Lazy Streams

Create streams lazily when they are read from or written to.
lazystream: 1.0.1

Why?

Sometimes you feel the itch to open all the files at once. You want to pass a bunch of streams around, so the consumer does not need to worry where the data comes from. From a software design point-of-view this sounds entirely reasonable. Then there is that neat little function fs.createReadStream() that opens a file and gives you a nice fs.ReadStream to pass around, so you use what the mighty creator deities of node bestowed upon you.

Error: EMFILE, too many open files
─ node

This package provides two classes based on the node's Streams3 API (courtesy of readable-stream to ensure a stable version).

Class: lazystream.Readable

A wrapper for readable streams. Extends stream.PassThrough.

new lazystream.Readable(fn [, options])

• fn {Function}
  The function that the lazy stream will call to obtain the stream to actually read from.
• options {Object}
  Options for the underlying PassThrough stream, accessible by fn.

Creates a new readable stream. Once the stream is accessed (for example when you call its read() method, or attach a data-event listener) the fn function is called with the outer lazystream.Readable instance bound to this.

If you pass an options object to the constuctor, you can access it in your fn function.

1new lazystream.Readable(function (options) {
2  return fs.createReadStream('/dev/urandom');
3});

Class: lazystream.Writable

A wrapper for writable streams. Extends stream.PassThrough.

new lazystream.Writable(fn [, options])

• fn {Function}
  The function that the lazy stream will call to obtain the stream to actually write to.
• options {Object}
  Options for the underlying PassThrough stream, accessible by fn.

Creates a new writable stream. Just like the one above but for writable streams.

1new lazystream.Writable(function () {
2  return fs.createWriteStream('/dev/null');
3});

Install

1$ npm install lazystream --save
2lazystream@1.0.1 node_modules/lazystream
3└── readable-stream@2.0.5

Changelog

v1.0.1

• #3: (finally) fixed a long-standing publishing error

v1.0.0

• #2: unconditionally use readable-stream 2.x.

v0.2.0

• #1: error events are now propagated

v0.1.0

• (this was the first release)

Contributing

Fork it, branch it, send me a pull request. We'll work out the rest together.

Credits

Chris Talkington and his node-archiver for providing a use-case.

License

Copyright (c) 2013 J. Pommerening, contributors.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.