Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
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).
- Loading branch information
Showing
3 changed files
with
180 additions
and
59 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,125 @@ | ||
| <?php | ||
|
|
||
| namespace Amp\Loop\Internal; | ||
|
|
||
| use Amp\Loop\Watcher; | ||
|
|
||
| /** | ||
| * Uses a binary tree stored in an array to implement a heap. | ||
| */ | ||
| class TimerQueue | ||
| { | ||
| /** @var TimerQueueEntry[] */ | ||
| private $data = []; | ||
|
|
||
| /** | ||
| * Inserts the watcher into the queue. Time complexity: O(log(n)). | ||
| * | ||
| * @param Watcher $watcher | ||
| * @param int $expiration | ||
| */ | ||
| public function insert(Watcher $watcher, int $expiration) | ||
| { | ||
| $entry = new TimerQueueEntry; | ||
| $entry->watcher = $watcher; | ||
| $entry->expiration = $expiration; | ||
|
|
||
| $node = \count($this->data); | ||
| $this->data[$node] = $entry; | ||
|
|
||
| while ($node !== 0 && $entry->expiration < $this->data[$parent = ($node - 1) >> 1]->expiration) { | ||
| $this->data[$node] = $this->data[$parent]; | ||
| $this->data[$parent] = $entry; | ||
|
|
||
| $node = $parent; | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Removes the given watcher from the queue. Time complexity: O(n). | ||
| * | ||
| * @param Watcher $watcher | ||
| */ | ||
| public function remove(Watcher $watcher) | ||
| { | ||
| foreach ($this->data as $node => $entry) { | ||
| if ($entry->watcher === $watcher) { | ||
| $this->removeAndRebuild($node); | ||
| return; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Deletes and returns the Watcher on top of the heap. Time complexity: O(log(n)). | ||
| * | ||
| * @return [Watcher, int] Tuple of the watcher and the expiration time. | ||
| */ | ||
| public function extract(): array | ||
| { | ||
| if ($this->isEmpty()) { | ||
| throw new \Error('No data left in the heap.'); | ||
| } | ||
|
|
||
| $data = $this->removeAndRebuild(0); | ||
|
|
||
| return [$data->watcher, $data->expiration]; | ||
| } | ||
|
|
||
| /** | ||
| * @param int $node Remove the given node and then rebuild the data array from that node downward. | ||
| * | ||
| * @return TimerQueueEntry Removed entry. | ||
| */ | ||
| private function removeAndRebuild(int $node): TimerQueueEntry | ||
| { | ||
| $length = \count($this->data) - 1; | ||
| $data = $this->data[$node]; | ||
| $this->data[$node] = $this->data[$length]; | ||
| unset($this->data[$length]); | ||
|
|
||
| while (($child = ($node << 1) + 1) < $length) { | ||
| if ($this->data[$child]->expiration < $this->data[$node]->expiration | ||
| && ($child + 1 >= $length || $this->data[$child]->expiration < $this->data[$child + 1]->expiration) | ||
| ) { | ||
| // Left child is less than parent and right child. | ||
| $swap = $child; | ||
| } elseif ($child + 1 < $length && $this->data[$child + 1]->expiration < $this->data[$node]->expiration) { | ||
| // Right child is less than parent and left child. | ||
| $swap = $child + 1; | ||
| } else { // Left and right child are greater than parent. | ||
| break; | ||
| } | ||
|
|
||
| $temp = $this->data[$node]; | ||
| $this->data[$node] = $this->data[$swap]; | ||
| $this->data[$swap] = $temp; | ||
| $node = $swap; | ||
| } | ||
|
|
||
| return $data; | ||
| } | ||
|
|
||
| /** | ||
| * Returns the value at the top of the heap (without removing it). Time complexity: O(1). | ||
| * | ||
| * @return [Watcher, int] Tuple of the watcher and the expiration time. | ||
| */ | ||
| public function peek(): array | ||
| { | ||
| if ($this->isEmpty()) { | ||
| throw new \Error('No data in the heap.'); | ||
| } | ||
|
|
||
| return [$this->data[0]->watcher, $this->data[0]->expiration]; | ||
| } | ||
|
|
||
| /** | ||
| * Determines if the heap is empty. | ||
| * @return bool | ||
| */ | ||
| public function isEmpty(): bool | ||
| { | ||
| return empty($this->data); | ||
| } | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| <?php | ||
|
|
||
| namespace Amp\Loop\Internal; | ||
|
|
||
| use Amp\Loop\Watcher; | ||
| use Amp\Struct; | ||
|
|
||
| class TimerQueueEntry | ||
| { | ||
| use Struct; | ||
|
|
||
| /** @var Watcher */ | ||
| public $watcher; | ||
|
|
||
| /** @var int */ | ||
| public $expiration; | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters