Cache.php

<?php
/**
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright 2005-2012, Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright 2005-2012, Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @package       Cake.Cache
 * @since         CakePHP(tm) v 1.2.0.4933
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */
namespace Cake\Cache;

use Cake\Core\App;
use Cake\Core\Configure;
use Cake\Error;
use Cake\Utility\Inflector;

/**
 * Cache provides a consistent interface to Caching in your application. It allows you
 * to use several different Cache engines, without coupling your application to a specific
 * implementation.  It also allows you to change out cache storage or configuration without effecting
 * the rest of your application.
 *
 * ### Configuring Cache engines
 *
 * You can configure Cache engines in your application's `Config/cache.php` file.
 * A sample configuration would be:
 *
 * {{{
 * Configure::write('Cache.shared', array(
 *    'engine' => 'Cake\Cache\Engine\ApcEngine',
 *    'prefix' => 'my_app_'
 * ));
 * }}}
 *
 * This would configure an APC cache engine to the 'shared' alias.  You could then read and write
 * to that cache alias by using it for the `$config` parameter in the various Cache methods.
 *
 * In general all Cache operations are supported by all cache engines.
 * However, Cache::increment() and Cache::decrement() are not supported by File caching.
 *
 * There are 5 built-in caching engines:
 *
 * - `FileEngine` - Uses simple files to store content. Poor performance, but good for
 *    storing large objects, or things that are not IO sensitive.  Well suited to development
 *    as it is an easy cache to inspect and manually flush.
 * - `ApcEngine` - Uses the APC object cache, one of the fastest caching engines.
 * - `MemcacheEngine` - Uses the PECL::Memcache extension and Memcached for storage.
 *   Fast reads/writes, and benefits from memcache being distributed.
 * - `XcacheEngine` - Uses the Xcache extension, an alternative to APC.
 * - `WincacheEngine` - Uses Windows Cache Extension for PHP. Supports wincache 1.1.0 and higher.
 *   This engine is recommended to people deploying on windows with IIS.
 * - `RedisEngine` - Uses redis and php-redis extension to store cache data.
 *
 * The following keys are used in core cache engines:
 *
 * - `duration` Specify how long items in this cache configuration last.
 * - `groups` List of groups or 'tags' associated to every key stored in this config.
 *    handy for deleting a complete group from cache.
 * - `prefix` Prefix appended to all entries. Good for when you need to share a keyspace
 *    with either another cache config or another application.
 * - `probability` Probability of hitting a cache gc cleanup.  Setting to 0 will disable
 *    cache::gc from ever being called automatically.
 * - `servers' Used by memcache. Give the address of the memcached servers to use.
 * - `compress` Used by memcache.  Enables memcache's compressed format.
 * - `serialize` Used by FileCache.  Should cache objects be serialized first.
 * - `path` Used by FileCache.  Path to where cachefiles should be saved.
 * - `lock` Used by FileCache.  Should files be locked before writing to them?
 * - `user` Used by Xcache.  Username for XCache
 * - `password` Used by Xcache/Redis.  Password for XCache/Redis
 *
 * ### Removing existing engines
 *
 * To remove an existing cache engine you can use:
 *
 * {{{
 * Cache::drop($configName);
 * }}}
 *
 * When an engine is dropped the connected engine will be deleted.
 *
 * ### Reconfiguring an engine
 *
 * If you need to change a connected engine at runtime, you can do one of two things.
 * Cache::set() will allow you to temporarily reconfigure an engine for one write operation.
 * If you need to permanetly alter a cache engine's configuration at runtime, you should drop it first 
 * and then update the configuration in Configure:
 *
 * {{{
 * Cache::drop('fast_cache');
 * Configure::write('Cache.fast_cache', [...]);
 * }}}
 *
 * Reconnecting an engine will reset any data stored in the engine instance as it
 * will be recreated.
 *
 * @package       Cake.Cache
 * @see app/Config/cache.php for configuration settings
 */
class Cache {

