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: A drop-in streams2-compatible replacement for the combined-stream module.
-
multistream: A stream that emits multiple other streams one after another.
Installation
npm install combined-stream
Usage
Here is a simple example that shows how you can use combined-stream to combine two files into one:
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
:
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:
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.