Initial Commit

dependencies/amphp/sync/composer-require-check.json

@@ -0,0 +1,41 @@
+{
+    "symbol-whitelist": [
+        "null",
+        "true",
+        "false",
+        "static",
+        "self",
+        "parent",
+        "array",
+        "string",
+        "int",
+        "float",
+        "bool",
+        "iterable",
+        "callable",
+        "void",
+        "object",
+        "MSG_EAGAIN",
+        "MSG_ENOMSG",
+        "msg_get_queue",
+        "MSG_IPC_NOWAIT",
+        "msg_queue_exists",
+        "msg_receive",
+        "msg_remove_queue",
+        "msg_send",
+        "msg_set_queue",
+        "msg_stat_queue",
+        "Threaded",
+        "transform",
+        "SysvMessageQueue"
+    ],
+    "php-core-extensions": [
+        "Core",
+        "date",
+        "pcre",
+        "Phar",
+        "Reflection",
+        "SPL",
+        "standard"
+    ]
+}

dependencies/amphp/sync/src/Barrier.php

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+<?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();
+    }
+}

dependencies/amphp/sync/src/ConcurrentIterator/functions.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync\ConcurrentIterator;
+
+use WP_Ultimo\Dependencies\Amp\CancelledException;
+use WP_Ultimo\Dependencies\Amp\Iterator;
+use WP_Ultimo\Dependencies\Amp\Producer;
+use WP_Ultimo\Dependencies\Amp\Promise;
+use WP_Ultimo\Dependencies\Amp\Sync\Barrier;
+use WP_Ultimo\Dependencies\Amp\Sync\Lock;
+use WP_Ultimo\Dependencies\Amp\Sync\Semaphore;
+use function WP_Ultimo\Dependencies\Amp\asyncCall;
+use function WP_Ultimo\Dependencies\Amp\call;
+use function WP_Ultimo\Dependencies\Amp\coroutine;
+/**
+ * Concurrently act on iterator values using {@code $processor}.
+ *
+ * @param Iterator  $iterator Values to process.
+ * @param Semaphore $semaphore Semaphore limiting the concurrency, e.g. {@code LocalSemaphore}
+ * @param callable  $processor Processing callable, which is run as coroutine. It should not throw any errors,
+ *     otherwise the entire operation is aborted.
+ *
+ * @return Iterator Result values.
+ */
+function transform(Iterator $iterator, Semaphore $semaphore, callable $processor) : Iterator
+{
+    return new Producer(static function (callable $emit) use($iterator, $semaphore, $processor) {
+        // one dummy item, because we can't start the barrier with a count of zero
+        $barrier = new Barrier(1);
+        /** @var \Throwable|null $error */
+        $error = null;
+        $locks = [];
+        $gc = \false;
+        $processor = coroutine($processor);
+        $processor = static function (Lock $lock, $currentElement) use($processor, $emit, $barrier, &$locks, &$error, &$gc) {
+            $done = \false;
+            try {
+                (yield $processor($currentElement, $emit));
+                $done = \true;
+            } catch (\Throwable $e) {
+                $error = $error ?? $e;
+                $done = \true;
+            } finally {
+                if (!$done) {
+                    $gc = \true;
+                }
+                unset($locks[$lock->getId()]);
+                $lock->release();
+                $barrier->arrive();
+            }
+        };
+        while ((yield $iterator->advance())) {
+            if ($error) {
+                break;
+            }
+            /** @var Lock $lock */
+            $lock = (yield $semaphore->acquire());
+            if ($gc || isset($locks[$lock->getId()])) {
+                // Throwing here causes a segfault on PHP 7.3
+                return;
+                // throw new CancelledException; // producer and locks have been GCed
+            }
+            $locks[$lock->getId()] = \true;
+            $barrier->register();
+            asyncCall($processor, $lock, $iterator->getCurrent());
+        }
+        $barrier->arrive();
+        // remove dummy item
+        (yield $barrier->await());
+        if ($error) {
+            throw $error;
+        }
+    });
+}
+/**
+ * Concurrently map all iterator values using {@code $processor}.
+ *
+ * The order of the items in the resulting iterator is not guaranteed in any way.
+ *
+ * @param Iterator  $iterator Values to map.
+ * @param Semaphore $semaphore Semaphore limiting the concurrency, e.g. {@code LocalSemaphore}
+ * @param callable  $processor Processing callable, which is run as coroutine. It should not throw any errors,
+ *     otherwise the entire operation is aborted.
+ *
+ * @return Iterator Mapped values.
+ */
+function map(Iterator $iterator, Semaphore $semaphore, callable $processor) : Iterator
+{
+    $processor = coroutine($processor);
+    return transform($iterator, $semaphore, static function ($value, callable $emit) use($processor) {
+        $value = (yield $processor($value));
+        (yield $emit($value));
+    });
+}
+/**
+ * Concurrently filter all iterator values using {@code $filter}.
+ *
+ * The order of the items in the resulting iterator is not guaranteed in any way.
+ *
+ * @param Iterator  $iterator Values to map.
+ * @param Semaphore $semaphore Semaphore limiting the concurrency, e.g. {@code LocalSemaphore}
+ * @param callable  $filter Processing callable, which is run as coroutine. It should not throw any errors,
+ *     otherwise the entire operation is aborted. Must resolve to a boolean, true to keep values in the resulting
+ *     iterator.
+ *
+ * @return Iterator Values, where {@code $filter} resolved to {@code true}.
+ */
+function filter(Iterator $iterator, Semaphore $semaphore, callable $filter) : Iterator
+{
+    $filter = coroutine($filter);
+    return transform($iterator, $semaphore, static function ($value, callable $emit) use($filter) {
+        $keep = (yield $filter($value));
+        if (!\is_bool($keep)) {
+            throw new \TypeError(__NAMESPACE__ . '\\filter\'s callable must resolve to a boolean value, got ' . \gettype($keep));
+        }
+        if ($keep) {
+            (yield $emit($value));
+        }
+    });
+}
+/**
+ * Concurrently invoke a callback on all iterator values using {@code $processor}.
+ *
+ * @param Iterator  $iterator Values to act on.
+ * @param Semaphore $semaphore Semaphore limiting the concurrency, e.g. {@code LocalSemaphore}
+ * @param callable  $processor Processing callable, which is run as coroutine. It should not throw any errors,
+ *     otherwise the entire operation is aborted.
+ *
+ * @return Promise
+ */
+function each(Iterator $iterator, Semaphore $semaphore, callable $processor) : Promise
+{
+    $processor = coroutine($processor);
+    $iterator = transform($iterator, $semaphore, static function ($value, callable $emit) use($processor) {
+        (yield $processor($value));
+        (yield $emit(null));
+    });
+    // Use Amp\Iterator\discard in the future
+    return call(static function () use($iterator) {
+        $count = 0;
+        while ((yield $iterator->advance())) {
+            $count++;
+        }
+        return $count;
+    });
+}

dependencies/amphp/sync/src/FileMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Coroutine;
+use WP_Ultimo\Dependencies\Amp\Delayed;
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A cross-platform mutex that uses exclusive files as the lock mechanism.
+ *
+ * This mutex implementation is not always atomic and depends on the operating
+ * system's implementation of file creation operations. Use this implementation
+ * only if no other mutex types are available.
+ *
+ * This implementation avoids using [flock()](https://www.php.net/flock)
+ * because flock() is known to have some atomicity issues on some systems. In
+ * addition, flock() does not work as expected when trying to lock a file
+ * multiple times in the same process on Linux. Instead, exclusive file creation
+ * is used to create a lock file, which is atomic on most systems.
+ *
+ * @see https://www.php.net/fopen
+ */
+class FileMutex implements Mutex
+{
+    public const LATENCY_TIMEOUT = 10;
+    /** @var string The full path to the lock file. */
+    private $fileName;
+    /**
+     * @param string $fileName Name of temporary file to use as a mutex.
+     */
+    public function __construct(string $fileName)
+    {
+        $this->fileName = $fileName;
+    }
+    /**
+     * {@inheritdoc}
+     */
+    public function acquire() : Promise
+    {
+        return new Coroutine($this->doAcquire());
+    }
+    /**
+     * @coroutine
+     *
+     * @return \Generator
+     */
+    private function doAcquire() : \Generator
+    {
+        // Try to create the lock file. If the file already exists, someone else
+        // has the lock, so set an asynchronous timer and try again.
+        while (($handle = @\fopen($this->fileName, 'x')) === \false) {
+            (yield new Delayed(self::LATENCY_TIMEOUT));
+        }
+        // Return a lock object that can be used to release the lock on the mutex.
+        $lock = new Lock(0, function () : void {
+            $this->release();
+        });
+        \fclose($handle);
+        return $lock;
+    }
+    /**
+     * Releases the lock on the mutex.
+     *
+     * @throws SyncException If the unlock operation failed.
+     */
+    protected function release()
+    {
+        $success = @\unlink($this->fileName);
+        if (!$success) {
+            throw new SyncException('Failed to unlock the mutex file.');
+        }
+    }
+}

dependencies/amphp/sync/src/Internal/MutexStorage.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync\Internal;
+
+use WP_Ultimo\Dependencies\Amp\Delayed;
+use WP_Ultimo\Dependencies\Amp\Promise;
+use WP_Ultimo\Dependencies\Amp\Sync\Lock;
+use function WP_Ultimo\Dependencies\Amp\call;
+/** @internal */
+final class MutexStorage extends \Threaded
+{
+    public const LATENCY_TIMEOUT = 10;
+    /** @var bool */
+    private $locked = \false;
+    public function acquire() : Promise
+    {
+        return call(function () : \Generator {
+            $tsl = function () : bool {
+                if ($this->locked) {
+                    return \true;
+                }
+                $this->locked = \true;
+                return \false;
+            };
+            while ($this->locked || $this->synchronized($tsl)) {
+                (yield new Delayed(self::LATENCY_TIMEOUT));
+            }
+            return new Lock(0, function () : void {
+                $this->locked = \false;
+            });
+        });
+    }
+}

dependencies/amphp/sync/src/Internal/SemaphoreStorage.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync\Internal;
+
+use WP_Ultimo\Dependencies\Amp\Delayed;
+use WP_Ultimo\Dependencies\Amp\Promise;
+use WP_Ultimo\Dependencies\Amp\Sync\Lock;
+use function WP_Ultimo\Dependencies\Amp\call;
+/** @internal */
+final class SemaphoreStorage extends \Threaded
+{
+    public const LATENCY_TIMEOUT = 10;
+    /**
+     * Creates a new semaphore with a given number of locks.
+     *
+     * @param int $locks The maximum number of locks that can be acquired from the semaphore.
+     */
+    public function __construct(int $locks)
+    {
+        foreach (\range(0, $locks - 1) as $lock) {
+            $this[] = $lock;
+        }
+    }
+    public function acquire() : Promise
+    {
+        /**
+         * Uses a double locking mechanism to acquire a lock without blocking. A
+         * synchronous mutex is used to make sure that the semaphore is queried one
+         * at a time to preserve the integrity of the semaphore itself. Then a lock
+         * count is used to check if a lock is available without blocking.
+         *
+         * If a lock is not available, we add the request to a queue and set a timer
+         * to check again in the future.
+         */
+        return call(function () : \Generator {
+            $tsl = function () : ?int {
+                // If there are no locks available or the wait queue is not empty,
+                // we need to wait our turn to acquire a lock.
+                if (!$this->count()) {
+                    return null;
+                }
+                return $this->shift();
+            };
+            while (!$this->count() || ($id = $this->synchronized($tsl)) === null) {
+                (yield new Delayed(self::LATENCY_TIMEOUT));
+            }
+            return new Lock($id, function (Lock $lock) : void {
+                $id = $lock->getId();
+                $this->synchronized(function () use($id) {
+                    $this[] = $id;
+                });
+            });
+        });
+    }
+}

dependencies/amphp/sync/src/KeyedMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A non-blocking synchronization primitive that can be used for mutual exclusion across contexts based on keys.
+ *
+ * Objects that implement this interface should guarantee that all operations are atomic. Implementations do not have to
+ * guarantee that acquiring a lock is first-come, first serve.
+ */
+interface KeyedMutex extends KeyedSemaphore
+{
+    /**
+     * Acquires a lock on the mutex.
+     *
+     * @param string $key Lock key
+     *
+     * @return Promise<Lock> Resolves with a lock object with an ID of 0. May fail with a SyncException
+     *     if an error occurs when attempting to obtain the lock (e.g. a shared memory segment closed).
+     */
+    public function acquire(string $key) : Promise;
+}

