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<?php
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/**
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 * TXCache class file
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 *
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 * @author Wei Zhuo <weizhuo[at]gmail[dot]com>
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 * @link http://www.pradosoft.com/
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 * @copyright Copyright &copy; 2005-2008 PradoSoft
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 * @license http://www.pradosoft.com/license/
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 * @version $Id: TXCache.php 1994 2007-06-11 16:02:28Z knut $
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 * @package System.Caching
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 */
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/**
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 * TXCache class
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 *
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 * TXCache implements a cache application module based on {@link http://xcache.lighttpd.net/ xcache}.
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 *
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 * By definition, cache does not ensure the existence of a value
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 * even if it never expires. Cache is not meant to be an persistent storage.
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 *
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 * To use this module, the xcache PHP extension must be loaded and configured in the php.ini.
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 *
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 * Some usage examples of TXCache are as follows,
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 * <code>
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 * $cache=new TXCache;  // TXCache may also be loaded as a Prado application module
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 * $cache->init(null);
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 * $cache->add('object',$object);
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 * $object2=$cache->get('object');
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 * </code>
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 *
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 * If loaded, TXCache will register itself with {@link TApplication} as the
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 * cache module. It can be accessed via {@link TApplication::getCache()}.
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 *
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 * TXCache may be configured in application configuration file as follows
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 * <code>
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 * <module id="cache" class="System.Caching.TXCache" />
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 * </code>
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 *
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 * @author Wei Zhuo <weizhuo[at]gmail[dot]com>
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 * @version $Id: TXCache.php 1994 2007-06-11 16:02:28Z knut $
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 * @package System.Caching
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 * @since 3.1.1
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 */
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class TXCache extends TCache
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{
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   /**
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    * Initializes this module.
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    * This method is required by the IModule interface.
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    * @param TXmlElement configuration for this module, can be null
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    * @throws TConfigurationException if xcache extension is not installed or not started, check your php.ini
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    */
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	public function init($config)
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	{
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		if(!function_exists('xcache_isset'))
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			throw new TConfigurationException('xcache_extension_required');
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		$enabled = (int)ini_get('xcache.cacher') !== 0;
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		$var_size = (int)ini_get('xcache.var_size');
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		if(!($enabled && $var_size > 0))
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			throw new TConfigurationException('xcache_extension_not_enabled');
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		parent::init($config);
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	}
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	/**
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	 * Retrieves a value from cache with a specified key.
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	 * This is the implementation of the method declared in the parent class.
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	 * @param string a unique key identifying the cached value
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	 * @return string the value stored in cache, false if the value is not in the cache or expired.
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	 */
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	protected function getValue($key)
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	{
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		return xcache_isset($key) ? xcache_get($key) : false;
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	}
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	/**
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	 * Stores a value identified by a key in cache.
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	 * This is the implementation of the method declared in the parent class.
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	 *
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	 * @param string the key identifying the value to be cached
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	 * @param string the value to be cached
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	 * @param integer the number of seconds in which the cached value will expire. 0 means never expire.
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	 * @return boolean true if the value is successfully stored into cache, false otherwise
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	 */
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	protected function setValue($key,$value,$expire)
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	{
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		return xcache_set($key,$value,$expire);
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	}
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	/**
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	 * Stores a value identified by a key into cache if the cache does not contain this key.
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	 * This is the implementation of the method declared in the parent class.
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	 *
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	 * @param string the key identifying the value to be cached
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	 * @param string the value to be cached
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	 * @param integer the number of seconds in which the cached value will expire. 0 means never expire.
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	 * @return boolean true if the value is successfully stored into cache, false otherwise
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	 */
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	protected function addValue($key,$value,$expire)
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	{
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		return !xcache_isset($key) ? $this->setValue($key,$value,$expire) : false;
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	}
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	/**
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	 * Deletes a value with the specified key from cache
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	 * This is the implementation of the method declared in the parent class.
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	 * @param string the key of the value to be deleted
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	 * @return boolean if no error happens during deletion
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	 */
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	protected function deleteValue($key)
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	{
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		return xcache_unset($key);
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	}
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	/**
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	 * Deletes all values from cache.
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	 * Be careful of performing this operation if the cache is shared by multiple applications.
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	 */
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	public function flush()
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	{
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		return xcache_clear_cache();
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	}
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}
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?>