/**
 * Cache configuration stack
 * Keeps the permanent/default settings for each cache engine.
 * These settings are used to reset the engines after temporary modification.
 *
 * @var array
 */
	protected static $_config = array();

/**
 * Whether to reset the settings with the next call to Cache::set();
 *
 * @var array
 */
	protected static $_reset = false;

/**
 * Engine instances keyed by configuration name.
 *
 * @var array
 */
	protected static $_engines = array();

/**
 * Deprecated method. Will be removed in 3.0.0
 *
 * @deprecated
 */
	public static function config($name = null, $settings = array()) {
		trigger_error(
			__d('cake_dev', 'You must use Configure::write() to define cache configuration. Or use engine() to inject new adapter.'),
			E_USER_WARNING
		);
	}

/**
 * Finds and builds the instance of the required engine class.
 *
 * @param string $name Name of the config array that needs an engine instance built
 * @return boolean
 * @throws Cake\Error\Exception
 */
	protected static function _buildEngine($name) {
		$config = Configure::read('Cache.' . $name);
		if (empty($config['engine'])) {
			return false;
		}
		$cacheClass = App::classname($config['engine'], 'Cache/Engine', 'Engine');
		if (!$cacheClass) {
			return false;
		}
		if (!is_subclass_of($cacheClass, 'Cake\Cache\CacheEngine')) {
			throw new Error\Exception(__d('cake_dev', 'Cache engines must use Cake\Cache\CacheEngine as a base class.'));
		}
		$engine = new $cacheClass();
		if ($engine->init($config)) {
			if ($engine->settings['probability'] && time() % $engine->settings['probability'] === 0) {
				$engine->gc();
			}
			static::$_engines[$name] = $engine;
			return true;
		}
		return false;
	}

/**
 * Returns an array containing the connected Cache engines.
 * This will not return engines that are configured, but have not
 * been used yet.
 *
 * @return array Array of connected Cache config names.
 */
	public static function configured() {
		return array_keys(static::$_engines);
	}

/**
 * Drops a constructed cache engine.
 *
 * The engine's configuration will remain in Configure.  If you wish to re-configure a 
 * cache engine you should drop it, change configuration and then re-use it.
 *
 * @param string $config A currently configured cache config you wish to remove.
 * @return boolean success of the removal, returns false when the config does not exist.
 */
	public static function drop($config) {
		if (isset(static::$_engines[$config])) {
			unset(static::$_engines[$config]);
			unset(static::$_config[$config]);
			return true;
		}
		return false;
	}

/**
 * Fetch the engine attached to a specific configuration name.
 * If the engine does not exist, configuration data will be read from
 * `Configure`.
 *
 * If the cache engine & configuration are missing an error will be 
 * triggered.
 *
 * @param string $config The configuration name you want an engine.
 * @param Cake\Cache\CacheEngine $engine An engine instance if you are manually
 *   injecting a cache engine.
 * @return Cake\Cache\Engine
 */
	public static function engine($config, CacheEngine $engine = null) {
		if (Configure::read('Cache.disable')) {
			return false;
		}
		if (isset(static::$_engines[$config])) {
			return static::$_engines[$config];
		}
		if (!$engine && !static::_buildEngine($config, $engine)) {
			$message = __d(
				'cake_dev',
				'The "%s" cache configuration does not exist, nor could configuration be found at "Cache.%s".',
				$config,
				$config
			);
			trigger_error($message, E_USER_WARNING);
		}
		if ($engine) {
			static::$_engines[$config] = $engine;
		}
		return static::$_engines[$config];
	}

