<?php
declare(strict_types=1);
namespace malkusch\lock\util;
use InvalidArgumentException;
use malkusch\lock\exception\DeadlineException;
use malkusch\lock\exception\LockAcquireException;
use RuntimeException;
/**
* Timeout based on a scheduled alarm.
*
* This class requires the pcntl module.
*
* @author Markus Malkusch <markus@malkusch.de>
* @link bitcoin:1335STSwu9hST4vcMRppEPgENMHD2r1REK Donations
* @license WTFPL
* @internal
*/
final class PcntlTimeout
{
/**
* @var int Timeout in seconds
*/
private $timeout;
/**
* Builds the timeout.
*
* @param int $timeout Timeout in seconds.
* @throws \RuntimeException When the PCNTL module is not enabled.
* @throws \InvalidArgumentException When the timeout is zero or negative.
*/
public function __construct(int $timeout)
{
if (!self::isSupported()) {
throw new RuntimeException('PCNTL module not enabled');
}
if ($timeout <= 0) {
throw new InvalidArgumentException(
'Timeout must be positive and non zero'
);
}
$this->timeout = $timeout;
}
/**
* Runs the code and would eventually time out.
*
* This method has the side effect, that any signal handler for SIGALRM will
* be reset to the default hanlder (SIG_DFL). It also expects that there is
* no previously scheduled alarm. If your application uses alarms
* ({@link pcntl_alarm()}) or a signal handler for SIGALRM, don't use this
* method. It will interfer with your application and lead to unexpected
* behaviour.
*
* @param callable $code Executed code block
* @throws \malkusch\lock\exception\DeadlineException Running the code hit
* the deadline.
* @throws \malkusch\lock\exception\LockAcquireException Installing the
* timeout failed.
* @return mixed Return value of the executed block
*/
public function timeBoxed(callable $code)
{
$existingHandler = pcntl_signal_get_handler(SIGALRM);
$signal = pcntl_signal(SIGALRM, function (): void {
throw new DeadlineException(sprintf(
'Timebox hit deadline of %d seconds',
$this->timeout
));
});
if (!$signal) {
throw new LockAcquireException('Could not install signal');
}
$oldAlarm = pcntl_alarm($this->timeout);
if ($oldAlarm != 0) {
throw new LockAcquireException('Existing alarm was not expected');
}
try {
return $code();
} finally {
pcntl_alarm(0);
pcntl_signal_dispatch();
pcntl_signal(SIGALRM, $existingHandler);
}
}
/**
* Returns if this class is supported by the PHP runtime.
*
* This class requires the pcntl module. This method checks if
* it is available.
*
* @return bool TRUE if this class is supported by the PHP runtime.
*/
public static function isSupported(): bool
{
return
PHP_SAPI === 'cli' &&
extension_loaded('pcntl') &&
function_exists('pcntl_alarm') &&
function_exists('pcntl_signal') &&
function_exists('pcntl_signal_dispatch');
}
}