模拟可读流，可写流实现

可读流模拟实现constfs=require("fs");constEventEmitter=require("events");classMyFileReadStreamextendsEventEmitter{constructor(path,options={}){super();this.path=路径；this.flag=options.flags||“r”；this.mode=options.mode||438；this.autoClose=options.autoClose||真的;this.start=options.start||0;this.end=options.end;this.highWaterMark=options.highWaterMark||64*1024;this.readOffset=0;这个.open();this.on("newListener",(type)=>{//判断监听类型console.log(type);if(type==="data"){this.read();}});}open(){//原open方法打开指定位置文件fs.open(this.path,this.flags,this.mode,(err,fd)=>{if(err){this.emit("error",err);}else{this.fd=fd;this.emit("open",fd);//发送文件标识符}});}read(){//这里不能直接获取fd，这里监听open时间，控制执行顺序if(typeofthis.fd!=="number"){returnthis.once("open",this.read);}让buf=Buffer.alloc(this.highWaterMark);让howMuchToRead；//用户设置结束值howMuchToRead=this.end?Math.min(this.end-this.readOffset+1,this.highWaterMark):this.highWaterMark;fs.read(this.fd,buf,0,howMuchToRead,this.readOffset,(err,readBytes)=>{if(readBytes){this.readOffset+=readBytes;this.emit("数据",buf.slice(0,readBytes));//返回数据this.read();//继续阅读}else{this.emit("end");this.close();}});}close(){fs.close(this.fd,()=>{this.emit("close");});}//管道简化操作pipe(ws){this.on("data",(data)=>{letflag=ws.write(data);if(!flag){this.pause();}});ws.on("drain",()=>{this.resume();});}}letrs=newMyFileReadStream("test.txt",{end:7,highWaterMark:3,});//事件触发测试//rs.on("open",(fd)=>{//console.log("open",fd);//});//rs.on("error",(err)=>{///console.log(err);//});rs.on("data",(chunk)=>{console.log(chunk);});//rs.on("end",()=>{//console.log("end");//});rs.on("close",()=>{console.log("close");});可写流模拟现实constfs=require("fs");constEventEmitter=require("events");const{Queue}=require("./linkedList");//队列类MyWriteStreamextendsEventEmitter{constructor(path,options={}){super()；this.path=path；this.flags=options.flags||“w”；this.mode=options.mode||438；this.autoClose=options.autoClose||true；this.start=options.start||0;this.encoding=options.编码||“utf8”；this.highWaterMark=options.highWaterMark||16*1024;这个.open();this.writeOffset=this.start;this.writing=false;//标识符是否正在写入this.writLen=0;this.needDrain=false;this.cache=newQueue();}open(){//原生fs.openfs.open(this.path,this.flags,(err,fd)=>{if(err){this.emit("error",err);}//正常打开文件this.fd=fd;this.emit("open",fd);});}write(chunk,encoding,cb){chunk=Buffer.isBuffer(chunk)?块:Buffer.from(块);//只考虑string或Buffer两种类型this.writLen+=chunk.length;让flag=this.writLen{cb();//清除队列内容this._clearBuffer();});}返回标志；}_write(chunk,encoding,cb){//写入操作，与可读流有相同的问题，需要在打开之后在拿fd操作if(typeofthis.fd!=="number"){returnthis.once("open",()=>{returnthis._write(chunk,encoding,cb);});}fs.write(this.fd,chunk,this.start,chunk.length,this.writeOffset,(err,written)=>{this.writeOffset+=written;this.writLen-=written;cb&&cb();});}_clearBuffer(){让数据=this.cache.deQueue();if(data){this._write(data.element.chunk,data.element.encoding,()=>{data.element.cb&&data.element.cb();this._clearBuffer();});}else{if(this.needDrain){this.needDrain=false;this.emit("drain");}}}}constws=newMyWriteStream("test.txt",{highWaterMark:1});ws.open("open",(fd)=>{console.log("open==>",fd);});letflag=ws.write("1","utf8",()=>{console.log("ok1");});//console.log(flag);flag=ws.write("10","utf8",()=>{console.log("ok2");});//console.log(flag);flag=ws.write("前端前端","utf8",()=>{console.log("ok222");});ws.on("drain",()=>{console.log("drain");});