Move CappedMemoryCache to OCP

This is an helpful helper that should be used in more place than just
server and this is already the case with groupfodlers, deck, user_oidc
and more using it, so let's make it public

Signed-off-by: Carl Schwan <carl@carlschwan.eu>

1 files changed, 160 insertions, 0 deletions

diff --git a/lib/public/Cache/CappedMemoryCache.php b/lib/public/Cache/CappedMemoryCache.php
new file mode 100644
index 00000000000..6699600d42c
--- /dev/null
+++ b/lib/public/Cache/CappedMemoryCache.php
@@ -0,0 +1,160 @@
+<?php
+/**
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ *
+ * @author Robin Appelman <robin@icewind.nl>
+ *
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * 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, version 3,
+ * along with this program. If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OCP\Cache;
+
+use OCP\ICache;
+
+/**
+ * In-memory cache with a capacity limit to keep memory usage in check
+ *
+ * Uses a simple FIFO expiry mechanism
+ *
+ * @since 25.0.0
+ * @template T
+ */
+class CappedMemoryCache implements ICache, \ArrayAccess {
+	private int $capacity;
+	/** @var T[] */
+	private array $cache = [];
+
+	/**
+	 * @inheritdoc
+	 * @since 25.0.0
+	 */
+	public function __construct(int $capacity = 512) {
+		$this->capacity = $capacity;
+	}
+
+	/**
+	 * @inheritdoc
+	 * @since 25.0.0
+	 */
+	public function hasKey($key): bool {
+		return isset($this->cache[$key]);
+	}
+
+	/**
+	 * @return ?T
+	 * @since 25.0.0
+	 */
+	public function get($key) {
+		return $this->cache[$key] ?? null;
+	}
+
+	/**
+	 * @inheritdoc
+	 * @param string $key
+	 * @param T $value
+	 * @param int $ttl
+	 * @since 25.0.0
+	 * @return bool
+	 */
+	public function set($key, $value, $ttl = 0): bool {
+		if (is_null($key)) {
+			$this->cache[] = $value;
+		} else {
+			$this->cache[$key] = $value;
+		}
+		$this->garbageCollect();
+		return true;
+	}
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function remove($key): bool {
+		unset($this->cache[$key]);
+		return true;
+	}
+
+	/**
+	 * @inheritdoc
+	 * @since 25.0.0
+	 */
+	public function clear($prefix = ''): bool {
+		$this->cache = [];
+		return true;
+	}
+
+	/**
+	 * @since 25.0.0
+	 */
+	public function offsetExists($offset): bool {
+		return $this->hasKey($offset);
+	}
+
+	/**
+	 * @inheritdoc
+	 * @return T
+	 * @since 25.0.0
+	 */
+	#[\ReturnTypeWillChange]
+	public function &offsetGet($offset) {
+		return $this->cache[$offset];
+	}
+
+	/**
+	 * @inheritdoc
+	 * @param string $offset
+	 * @param T $value
+	 * @since 25.0.0
+	 */
+	public function offsetSet($offset, $value): void {
+		$this->set($offset, $value);
+	}
+
+	/**
+	 * @inheritdoc
+	 * @since 25.0.0
+	 */
+	public function offsetUnset($offset): void {
+		$this->remove($offset);
+	}
+
+	/**
+	 * @return T[]
+	 * @since 25.0.0
+	 */
+	public function getData(): array {
+		return $this->cache;
+	}
+
+
+	/**
+	 * @since 25.0.0
+	 */
+	private function garbageCollect(): void {
+		while (count($this->cache) > $this->capacity) {
+			reset($this->cache);
+			$key = key($this->cache);
+			$this->remove($key);
+		}
+	}
+
+	/**
+	 * @inheritdoc
+	 * @since 25.0.0
+	 */
+	public static function isAvailable(): bool {
+		return true;
+	}
+}