Use new APCu API

This one is available since APCu 4.0, since we require APCu 4.0.6 this works fine. Also it brings us PHP 7 compatibility and thus fixes https://github.com/owncloud/core/issues/21095

lib/private/memcache/apcu.php

@@ -24,7 +24,101 @@
 
 namespace OC\Memcache;
 
-class APCu extends APC {
+use OCP\IMemcache;
+
+class APCu extends Cache implements IMemcache {
+	use CASTrait {
+		cas as casEmulated;
+	}
+
+	use CADTrait;
+
+	public function get($key) {
+		$result = apcu_fetch($this->getPrefix() . $key, $success);
+		if (!$success) {
+			return null;
+		}
+		return $result;
+	}
+
+	public function set($key, $value, $ttl = 0) {
+		return apcu_store($this->getPrefix() . $key, $value, $ttl);
+	}
+
+	public function hasKey($key) {
+		return apcu_exists($this->getPrefix() . $key);
+	}
+
+	public function remove($key) {
+		return apcu_delete($this->getPrefix() . $key);
+	}
+
+	public function clear($prefix = '') {
+		$ns = $this->getPrefix() . $prefix;
+		$ns = preg_quote($ns, '/');
+		if(class_exists('\APCIterator')) {
+			$iter = new \APCIterator('user', '/^' . $ns . '/', APC_ITER_KEY);
+		} else {
+			$iter = new \APCUIterator('user', '/^' . $ns . '/', APC_ITER_KEY);
+		}
+		return apcu_delete($iter);
+	}
+
+	/**
+	 * Set a value in the cache if it's not already stored
+	 *
+	 * @param string $key
+	 * @param mixed $value
+	 * @param int $ttl Time To Live in seconds. Defaults to 60*60*24
+	 * @return bool
+	 */
+	public function add($key, $value, $ttl = 0) {
+		return apcu_add($this->getPrefix() . $key, $value, $ttl);
+	}
+
+	/**
+	 * Increase a stored number
+	 *
+	 * @param string $key
+	 * @param int $step
+	 * @return int | bool
+	 */
+	public function inc($key, $step = 1) {
+		$this->add($key, 0);
+		return apcu_inc($this->getPrefix() . $key, $step);
+	}
+
+	/**
+	 * Decrease a stored number
+	 *
+	 * @param string $key
+	 * @param int $step
+	 * @return int | bool
+	 */
+	public function dec($key, $step = 1) {
+		return apcu_dec($this->getPrefix() . $key, $step);
+	}
+
+	/**
+	 * Compare and set
+	 *
+	 * @param string $key
+	 * @param mixed $old
+	 * @param mixed $new
+	 * @return bool
+	 */
+	public function cas($key, $old, $new) {
+		// apc only does cas for ints
+		if (is_int($old) and is_int($new)) {
+			return apcu_cas($this->getPrefix() . $key, $old, $new);
+		} else {
+			return $this->casEmulated($key, $old, $new);
+		}
+	}
+
+	/**
+	 * @return bool
+	 */
 	static public function isAvailable() {
 		if (!extension_loaded('apcu')) {
 			return false;
@@ -32,7 +126,10 @@ class APCu extends APC {
 			return false;
 		} elseif (!\OC::$server->getIniWrapper()->getBool('apc.enable_cli') && \OC::$CLI) {
 			return false;
-		} elseif (version_compare(phpversion('apc'), '4.0.6') === -1) {
+		} elseif (
+				version_compare(phpversion('apc'), '4.0.6') === -1 &&
+				version_compare(phpversion('apcu'), '5.1.0') === -1
+		) {
 			return false;
 		} else {
 			return true;