Stream-copier NPM

Stream Copier

Collect a Stream into a Buffer, providing a fully readable stream to any consumers, even when they start reading late.

License, donations

GPL-3.0. If you want to support my work, you can:

Example

see example.js in the repo:

"use strict";

const {streamCopier} = require("stream-copier");

const { Readable, Writable } = require('stream');

function namedWritable(name) {
	return Writable({
		write: function(chunk, enc, next) {
			console.log(name, chunk.toString());
			next();
		}
	});
}

let c = 96;
const letters = new Readable();
letters._read = function () {
	if (c >= 'z'.charCodeAt(0)) {
		c = 96;
		return letters.push(null);
	}

	setTimeout(function () {
		letters.push(String.fromCharCode(++c));
	}, 10);
};

const splitter = streamCopier(letters);

splitter.getStream().pipe(namedWritable("first"));

setTimeout(() => {
	// second consumer starts late, still gets all the data
	splitter.getStream().pipe(namedWritable("late"));
}, 100);

splitter.on("end", () => {
	// and even when the stream has finished
	splitter.getStream().pipe(namedWritable("end"));
});

/* 
  You should see the following result:	
  block of first <letter>
  block of late <letter> as it starts streaming and receives all the missed chunks at once
  first <letter> and late <letter> interleaving as they are both getting the newer chunks
  block of end <letter> as end starts streaming when everything is done, receiving all the chunks at once 
*/

API

streamCopier(inputStream, options, callback)

inputStream: Readable Stream
options: Optional object with * maxLength: Maximum length of the internal buffer collection, in bytes
callback: Callback function called when the inputStream has end-ed.

Returns an EventEmitter with the end and error events, getStream() function that returns a new copy of the split stream to pipe elsewhere, length() function to get the size in bytes (so far).