72 lines
2.0 KiB
PHP
72 lines
2.0 KiB
PHP
<?php
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namespace WP_Ultimo\Dependencies\Amp\Sync;
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use WP_Ultimo\Dependencies\Amp\Deferred;
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use WP_Ultimo\Dependencies\Amp\Promise;
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/**
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* A barrier is a synchronization primitive.
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*
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* The barrier is initialized with a certain count, which can be increased and decreased until it reaches zero.
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*
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* A count of one can be used to block multiple coroutines until a certain condition is met.
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*
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* A count of N can be used to await multiple coroutines doing an action to complete.
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*
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* **Example**
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*
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* ```php
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* $barrier = new Amp\Sync\Barrier(2);
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* $barrier->arrive();
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* $barrier->arrive(); // promise returned from Barrier::await() is now resolved
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*
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* yield $barrier->await();
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* ```
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*/
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final class Barrier
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{
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/** @var int */
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private $count;
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/** @var Deferred */
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private $deferred;
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public function __construct(int $count)
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{
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if ($count < 1) {
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throw new \Error('Count must be positive, got ' . $count);
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}
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$this->count = $count;
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$this->deferred = new Deferred();
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}
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public function getCount() : int
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{
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return $this->count;
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}
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public function arrive(int $count = 1) : void
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{
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if ($count < 1) {
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throw new \Error('Count must be at least 1, got ' . $count);
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}
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if ($count > $this->count) {
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throw new \Error('Count cannot be greater than remaining count: ' . $count . ' > ' . $this->count);
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}
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$this->count -= $count;
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if ($this->count === 0) {
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$this->deferred->resolve();
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}
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}
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public function register(int $count = 1) : void
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{
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if ($count < 1) {
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throw new \Error('Count must be at least 1, got ' . $count);
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}
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if ($this->count === 0) {
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throw new \Error('Can\'t increase count, because the barrier already broke');
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}
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$this->count += $count;
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}
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public function await() : Promise
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{
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return $this->deferred->promise();
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}
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}
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