stream

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reactphp / stream

Event-driven readable and writable streams for non-blocking I/O in ReactPHP.

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Stream

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Event-driven readable and writable streams for non-blocking I/O in ReactPHP.

In order to make the EventLoop easier to use, this component introduces the powerful concept of "streams". Streams allow you to efficiently process huge amounts of data (such as a multi Gigabyte file download) in small chunks without having to store everything in memory at once. They are very similar to the streams found in PHP itself, but have an interface more suited for async, non-blocking I/O.

Table of contents

Stream usage

ReactPHP uses the concept of "streams" throughout its ecosystem to provide a consistent higher-level abstraction for processing streams of arbitrary data contents and size. While a stream itself is a quite low-level concept, it can be used as a powerful abstraction to build higher-level components and protocols on top.

If you're new to this concept, it helps to think of them as a water pipe: You can consume water from a source or you can produce water and forward (pipe) it to any destination (sink).

Similarly, streams can either be

  • readable (such as
    STDIN
    terminal input) or
  • writable (such as
    STDOUT
    terminal output) or
  • duplex (both readable and writable, such as a TCP/IP connection)

Accordingly, this package defines the following three interfaces

ReadableStreamInterface

The

ReadableStreamInterface
is responsible for providing an interface for read-only streams and the readable side of duplex streams.

Besides defining a few methods, this interface also implements the

EventEmitterInterface
which allows you to react to certain events.

The event callback functions MUST be a valid

callable
that obeys strict parameter definitions and MUST accept event parameters exactly as documented. The event callback functions MUST NOT throw an
Exception
. The return value of the event callback functions will be ignored and has no effect, so for performance reasons you're recommended to not return any excessive data structures.

Every implementation of this interface MUST follow these event semantics in order to be considered a well-behaving stream.

Note that higher-level implementations of this interface may choose to define additional events with dedicated semantics not defined as part of this low-level stream specification. Conformance with these event semantics is out of scope for this interface, so you may also have to refer to the documentation of such a higher-level implementation.

data event

The

data
event will be emitted whenever some data was read/received from this source stream. The event receives a single mixed argument for incoming data.
$stream->on('data', function ($data) {
    echo $data;
});

This event MAY be emitted any number of times, which may be zero times if this stream does not send any data at all. It SHOULD not be emitted after an

end
or
close
event.

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 emit the raw (binary) payload data that is received 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 event

The

end
event will be emitted once the source stream has successfully reached the end of the stream (EOF).
$stream->on('end', function () {
    echo 'END';
});

This event SHOULD be emitted once or never at all, depending on whether a successful end was detected. It SHOULD NOT be emitted after a previous

end
or
close
event. It MUST NOT be emitted if the stream closes due to a non-successful end, such as after a previous
error
event.

After the stream is ended, it MUST switch to non-readable mode, see also

isReadable()
.

This event will only be emitted if the end was reached successfully, not if the stream was interrupted by an unrecoverable error or explicitly closed. Not all streams know this concept of a "successful end". Many use-cases involve detecting when the stream closes (terminates) instead, in this case you should use the

close
event. After the stream emits an
end
event, it SHOULD usually be followed by a
close
event.

Many common streams (such as a TCP/IP connection or a file-based stream) will emit this event if either the remote side closes the connection or a file handle was successfully read until reaching its end (EOF).

Note that this event should not be confused with the

end()
method. This event defines a successful end reading from a source stream, while the
end()
method defines writing a successful end to a destination stream.

error event

The

error
event will be emitted once a fatal error occurs, usually while trying to read from this stream. The event receives a single
Exception
argument for the error instance.
$server->on('error', function (Exception $e) {
    echo 'Error: ' . $e->getMessage() . PHP_EOL;
});

This event SHOULD be emitted once the stream detects a fatal error, such as a fatal transmission error or after an unexpected

data
or premature
end
event. It SHOULD NOT be emitted after a previous
error
,
end
or
close
event. It MUST NOT be emitted if this is not a fatal error condition, such as a temporary network issue that did not cause any data to be lost.