dependencies/amphp/sync/src/KeyedSemaphore.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A non-blocking counting semaphore based on keys.
+ *
+ * Objects that implement this interface should guarantee that all operations are atomic. Implementations do not have to
+ * guarantee that acquiring a lock is first-come, first serve.
+ */
+interface KeyedSemaphore
+{
+    /**
+     * Acquires a lock on the semaphore.
+     *
+     * @param string $key Lock key
+     *
+     * @return Promise<Lock> Resolves with an integer keyed lock object. Identifiers returned by the
+     *    locks should be 0-indexed. Releasing an identifier MUST make that same identifier available. May fail with
+     *    a SyncException if an error occurs when attempting to obtain the lock (e.g. a shared memory segment closed).
+     */
+    public function acquire(string $key) : Promise;
+}

dependencies/amphp/sync/src/LocalKeyedMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+use function WP_Ultimo\Dependencies\Amp\call;
+final class LocalKeyedMutex implements KeyedMutex
+{
+    /** @var LocalMutex[] */
+    private $mutex = [];
+    /** @var int[] */
+    private $locks = [];
+    public function acquire(string $key) : Promise
+    {
+        if (!isset($this->mutex[$key])) {
+            $this->mutex[$key] = new LocalMutex();
+            $this->locks[$key] = 0;
+        }
+        return call(function () use($key) {
+            $this->locks[$key]++;
+            /** @var Lock $lock */
+            $lock = (yield $this->mutex[$key]->acquire());
+            return new Lock(0, function () use($lock, $key) {
+                if (--$this->locks[$key] === 0) {
+                    unset($this->mutex[$key], $this->locks[$key]);
+                }
+                $lock->release();
+            });
+        });
+    }
+}

dependencies/amphp/sync/src/LocalKeyedSemaphore.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+use function WP_Ultimo\Dependencies\Amp\call;
+final class LocalKeyedSemaphore implements KeyedSemaphore
+{
+    /** @var LocalSemaphore[] */
+    private $semaphore = [];
+    /** @var int[] */
+    private $locks = [];
+    /** @var int */
+    private $maxLocks;
+    public function __construct(int $maxLocks)
+    {
+        $this->maxLocks = $maxLocks;
+    }
+    public function acquire(string $key) : Promise
+    {
+        if (!isset($this->semaphore[$key])) {
+            $this->semaphore[$key] = new LocalSemaphore($this->maxLocks);
+            $this->locks[$key] = 0;
+        }
+        return call(function () use($key) {
+            $this->locks[$key]++;
+            /** @var Lock $lock */
+            $lock = (yield $this->semaphore[$key]->acquire());
+            return new Lock(0, function () use($lock, $key) {
+                if (--$this->locks[$key] === 0) {
+                    unset($this->semaphore[$key], $this->locks[$key]);
+                }
+                $lock->release();
+            });
+        });
+    }
+}

dependencies/amphp/sync/src/LocalMutex.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\CallableMaker;
+use WP_Ultimo\Dependencies\Amp\Deferred;
+use WP_Ultimo\Dependencies\Amp\Promise;
+use WP_Ultimo\Dependencies\Amp\Success;
+class LocalMutex implements Mutex
+{
+    use CallableMaker;
+    // kept for BC only
+    /** @var bool */
+    private $locked = \false;
+    /** @var Deferred[] */
+    private $queue = [];
+    /** {@inheritdoc} */
+    public function acquire() : Promise
+    {
+        if (!$this->locked) {
+            $this->locked = \true;
+            return new Success(new Lock(0, \Closure::fromCallable([$this, 'release'])));
+        }
+        $this->queue[] = $deferred = new Deferred();
+        return $deferred->promise();
+    }
+    private function release() : void
+    {
+        if (!empty($this->queue)) {
+            $deferred = \array_shift($this->queue);
+            $deferred->resolve(new Lock(0, \Closure::fromCallable([$this, 'release'])));
+            return;
+        }
+        $this->locked = \false;
+    }
+}

