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Stream Component

Build Status

Basic readable and writable stream interfaces that support piping.

In order to make the event loop easier to use, this component introduces the concept of streams. They are very similar to the streams found in PHP itself, but have an interface more suited for async I/O.

Mainly it provides interfaces for readable and writable streams, plus a file descriptor based implementation with an in-memory write buffer.

This component depends on événement, which is an implementation of the EventEmitter.

Table of contents

API

ReadableStreamInterface

EventEmitter Events

  • data: Emitted whenever data was read from the source with a single mixed argument for incoming data.
  • end: Emitted when the source has successfully reached the end of the stream (EOF). This event will only be emitted if the end was reached successfully, not if the stream was interrupted due to an error or explicitly closed. Also note that not all streams know the concept of a "successful end".
  • error: Emitted when an error occurs with a single Exception argument for error instance.
  • close: Emitted when the stream is closed.

isReadable()

The isReadable(): bool method can be used to check whether this stream is in a readable state (not closed already).

This method can be used to check if the stream still accepts incoming data events or if it is ended or closed already. Once the stream is non-readable, no further data or end events SHOULD be emitted.

assert($stream->isReadable() === false);

$stream->on('data', assertNeverCalled());
$stream->on('end', assertNeverCalled());

A successfully opened stream always MUST start in readable mode.

Once the stream ends or closes, it MUST switch to non-readable mode. This can happen any time, explicitly through close() or implicitly due to a remote close or an unrecoverable transmission error. Once a stream has switched to non-readable mode, it MUST NOT transition back to readable mode.

If this stream is a DuplexStreamInterface, you should also notice how the writable side of the stream also implements an isWritable() method. Unless this is a half-open duplex stream, they SHOULD usually have the same return value.

pause()

The pause(): void method can be used to pause reading incoming data events.

Removes the data source file descriptor from the event loop. This allows you to throttle incoming data.

Unless otherwise noted, a successfully opened stream SHOULD NOT start in paused state.

Once the stream is paused, no futher data or end events SHOULD be emitted.

$stream->pause();

$stream->on('data', assertShouldNeverCalled());
$stream->on('end', assertShouldNeverCalled());

This method is advisory-only, though generally not recommended, the stream MAY continue emitting data events.

You can continue processing events by calling resume() again.

Note that both methods can be called any number of times, in particular calling pause() more than once SHOULD NOT have any effect.

See also resume().

resume()

The resume(): void method can be used to resume reading incoming data events.

Re-attach the data source after a previous pause().

$stream->pause();

$loop->addTimer(1.0, function () use ($stream) {
    $stream->resume();
});

Note that both methods can be called any number of times, in particular calling resume() without a prior pause() SHOULD NOT have any effect.

See also pause().

pipe()

The pipe(WritableStreamInterface $dest, array $options = []) method can be used to pipe all the data from this readable source into the given writable destination.

Automatically sends all incoming data to the destination. Automatically throttles the source based on what the destination can handle.

$source->pipe($dest);

Similarly, you can also pipe an instance implementing DuplexStreamInterface into itself in order to write back all the data that is received. This may be a useful feature for a TCP/IP echo service:

$connection->pipe($connection);

This method returns the destination stream as-is, which can be used to set up chains of piped streams:

$source->pipe($decodeGzip)->pipe($filterBadWords)->pipe($dest);

By default, this will call end() on the destination stream once the source stream emits an end event. This can be disabled like this:

$source->pipe($dest, array('end' => false));

Note that this only applies to the end event. If an error or explicit close event happens on the source stream, you'll have to manually close the destination stream:

$source->pipe($dest);
$source->on('close', function () use ($dest) {
    $dest->end('BYE!');
});

If the source stream is not readable (closed state), then this is a NO-OP.

$source->close();
$source->pipe($dest); // NO-OP

If the destinantion stream is not writable (closed state), then this will simply throttle (pause) the source stream:

$dest->close();
$source->pipe($dest); // calls $source->pause()

Similarly, if the destination stream is closed while the pipe is still active, it will also throttle (pause) the source stream:

$source->pipe($dest);
$dest->close(); // calls $source->pause()

close()

The close(): void method can be used to close the stream (forcefully).

This method can be used to (forcefully) close the stream.

$stream->close();

After calling this method, the stream MUST switch into a non-readable mode, see also isReadable(). This means that no further data or end events SHOULD be emitted.

$stream->close();
assert($stream->isReadable() === false);

$stream->on('data', assertNeverCalled());
$stream->on('end', assertNeverCalled());

If this stream is a DuplexStreamInterface, you should also notice how the writable side of the stream also implements a close() method. In other words, after calling this method, the stream MUST switch into non-writable AND non-readable mode, see also isWritable(). Note that this method should not be confused with the end() method.

WritableStreamInterface

EventEmitter Events

  • drain: Emitted if the write buffer became full previously and is now ready to accept more data.
  • error: Emitted whenever an error occurs with a single Exception argument for error instance.
  • close: Emitted whenever the stream is closed.
  • pipe: Emitted whenever a readable stream is pipe()d into this stream with a single ReadableStreamInterface argument for source stream.

isWritable()

The isWritable(): bool method can be used to check whether this stream is in a writable state (not closed already).

