mirror of
https://github.com/actions/setup-python.git
synced 2024-11-23 17:17:36 +00:00
138 lines
4.4 KiB
Markdown
138 lines
4.4 KiB
Markdown
# combined-stream
|
|
|
|
A stream that emits multiple other streams one after another.
|
|
|
|
**NB** Currently `combined-stream` works with streams version 1 only. There is ongoing effort to switch this library to streams version 2. Any help is welcome. :) Meanwhile you can explore other libraries that provide streams2 support with more or less compatibility with `combined-stream`.
|
|
|
|
- [combined-stream2](https://www.npmjs.com/package/combined-stream2): A drop-in streams2-compatible replacement for the combined-stream module.
|
|
|
|
- [multistream](https://www.npmjs.com/package/multistream): A stream that emits multiple other streams one after another.
|
|
|
|
## Installation
|
|
|
|
``` bash
|
|
npm install combined-stream
|
|
```
|
|
|
|
## Usage
|
|
|
|
Here is a simple example that shows how you can use combined-stream to combine
|
|
two files into one:
|
|
|
|
``` javascript
|
|
var CombinedStream = require('combined-stream');
|
|
var fs = require('fs');
|
|
|
|
var combinedStream = CombinedStream.create();
|
|
combinedStream.append(fs.createReadStream('file1.txt'));
|
|
combinedStream.append(fs.createReadStream('file2.txt'));
|
|
|
|
combinedStream.pipe(fs.createWriteStream('combined.txt'));
|
|
```
|
|
|
|
While the example above works great, it will pause all source streams until
|
|
they are needed. If you don't want that to happen, you can set `pauseStreams`
|
|
to `false`:
|
|
|
|
``` javascript
|
|
var CombinedStream = require('combined-stream');
|
|
var fs = require('fs');
|
|
|
|
var combinedStream = CombinedStream.create({pauseStreams: false});
|
|
combinedStream.append(fs.createReadStream('file1.txt'));
|
|
combinedStream.append(fs.createReadStream('file2.txt'));
|
|
|
|
combinedStream.pipe(fs.createWriteStream('combined.txt'));
|
|
```
|
|
|
|
However, what if you don't have all the source streams yet, or you don't want
|
|
to allocate the resources (file descriptors, memory, etc.) for them right away?
|
|
Well, in that case you can simply provide a callback that supplies the stream
|
|
by calling a `next()` function:
|
|
|
|
``` javascript
|
|
var CombinedStream = require('combined-stream');
|
|
var fs = require('fs');
|
|
|
|
var combinedStream = CombinedStream.create();
|
|
combinedStream.append(function(next) {
|
|
next(fs.createReadStream('file1.txt'));
|
|
});
|
|
combinedStream.append(function(next) {
|
|
next(fs.createReadStream('file2.txt'));
|
|
});
|
|
|
|
combinedStream.pipe(fs.createWriteStream('combined.txt'));
|
|
```
|
|
|
|
## API
|
|
|
|
### CombinedStream.create([options])
|
|
|
|
Returns a new combined stream object. Available options are:
|
|
|
|
* `maxDataSize`
|
|
* `pauseStreams`
|
|
|
|
The effect of those options is described below.
|
|
|
|
### combinedStream.pauseStreams = `true`
|
|
|
|
Whether to apply back pressure to the underlaying streams. If set to `false`,
|
|
the underlaying streams will never be paused. If set to `true`, the
|
|
underlaying streams will be paused right after being appended, as well as when
|
|
`delayedStream.pipe()` wants to throttle.
|
|
|
|
### combinedStream.maxDataSize = `2 * 1024 * 1024`
|
|
|
|
The maximum amount of bytes (or characters) to buffer for all source streams.
|
|
If this value is exceeded, `combinedStream` emits an `'error'` event.
|
|
|
|
### combinedStream.dataSize = `0`
|
|
|
|
The amount of bytes (or characters) currently buffered by `combinedStream`.
|
|
|
|
### combinedStream.append(stream)
|
|
|
|
Appends the given `stream` to the combinedStream object. If `pauseStreams` is
|
|
set to `true, this stream will also be paused right away.
|
|
|
|
`streams` can also be a function that takes one parameter called `next`. `next`
|
|
is a function that must be invoked in order to provide the `next` stream, see
|
|
example above.
|
|
|
|
Regardless of how the `stream` is appended, combined-stream always attaches an
|
|
`'error'` listener to it, so you don't have to do that manually.
|
|
|
|
Special case: `stream` can also be a String or Buffer.
|
|
|
|
### combinedStream.write(data)
|
|
|
|
You should not call this, `combinedStream` takes care of piping the appended
|
|
streams into itself for you.
|
|
|
|
### combinedStream.resume()
|
|
|
|
Causes `combinedStream` to start drain the streams it manages. The function is
|
|
idempotent, and also emits a `'resume'` event each time which usually goes to
|
|
the stream that is currently being drained.
|
|
|
|
### combinedStream.pause();
|
|
|
|
If `combinedStream.pauseStreams` is set to `false`, this does nothing.
|
|
Otherwise a `'pause'` event is emitted, this goes to the stream that is
|
|
currently being drained, so you can use it to apply back pressure.
|
|
|
|
### combinedStream.end();
|
|
|
|
Sets `combinedStream.writable` to false, emits an `'end'` event, and removes
|
|
all streams from the queue.
|
|
|
|
### combinedStream.destroy();
|
|
|
|
Same as `combinedStream.end()`, except it emits a `'close'` event instead of
|
|
`'end'`.
|
|
|
|
## License
|
|
|
|
combined-stream is licensed under the MIT license.
|