dependencies/amphp/sync/src/LocalSemaphore.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\CallableMaker;
+use WP_Ultimo\Dependencies\Amp\Deferred;
+use WP_Ultimo\Dependencies\Amp\Promise;
+use WP_Ultimo\Dependencies\Amp\Success;
+class LocalSemaphore implements Semaphore
+{
+    use CallableMaker;
+    // kept for BC only
+    /** @var int[] */
+    private $locks;
+    /** @var Deferred[] */
+    private $queue = [];
+    public function __construct(int $maxLocks)
+    {
+        if ($maxLocks < 1) {
+            throw new \Error('The number of locks must be greater than 0');
+        }
+        $this->locks = \range(0, $maxLocks - 1);
+    }
+    /** {@inheritdoc} */
+    public function acquire() : Promise
+    {
+        if (!empty($this->locks)) {
+            return new Success(new Lock(\array_shift($this->locks), \Closure::fromCallable([$this, 'release'])));
+        }
+        $this->queue[] = $deferred = new Deferred();
+        return $deferred->promise();
+    }
+    private function release(Lock $lock) : void
+    {
+        $id = $lock->getId();
+        if (!empty($this->queue)) {
+            $deferred = \array_shift($this->queue);
+            $deferred->resolve(new Lock($id, \Closure::fromCallable([$this, 'release'])));
+            return;
+        }
+        $this->locks[] = $id;
+    }
+}

dependencies/amphp/sync/src/Lock.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+/**
+ * A handle on an acquired lock from a synchronization object.
+ *
+ * This object is not thread-safe; after acquiring a lock from a mutex or
+ * semaphore, the lock should reside in the same thread or process until it is
+ * released.
+ */
+class Lock
+{
+    /** @var callable|null The function to be called on release or null if the lock has been released. */
+    private $releaser;
+    /** @var int */
+    private $id;
+    /**
+     * Creates a new lock permit object.
+     *
+     * @param int $id The lock identifier.
+     * @param callable(self): void $releaser A function to be called upon release.
+     */
+    public function __construct(int $id, callable $releaser)
+    {
+        $this->id = $id;
+        $this->releaser = $releaser;
+    }
+    /**
+     * Checks if the lock has already been released.
+     *
+     * @return bool True if the lock has already been released, otherwise false.
+     */
+    public function isReleased() : bool
+    {
+        return !$this->releaser;
+    }
+    /**
+     * @return int Lock identifier.
+     */
+    public function getId() : int
+    {
+        return $this->id;
+    }
+    /**
+     * Releases the lock. No-op if the lock has already been released.
+     */
+    public function release()
+    {
+        if (!$this->releaser) {
+            return;
+        }
+        // Invoke the releaser function given to us by the synchronization source
+        // to release the lock.
+        $releaser = $this->releaser;
+        $this->releaser = null;
+        $releaser($this);
+    }
+    /**
+     * Releases the lock when there are no more references to it.
+     */
+    public function __destruct()
+    {
+        if (!$this->isReleased()) {
+            $this->release();
+        }
+    }
+}

dependencies/amphp/sync/src/Mutex.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A non-blocking synchronization primitive that can be used for mutual exclusion across contexts.
+ *
+ * Objects that implement this interface should guarantee that all operations are atomic. Implementations do not have to
+ * guarantee that acquiring a lock is first-come, first serve.
+ */
+interface Mutex extends Semaphore
+{
+    /**
+     * Acquires a lock on the mutex.
+     *
+     * @return Promise<Lock> Resolves with a lock object with an ID of 0. May fail with a SyncException
+     *     if an error occurs when attempting to obtain the lock (e.g. a shared memory segment closed).
+     */
+    public function acquire() : Promise;
+}