After the stream errors, it MUST close the stream and SHOULD thus be followed by a

close
event and then switch to non-readable mode, see also
close()
and
isReadable()
.

Many common streams (such as a TCP/IP connection or a file-based stream) only deal with data transmission and do not make assumption about data boundaries (such as unexpected

data
or premature
end
events). In other words, many lower-level protocols (such as TCP/IP) may choose to only emit this for a fatal transmission error once and will then close (terminate) the stream in response.

If this stream is a

DuplexStreamInterface
, you should also notice how the writable side of the stream also implements an
error
event. In other words, an error may occur while either reading or writing the stream which should result in the same error processing.

close event

The

close
event will be emitted once the stream closes (terminates).
$stream->on('close', function () {
    echo 'CLOSED';
});

This event SHOULD be emitted once or never at all, depending on whether the stream ever terminates. It SHOULD NOT be emitted after a previous

close
event.

After the stream is closed, it MUST switch to non-readable mode, see also

isReadable()
.

Unlike the

end
event, this event SHOULD be emitted whenever the stream closes, irrespective of whether this happens implicitly due to an unrecoverable error or explicitly when either side closes the stream. If you only want to detect a successful end, you should use the
end
event instead.

Many common streams (such as a TCP/IP connection or a file-based stream) will likely choose to emit this event after reading a successful

end
event or after a fatal transmission
error
event.

If this stream is a

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

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()

Once the pipe is set up successfully, the destination stream MUST emit a

pipe
event with this source stream an event argument.

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();

Once the stream is closed, it SHOULD emit a

close
event. Note that this event SHOULD NOT be emitted more than once, in particular if this method is called multiple times.

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

The

WritableStreamInterface
is responsible for providing an interface for write-only streams and the writable side of duplex streams.

Besides defining a few methods, this interface also implements the

EventEmitterInterface
which allows you to react to certain events.

The event callback functions MUST be a valid

callable
that obeys strict parameter definitions and MUST accept event parameters exactly as documented. The event callback functions MUST NOT throw an
Exception
. The return value of the event callback functions will be ignored and has no effect, so for performance reasons you're recommended to not return any excessive data structures.

Every implementation of this interface MUST follow these event semantics in order to be considered a well-behaving stream.

Note that higher-level implementations of this interface may choose to define additional events with dedicated semantics not defined as part of this low-level stream specification. Conformance with these event semantics is out of scope for this interface, so you may also have to refer to the documentation of such a higher-level implementation.

drain event

The

drain
event will be emitted whenever the write buffer became full previously and is now ready to accept more data.
$stream->on('drain', function () use ($stream) {
    echo 'Stream is now ready to accept more data';
});

This event SHOULD be emitted once every time the buffer became full previously and is now ready to accept more data. In other words, this event MAY be emitted any number of times, which may be zero times if the buffer never became full in the first place. This event SHOULD NOT be emitted if the buffer has not become full previously.

This event is mostly used internally, see also

write()
for more details.

pipe event

The

pipe
event will be emitted whenever a readable stream is
pipe()
d into this stream. The event receives a single
ReadableStreamInterface
argument for the source stream.
$stream->on('pipe', function (ReadableStreamInterface $source) use ($stream) {
    echo 'Now receiving piped data';

// explicitly close target if source emits an error
$source->on('error', function () use ($stream) {
    $stream->close();
});

});

$source->pipe($stream);

This event MUST be emitted once for each readable stream that is successfully piped into this destination stream. In other words, this event MAY be emitted any number of times, which may be zero times if no stream is ever piped into this stream. This event MUST NOT be emitted if either the source is not readable (closed already) or this destination is not writable (closed already).

