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Use a custom priority queue for timers
Fixes #220 by allowing immediate removal of the watcher from the queue. Insert and extract is O(log(n)), peeking is O(1), and removal is O(n).
This commit is contained in:
Aaron Piotrowski
parent
b6fc1e12d4
commit
c6f8425473
125
lib/Loop/Internal/TimerQueue.php
Normal file
125
lib/Loop/Internal/TimerQueue.php
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@ -0,0 +1,125 @@
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<?php
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namespace Amp\Loop\Internal;
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use Amp\Loop\Watcher;
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/**
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* Uses a binary tree stored in an array to implement a heap.
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*/
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class TimerQueue
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{
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/** @var TimerQueueEntry[] */
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private $data = [];
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/**
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* Inserts the watcher into the queue. Time complexity: O(log(n)).
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*
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* @param Watcher $watcher
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* @param int $expiration
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*/
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public function insert(Watcher $watcher, int $expiration)
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{
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$entry = new TimerQueueEntry;
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$entry->watcher = $watcher;
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$entry->expiration = $expiration;
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$node = \count($this->data);
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$this->data[$node] = $entry;
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while ($node !== 0 && $entry->expiration < $this->data[$parent = ($node - 1) >> 1]->expiration) {
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$this->data[$node] = $this->data[$parent];
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$this->data[$parent] = $entry;
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$node = $parent;
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}
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}
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/**
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* Removes the given watcher from the queue. Time complexity: O(n).
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*
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* @param Watcher $watcher
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*/
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public function remove(Watcher $watcher)
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{
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foreach ($this->data as $node => $entry) {
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if ($entry->watcher === $watcher) {
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$this->removeAndRebuild($node);
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return;
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}
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}
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}
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/**
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* Deletes and returns the Watcher on top of the heap. Time complexity: O(log(n)).
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*
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* @return [Watcher, int] Tuple of the watcher and the expiration time.
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*/
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public function extract(): array
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{
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if ($this->isEmpty()) {
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throw new \Error('No data left in the heap.');
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}
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$data = $this->removeAndRebuild(0);
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return [$data->watcher, $data->expiration];
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}
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/**
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* @param int $node Remove the given node and then rebuild the data array from that node downward.
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*
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* @return TimerQueueEntry Removed entry.
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*/
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private function removeAndRebuild(int $node): TimerQueueEntry
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{
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$length = \count($this->data) - 1;
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$data = $this->data[$node];
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$this->data[$node] = $this->data[$length];
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unset($this->data[$length]);
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while (($child = ($node << 1) + 1) < $length) {
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if ($this->data[$child]->expiration < $this->data[$node]->expiration
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&& ($child + 1 >= $length || $this->data[$child]->expiration < $this->data[$child + 1]->expiration)
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) {
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// Left child is less than parent and right child.
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$swap = $child;
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} elseif ($child + 1 < $length && $this->data[$child + 1]->expiration < $this->data[$node]->expiration) {
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// Right child is less than parent and left child.
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$swap = $child + 1;
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} else { // Left and right child are greater than parent.
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break;
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}
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$temp = $this->data[$node];
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$this->data[$node] = $this->data[$swap];
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$this->data[$swap] = $temp;
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$node = $swap;
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}
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return $data;
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}
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/**
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* Returns the value at the top of the heap (without removing it). Time complexity: O(1).
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*
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* @return [Watcher, int] Tuple of the watcher and the expiration time.
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*/
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public function peek(): array
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{
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if ($this->isEmpty()) {
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throw new \Error('No data in the heap.');
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}
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return [$this->data[0]->watcher, $this->data[0]->expiration];
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}
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/**
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* Determines if the heap is empty.