This method can be used to check if the stream still accepts writing any data or if it is ended or closed already. Writing any data to a non-writable stream is a NO-OP:

assert($stream->isWritable() === false);

$stream->write('end'); // NO-OP
$stream->end('end'); // NO-OP

A successfully opened stream always MUST start in writable mode.

Once the stream ends or closes, it MUST switch to non-writable mode. This can happen any time, explicitly through end() or close() or implicitly due to a remote close or an unrecoverable transmission error. Once a stream has switched to non-writable mode, it MUST NOT transition back to writable mode.

If this stream is a DuplexStreamInterface, you should also notice how the readable side of the stream also implements an isReadable() method. Unless this is a half-open duplex stream, they SHOULD usually have the same return value.

write()

The write(mixed $data): bool method can be used to write some data into the stream.

A successful write MUST be confirmed with a boolean true, which means that either the data was written (flushed) immediately or is buffered and scheduled for a future write. Note that this interface gives you no control over explicitly flushing the buffered data, as finding the appropriate time for this is beyond the scope of this interface and left up to the implementation of this interface.

Many common streams (such as a TCP/IP connection or file-based stream) may choose to buffer all given data and schedule a future flush by using an underlying EventLoop to check when the resource is actually writable.

If a stream cannot handle writing (or flushing) the data, it SHOULD emit an error event and MAY close() the stream if it can not recover from this error.

If the internal buffer is full after adding $data, then write() SHOULD return false, indicating that the caller should stop sending data until the buffer drains.

Similarly, if the the stream is not writable (already in a closed state) it MUST NOT process the given $data and SHOULD return false, indicating that the caller should stop sending data.

The given $data argument MAY be of mixed type, but it's usually recommended it SHOULD be a string value or MAY use a type that allows representation as a string for maximum compatibility.

Many common streams (such as a TCP/IP connection or a file-based stream) will only accept the raw (binary) payload data that is transferred over the wire as chunks of string values.

Due to the stream-based nature of this, the sender may send any number of chunks with varying sizes. There are no guarantees that these chunks will be received with the exact same framing the sender intended to send. In other words, many lower-level protocols (such as TCP/IP) transfer the data in chunks that may be anywhere between single-byte values to several dozens of kilobytes. You may want to apply a higher-level protocol to these low-level data chunks in order to achieve proper message framing.

end()

The end(mixed $data = null): void method can be used to successfully end the stream (after optionally sending some final data).

This method can be used to successfully end the stream, i.e. close the stream after sending out all data that is currently buffered.

$stream->write('hello');
$stream->write('world');
$stream->end();

If there's no data currently buffered and nothing to be flushed, then this method MAY close() the stream immediately.

If there's still data in the buffer that needs to be flushed first, then this method SHOULD try to write out this data and only then close() the stream.

Note that this interface gives you no control over explicitly flushing the buffered data, as finding the appropriate time for this is beyond the scope of this interface and left up to the implementation of this interface.

Many common streams (such as a TCP/IP connection or file-based stream) may choose to buffer all given data and schedule a future flush by using an underlying EventLoop to check when the resource is actually writable.

You can optionally pass some final data that is written to the stream before ending the stream. If a non-null value is given as $data, then this method will behave just like calling write($data) before ending with no data.

// shorter version
$stream->end('bye');

// same as longer version
$stream->write('bye');
$stream->end();

After calling this method, the stream MUST switch into a non-writable mode, see also isWritable(). This means that no further writes are possible, so any additional write() or end() calls have no effect.

$stream->end();
assert($stream->isWritable() === false);

$stream->write('nope'); // NO-OP
$stream->end(); // NO-OP

Note that this method should not be confused with the close() method.

close()

The close(): void method can be used to close the stream (forcefully).

This method can be used to forcefully close the stream, i.e. close the stream without waiting for any buffered data to be flushed. If there's still data in the buffer, this data SHOULD be discarded.

$stream->close();

After calling this method, the stream MUST switch into a non-writable mode, see also isWritable(). This means that no further writes are possible, so any additional write() or end() calls have no effect.

$stream->close();
assert($stream->isWritable() === false);

$stream->write('nope'); // NO-OP
$stream->end(); // NO-OP

Note that this method should not be confused with the end() method. Unlike the end() method, this method does not take care of any existing buffers and simply discards any buffer contents. Likewise, this method may also be called after calling end() on a stream in order to stop waiting for the stream to flush its final data.

$stream->end();
$loop->addTimer(1.0, function () use ($stream) {
    $stream->close();
});

If this stream is a DuplexStreamInterface, you should also notice how the readable side of the stream also implements a close() method. In other words, after calling this method, the stream MUST switch into non-writable AND non-readable mode, see also isReadable().

Usage

    $loop = React\EventLoop\Factory::create();

    $source = new React\Stream\Stream(fopen('omg.txt', 'r'), $loop);
    $dest = new React\Stream\Stream(fopen('wtf.txt', 'w'), $loop);

    $source->pipe($dest);

    $loop->run();

Install

The recommended way to install this library is through Composer. New to Composer?

This will install the latest supported version:

$ composer require react/stream:^0.4.6

More details about version upgrades can be found in the CHANGELOG.

Tests

To run the test suite, you first need to clone this repo and then install all dependencies through Composer:

$ composer install

To run the test suite, go to the project root and run:

$ php vendor/bin/phpunit