1 files changed, 74 insertions, 0 deletions
diff --git a/lib/classes/FileLock.php b/lib/classes/FileLock.php
new file mode 100644
index 0000000..064d41e
--- /dev/null
+++ b/lib/classes/FileLock.php
@@ -0,0 +1,74 @@
+<?php
+/**
+ * file_lock.php
+ * Simple lock mechanism on a file basis.
+ *
+ * With the help of this class you can manage persistent locks. Locks are
+ * stored in files and potential additional data is stored as json.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * @author    Jan-Hendrik Willms <tleilax+studip@gmail.com>
+ * @copyright 2013 Stud.IP Core-Group
+ * @license   http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category  Stud.IP
+ * @since     2.4
+ */
+
+class FileLock
+{
+    protected $file;
+
+    /**
+     * Constructs a new lock object with the provided id.
+     *
+     * @param String $id Identifier of the lock
+     */
+    public function __construct($id)
+    {
+        $this->file = fopen("{$GLOBALS['TMP_PATH']}/$id.json", 'c+');
+
+        if (!$this->file) {
+            throw new RuntimeException('failed to create lock file.');
+        }
+    }
+    
+    /**
+     * Try to aquire a file lock. The provided lock information will
+     * be stored with the lock. If the lock cannot be aquired, the
+     * lock information in $data is updated from the lock file.
+     *
+     * @param array $data additional data to be stored with the lock
+     * @return boolean true on success or false on failure
+     */
+    public function tryLock(&$data = [])
+    {
+        rewind($this->file);
+
+        if (flock($this->file, LOCK_EX | LOCK_NB)) {
+            ftruncate($this->file, 0);
+            fwrite($this->file, json_encode($data));
+            fflush($this->file);
+
+            return true;
+        } else {
+            $json = stream_get_contents($this->file);
+            $data = json_decode($json, true);
+
+            return false;
+        }
+    }
+
+    /**
+     * Releases a previously obtained lock
+     *
+     * @return boolean true on success or false on failure
+     */
+    public function release()
+    {
+        return flock($this->file, LOCK_UN);
+    }
+}