Initial Commit

dependencies/amphp/sync/src/Barrier.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Deferred;
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A barrier is a synchronization primitive.
+ *
+ * The barrier is initialized with a certain count, which can be increased and decreased until it reaches zero.
+ *
+ * A count of one can be used to block multiple coroutines until a certain condition is met.
+ *
+ * A count of N can be used to await multiple coroutines doing an action to complete.
+ *
+ * **Example**
+ *
+ * ```php
+ * $barrier = new Amp\Sync\Barrier(2);
+ * $barrier->arrive();
+ * $barrier->arrive(); // promise returned from Barrier::await() is now resolved
+ *
+ * yield $barrier->await();
+ * ```
+ */
+final class Barrier
+{
+    /** @var int */
+    private $count;
+    /** @var Deferred */
+    private $deferred;
+    public function __construct(int $count)
+    {
+        if ($count < 1) {
+            throw new \Error('Count must be positive, got ' . $count);
+        }
+        $this->count = $count;
+        $this->deferred = new Deferred();
+    }
+    public function getCount() : int
+    {
+        return $this->count;
+    }
+    public function arrive(int $count = 1) : void
+    {
+        if ($count < 1) {
+            throw new \Error('Count must be at least 1, got ' . $count);
+        }
+        if ($count > $this->count) {
+            throw new \Error('Count cannot be greater than remaining count: ' . $count . ' > ' . $this->count);
+        }
+        $this->count -= $count;
+        if ($this->count === 0) {
+            $this->deferred->resolve();
+        }
+    }
+    public function register(int $count = 1) : void
+    {
+        if ($count < 1) {
+            throw new \Error('Count must be at least 1, got ' . $count);
+        }
+        if ($this->count === 0) {
+            throw new \Error('Can\'t increase count, because the barrier already broke');
+        }
+        $this->count += $count;
+    }
+    public function await() : Promise
+    {
+        return $this->deferred->promise();
+    }
+}