Singleton pattern trait.

lib/HashAlgorithm/Singleton.php

@@ -0,0 +1,49 @@
+<?php
+/**
+ * Nextcloud - user_sql
+ * Copyright (C) 2012-2018 Andreas Böhler <dev (at) aboehler (dot) at>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\user_sql\HashAlgorithm;
+
+/**
+ * Singleton pattern trait.
+ * @author Marcin Łojewski <dev@mlojewski.me>
+ */
+trait Singleton
+{
+    private static $instance;
+
+    final private function __construct()
+    {
+        $this->init();
+    }
+
+    protected function init()
+    {
+    }
+
+    final public static function getInstance()
+    {
+        return isset(static::$instance)
+            ? static::$instance
+            : static::$instance = new static;
+    }
+
+    final private function __clone()
+    {
+    }
+}