nodejs stream

简单的流读写实现

var Readable = require('stream').Readable;var Writable = require('stream').Writable;var rs = Readable();var ws = Writable();var c = 97 - 1;rs._read = function () {    if (c >= 'z'.charCodeAt(0)) return rs.push(null);    setTimeout(function () {        rs.push(String.fromCharCode(++c));    }, 1000);};rs.pipe(ws);ws._write = function (chunk, enc, next) {    process.stdout.write(chunk);    next();};process.on('exit', function () {    console.error('\n_read() called ' + (c - 97) + ' times');});process.stdout.on('error', process.exit);

Transform Stream 实现字符过滤

const Transform = require('stream').Transform;const util = require('util');const fs= require('fs');function MyTransform(filter) {  if (!(this instanceof MyTransform))    return new MyTransform(null);  Transform.call(this, null);  this.temp = new Buffer(6);//utf-8最多6个字节  this.filter = filter;//要过滤的字符}util.inherits(MyTransform, Transform);MyTransform.prototype._transform = function (data, encoding, callback) {       let len=0;//数据长度（单位字节） 用于递减    let blen=0;//数据长度（单位字节）最终从temp提取的长度    let c=null;//解析出的字符    for (let b of data) {       //如果只有一个字节则其最高二进制位为0；如果是多字节，其第一个字节从最高位开始，连续的二进制位值为1的个数决定了其编码的位数      if(len == 0){        if(b<128){            len=1;        }else if(b<224){            len=2;        }else if(b<240){            len=3;        }else if(b<248){            len=4;        }else if(b<252){            len=5;        }else if(b<254){            len=6;        }else{            continue;        }        blen=len;      }else{      //其余各字节均以10开头,这边是为了排错        if( b<128 || 191<b){            len=0;            blen=0;            continue;        }      }       len--;      this.temp[blen-len-1]=b;      if(len < 1){        c = this.temp.slice(0, blen);        if(c.toString()!=this.filter){          this.push(c);         }      }    }    callback();};//testconst is = fs.createReadStream('a.txt');//过滤字符‘a’is.pipe(new MyTransform('a')).pipe(process.stdout);