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parallel/lib/Threading/Thread.php

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<?php declare(strict_types = 1);
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namespace Amp\Parallel\Threading;
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use Amp\Coroutine;
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use Amp\Parallel\{ ContextException, StatusError, SynchronizationError, Strand };
use Amp\Parallel\Sync\{ ChannelledStream, Internal\ExitStatus };
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use Amp\Socket\Socket;
use Interop\Async\Awaitable;
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/**
* Implements an execution context using native multi-threading.
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*
* The thread context is not itself threaded. A local instance of the context is
* maintained both in the context that creates the thread and in the thread
* itself.
*/
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class Thread implements Strand {
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/**
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* @var Internal\Thread An internal thread instance.
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*/
private $thread;
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/**
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* @var \Amp\Parallel\Sync\Channel A channel for communicating with the thread.
*/
private $channel;
/**
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* @var \Amp\Socket\Socket
*/
private $pipe;
/**
* @var resource
*/
private $socket;
/**
* @var callable
*/
private $function;
/**
* @var mixed[]
*/
private $args;
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/**
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* @var int
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*/
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private $oid = 0;
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/**
* Checks if threading is enabled.
*
* @return bool True if threading is enabled, otherwise false.
*/
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public static function supported(): bool {
return \extension_loaded('pthreads');
}
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/**
* Spawns a new thread and runs it.
*
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* @param callable $function The callable to invoke in the thread.
*
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* @return Thread The thread object that was spawned.
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*/
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public static function spawn(callable $function, ...$args) {
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$thread = new self($function, ...$args);
$thread->start();
return $thread;
}
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/**
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* Creates a new thread.
*
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* @param callable $function The callable to invoke in the thread when run.
*
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* @throws \Error Thrown if the pthreads extension is not available.
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*/
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public function __construct(callable $function, ...$args) {
if (!self::supported()) {
throw new \Error("The pthreads extension is required to create threads.");
}
$this->function = $function;
$this->args = $args;
}
/**
* Returns the thread to the condition before starting. The new thread can be started and run independently of the
* first thread.
*/
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public function __clone() {
$this->thread = null;
$this->socket = null;
$this->pipe = null;
$this->channel = null;
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$this->oid = 0;
}
/**
* Kills the thread if it is still running.
*
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* @throws \Amp\Parallel\ContextException
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*/
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public function __destruct() {
if (\getmypid() === $this->oid) {
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$this->kill();
}
}
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/**
* Checks if the context is running.
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*
* @return bool True if the context is running, otherwise false.
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*/
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public function isRunning(): bool {
return null !== $this->pipe && $this->pipe->isReadable();
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}
/**
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* Spawns the thread and begins the thread's execution.
*
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* @throws \Amp\Parallel\StatusError If the thread has already been started.
* @throws \Amp\Parallel\ContextException If starting the thread was unsuccessful.
*/
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public function start() {
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if ($this->oid !== 0) {
throw new StatusError('The thread has already been started.');
}
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$this->oid = \getmypid();
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list($channel, $this->socket) = \Amp\Socket\pair();
$this->thread = new Internal\Thread($this->socket, $this->function, $this->args);
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if (!$this->thread->start(PTHREADS_INHERIT_INI)) {
throw new ContextException('Failed to start the thread.');
}
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$this->channel = new ChannelledStream($this->pipe = new Socket($channel));
}
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/**
* Immediately kills the context.
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*
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* @throws ContextException If killing the thread was unsuccessful.
*/
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public function kill() {
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if ($this->thread !== null) {
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try {
if ($this->thread->isRunning() && !$this->thread->kill()) {
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throw new ContextException('Could not kill thread.');
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}
} finally {
$this->close();
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}
}
}
/**
* Closes channel and socket if still open.
*/
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private function close() {
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if ($this->pipe !== null && $this->pipe->isReadable()) {
$this->pipe->close();
}
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if (\is_resource($this->socket)) {
@\fclose($this->socket);
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}
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$this->thread = null;
$this->channel = null;
}
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/**
* Gets a promise that resolves when the context ends and joins with the
* parent context.
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*
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* @return \Interop\Async\Awaitable<mixed>
*
* @throws StatusError Thrown if the context has not been started.
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* @throws SynchronizationError Thrown if an exit status object is not received.
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*/
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public function join(): Awaitable {
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if ($this->channel == null || $this->thread === null) {
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throw new StatusError('The thread has not been started or has already finished.');
}
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return new Coroutine($this->doJoin());
}
/**
* @coroutine
*
* @return \Generator
*
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* @throws \Amp\Parallel\SynchronizationError If the thread does not send an exit status.
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*/
private function doJoin(): \Generator {
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try {
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$response = yield $this->channel->receive();
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if (!$response instanceof ExitStatus) {
throw new SynchronizationError('Did not receive an exit status from thread.');
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}
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$result = $response->getResult();
$this->thread->join();
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} catch (\Throwable $exception) {
$this->kill();
throw $exception;
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}
$this->close();
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return $result;
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}
/**
* {@inheritdoc}
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*/
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public function receive(): Awaitable {
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if ($this->channel === null) {
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throw new StatusError('The process has not been started.');
}
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return \Amp\pipe($this->channel->receive(), static function ($data) {
if ($data instanceof ExitStatus) {
$data = $data->getResult();
throw new SynchronizationError(\sprintf(
'Thread unexpectedly exited with result of type: %s',
\is_object($data) ? \get_class($data) : \gettype($data)
));
}
return $data;
});
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}
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/**
* {@inheritdoc}
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*/
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public function send($data): Awaitable {
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if ($this->channel === null) {
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throw new StatusError('The thread has not been started or has already finished.');
}
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if ($data instanceof ExitStatus) {
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throw new \Error('Cannot send exit status objects.');
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}
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return $this->channel->send($data);
}
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}