/**
* 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;
}