dependencies/amphp/sync/src/PosixSemaphore.php

@@ -0,0 +1,211 @@
+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Coroutine;
+use WP_Ultimo\Dependencies\Amp\Delayed;
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A non-blocking, inter-process POSIX semaphore.
+ *
+ * Uses a POSIX message queue to store a queue of permits in a lock-free data structure. This semaphore implementation
+ * is preferred over other implementations when available, as it provides the best performance.
+ *
+ * Not compatible with Windows.
+ */
+class PosixSemaphore implements Semaphore
+{
+    public const LATENCY_TIMEOUT = 10;
+    /** @var string */
+    private $id;
+    /** @var int The semaphore key. */
+    private $key;
+    /** @var int PID of the process that created the semaphore. */
+    private $initializer = 0;
+    /** @var resource A message queue of available locks. */
+    private $queue;
+    /**
+     * Creates a new semaphore with a given ID and number of locks.
+     *
+     * @param string $id The unique name for the new semaphore.
+     * @param int    $maxLocks The maximum number of locks that can be acquired from the semaphore.
+     * @param int    $permissions Permissions to access the semaphore. Use file permission format specified as 0xxx.
+     *
+     * @return PosixSemaphore
+     * @throws SyncException If the semaphore could not be created due to an internal error.
+     */
+    public static function create(string $id, int $maxLocks, int $permissions = 0600) : self
+    {
+        if ($maxLocks < 1) {
+            throw new \Error('Number of locks must be greater than 0');
+        }
+        $semaphore = new self($id);
+        $semaphore->init($maxLocks, $permissions);
+        return $semaphore;
+    }
+    /**
+     * @param string $id The unique name of the semaphore to use.
+     *
+     * @return \Amp\Sync\PosixSemaphore
+     */
+    public static function use(string $id) : self
+    {
+        $semaphore = new self($id);
+        $semaphore->open();
+        return $semaphore;
+    }
+    /**
+     * @param string $id
+     *
+     * @throws \Error If the sysvmsg extension is not loaded.
+     */
+    private function __construct(string $id)
+    {
+        if (!\extension_loaded("sysvmsg")) {
+            throw new \Error(__CLASS__ . " requires the sysvmsg extension.");
+        }
+        $this->id = $id;
+        $this->key = self::makeKey($this->id);
+    }
+    /**
+     * Private method to prevent cloning.
+     */
+    private function __clone()
+    {
+    }
+    /**
+     * Prevent serialization.
+     */
+    public function __sleep()
+    {
+        throw new \Error('A semaphore cannot be serialized!');
+    }
+    public function getId() : string
+    {
+        return $this->id;
+    }
+    private function open() : void
+    {
+        if (!\msg_queue_exists($this->key)) {
+            throw new SyncException('No semaphore with that ID found');
+        }
+        $this->queue = \msg_get_queue($this->key);
+        if (!$this->queue) {
+            throw new SyncException('Failed to open the semaphore.');
+        }
+    }
+    /**
+     * @param int $maxLocks    The maximum number of locks that can be acquired from the semaphore.
+     * @param int $permissions Permissions to access the semaphore.
+     *
+     * @throws SyncException If the semaphore could not be created due to an internal error.
+     */
+    private function init(int $maxLocks, int $permissions) : void
+    {
+        if (\msg_queue_exists($this->key)) {
+            throw new SyncException('A semaphore with that ID already exists');
+        }
+        $this->queue = \msg_get_queue($this->key, $permissions);
+        if (!$this->queue) {
+            throw new SyncException('Failed to create the semaphore.');
+        }
+        $this->initializer = \getmypid();
+        // Fill the semaphore with locks.
+        while (--$maxLocks >= 0) {
+            $this->release($maxLocks);
+        }
+    }
+    /**
+     * Gets the access permissions of the semaphore.
+     *
+     * @return int A permissions mode.
+     */
+    public function getPermissions() : int
+    {
+        $stat = \msg_stat_queue($this->queue);
+        return $stat['msg_perm.mode'];
+    }
+    /**
+     * Sets the access permissions of the semaphore.
+     *
+     * The current user must have access to the semaphore in order to change the permissions.
+     *
+     * @param int $mode A permissions mode to set.
+     *
+     * @throws SyncException If the operation failed.
+     */
+    public function setPermissions(int $mode)
+    {
+        if (!\msg_set_queue($this->queue, ['msg_perm.mode' => $mode])) {
+            throw new SyncException('Failed to change the semaphore permissions.');
+        }
+    }
+    public function acquire() : Promise
+    {
+        return new Coroutine($this->doAcquire());
+    }
+    /**
+     * {@inheritdoc}
+     */
+    private function doAcquire() : \Generator
+    {
+        do {
+            // Attempt to acquire a lock from the semaphore.
+            if (@\msg_receive($this->queue, 0, $type, 1, $id, \false, \MSG_IPC_NOWAIT, $errno)) {
+                // A free lock was found, so resolve with a lock object that can
+                // be used to release the lock.
+                return new Lock(\unpack("C", $id)[1], function (Lock $lock) {
+                    $this->release($lock->getId());
+                });
+            }
+            // Check for unusual errors.
+            if ($errno !== \MSG_ENOMSG) {
+                throw new SyncException(\sprintf('Failed to acquire a lock; errno: %d', $errno));
+            }
+        } while ((yield new Delayed(self::LATENCY_TIMEOUT, \true)));
+    }
+    /**
+     * Removes the semaphore if it still exists.
+     *
+     * @throws SyncException If the operation failed.
+     */
+    public function __destruct()
+    {
+        if ($this->initializer === 0 || $this->initializer !== \getmypid()) {
+            return;
+        }
+        if (\PHP_VERSION_ID < 80000 && (!\is_resource($this->queue) || !\msg_queue_exists($this->key))) {
+            return;
+        }
+        if (\PHP_VERSION_ID >= 80000 && (!$this->queue instanceof \SysvMessageQueue || !\msg_queue_exists($this->key))) {
+            return;
+        }
+        \msg_remove_queue($this->queue);
+    }
+    /**
+     * Releases a lock from the semaphore.
+     *
+     * @param int $id Lock identifier.
+     *
+     * @throws SyncException If the operation failed.
+     */
+    protected function release(int $id)
+    {
+        if (!$this->queue) {
+            return;
+            // Queue already destroyed.
+        }
+        // Call send in non-blocking mode. If the call fails because the queue
+        // is full, then the number of locks configured is too large.
+        if (!@\msg_send($this->queue, 1, \pack("C", $id), \false, \false, $errno)) {
+            if ($errno === \MSG_EAGAIN) {
+                throw new SyncException('The semaphore size is larger than the system allows.');
+            }
+            throw new SyncException('Failed to release the lock.');
+        }
+    }
+    private static function makeKey(string $id) : int
+    {
+        return \abs(\unpack("l", \md5($id, \true))[1]);
+    }
+}

