1 files changed, 56 insertions, 0 deletions
diff --git a/lib/private/Memcache/CADTrait.php b/lib/private/Memcache/CADTrait.php
new file mode 100644
index 00000000000..d0f6611c4f3
--- /dev/null
+++ b/lib/private/Memcache/CADTrait.php
@@ -0,0 +1,56 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+namespace OC\Memcache;
+
+trait CADTrait {
+	abstract public function get($key);
+
+	abstract public function remove($key);
+
+	abstract public function add($key, $value, $ttl = 0);
+
+	/**
+	 * Compare and delete
+	 *
+	 * @param string $key
+	 * @param mixed $old
+	 * @return bool
+	 */
+	public function cad($key, $old) {
+		//no native cas, emulate with locking
+		if ($this->add($key . '_lock', true)) {
+			if ($this->get($key) === $old) {
+				$this->remove($key);
+				$this->remove($key . '_lock');
+				return true;
+			} else {
+				$this->remove($key . '_lock');
+				return false;
+			}
+		} else {
+			return false;
+		}
+	}
+
+	public function ncad(string $key, mixed $old): bool {
+		//no native cad, emulate with locking
+		if ($this->add($key . '_lock', true)) {
+			$value = $this->get($key);
+			if ($value !== null && $value !== $old) {
+				$this->remove($key);
+				$this->remove($key . '_lock');
+				return true;
+			} else {
+				$this->remove($key . '_lock');
+				return false;
+			}
+		} else {
+			return false;
+		}
+	}
+}