https://github.com/gsf/throughout

apply a through stream to the output side of another through stream
https://github.com/gsf/throughout

Last synced: 19 days ago
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apply a through stream to the output side of another through stream

• Host: GitHub
• URL: https://github.com/gsf/throughout
• Owner: gsf
• License: other
• Created: 2013-05-20T17:32:16.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2013-05-20T17:32:33.000Z (over 11 years ago)
• Last Synced: 2024-11-10T01:31:17.640Z (2 months ago)
• Language: JavaScript
• Size: 94.7 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: readme.markdown
  • License: LICENSE

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README

        
# throughout

Apply a through stream to the output side of another through stream,

preserving the first stream as input in the returned stream.

[![build status](https://secure.travis-ci.org/substack/throughout.png)](http://travis-ci.org/substack/throughout)

[![browser support](https://ci.testling.com/substack/throughout.png)](http://ci.testling.com/substack/throughout)

# example

``` js

var through = require('through');

var throughout = require('throughput');

var doubler = through(function (buf) {

    var dbuf = new Buffer(buf.length * 2);

    for (var i = 0; i < dbuf.length; i++) {

        dbuf[i] = buf[Math.floor(i/2)];

    }

    this.queue(dbuf);

});

var counter = through(

    function (buf) {

        this._count = (this._count || 0) + buf.length;

    },

    function () {

        this.queue(this._count + '\n');

        this.queue(null);

    }

);

process.stdin

    .pipe(throughout(doubler, counter))

    .pipe(process.stdout)

;

```

# rationale

If you want to transform just the output side of a through stream, this is

actually somewhat difficult and it's not immediately obvious why something like:

``` js

var duplexer = require('duplexer');

function filterOutput (a, b) {

    a.pipe(b);

    return duplexer(a, b);

}

```

shouldn't just work. The worst part is that it *does* work, until you try to

pipe the results to a slow endpoint that will throttle with pause and resume.

The problem is that both `duplexer` and `.pipe()` will handle pause and resume

in a mutually exclusive way that will cause the stream to hang indefinitely if a

slow downstream consumer ever triggers a pause.

If you try to use event-stream's .pipeline() function you will get the same

problem.

# methods

``` js

var throughout = require('throughout');

```

## var c = throughout(a, b)

Pipe the output of a through stream `a` into the input of a through stream `b`,

returning a new stream `c` that writes its input to `a` and forwards the output

from `b`.

# install

With [npm](https://npmjs.org) do:

```

npm install throughout

```

# license

MIT