This event is mostly used internally, see also

pipe()
for more details.

error event

The

error
event will be emitted once a fatal error occurs, usually while trying to write to this stream. The event receives a single
Exception
argument for the error instance.
$stream->on('error', function (Exception $e) {
    echo 'Error: ' . $e->getMessage() . PHP_EOL;
});

This event SHOULD be emitted once the stream detects a fatal error, such as a fatal transmission error. It SHOULD NOT be emitted after a previous

error
or
close
event. It MUST NOT be emitted if this is not a fatal error condition, such as a temporary network issue that did not cause any data to be lost.

After the stream errors, it MUST close the stream and SHOULD thus be followed by a

close
event and then switch to non-writable mode, see also
close()
and
isWritable()
.

Many common streams (such as a TCP/IP connection or a file-based stream) only deal with data transmission and may choose to only emit this for a fatal transmission error once and will then close (terminate) the stream in response.

If this stream is a

DuplexStreamInterface
, you should also notice how the readable side of the stream also implements an
error
event. In other words, an error may occur while either reading or writing the stream which should result in the same error processing.

close event

The

close
event will be emitted once the stream closes (terminates).
$stream->on('close', function () {
    echo 'CLOSED';
});

This event SHOULD be emitted once or never at all, depending on whether the stream ever terminates. It SHOULD NOT be emitted after a previous

close
event.

After the stream is closed, it MUST switch to non-writable mode, see also

isWritable()
.

This event SHOULD be emitted whenever the stream closes, irrespective of whether this happens implicitly due to an unrecoverable error or explicitly when either side closes the stream.

Many common streams (such as a TCP/IP connection or a file-based stream) will likely choose to emit this event after flushing the buffer from the

end()
method, after receiving a successful
end
event or after a fatal transmission
error
event.

If this stream is a

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

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. The stream SHOULD send a
drain
event once the buffer is ready to accept more data.

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. Once the stream is closed, it SHOULD emit a
close
event.

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

If this stream is a

DuplexStreamInterface
, calling this method SHOULD also end its readable side, unless the stream supports half-open mode. In other words, after calling this method, these streams SHOULD switch into non-writable AND non-readable mode, see also
isReadable()
. This implies that in this case, the stream SHOULD NOT emit any
data
or
end
events anymore. Streams MAY choose to use the
pause()
method logic for this, but special care may have to be taken to ensure a following call to the
resume()
method SHOULD NOT continue emitting readable events.

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();

Once the stream is closed, it SHOULD emit a

close
event. Note that this event SHOULD NOT be emitted more than once, in particular if this method is called multiple times.

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()
.

DuplexStreamInterface

The

DuplexStreamInterface
is responsible for providing an interface for duplex streams (both readable and writable).

It builds on top of the existing interfaces for readable and writable streams and follows the exact same method and event semantics. If you're new to this concept, you should look into the

ReadableStreamInterface
and
WritableStreamInterface
first.

Besides defining a few methods, this interface also implements the

EventEmitterInterface
which allows you to react to the same events defined on the
ReadbleStreamInterface
and
WritableStreamInterface
.

The event callback functions MUST be a valid

callable
that obeys strict parameter definitions and MUST accept event parameters exactly as documented. The event callback functions MUST NOT throw an
Exception
. The return value of the event callback functions will be ignored and has no effect, so for performance reasons you're recommended to not return any excessive data structures.

Every implementation of this interface MUST follow these event semantics in order to be considered a well-behaving stream.

Note that higher-level implementations of this interface may choose to define additional events with dedicated semantics not defined as part of this low-level stream specification. Conformance with these event semantics is out of scope for this interface, so you may also have to refer to the documentation of such a higher-level implementation.

See also

ReadableStreamInterface
and
WritableStreamInterface
for more details.

Creating streams

ReactPHP uses the concept of "streams" throughout its ecosystem, so that many higher-level consumers of this package only deal with stream usage. This implies that stream instances are most often created within some higher-level components and many consumers never actually have to deal with creating a stream instance.

  • Use react/socket if you want to accept incoming or establish outgoing plaintext TCP/IP or secure TLS socket connection streams.
  • Use react/http if you want to receive an incoming HTTP request body streams.
  • Use react/child-process if you want to communicate with child processes via process pipes such as STDIN, STDOUT, STDERR etc.
  • Use experimental react/filesystem if you want to read from / write to the filesystem.
  • See also the last chapter for more real-world applications.

