;
列印列表,或新增的節日。
互動的最直接的方式 – 通過捲曲:

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伺服器:HTTP進行使用者控制的裝置和向所述的WebSocket HTTP來安裝節點之間的P2P連線。

如下為js 200行程式碼


<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行程式碼實現blockchain 區塊鏈例項詳解,希望對大家有所幫助,如果大家有任何疑問請給我留言,小編會及時回覆大家的。在此也非常感謝大家對指令碼之家網站的支援!

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