/**
 * Temporarily change the settings on a cache config.  The settings will persist for the next write
 * operation (write, decrement, increment, clear). Any reads that are done before the write, will
 * use the modified settings. If `$settings` is empty, the settings will be reset to the
 * original configuration.
 *
 * Can be called with 2 or 3 parameters. To set multiple values at once.
 *
 * `Cache::set(array('duration' => '+30 minutes'), 'my_config');`
 *
 * Or to set one value.
 *
 * `Cache::set('duration', '+30 minutes', 'my_config');`
 *
 * To reset a config back to the originally configured values.
 *
 * `Cache::set(null, 'my_config');`
 *
 * @param string|array $settings Optional string for simple name-value pair or array
 * @param string $value Optional for a simple name-value pair. Otherwise this param
 *   should be used for the cache config name.
 * @param string $config The configuration name you are changing. Defaults to 'default'
 * @return array Array of settings.
 */
	public static function set($settings = array(), $value = null, $config = 'default') {
		$args = func_num_args();
		if ($args === 2) {
			$config = $value;
		}
		if ($args === 3) {
			$settings = array($settings => $value);
		}

		$engine = static::engine($config);
		if (!$engine) {
			return false;
		}

		if (empty(static::$_config[$config])) {
			static::$_config[$config] = $engine->settings();
		}

		if (!empty($settings)) {
			static::$_reset = true;
		}

		if (static::$_reset === true) {
			static::_modifySettings($engine, $config, $settings);
		}
		return static::settings($config);
	}

/**
 * Used to temporarily modify the settings of a caching engine.
 * If $settings is empty the previous settings values will be restored.
 *
 * @param Cake\Cache\CacheEngine $engine The engine to modify
 * @param array $settings The settings to temporarily set.
 * @return void
 */
	protected static function _modifySettings($engine, $config, $settings) {
		$restore = static::$_config[$config];
		if (empty($settings)) {
			static::$_reset = false;
			$settings = $restore;
			unset(static::$_config[$config]);
		} else {
			$settings = array_merge($restore, $settings);
			if (isset($settings['duration']) && !is_numeric($settings['duration'])) {
				$settings['duration'] = strtotime($settings['duration']) - time();
			}
		}
		$engine->settings = $settings;
	}

/**
 * Garbage collection
 *
 * Permanently remove all expired and deleted data
 *
 * @param string $config [optional] The config name you wish to have garbage collected. Defaults to 'default'
 * @param integer $expires [optional] An expires timestamp. Defaults to NULL
 * @return void
 */
	public static function gc($config = 'default', $expires = null) {
		$engine = static::engine($config);
		if (!$engine) {
			return;
		}
		$engine->gc($expires);
	}

/**
 * Write data for key into cache.
 *
 * ### Usage:
 *
 * Writing to the active cache config:
 *
 * `Cache::write('cached_data', $data);`
 *
 * Writing to a specific cache config:
 *
 * `Cache::write('cached_data', $data, 'long_term');`
 *
 * @param string $key Identifier for the data
 * @param mixed $value Data to be cached - anything except a resource
 * @param string $config Optional string configuration name to write to. Defaults to 'default'
 * @return boolean True if the data was successfully cached, false on failure
 */
	public static function write($key, $value, $config = 'default') {
		$engine = static::engine($config);
		$settings = static::settings($config);

		if (!$engine) {
			return false;
		}
		$key = $engine->key($key);

		if (!$key || is_resource($value)) {
			return false;
		}
		$success = $engine->write($settings['prefix'] . $key, $value, $settings['duration']);
		static::set(null, $config);
		if ($success === false && $value !== '') {
			trigger_error(
				__d('cake_dev',
					"%s cache was unable to write '%s' to %s cache",
					$config,
					$key,
					$settings['engine']
				),
				E_USER_WARNING
			);
		}
		return $success;
	}

