*/ private readonly \SplQueue $waiting; /** * @param positive-int $maxLocks */ public function __construct(private readonly int $maxLocks) { /** @psalm-suppress TypeDoesNotContainType */ if ($maxLocks < 1) { throw new \ValueError('The number of locks must be greater than 0, got ' . $maxLocks); } $this->waiting = new \SplQueue(); } public function acquire(): Lock { if ($this->locks < $this->maxLocks) { ++$this->locks; return $this->createLock(); } $this->waiting->enqueue($suspension = EventLoop::getSuspension()); return $suspension->suspend(); } private function release(): void { if (!$this->waiting->isEmpty()) { $suspension = $this->waiting->dequeue(); $suspension->resume($this->createLock()); return; } --$this->locks; } private function createLock(): Lock { return new Lock($this->release(...)); } }