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<?php |
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namespace GuzzleHttp\Promise; |
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|
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/** |
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* Represents a promise that iterates over many promises and invokes |
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* side-effect functions in the process. |
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*/ |
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class EachPromise implements PromisorInterface |
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{ |
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private $pending = []; |
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|
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/** @var \Iterator */ |
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private $iterable; |
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|
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/** @var callable|int */ |
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private $concurrency; |
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|
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/** @var callable */ |
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private $onFulfilled; |
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|
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/** @var callable */ |
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private $onRejected; |
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|
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/** @var Promise */ |
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private $aggregate; |
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|
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/** @var bool */ |
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private $mutex; |
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|
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/** |
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* Configuration hash can include the following key value pairs: |
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* |
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* - fulfilled: (callable) Invoked when a promise fulfills. The function |
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* is invoked with three arguments: the fulfillment value, the index |
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* position from the iterable list of the promise, and the aggregate |
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* promise that manages all of the promises. The aggregate promise may |
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* be resolved from within the callback to short-circuit the promise. |
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* - rejected: (callable) Invoked when a promise is rejected. The |
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* function is invoked with three arguments: the rejection reason, the |
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* index position from the iterable list of the promise, and the |
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* aggregate promise that manages all of the promises. The aggregate |
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* promise may be resolved from within the callback to short-circuit |
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* the promise. |
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* - concurrency: (integer) Pass this configuration option to limit the |
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* allowed number of outstanding concurrently executing promises, |
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* creating a capped pool of promises. There is no limit by default. |
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* |
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* @param mixed $iterable Promises or values to iterate. |
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* @param array $config Configuration options |
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*/ |
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public function __construct($iterable, array $config = []) |
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{ |
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$this->iterable = iter_for($iterable); |
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|
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if (isset($config['concurrency'])) { |
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$this->concurrency = $config['concurrency']; |
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} |
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|
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if (isset($config['fulfilled'])) { |
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$this->onFulfilled = $config['fulfilled']; |
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} |
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|
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if (isset($config['rejected'])) { |
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$this->onRejected = $config['rejected']; |
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} |
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} |
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|
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public function promise() |
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{ |
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if ($this->aggregate) { |
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return $this->aggregate; |
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} |
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|
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try { |
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$this->createPromise(); |
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$this->iterable->rewind(); |
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if (!$this->checkIfFinished()) { |
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$this->refillPending(); |
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} |
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} catch (\Throwable $e) { |
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$this->aggregate->reject($e); |
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} catch (\Exception $e) { |
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$this->aggregate->reject($e); |
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} |
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|
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return $this->aggregate; |
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} |
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|
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private function createPromise() |
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{ |
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$this->mutex = false; |
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$this->aggregate = new Promise(function () { |
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reset($this->pending); |
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// Consume a potentially fluctuating list of promises while |
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// ensuring that indexes are maintained (precluding array_shift). |
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while ($promise = current($this->pending)) { |
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next($this->pending); |
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$promise->wait(); |
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if ($this->aggregate->getState() !== PromiseInterface::PENDING) { |
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return; |
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} |
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} |
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}); |
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|
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// Clear the references when the promise is resolved. |
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$clearFn = function () { |
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$this->iterable = $this->concurrency = $this->pending = null; |
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$this->onFulfilled = $this->onRejected = null; |
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}; |
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|
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$this->aggregate->then($clearFn, $clearFn); |
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} |
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|
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private function refillPending() |
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{ |
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if (!$this->concurrency) { |
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// Add all pending promises. |
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while ($this->addPending() && $this->advanceIterator()); |
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return; |
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} |
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|
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// Add only up to N pending promises. |
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$concurrency = is_callable($this->concurrency) |
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? call_user_func($this->concurrency, count($this->pending)) |
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: $this->concurrency; |
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$concurrency = max($concurrency - count($this->pending), 0); |
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// Concurrency may be set to 0 to disallow new promises. |
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if (!$concurrency) { |
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return; |
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} |
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// Add the first pending promise. |
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$this->addPending(); |
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// Note this is special handling for concurrency=1 so that we do |
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// not advance the iterator after adding the first promise. This |
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// helps work around issues with generators that might not have the |
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// next value to yield until promise callbacks are called. |
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while (--$concurrency |
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&& $this->advanceIterator() |
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&& $this->addPending()); |
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} |
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|
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private function addPending() |
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{ |
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if (!$this->iterable || !$this->iterable->valid()) { |
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return false; |
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} |
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|
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$promise = promise_for($this->iterable->current()); |
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$key = $this->iterable->key(); |
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|
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// Iterable keys may not be unique, so we add the promises at the end |
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// of the pending array and retrieve the array index being used |
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$this->pending[] = null; |
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end($this->pending); |
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$idx = key($this->pending); |
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|
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$this->pending[$idx] = $promise->then( |
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function ($value) use ($idx, $key) { |
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if ($this->onFulfilled) { |
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call_user_func( |
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$this->onFulfilled, $value, $key, $this->aggregate |
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); |
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} |
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$this->step($idx); |
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}, |
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function ($reason) use ($idx, $key) { |
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if ($this->onRejected) { |
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call_user_func( |
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$this->onRejected, $reason, $key, $this->aggregate |
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); |
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} |
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$this->step($idx); |
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} |
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); |
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|
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return true; |
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} |
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|
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private function advanceIterator() |
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{ |
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// Place a lock on the iterator so that we ensure to not recurse, |
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// preventing fatal generator errors. |
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if ($this->mutex) { |
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return false; |
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} |
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|
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$this->mutex = true; |
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|
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try { |
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$this->iterable->next(); |
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$this->mutex = false; |
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return true; |
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} catch (\Throwable $e) { |
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$this->aggregate->reject($e); |
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$this->mutex = false; |
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return false; |
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} catch (\Exception $e) { |
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$this->aggregate->reject($e); |
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$this->mutex = false; |
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return false; |
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} |
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} |
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|
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private function step($idx) |
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{ |
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// If the promise was already resolved, then ignore this step. |
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if ($this->aggregate->getState() !== PromiseInterface::PENDING) { |
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return; |
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} |
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|
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unset($this->pending[$idx]); |
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|
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// Only refill pending promises if we are not locked, preventing the |
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// EachPromise to recursively invoke the provided iterator, which |
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// cause a fatal error: "Cannot resume an already running generator" |
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if ($this->advanceIterator() && !$this->checkIfFinished()) { |
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// Add more pending promises if possible. |
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$this->refillPending(); |
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} |
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} |
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|
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private function checkIfFinished() |
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{ |
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if (!$this->pending && !$this->iterable->valid()) { |
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// Resolve the promise if there's nothing left to do. |
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$this->aggregate->resolve(null); |
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return true; |
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} |
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|
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return false; |
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} |
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} |
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|