/**
 * Read a key from the cache.
 *
 * ### Usage:
 *
 * Reading from the active cache configuration.
 *
 * `Cache::read('my_data');`
 *
 * Reading from a specific cache configuration.
 *
 * `Cache::read('my_data', 'long_term');`
 *
 * @param string $key Identifier for the data
 * @param string $config optional name of the configuration to use. Defaults to 'default'
 * @return mixed The cached data, or false if the data doesn't exist, has expired, or if there was an error fetching it
 */
	public static function read($key, $config = 'default') {
		$engine = static::engine($config);
		$settings = static::settings($config);
		if (!$engine) {
			return false;
		}
		$key = $engine->key($key);
		if (!$key) {
			return false;
		}
		return $engine->read($settings['prefix'] . $key);
	}

/**
 * Increment a number under the key and return incremented value.
 *
 * @param string $key Identifier for the data
 * @param integer $offset How much to add
 * @param string $config Optional string configuration name. Defaults to 'default'
 * @return mixed new value, or false if the data doesn't exist, is not integer,
 *    or if there was an error fetching it.
 */
	public static function increment($key, $offset = 1, $config = 'default') {
		$engine = static::engine($config);
		$settings = static::settings($config);

		if (!$engine) {
			return false;
		}
		$key = $engine->key($key);

		if (!$key || !is_int($offset) || $offset < 0) {
			return false;
		}
		$success = $engine->increment($settings['prefix'] . $key, $offset);
		static::set(null, $config);
		return $success;
	}

/**
 * Decrement a number under the key and return decremented value.
 *
 * @param string $key Identifier for the data
 * @param integer $offset How much to subtract
 * @param string $config Optional string configuration name. Defaults to 'default'
 * @return mixed new value, or false if the data doesn't exist, is not integer,
 *   or if there was an error fetching it
 */
	public static function decrement($key, $offset = 1, $config = 'default') {
		$engine = static::engine($config);
		$settings = static::settings($config);

		if (!$engine) {
			return false;
		}
		$key = $engine->key($key);

		if (!$key || !is_int($offset) || $offset < 0) {
			return false;
		}
		$success = $engine->decrement($settings['prefix'] . $key, $offset);
		static::set(null, $config);
		return $success;
	}

/**
 * Delete a key from the cache.
 *
 * ### Usage:
 *
 * Deleting from the active cache configuration.
 *
 * `Cache::delete('my_data');`
 *
 * Deleting from a specific cache configuration.
 *
 * `Cache::delete('my_data', 'long_term');`
 *
 * @param string $key Identifier for the data
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return boolean True if the value was successfully deleted, false if it didn't exist or couldn't be removed
 */
	public static function delete($key, $config = 'default') {
		$settings = static::settings($config);
		$engine = static::engine($config);

		if (!$engine) {
			return false;
		}

		$key = $engine->key($key);
		if (!$key) {
			return false;
		}

		$success = $engine->delete($settings['prefix'] . $key);
		static::set(null, $config);
		return $success;
	}

/**
 * Delete all keys from the cache.
 *
 * @param boolean $check if true will check expiration, otherwise delete all
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return boolean True if the cache was successfully cleared, false otherwise
 */
	public static function clear($check = false, $config = 'default') {
		$engine = static::engine($config);
		if (!$engine) {
			return false;
		}
		$success = $engine->clear($check);
		static::set(null, $config);
		return $success;
	}

/**
 * Delete all keys from the cache belonging to the same group.
 *
 * @param string $group name of the group to be cleared
 * @param string $config name of the configuration to use. Defaults to 'default'
 * @return boolean True if the cache group was successfully cleared, false otherwise
 */
	public static function clearGroup($group, $config = 'default') {
		$engine = static::engine($config);
		if (!$engine) {
			return false;
		}
		$success = $engine->clearGroup($group);
		static::set(null, $config);
		return $success;
	}

/**
 * Return the settings for the named cache engine.
 *
 * @param string $name Name of the configuration to get settings for. Defaults to 'default'
 * @return array list of settings for this engine
 * @see Cache::config()
 */
	public static function settings($config = 'default') {
		$engine = static::engine($config);
		if (!$engine) {
			return [];
		}
		return $engine->settings();
	}

}