stream-master

A stream that controls child streams

npm install stream-master
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stream-master

stream-master is an API for joining multiple streams together under a single streaming parent. At the current moment, stream-master just combines child streams in arbitrary fashion, but in the future it will emit data events per each child stream in more ordered fashion. It is still possible to isolate individual streams within stream-master because the child function will return the specific stream that has become a child of stream-master.

stream-master also emits a zeroChildren event when all its child streams have emitted end. This is useful if you want all your child streams to finish before doing something else with them.

API

var master = require('stream-master')(opts) master is a readable stream in this case, not writable. stream-master exports a single function that takes an options object as an argument. opts.bufSize is the buffer size for the children streams of stream-master (when not passed an argument to the child function). When child streams surpass this buffer limit, they will emit the buffered data. stream-master also has the property numberOfChildren which indicates the number of childs streams it's listening on data events for.

Possible arguments to the child function are either a readable stream or a number representing the bufSize of that child stream. If it is a number, that child stream will buffer that many bytes before emitting data. Pass in zero for no buffering. If you pass in no arguments, then a child stream is returned that buffers data for as many bytes as the master's bufSize.

child function ... and usage

//bufSize indicates how much data child streams should buffer before emmiting data. pass 0 for data to be emmited without buffering
var master = require('stream-master')({bufSize:1024 * 5}) //returns a readable stream.
  , fs = require('fs')
  , assert = require('assert')

//each child stream emits data normally so you can just pipe the child as a single stream,
//
//instances of {Child} (the stream returned from master.child() when no argument is passed in) buffer data according to master.bufSize
//children don't emit data until the max buffer limit has been exceeded or it has been ended.
//to not have children buffer data, set master.bufSize to 0
//
//master doesn't emit data until its children emit data

var child1 = request('http://npmjs.org').pipe(master.child()) //child returns a readable/writable stream. it is essentially a passthrough stream for request('http://npmjs.org')
child1.pipe(fs.createWriteStream(fileName)) //child emits data from the 'request' pipe
//same as:   request('http://saambarati.org/').pipe(master.child()).pipe(fs.createWriteStream(fileName))

var child2 = request('http://nodejs.org').pipe(master.child())

//pass a readable stream as an argument to master.child()
var child3 = master.child( request('http://github.com') ) // child3 === request('http://github.com')
child3.pipe(process.stdout)

master.pipe( fs.createWriteStream(masterFile) ) //master emits data of both child1 and child2 and child 3

master.on('zeroChildren', function() {
  //child1, child2, child3 have all emmitted 'end'
  console.log('all children in "master" have emitted end')
  assert(master.numberOfChildren === 0)
})
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