以文件流的方式读取文件内容

目录结构

|— 16.createStream.js

|— blood.lrc

const fs = require("fs");
const path = require("path");
const iconv = require("iconv-lite");

const filename = path.join(__dirname,"./blood.lrc");
//创建一个文件读取流
let stream = fs.createReadStream(filename);
//让文件流通过iconv过滤编码
stream = stream.pipe(iconv.decodeStream("gbk"));

let content = "";
stream.on("data",(chunk) => {
  content += chunk;
});

//读取结束
stream.on("end",() => {
  console.log(content);
})

我们来执行一下它

$ node 16-createStream.js 
[ti:血染的风采]
[ar:黄耀明]
...中间省略
[03:19.42] 共和国的旗帜上有我们血染的风采
[03:25.51] * * *
[03:32.98] ---End---

---

我们尝试着让歌词滚动显示

|— 17-showLyric.js

const fs = require("fs");
const path = require("path");
const iconv = require("iconv-lite");

const filename = path.join(__dirname,"./blood.lrc");
fs.readFile(filename,(err,data) => {
  if(err) throw err;
  let lines = iconv.decode(data,"gbk").split("\n");
  //[00:32.67] 也许我告别 将不再回来
  let regexp = /\[(\d{2}):(\d{2})\.(\d{2})]\s(.+)/;
  let start = new Date().getTime();
  //遍历
  lines.forEach((line) => {
    // [00:32.67] 也许我告别 将不再回来
    let matches = regexp.exec(line);
    if(matches){
      let min = matches[0];
      let sec = parseFloat(matches[2]);
      let ms = parseFloat(matches[3]);
      let lyric = matches[4];
      let time = min * 60 * 1000 + sec * 1000 + ms;
      //当前歌词不是立即执行，由于下达任务的时刻不同我们要设置时间偏移量
      let offset = new Date().getTime();
      
      setTimeout(() => {
        console.log(lyric)
      },time - offset);
    }else{
      //不是一句歌词
      console.log(line);
    }
  })
})

执行16.showLyric.js

$ node 17-showLyric.js 
[ti:血染的风采]
[ar:黄耀明]
[al:人山人海]
[offset:500]
[00:55.04]中文歌词库 www.CnLyric.com

歌曲：血染的风采
歌手：黄耀明
^C

我们成功了。

我们以上拆分歌词是用split("\n")拆分成数组，然后再遍历每一句这样做的。然而node给我们提供了一个模块叫做readline.我们下面用readline模块完成同样的业务。

18-readline.js

//readline实现一行一行读取歌词
const fs = require("fs");
const path = require("path");
const iconv = require("iconv-lite");
const readline = require("readline");

const filename = path.join(__dirname,"./blood");
const readStream = fs.createReadStream(filename)
					 .pipe(iconv.decodeStream("gbk"));
let rl = readline.createInterface({input:readStream});
let regexp = /\[(\d{2}):(\d{2})\.(\d{2})]\s(.+)/;
let start = new Date().getTime();

rl.on("line",(line) => {
  if(matches){
    let min = parseFloat(matches[1]);
    let sec = parseFloat(matches[2]);

    let ms = parseFloat(matches[3]);
    let lyric = matches[4];
    let time = min * 60 * 1000 + sec * 1000 + ms;
    //当前歌词不是立即执行，由于下达任务的时刻不同我们要设置时间偏移量
    let offset = new Date().getTime() - start;
    setTimeout(() => {
        console.log(lyric);
    },time - offset);
  }else{
      //不是一句歌词
      console.log(line);
  }
})

执行18-readline.js

$ node 18-readline.js 
[ti:血染的风采]
[ar:黄耀明]
[al:人山人海]
[offset:500]
[00:55.04]中文歌词库 www.CnLyric.com

歌曲：血染的风采
歌手：黄耀明
^C

​

​

---

本文结束，感谢阅读。

本文作者：melody0z
本文链接：https://melodyvoid/Node/reads-file-contents-in-a-file-stream.html
欢迎转载，转载请注明文本链接