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* @return bool
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*/
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public function isEmpty(): bool
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{
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return empty($this->data);
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}
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}
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17
lib/Loop/Internal/TimerQueueEntry.php
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17
lib/Loop/Internal/TimerQueueEntry.php
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@ -0,0 +1,17 @@
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<?php
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namespace Amp\Loop\Internal;
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use Amp\Loop\Watcher;
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use Amp\Struct;
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class TimerQueueEntry
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{
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use Struct;
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/** @var Watcher */
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public $watcher;
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/** @var int */
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public $expiration;
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}
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@ -22,10 +22,7 @@ class NativeDriver extends Driver
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/** @var \Amp\Loop\Watcher[][] */
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private $writeWatchers = [];
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/** @var int[] */
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private $timerExpires = [];
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/** @var \SplPriorityQueue */
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/** @var Internal\TimerQueue */
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private $timerQueue;
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/** @var \Amp\Loop\Watcher[][] */
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@ -45,7 +42,7 @@ class NativeDriver extends Driver
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public function __construct()
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{
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$this->timerQueue = new \SplPriorityQueue();
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$this->timerQueue = new Internal\TimerQueue;
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$this->signalHandling = \extension_loaded("pcntl");
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$this->nowOffset = getCurrentTime();
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$this->now = \random_int(0, $this->nowOffset);
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@ -97,56 +94,48 @@ class NativeDriver extends Driver
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$blocking ? $this->getTimeout() : 0
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);
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if (!empty($this->timerExpires)) {
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$scheduleQueue = [];
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$scheduleQueue = [];
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try {
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while (!$this->timerQueue->isEmpty()) {
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list($watcher, $expiration) = $this->timerQueue->top();
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try {
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while (!$this->timerQueue->isEmpty()) {
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list($watcher, $expiration) = $this->timerQueue->peek();
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$id = $watcher->id;
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if ($expiration > $this->now()) { // Timer at top of queue has not expired.
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break;
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}
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if (!isset($this->timerExpires[$id]) || $expiration !== $this->timerExpires[$id]) {
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$this->timerQueue->extract(); // Timer was removed from queue.
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$this->timerQueue->extract();
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if ($watcher->type & Watcher::REPEAT) {
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$expiration = $this->now() + $watcher->value;
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$scheduleQueue[] = [$watcher, $expiration];
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} else {
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$this->cancel($watcher->id);
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}
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try {
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// Execute the timer.
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$result = ($watcher->callback)($watcher->id, $watcher->data);
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if ($result === null) {
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continue;
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}
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if ($this->timerExpires[$id] > $this->now()) { // Timer at top of queue has not expired.
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break;
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if ($result instanceof \Generator) {
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$result = new Coroutine($result);
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}
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$this->timerQueue->extract();
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if ($watcher->type & Watcher::REPEAT) {
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$expiration = $this->now() + $watcher->value;
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$this->timerExpires[$watcher->id] = $expiration;
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$scheduleQueue[] = [$watcher, $expiration];
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} else {
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$this->cancel($id);
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}
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try {
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// Execute the timer.
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$result = ($watcher->callback)($id, $watcher->data);
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if ($result === null) {
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continue;
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}
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if ($result instanceof \Generator) {
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$result = new Coroutine($result);
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}
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if ($result instanceof Promise || $result instanceof ReactPromise) {
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rethrow($result);
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}
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} catch (\Throwable $exception) {
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$this->error($exception);
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if ($result instanceof Promise || $result instanceof ReactPromise) {
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rethrow($result);
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}
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} catch (\Throwable $exception) {
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$this->error($exception);
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}
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} finally {
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foreach ($scheduleQueue as $item) {
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$this->timerQueue->insert($item, -$item[1]);
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}
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} finally {
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foreach ($scheduleQueue as list($watcher, $expiration)) {
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if ($watcher->enabled) {
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$this->timerQueue->insert($watcher, $expiration);
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}
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}
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}
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@ -266,24 +255,15 @@ class NativeDriver extends Driver
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*/
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private function getTimeout(): int
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{
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while (!$this->timerQueue->isEmpty()) {
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list($watcher, $expiration) = $this->timerQueue->top();
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if (!$this->timerQueue->isEmpty()) {
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list($watcher, $expiration) = $this->timerQueue->peek();
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$id = $watcher->id;
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if (!isset($this->timerExpires[$id]) || $expiration !== $this->timerExpires[$id]) {
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$this->timerQueue->extract(); // Timer was removed from queue.
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continue;
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}
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$expiration -= $this->now();
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$expiration -= getCurrentTime() - $this->nowOffset;
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if ($expiration < 0) {
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return 0;
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}
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$this->nowUpdateNeeded = true; // Loop will block, so trigger now update after blocking.
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return $expiration;
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}
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@ -312,8 +292,7 @@ class NativeDriver extends Driver
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case Watcher::DELAY:
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case Watcher::REPEAT:
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$expiration = $this->now() + $watcher->value;
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$this->timerExpires[$watcher->id] = $expiration;
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$this->timerQueue->insert([$watcher, $expiration], -$expiration);
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$this->timerQueue->insert($watcher, $expiration);
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break;
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case Watcher::SIGNAL:
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@ -362,7 +341,7 @@ class NativeDriver extends Driver
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case Watcher::DELAY:
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case Watcher::REPEAT:
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unset($this->timerExpires[$watcher->id]);
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$this->timerQueue->remove($watcher);
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break;
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case Watcher::SIGNAL:
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