200行代码实现blockchain 区块链实例详解
了解blockchain的概念很简单(区块链,交易链块):它是分布式的(即不是放置在同一台机器上,不同的网络设备上的)数据库支持主办记录日益增长的名单。但是,这也是容易混淆blockchain与我们试图帮他解决了目标 - 在人们心中的那一刻,这个词是相当强烈的交易,合同或智能cryptocurrency的概念有关。
只有在这里blockchain - 是不是一回事比特币,并理解链块的基本知识比它似乎更容易,尤其是在,它是基于源代码的情况下。在本文中,我们提出了建立与在javascript中200行代码的简单模型。这个项目,我们称之为naivechain的源代码,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,使用我们的备忘单,我们将使用标准的ecmascript 6。
块结构
第一步 - 确定应包含块的元素。为简单起见,我们只包括最必要的:先前块的指数(指数),时间标记(时间戳),数据(数据),散列和散列,要录制,以保持电路的结构完整性。
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(); } }
散列单元
哈希块需要保持数据的完整性。在我们的例子,这适用于算法sha-256。这种类型的散列是不相关的开采,因为在这种情况下,我们并没有用表现证明实施保护。
var calculatehash = (index, previoushash, timestamp, data) => { return cryptojs.sha256(index + previoushash + timestamp + data).tostring(); };
产生单元
要生成块,我们需要知道前一个块的哈希,使我们在结构已经确定了元素的其余部分。数据由最终用户提供。
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); };
存储单元
使用blockchain 存储阵列。第一个块总是硬编码“创世纪块”。
var getgenesisblock = () => { return new block(0, "0", 1465154705, "my genesis block!!", "816534932c2b7154836da6afc367695e6337db8a921823784c14378abed4f7d7"); }; var blockchain = [getgenesisblock()];
确认块的完整性
我们必须始终能够确认单元或电路的完整性。尤其是当你从其他单位新的单位,必须决定是否接受它们。
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; };
选择链最长的
在电路块的顺序必须被明确指定,但是在发生冲突的情况下(例如,两个节点同时在同一生成的块和相同数量),我们选择电路,其中包含的块的数量较多。
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'); } };
消息到其它网络节点
该网站的一个组成部分 - 与其他节点的数据交换。下列规则用于维护网络同步:
当一个节点产生新的单元,它会报告给网络;
当本机连接到新的盛宴,他要求有关最后生成的块信息;
当一个节点正面临着一个块,其中有一个指标比他还大,他增加了一个块到电路或请求的完整链条的信息。
自动搜索同龄人不执行,所有环节都手动添加。
单元的控制
用户应该能够以某种方式控制节点,通过将http服务器解决。当与节点相互作用有以下功能:
打印所有单元的列表;
创建用户生成内容的新单元;
打印列表,或添加的节日。
互动的最直接的方式 - 通过卷曲:
一个节点上的所有块#名单
curl
架构
值得注意的是,该网站是指两个web服务器:http进行用户控制的装置和向所述的websocket http来安装节点之间的p2p连接。
如下为js 200行代码
<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();
总结
以上所述是小编给大家介绍的200行代码实现blockchain 区块链实例详解,希望对大家有所帮助