nextcloud_server/lib/private/Memcache/CADTrait.php

<?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;
		}
	}
}