的Node.js - 創建一個新的ReadStream一個新的文件，當文件達到一定規模

Question

從Node - how can i pipe to a new READABLE stream?

我想開始新的ReadStream我的直播編碼的MP3文件，當它到達一個繼通過使用fs.watch和fs.stat確定尺寸（預緩衝，基本上）。

它可以工作，但一旦ReadStream已經啓動，我不知道如何退出觀察器並保持流運行。

我已經嘗試了承諾如下，但從來沒有得到解決，所以streamEncodedFile被一再呼籲：

var watcher = fs.watch(mp3RecordingFile); 

watcher.on('change', (event, path) => { 

    fs.stat(mp3RecordingFile, function (err, stats) { 

    if (stats.size > 75533) { 

     new Promise(function(resolve, reject) { 
       streamEncodedFile(); 
     }) 
     .then(function(result) { 
       watcher.close(); 
       console.log('watcher closed'); 
     }); 

    } 

    }); 
}); 

function streamEncodedFile() { 

    var mp3File = fs.createReadStream(mp3RecordingFile); 

      mp3File.on('data', function(buffer){ 
       io.sockets.emit('audio', { buffer: buffer }); 
      }); 

} 

我的另一個可憐的企圖是儘量只在某個文件的大小開始流：

watcher.on('change', (event, path) => { 

    fs.stat(mp3RecordingFile, function (err, stats) { 

    console.log(stats.size); 

    if (stats.size > 75533 && stats.size < 75535) { 
       streamEncodedFile(); 
    } else if (stats.size > 75535) { 
       watcher.close(); 
    } 

    }); 
}); 

Answer 1

試試這個解決方案，通過緩衝和寫入文件。

const Writable = require('stream').Writable; 
const fs = require('fs'); 

let mp3File = fs.createWriteStream('path/to/file.mp3'); 

var buffer = new Buffer([]); 
//in bytes 
const CHUNK_SIZE = 102400; //100kb 

//Proxy for emitting and writing to file 
const myWritable = new Writable({ 
    write(chunk, encoding, callback) { 
    buffer = Buffer.concat([buffer, chunk]); 
    if(buffer.length >= CHUNK_SIZE) { 
     mp3File.write(buffer); 
     io.sockets.emit('audio', { buffer: buffer}); 
     buffer = new Buffer([]); 
    } 

    callback(); 
    } 
}); 

myWritable.on('finish',() => { 
    //emit final part if there is data to emit 
    if(buffer.length) { 
     //write final chunk and close fd 
     mp3File.end(buffer); 
     io.sockets.emit('audio', { buffer: buffer}); 
    } 
}); 


inbound_stream.pipe(encoder).pipe(myWritable);