MDL-82158 core_cache: Move interfaces

cache/classes/lockable_cache_interface.php

@@ -0,0 +1,56 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle 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 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Cache store feature: locking
+ *
+ * This is a feature that cache stores can implement if they wish to support locking themselves rather
+ * than having the cache loader handle it for them.
+ *
+ * Can be implemented by classes already implementing cache_store.
+ */
+interface cache_is_lockable {
+
+    /**
+     * Acquires a lock on the given key for the given identifier.
+     *
+     * @param string $key The key we are locking.
+     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
+     *      The use of this property is entirely optional and implementations can act as they like upon it.
+     * @return bool True if the lock could be acquired, false otherwise.
+     */
+    public function acquire_lock($key, $ownerid);
+
+    /**
+     * Test if there is already a lock for the given key and if there is whether it belongs to the calling code.
+     *
+     * @param string $key The key we are locking.
+     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
+     * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there
+     *      is no lock.
+     */
+    public function check_lock_state($key, $ownerid);
+
+    /**
+     * Releases the lock on the given key.
+     *
+     * @param string $key The key we are locking.
+     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
+     *      The use of this property is entirely optional and implementations can act as they like upon it.
+     * @return bool True if the lock has been released, false if there was a problem releasing the lock.
+     */
+    public function release_lock($key, $ownerid);
+}