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<?php
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namespace ResourcePool;
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use React\Promise\FulfilledPromise;
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use React\Promise\Deferred;
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/**
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* This class exists to keep the public interface of Pool clean. Once PHP 5.3 support is dropped,
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* this functionality will probably be moved to Pool in the form of private methods.
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*
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* @author Josh Di Fabio <[email protected]>
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*
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* @internal
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*/
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class PoolInternal
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{
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private $size;
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private $usage = 0;
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private $queue;
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private $whenNextIdle;
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public function __construct($size = null)
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{
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$this->size = $size;
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$this->queue = new \SplQueue;
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$this->whenNextIdle = new Deferred;
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$this->whenNextIdle->resolve();
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}
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public function allocate($count)
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{
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return $this->createAllocationPromise('ResourcePool\PartialAllocationPromise', $count);
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}
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public function allocateAll()
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{
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return $this->createAllocationPromise('ResourcePool\AllocationPromise');
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}
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private function createAllocationPromise($promiseClass, $count = null)
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{
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$this->beforeAllocate();
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if ($this->canAllocate($count)) {
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$allocation = $this->createAllocation($count);
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$promise = new FulfilledPromise($allocation);
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$resolver = null;
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} else {
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$deferred = new Deferred;
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$promise = $deferred->promise();
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$isResolved = false;
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$resolver = $this->createResolver($isResolved, $count, $deferred);
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$promise->then(null, array($this, 'afterPromiseCancelled'));
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$this->queue->enqueue(array($count, $deferred, &$isResolved));
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}
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return new $promiseClass($promise, $resolver);
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}
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public function setSize($size)
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{
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$this->size = $size;
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$this->processQueue();
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}
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public function getAvailability()
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{
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return max(0, $this->size - $this->usage);
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}
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public function getUsage()
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{
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return $this->usage;
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}
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private function processQueue()
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{
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foreach ($this->queue as $allocationInfo) {
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if (true === $allocationInfo[2]) {
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$this->queue->dequeue();
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continue;
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}
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if (!$this->canAllocate($allocationInfo[0])) {
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break;
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}
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$this->queue->dequeue();
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$allocation = $this->createAllocation($allocationInfo[0]);
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$allocationInfo[1]->resolve($allocation);
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}
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}
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public function afterPromiseCancelled()
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{
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$this->decrementUsage(0);
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}
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public function decrementUsage($amount)
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{
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$this->usage -= $amount;
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$this->processQueue();
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if ($this->isIdle()) {
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$this->whenNextIdle->resolve();
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}
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}
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public function canAllocate($count = null)
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{
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if (null === $count) {
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return 0 === $this->usage && $this->size > 0;
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}
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return $count <= $this->getAvailability();
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}
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public function createAllocation($size)
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{
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if (null === $size) {
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$size = $this->size;
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}
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$this->usage += $size;
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return new Allocation(array($this, 'decrementUsage'), $size);
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}
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public function whenNextIdle($fulfilledHandler = null)
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{
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$promise = $this->whenNextIdle->promise();
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if (null !== $fulfilledHandler) {
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return $promise->then($fulfilledHandler);
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}
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return $promise;
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}
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private function beforeAllocate()
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{
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if ($this->isIdle()) {
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$this->whenNextIdle = new Deferred;
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}
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}
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private function isIdle()
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{
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return (0 == $this->usage && 0 == $this->queue->count());
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}
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private function createResolver(&$isResolved, $count, $deferred)
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{
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$that = $this;
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return function ($burst) use (&$isResolved, $that, $count, $deferred) {
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if ($isResolved) {
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throw new \LogicException;
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}
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$isResolved = true;
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if ($burst || $that->canAllocate($count)) {
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$allocation = $that->createAllocation($count);
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$deferred->resolve($allocation);
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} else {
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$deferred->reject(new \RuntimeException('The resource pool cannot allocate the specified number of resources'));
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}
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};
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}
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}
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