dependencies/amphp/sync/src/PrefixedKeyedMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+final class PrefixedKeyedMutex implements KeyedMutex
+{
+    /** @var KeyedMutex */
+    private $mutex;
+    /** @var string */
+    private $prefix;
+    public function __construct(KeyedMutex $mutex, string $prefix)
+    {
+        $this->mutex = $mutex;
+        $this->prefix = $prefix;
+    }
+    public function acquire(string $key) : Promise
+    {
+        return $this->mutex->acquire($this->prefix . $key);
+    }
+}

dependencies/amphp/sync/src/PrefixedKeyedSemaphore.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+final class PrefixedKeyedSemaphore implements KeyedSemaphore
+{
+    /** @var KeyedSemaphore */
+    private $semaphore;
+    /** @var string */
+    private $prefix;
+    public function __construct(KeyedSemaphore $semaphore, string $prefix)
+    {
+        $this->semaphore = $semaphore;
+        $this->prefix = $prefix;
+    }
+    public function acquire(string $key) : Promise
+    {
+        return $this->semaphore->acquire($this->prefix . $key);
+    }
+}

dependencies/amphp/sync/src/Semaphore.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A non-blocking counting semaphore.
+ *
+ * Objects that implement this interface should guarantee that all operations are atomic. Implementations do not have to
+ * guarantee that acquiring a lock is first-come, first serve.
+ */
+interface Semaphore
+{
+    /**
+     * Acquires a lock on the semaphore.
+     *
+     * @return Promise<Lock> Resolves with an integer keyed lock object. Identifiers returned by the
+     *    locks should be 0-indexed. Releasing an identifier MUST make that same identifier available. May fail with
+     *    a SyncException if an error occurs when attempting to obtain the lock (e.g. a shared memory segment closed).
+     */
+    public function acquire() : Promise;
+}

