feat: Add factory method for in-memory caches

lib/private/Memcache/Factory.php

@@ -31,6 +31,7 @@
  */
 namespace OC\Memcache;
 
+use OCP\Cache\CappedMemoryCache;
 use OCP\Profiler\IProfiler;
 use OCP\ICache;
 use OCP\ICacheFactory;
@@ -184,6 +185,10 @@ public function isAvailable(): bool {
 		return $this->distributedCacheClass !== self::NULL_CACHE;
 	}
 
+	public function createInMemory(int $capacity = 512): ICache {
+		return new CappedMemoryCache($capacity);
+	}
+
 	/**
 	 * Check if a local memory cache backend is available
 	 *

lib/public/ICacheFactory.php

@@ -75,4 +75,20 @@ public function createDistributed(string $prefix = ''): ICache;
 	 * @since 13.0.0
 	 */
 	public function createLocal(string $prefix = ''): ICache;
+
+	/**
+	 * Create an in-memory cache instance
+	 *
+	 * Useful for remembering values inside one process. Cache memory is cleared
+	 * when the object is garbage-collected. Implementation may also expire keys
+	 * earlier when the TTL is reached or too much memory is consumed.
+	 *
+	 * Cache keys are local to the cache object. When building two in-memory
+	 * caches, there is no data exchange between the instances.
+	 *
+	 * @param int $capacity maximum number of cache keys
+	 * @return ICache
+	 * @since 28.0.0
+	 */
+	public function createInMemory(int $capacity = 512): ICache;
 }

tests/lib/Memcache/FactoryTest.php

@@ -140,4 +140,15 @@ public function testCacheNotAvailableException($localCache, $distributedCache) {
 		$profiler = $this->getMockBuilder(IProfiler::class)->getMock();
 		new \OC\Memcache\Factory('abc', $logger, $profiler, $localCache, $distributedCache);
 	}
+
+	public function testCreateInMemory(): void {
+		$logger = $this->getMockBuilder(LoggerInterface::class)->getMock();
+		$profiler = $this->getMockBuilder(IProfiler::class)->getMock();
+		$factory = new \OC\Memcache\Factory('abc', $logger, $profiler, null, null, null);
+
+		$cache = $factory->createInMemory();
+		$cache->set('test', 48);
+
+		self::assertSame(48, $cache->get('test'));
+	}
 }