javascript
blockchain 区块链200行代码：在JavaScript实现的一个简单的例子
blockchain 區塊鏈200行代碼：在JavaScript實現的一個簡單的例子
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。
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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。
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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();
}
}
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散列單元
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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。
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var calculateHash = (index, previousHash, timestamp, data) => {
return CryptoJS.SHA256(index + previousHash + timestamp + data).toString();
};
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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。
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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);
};
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存儲單元
使用blockchain?存儲陣列。第一個塊總是硬編碼“創世紀塊”。
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var getGenesisBlock = () => {
return new Block(0, "0", 1465154705, "my genesis block!!", "816534932c2b7154836da6afc367695e6337db8a921823784c14378abed4f7d7");
};
var blockchain = [getGenesisBlock()];
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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。
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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;
};
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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。
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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：
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一個節點上的所有塊＃名單
curl?http://localhost:3001/blocks
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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。
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如下為js 200行代碼
'use strict';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();
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