However, if you are writing a lower-level component or want to create a stream instance from a stream resource, then the following chapter is for you.

Note that the following examples use

fopen()
and
stream_socket_client()
for illustration purposes only. These functions SHOULD NOT be used in a truly async program because each call may take several seconds to complete and would block the EventLoop otherwise. Additionally, the
fopen()
call will return a file handle on some platforms which may or may not be supported by all EventLoop implementations. As an alternative, you may want to use higher-level libraries listed above.

ReadableResourceStream

The

ReadableResourceStream
is a concrete implementation of the
ReadableStreamInterface
for PHP's stream resources.

This can be used to represent a read-only resource like a file stream opened in readable mode or a stream such as

STDIN
:
$stream = new ReadableResourceStream(STDIN, $loop);
$stream->on('data', function ($chunk) {
    echo $chunk;
});
$stream->on('end', function () {
    echo 'END';
});

See also

ReadableStreamInterface
for more details.

The first parameter given to the constructor MUST be a valid stream resource that is opened in reading mode (e.g.

fopen()
mode
r
). Otherwise, it will throw an
InvalidArgumentException
:
// throws InvalidArgumentException
$stream = new ReadableResourceStream(false, $loop);

See also the

DuplexResourceStream
for read-and-write stream resources otherwise.

Internally, this class tries to enable non-blocking mode on the stream resource which may not be supported for all stream resources. Most notably, this is not supported by pipes on Windows (STDIN etc.). If this fails, it will throw a

RuntimeException
:
// throws RuntimeException on Windows
$stream = new ReadableResourceStream(STDIN, $loop);

Once the constructor is called with a valid stream resource, this class will take care of the underlying stream resource. You SHOULD only use its public API and SHOULD NOT interfere with the underlying stream resource manually.

This class takes an optional

int|null $readChunkSize
parameter that controls the maximum buffer size in bytes to read at once from the stream. You can use a
null
value here in order to apply its default value. This value SHOULD NOT be changed unless you know what you're doing. This can be a positive number which means that up to X bytes will be read at once from the underlying stream resource. Note that the actual number of bytes read may be lower if the stream resource has less than X bytes currently available. This can be
-1
which means "read everything available" from the underlying stream resource. This should read until the stream resource is not readable anymore (i.e. underlying buffer drained), note that this does not neccessarily mean it reached EOF.
$stream = new ReadableResourceStream(STDIN, $loop, 8192);

PHP bug warning: If the PHP process has explicitly been started without a

STDIN
stream, then trying to read from
STDIN
may return data from another stream resource. This does not happen if you start this with an empty stream like
php test.php < /dev/null
instead of
php test.php .
  See #81 for more details.

WritableResourceStream

The

WritableResourceStream
is a concrete implementation of the
WritableStreamInterface
for PHP's stream resources.

This can be used to represent a write-only resource like a file stream opened in writable mode or a stream such as

STDOUT
or
STDERR
:
$stream = new WritableResourceStream(STDOUT, $loop);
$stream->write('hello!');
$stream->end();

See also

WritableStreamInterface
for more details.

The first parameter given to the constructor MUST be a valid stream resource that is opened for writing. Otherwise, it will throw an

InvalidArgumentException
:
// throws InvalidArgumentException
$stream = new WritableResourceStream(false, $loop);

See also the

DuplexResourceStream
for read-and-write stream resources otherwise.

Internally, this class tries to enable non-blocking mode on the stream resource which may not be supported for all stream resources. Most notably, this is not supported by pipes on Windows (STDOUT, STDERR etc.). If this fails, it will throw a

RuntimeException
:
// throws RuntimeException on Windows
$stream = new WritableResourceStream(STDOUT, $loop);

Once the constructor is called with a valid stream resource, this class will take care of the underlying stream resource. You SHOULD only use its public API and SHOULD NOT interfere with the underlying stream resource manually.

