111 lines
4.1 KiB
Markdown
111 lines
4.1 KiB
Markdown
# Lazy Streams
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> *Create streams lazily when they are read from or written to.*
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> `lazystream: 1.0.0` [](https://travis-ci.org/jpommerening/node-lazystream)
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## Why?
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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.
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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.
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> `Error: EMFILE, too many open files`
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> ─ *node*
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This package provides two classes based on the node's Streams3 API (courtesy of `readable-stream` to ensure a stable version).
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## Class: lazystream.Readable
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A wrapper for readable streams. Extends [`stream.PassThrough`](http://nodejs.org/api/stream.html#stream_class_stream_passthrough).
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### new lazystream.Readable(fn [, options])
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* `fn` *{Function}*
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The function that the lazy stream will call to obtain the stream to actually read from.
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* `options` *{Object}*
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Options for the underlying `PassThrough` stream, accessible by `fn`.
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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`.
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If you pass an `options` object to the constuctor, you can access it in your `fn` function.
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```javascript
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new lazystream.Readable(function (options) {
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return fs.createReadStream('/dev/urandom');
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});
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```
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## Class: lazystream.Writable
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A wrapper for writable streams. Extends [`stream.PassThrough`](http://nodejs.org/api/stream.html#stream_class_stream_passthrough).
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### new lazystream.Writable(fn [, options])
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* `fn` *{Function}*
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The function that the lazy stream will call to obtain the stream to actually write to.
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* `options` *{Object}*
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Options for the underlying `PassThrough` stream, accessible by `fn`.
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Creates a new writable stream. Just like the one above but for writable streams.
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```javascript
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new lazystream.Writable(function () {
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return fs.createWriteStream('/dev/null');
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});
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```
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## Install
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```console
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$ npm install lazystream --save
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lazystream@1.0.0 node_modules/lazystream
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└── readable-stream@2.0.5
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```
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## Changelog
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### v1.0.0
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- [#2](https://github.com/jpommerening/node-lazystream/pull/2): [unconditionally](https://r.va.gg/2014/06/why-i-dont-use-nodes-core-stream-module.html) use `readable-stream` _2.x_.
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### v0.2.0
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- [#1](https://github.com/jpommerening/node-lazystream/pull/1): error events are now propagated
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### v0.1.0
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- _(this was the first release)_
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## Contributing
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Fork it, branch it, send me a pull request. We'll work out the rest together.
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## Credits
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[Chris Talkington](https://github.com/ctalkington) and his [node-archiver](https://github.com/ctalkington/node-archiver) for providing a use-case.
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## [License](LICENSE-MIT)
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Copyright (c) 2013 J. Pommerening, contributors.
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation
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files (the "Software"), to deal in the Software without
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restriction, including without limitation the rights to use,
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copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the
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Software is furnished to do so, subject to the following
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conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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OTHER DEALINGS IN THE SOFTWARE.
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