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nodejs stream 创建读写流

const fs = require("fs");
const { Writable, Readable, Duplex, Transform } = require("stream");

// 双向流
const inoutStream = new Duplex({

  // 获取写入的数据
  write(chunk, encoding, callback) {
    console.log(chunk.toString());
    callback();
  },

  // 一直读直到null为止
  read(size) {
    this.push(String.fromCharCode(this.currentCharCode++));
    if (this.currentCharCode > 90) this.push(null);
  },
});

inoutStream.currentCharCode = 65;
process.stdin.pipe(inoutStream).pipe(inoutStream);


const sizeStream = new Transform({
  readableObjectMode: true,
  writableObjectMode: true,

  // 转换流，可以改变数据
  transform(chunk, encoding, callback) {
    this.push(chunk.toString() + `
 // size(${chunk.length})`);
    callback();
  },
});

const outStream = new Writable({
  write(chunk, encoding, callback) {
    console.log(chunk.toString("utf-8"));
    callback();
  },
});

fs.createReadStream("./x.txt").pipe(sizeStream).pipe(outStream);