Any

write()
calls to this class will not be performed instantly, but will be performed asynchronously, once the EventLoop reports the stream resource is ready to accept data. For this, it uses an in-memory buffer string to collect all outstanding writes. This buffer has a soft-limit applied which defines how much data it is willing to accept before the caller SHOULD stop sending further data.

This class takes an optional

int|null $writeBufferSoftLimit
parameter that controls this maximum buffer size in bytes. You can use a
null
value here in order to apply its default value. This value SHOULD NOT be changed unless you know what you're doing.
$stream = new WritableResourceStream(STDOUT, $loop, 8192);

This class takes an optional

int|null $writeChunkSize
parameter that controls this maximum buffer size in bytes to write at once to the stream. You can use a
null
value here in order to apply its default value. This value SHOULD NOT be changed unless you know what you're doing. This can be a positive number which means that up to X bytes will be written at once to the underlying stream resource. Note that the actual number of bytes written may be lower if the stream resource has less than X bytes currently available. This can be
-1
which means "write everything available" to the underlying stream resource.
$stream = new WritableResourceStream(STDOUT, $loop, null, 8192);

See also

write()
for more details.

DuplexResourceStream

The

DuplexResourceStream
is a concrete implementation of the
DuplexStreamInterface
for PHP's stream resources.

This can be used to represent a read-and-write resource like a file stream opened in read and write mode mode or a stream such as a TCP/IP connection:

$conn = stream_socket_client('tcp://google.com:80');
$stream = new DuplexResourceStream($conn, $loop);
$stream->write('hello!');
$stream->end();

See also

DuplexStreamInterface
for more details.

The first parameter given to the constructor MUST be a valid stream resource that is opened for reading and writing. Otherwise, it will throw an

InvalidArgumentException
:
// throws InvalidArgumentException
$stream = new DuplexResourceStream(false, $loop);

See also the

ReadableResourceStream
for read-only and the
WritableResourceStream
for write-only stream resources otherwise.

Internally, this class tries to enable non-blocking mode on the stream resource which may not be supported for all stream resources. Most notably, this is not supported by pipes on Windows (STDOUT, STDERR etc.). If this fails, it will throw a

RuntimeException
:
// throws RuntimeException on Windows
$stream = new DuplexResourceStream(STDOUT, $loop);

Once the constructor is called with a valid stream resource, this class will take care of the underlying stream resource. You SHOULD only use its public API and SHOULD NOT interfere with the underlying stream resource manually.

This class takes an optional

int|null $readChunkSize
parameter that controls the maximum buffer size in bytes to read at once from the stream. You can use a
null
value here in order to apply its default value. This value SHOULD NOT be changed unless you know what you're doing. This can be a positive number which means that up to X bytes will be read at once from the underlying stream resource. Note that the actual number of bytes read may be lower if the stream resource has less than X bytes currently available. This can be
-1
which means "read everything available" from the underlying stream resource. This should read until the stream resource is not readable anymore (i.e. underlying buffer drained), note that this does not neccessarily mean it reached EOF.
$conn = stream_socket_client('tcp://google.com:80');
$stream = new DuplexResourceStream($conn, $loop, 8192);

Any

write()
calls to this class will not be performed instantly, but will be performed asynchronously, once the EventLoop reports the stream resource is ready to accept data. For this, it uses an in-memory buffer string to collect all outstanding writes. This buffer has a soft-limit applied which defines how much data it is willing to accept before the caller SHOULD stop sending further data.

This class takes another optional

WritableStreamInterface|null $buffer
parameter that controls this write behavior of this stream. You can use a
null
value here in order to apply its default value. This value SHOULD NOT be changed unless you know what you're doing.

If you want to change the write buffer soft limit, you can pass an instance of

WritableResourceStream
like this:

$conn = stream_socket_client('tcp://google.com:80');
$buffer = new WritableResourceStream($conn, $loop, 8192);
$stream = new DuplexResourceStream($conn, $loop, null, $buffer);

See also

WritableResourceStream
for more details.

