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<?php
namespace GuzzleHttp\Stream;
/**
* Represents an asynchronous read-only stream that supports a drain event and
* pumping data from a source stream.
*
* The AsyncReadStream can be used as a completely asynchronous stream, meaning
* the data you can read from the stream will immediately return only
* the data that is currently buffered.
*
* AsyncReadStream can also be used in a "blocking" manner if a "pump" function
* is provided. When a caller requests more bytes than are available in the
* buffer, then the pump function is used to block until the requested number
* of bytes are available or the remote source stream has errored, closed, or
* timed-out. This behavior isn't strictly "blocking" because the pump function
* can send other transfers while waiting on the desired buffer size to be
* ready for reading (e.g., continue to tick an event loop).
*
* @unstable This class is subject to change.
*/
class AsyncReadStream implements StreamInterface
{
use StreamDecoratorTrait;
/** @var callable|null Fn used to notify writers the buffer has drained */
private $drain;
/** @var callable|null Fn used to block for more data */
private $pump;
/** @var int|null Highwater mark of the underlying buffer */
private $hwm;
/** @var bool Whether or not drain needs to be called at some point */
private $needsDrain;
/** @var int The expected size of the remote source */
private $size;
/**
* In order to utilize high water marks to tell writers to slow down, the
* provided stream must answer to the "hwm" stream metadata variable,
* providing the high water mark. If no "hwm" metadata value is available,
* then the "drain" functionality is not utilized.
*
* This class accepts an associative array of configuration options.
*
* - drain: (callable) Function to invoke when the stream has drained,
* meaning the buffer is now writable again because the size of the
* buffer is at an acceptable level (e.g., below the high water mark).
* The function accepts a single argument, the buffer stream object that
* has drained.
* - pump: (callable) A function that accepts the number of bytes to read
* from the source stream. This function will block until all of the data
* that was requested has been read, EOF of the source stream, or the
* source stream is closed.
* - size: (int) The expected size in bytes of the data that will be read
* (if known up-front).
*
* @param StreamInterface $buffer Buffer that contains the data that has
* been read by the event loop.
* @param array $config Associative array of options.
*
* @throws \InvalidArgumentException if the buffer is not readable and
* writable.
*/
public function __construct(
StreamInterface $buffer,
array $config = []
) {
if (!$buffer->isReadable() || !$buffer->isWritable()) {
throw new \InvalidArgumentException(
'Buffer must be readable and writable'
);
}
if (isset($config['size'])) {
$this->size = $config['size'];
}
static $callables = ['pump', 'drain'];
foreach ($callables as $check) {
if (isset($config[$check])) {
if (!is_callable($config[$check])) {
throw new \InvalidArgumentException(
$check . ' must be callable'
);
}
$this->{$check} = $config[$check];
}
}
$this->hwm = $buffer->getMetadata('hwm');
// Cannot drain when there's no high water mark.
if ($this->hwm === null) {
$this->drain = null;
}
$this->stream = $buffer;
}
/**
* Factory method used to create new async stream and an underlying buffer
* if no buffer is provided.
*
* This function accepts the same options as AsyncReadStream::__construct,
* but added the following key value pairs:
*
* - buffer: (StreamInterface) Buffer used to buffer data. If none is
* provided, a default buffer is created.
* - hwm: (int) High water mark to use if a buffer is created on your
* behalf.
* - max_buffer: (int) If provided, wraps the utilized buffer in a
* DroppingStream decorator to ensure that buffer does not exceed a given
* length. When exceeded, the stream will begin dropping data. Set the
* max_buffer to 0, to use a NullStream which does not store data.
* - write: (callable) A function that is invoked when data is written
* to the underlying buffer. The function accepts the buffer as the first
* argument, and the data being written as the second. The function MUST
* return the number of bytes that were written or false to let writers
* know to slow down.
* - drain: (callable) See constructor documentation.
* - pump: (callable) See constructor documentation.
*
* @param array $options Associative array of options.
*
* @return array Returns an array containing the buffer used to buffer
* data, followed by the ready to use AsyncReadStream object.
*/
public static function create(array $options = [])
{
$maxBuffer = isset($options['max_buffer'])
? $options['max_buffer']
: null;
if ($maxBuffer === 0) {
$buffer = new NullStream();
} elseif (isset($options['buffer'])) {
$buffer = $options['buffer'];
} else {
$hwm = isset($options['hwm']) ? $options['hwm'] : 16384;
$buffer = new BufferStream($hwm);
}
if ($maxBuffer > 0) {
$buffer = new DroppingStream($buffer, $options['max_buffer']);
}
// Call the on_write callback if an on_write function was provided.
if (isset($options['write'])) {
$onWrite = $options['write'];
$buffer = FnStream::decorate($buffer, [
'write' => function ($string) use ($buffer, $onWrite) {
$result = $buffer->write($string);
$onWrite($buffer, $string);
return $result;
}
]);
}
return [$buffer, new self($buffer, $options)];
}
public function getSize()
{
return $this->size;
}
public function isWritable()
{
return false;
}
public function write($string)
{
return false;
}
public function read($length)
{
if (!$this->needsDrain && $this->drain) {
$this->needsDrain = $this->stream->getSize() >= $this->hwm;
}
$result = $this->stream->read($length);
// If we need to drain, then drain when the buffer is empty.
if ($this->needsDrain && $this->stream->getSize() === 0) {
$this->needsDrain = false;
$drainFn = $this->drain;
$drainFn($this->stream);
}
$resultLen = strlen($result);
// If a pump was provided, the buffer is still open, and not enough
// data was given, then block until the data is provided.
if ($this->pump && $resultLen < $length) {
$pumpFn = $this->pump;
$result .= $pumpFn($length - $resultLen);
}
return $result;
}
}