dependencies/amphp/sync/src/SemaphoreMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+use function WP_Ultimo\Dependencies\Amp\call;
+class SemaphoreMutex implements Mutex
+{
+    /** @var Semaphore */
+    private $semaphore;
+    /**
+     * @param Semaphore $semaphore A semaphore with a single lock.
+     */
+    public function __construct(Semaphore $semaphore)
+    {
+        $this->semaphore = $semaphore;
+    }
+    /** {@inheritdoc} */
+    public function acquire() : Promise
+    {
+        return call(function () : \Generator {
+            /** @var \Amp\Sync\Lock $lock */
+            $lock = (yield $this->semaphore->acquire());
+            if ($lock->getId() !== 0) {
+                $lock->release();
+                throw new \Error("Cannot use a semaphore with more than a single lock");
+            }
+            return $lock;
+        });
+    }
+}

dependencies/amphp/sync/src/StaticKeyMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+final class StaticKeyMutex implements Mutex
+{
+    /** @var KeyedMutex */
+    private $mutex;
+    /** @var string */
+    private $key;
+    public function __construct(KeyedMutex $mutex, string $key)
+    {
+        $this->mutex = $mutex;
+        $this->key = $key;
+    }
+    public function acquire() : Promise
+    {
+        return $this->mutex->acquire($this->key);
+    }
+}

dependencies/amphp/sync/src/SyncException.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+class SyncException extends \Exception
+{
+}

dependencies/amphp/sync/src/ThreadedMutex.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * A thread-safe, asynchronous mutex using the pthreads locking mechanism.
+ *
+ * Compatible with POSIX systems and Microsoft Windows.
+ *
+ * @deprecated ext-pthreads development has been halted, see https://github.com/krakjoe/pthreads/issues/929
+ */
+class ThreadedMutex implements Mutex
+{
+    /** @var Internal\MutexStorage */
+    private $mutex;
+    /**
+     * Creates a new threaded mutex.
+     */
+    public function __construct()
+    {
+        $this->mutex = new Internal\MutexStorage();
+    }
+    /**
+     * {@inheritdoc}
+     */
+    public function acquire() : Promise
+    {
+        return $this->mutex->acquire();
+    }
+}

dependencies/amphp/sync/src/ThreadedSemaphore.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+/**
+ * An asynchronous semaphore based on pthreads' synchronization methods.
+ *
+ * This is an implementation of a thread-safe semaphore that has non-blocking
+ * acquire methods. There is a small tradeoff for asynchronous semaphores; you
+ * may not acquire a lock immediately when one is available and there may be a
+ * small delay. However, the small delay will not block the thread.
+ *
+ * @deprecated ext-pthreads development has been halted, see https://github.com/krakjoe/pthreads/issues/929
+ */
+class ThreadedSemaphore implements Semaphore
+{
+    /** @var \Threaded */
+    private $semaphore;
+    /**
+     * Creates a new semaphore with a given number of locks.
+     *
+     * @param int $locks The maximum number of locks that can be acquired from the semaphore.
+     */
+    public function __construct(int $locks)
+    {
+        if ($locks < 1) {
+            throw new \Error("The number of locks should be a positive integer");
+        }
+        $this->semaphore = new Internal\SemaphoreStorage($locks);
+    }
+    /**
+     * {@inheritdoc}
+     */
+    public function acquire() : Promise
+    {
+        return $this->semaphore->acquire();
+    }
+}

dependencies/amphp/sync/src/functions.php

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+<?php
+
+namespace WP_Ultimo\Dependencies\Amp\Sync;
+
+use WP_Ultimo\Dependencies\Amp\Promise;
+use function WP_Ultimo\Dependencies\Amp\call;
+/**
+ * Invokes the given callback while maintaining a lock from the provided mutex. The lock is automatically released after
+ * invoking the callback or once the promise returned by the callback is resolved. If the callback returns a Generator,
+ * it will be run as a coroutine. See Amp\call().
+ *
+ * @param Mutex    $mutex
+ * @param callable $callback
+ * @param array    ...$args
+ *
+ * @return Promise Resolves with the return value of the callback.
+ */
+function synchronized(Mutex $mutex, callable $callback, ...$args) : Promise
+{
+    return call(static function () use($mutex, $callback, $args) : \Generator {
+        /** @var Lock $lock */
+        $lock = (yield $mutex->acquire());
+        try {
+            return (yield call($callback, ...$args));
+        } finally {
+            $lock->release();
+        }
+    });
+}