ThroughStream

The

ThroughStream
implements the
DuplexStreamInterface
and will simply pass any data you write to it through to its readable end.
$through = new ThroughStream();
$through->on('data', $this->expectCallableOnceWith('hello'));

$through->write('hello');

Similarly, the

end()
method will end the stream and emit an
end
event
and then
close()
the stream. The
close()
method
will close the stream and emit a
close
event
. Accordingly, this is can also be used in a
pipe()
context like this:

$through = new ThroughStream();
$source->pipe($through)->pipe($dest);

Optionally, its constructor accepts any callable function which will then be used to filter any data written to it. This function receives a single data argument as passed to the writable side and must return the data as it will be passed to its readable end:

$through = new ThroughStream('strtoupper');
$source->pipe($through)->pipe($dest);

Note that this class makes no assumptions about any data types. This can be used to convert data, for example for transforming any structured data into a newline-delimited JSON (NDJSON) stream like this:

$through = new ThroughStream(function ($data) {
    return json_encode($data) . PHP_EOL;
});
$through->on('data', $this->expectCallableOnceWith("[2, true]\n"));

$through->write(array(2, true));

The callback function is allowed to throw an

Exception
. In this case, the stream will emit an
error
event and then
close()
the stream.
$through = new ThroughStream(function ($data) {
    if (!is_string($data)) {
        throw new \UnexpectedValueException('Only strings allowed');
    }
    return $data;
});
$through->on('error', $this->expectCallableOnce()));
$through->on('close', $this->expectCallableOnce()));
$through->on('data', $this->expectCallableNever()));

$through->write(2);

CompositeStream

The

CompositeStream
implements the
DuplexStreamInterface
and can be used to create a single duplex stream from two individual streams implementing
ReadableStreamInterface
and
WritableStreamInterface
respectively.

This is useful for some APIs which may require a single

DuplexStreamInterface
or simply because it's often more convenient to work with a single stream instance like this:

$stdin = new ReadableResourceStream(STDIN, $loop);
$stdout = new WritableResourceStream(STDOUT, $loop);

$stdio = new CompositeStream($stdin, $stdout);

$stdio->on('data', function ($chunk) use ($stdio) { $stdio->write('You said: ' . $chunk); });

This is a well-behaving stream which forwards all stream events from the underlying streams and forwards all streams calls to the underlying streams.

If you

write()
to the duplex stream, it will simply
write()
to the writable side and return its status.

If you

end()
the duplex stream, it will
end()
the writable side and will
pause()
the readable side.

If you

close()
the duplex stream, both input streams will be closed. If either of the two input streams emits a
close
event, the duplex stream will also close. If either of the two input streams is already closed while constructing the duplex stream, it will
close()
the other side and return a closed stream.

Usage

The following example can be used to pipe the contents of a source file into a destination file without having to ever read the whole file into memory:

$loop = new React\EventLoop\StreamSelectLoop;

$source = new React\Stream\ReadableResourceStream(fopen('source.txt', 'r'), $loop); $dest = new React\Stream\WritableResourceStream(fopen('destination.txt', 'w'), $loop);

$source->pipe($dest);

$loop->run();

Note that this example uses

fopen()
for illustration purposes only. This should not be used in a truly async program because the filesystem is inherently blocking and each call could potentially take several seconds. See also creating streams for more sophisticated examples.

Install

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

This project follows SemVer. This will install the latest supported version:

$ composer require react/stream:^1.1.1

See also the CHANGELOG for details about version upgrades.

This project aims to run on any platform and thus does not require any PHP extensions and supports running on legacy PHP 5.3 through current PHP 7+ and HHVM. It's highly recommended to use PHP 7+ for this project due to its vast performance improvements.

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

The test suite also contains a number of functional integration tests that rely on a stable internet connection. If you do not want to run these, they can simply be skipped like this:

$ php vendor/bin/phpunit --exclude-group internet

License

MIT, see LICENSE file.

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