From 8dd597238d8f6bce72d1902e70ee99958b243df2 Mon Sep 17 00:00:00 2001
From: coderstephen <me@stephencoakley.com>
Date: Fri, 10 Jul 2015 16:17:18 -0500
Subject: [PATCH] Semaphore handles can be serialized across contexts

---
 src/Semaphore.php | 67 ++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 55 insertions(+), 12 deletions(-)

diff --git a/src/Semaphore.php b/src/Semaphore.php
index d0ded07..5605336 100644
--- a/src/Semaphore.php
+++ b/src/Semaphore.php
@@ -1,33 +1,53 @@
 <?php
 namespace Icicle\Concurrent;
 
+use Icicle\Concurrent\Exception\SemaphoreException;
+
 /**
  * A synchronous semaphore that uses System V IPC semaphores.
  */
-class Semaphore
+class Semaphore implements \Serializable
 {
+    /**
+     * @var int The key to the semaphore.
+     */
     private $key;
-    private $identifier;
+
+    /**
+     * @var int The maximum number of locks.
+     */
+    private $maxLocks;
+
+    /**
+     * @var resource An open handle to the semaphore.
+     */
+    private $handle;
 
     /**
      * Creates a new semaphore.
      *
-     * @param int $max         The maximum number of processes that can lock the semaphore.
+     * @param int $maxLocks    The maximum number of processes that can lock the semaphore.
      * @param int $permissions Permissions to access the semaphore.
      */
-    public function __construct($max = 1, $permissions = 0666)
+    public function __construct($maxLocks = 1, $permissions = 0666)
     {
         $this->key = abs(crc32(spl_object_hash($this)));
-        $this->identifier = sem_get($this->key, $max, $permissions);
+        $this->maxLocks = $maxLocks;
+        $this->handle = sem_get($this->key, $maxLocks, $permissions, 0);
 
-        if ($this->identifier === false) {
+        if ($this->handle === false) {
             throw new SemaphoreException('Failed to create the semaphore.');
         }
     }
 
-    public function __destruct()
+    /**
+     * Gets the maximum number of locks.
+     *
+     * @return int The maximum number of locks.
+     */
+    public function getMaxLocks()
     {
-        $this->remove();
+        return $this->maxLocks;
     }
 
     /**
@@ -37,7 +57,7 @@ class Semaphore
      */
     public function lock()
     {
-        if (!sem_acquire($this->identifier)) {
+        if (!sem_acquire($this->handle)) {
             throw new SemaphoreException('Failed to lock the semaphore.');
         }
     }
@@ -47,7 +67,7 @@ class Semaphore
      */
     public function unlock()
     {
-        if (!sem_release($this->identifier)) {
+        if (!sem_release($this->handle)) {
             throw new SemaphoreException('Failed to unlock the semaphore.');
         }
     }
@@ -55,9 +75,9 @@ class Semaphore
     /**
      * Removes the semaphore if it still exists.
      */
-    public function remove()
+    public function destroy()
     {
-        if (!@sem_remove($this->identifier)) {
+        if (!@sem_remove($this->handle)) {
             $error = error_get_last();
 
             if ($error['type'] !== E_WARNING) {
@@ -65,4 +85,27 @@ class Semaphore
             }
         }
     }
+
+    /**
+     * Serializes the semaphore.
+     *
+     * @return string The serialized semaphore.
+     */
+    public function serialize()
+    {
+        return serialize([$this->key, $this->maxLocks]);
+    }
+
+    /**
+     * Unserializes a serialized semaphore.
+     *
+     * @param string $serialized The serialized semaphore.
+     */
+    public function unserialize($serialized)
+    {
+        // Get the semaphore key and attempt to re-connect to the semaphore in
+        // memory.
+        list($this->key, $this->maxLocks) = unserialize($serialized);
+        $this->handle = sem_get($this->key, $maxLocks);
+    }
 }