combine-stream

Combine multiple duplex streams into just one

npm install combine-stream
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Combine multiple duplex streams into just one.

Overview

combine-stream lets you treat a few streams as just one, in a parallel fashion. When you combine a bunch of streams, you write to it as if it was one, and read from it as if it was one, but you are simultaneously writing to all the streams and getting the output from all the streams.

Error events are also aggregated from all the streams and forwarded up through the combining stream for you to listen to in one place.

Super Quickstart

Code:

var stream = require("stream");

var CombineStream = require("combine-stream");

var streamA = new stream.PassThrough({objectMode: true}),
    streamB = new stream.PassThrough({objectMode: true}),
    streamC = new stream.PassThrough({objectMode: true});

var combine = new CombineStream([streamA, streamB, streamC]);

combine.on("data", console.log);

combine.write("hello");

combine.end();

Output:

hello
hello
hello

Installation

Available via npm:

$ npm install combine-stream

Or via git:

$ git clone git://github.com/deoxxa/combine-stream.git node_modules/combine-stream

NOTE:

Currently this is relying on my fork of readable-stream. Hopefully my patch gets merged and I can remove the hardcoded github dependency.

API

constructor

Creates a new combine-stream.

new CombineStream(options);
var combine = new CombineStream({
  logSize: 100,
  recordDuplicates: true,
  comparator: functon compare(a, b) {
    return a === b;
  },
});

Arguments

  • options - an object containing, as well as the regular TransformStream options, the parameters described below. If this argument is an array, it will be wrapped in {streams: ...}.

options

  • streams - an array of streams to add at instantiation time.
  • bubbleErrors - a boolean value specifying whether to bubble errors up from the wrapped streams.

Example

Also see example.js.

var stream = require("stream");

var CombineStream = require("combine-stream");

var delayed = function delayed(n) {
  var s = new stream.Transform({objectMode: true});

  s._transform = function _transform(input, encoding, done) {
    var self = this;

    return setTimeout(function() {
      self.push(input + " " + n);

      return done();
    }, n);
  };

  s._flush = function _flush(done) {
    console.log("ending!", n);

    setTimeout(done, n);
  };

  return s;
};

var combine = new CombineStream();

var streamA = delayed(100),
    streamB = delayed(500);

var combine = new CombineStream([streamA, streamB]);

combine.on("data", console.log);
combine.on("error", console.log);

combine.write("hello 1");
combine.write("hello 2");
combine.write("hello 3");

combine.end(function() {
  console.log("everything finished");
});

Output:

hello 1 100
hello 1 500
hello 2 100
hello 2 500
hello 3 100
hello 3 500
ending! 100
ending! 500
everything finished

License

3-clause BSD. A copy is included with the source.

Contact

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