Subversion-Projekte lars-tiefland.prado

<?php

/**

 * TSqliteCache class file

 *

 * @author Qiang Xue <qiang.xue@gmail.com>

 * @link http://www.pradosoft.com/

 * @copyright Copyright © 2005-2008 PradoSoft

 * @license http://www.pradosoft.com/license/

 * @version $Id: TSqliteCache.php 2541 2008-10-21 15:05:13Z qiang.xue $

 * @package System.Caching

 */

/**

 * TSqliteCache class

 *

 * TSqliteCache implements a cache application module based on SQLite database.

 *

 * To use this module, the sqlite PHP extension must be loaded. Note, Sqlite extension

 * is no longer loaded by default since PHP 5.1.

 *

 * Sine PRADO v3.1.0, a new DB-based cache module called {@link TDbCache}

 * is provided. If you have PDO extension installed, you may consider using

 * the new cache module instead as it allows you to use different database

 * to store the cached data.

 *

 * The database file is specified by the {@link setDbFile DbFile} property.

 * If not set, the database file will be created under the system state path.

 * If the specified database file does not exist, it will be created automatically.

 * Make sure the directory containing the specified DB file and the file itself is

 * writable by the Web server process.

 *

 * The following basic cache operations are implemented:

 * - {@link get} : retrieve the value with a key (if any) from cache

 * - {@link set} : store the value with a key into cache

 * - {@link add} : store the value only if cache does not have this key

 * - {@link delete} : delete the value with the specified key from cache

 * - {@link flush} : delete all values from cache

 *

 * Each value is associated with an expiration time. The {@link get} operation

 * ensures that any expired value will not be returned. The expiration time by

 * the number of seconds. A expiration time 0 represents never expire.

 *

 * By definition, cache does not ensure the existence of a value

 * even if it never expires. Cache is not meant to be an persistent storage.

 *

 * Do not use the same database file for multiple applications using TSqliteCache.

 * Also note, cache is shared by all user sessions of an application.

 *

 * Some usage examples of TSqliteCache are as follows,

 * <code>

 * $cache=new TSqliteCache;  // TSqliteCache may also be loaded as a Prado application module

 * $cache->setDbFile($dbFilePath);

 * $cache->init(null);

 * $cache->add('object',$object);

 * $object2=$cache->get('object');

 * </code>

 *

 * If loaded, TSqliteCache will register itself with {@link TApplication} as the

 * cache module. It can be accessed via {@link TApplication::getCache()}.

 *

 * TSqliteCache may be configured in application configuration file as follows

 * <code>

 * <module id="cache" class="System.Caching.TSqliteCache" DbFile="Application.Data.site" />

 * </code>

 * where {@link getDbFile DbFile} is a property specifying the location of the

 * SQLite DB file (in the namespace format).

 *

 * @author Qiang Xue <qiang.xue@gmail.com>

 * @version $Id: TSqliteCache.php 2541 2008-10-21 15:05:13Z qiang.xue $

 * @package System.Caching

 * @since 3.0

 */

class TSqliteCache extends TCache

{

	/**

	 * name of the table storing cache data

	 */

	const CACHE_TABLE='cache';

	/**

	 * extension of the db file name

	 */

	const DB_FILE_EXT='.db';

	/**

	 * @var boolean if the module has been initialized

	 */

	private $_initialized=false;

	/**

	 * @var SQLiteDatabase the sqlite database instance

	 */

	private $_db=null;

	/**

	 * @var string the database file name

	 */

	private $_file=null;

	/**

	 * Destructor.

	 * Disconnect the db connection.

	 */

	public function __destruct()

	{

		$this->_db=null;

	}

	/**

	 * Initializes this module.

	 * This method is required by the IModule interface. It checks if the DbFile

	 * property is set, and creates a SQLiteDatabase instance for it.

	 * The database or the cache table does not exist, they will be created.

	 * Expired values are also deleted.

	 * @param TXmlElement configuration for this module, can be null

	 * @throws TConfigurationException if sqlite extension is not installed,

	 *         DbFile is set invalid, or any error happens during creating database or cache table.

	 */

	public function init($config)

	{

		if(!function_exists('sqlite_open'))

			throw new TConfigurationException('sqlitecache_extension_required');

		if($this->_file===null)

			$this->_file=$this->getApplication()->getRuntimePath().'/sqlite.cache';

		$error='';

		if(($this->_db=new SQLiteDatabase($this->_file,0666,$error))===false)

			throw new TConfigurationException('sqlitecache_connection_failed',$error);

		if(@$this->_db->query('DELETE FROM '.self::CACHE_TABLE.' WHERE expire<>0 AND expire<'.time())===false)

		{

			if($this->_db->query('CREATE TABLE '.self::CACHE_TABLE.' (key CHAR(128) PRIMARY KEY, value BLOB, expire INT)')===false)

				throw new TConfigurationException('sqlitecache_table_creation_failed',sqlite_error_string(sqlite_last_error()));

		}

		$this->_initialized=true;

		parent::init($config);

	}

	/**

	 * @return string database file path (in namespace form)

	 */

	public function getDbFile()

	{

		return $this->_file;

	}

	/**

	 * @param string database file path (in namespace form)

	 * @throws TInvalidOperationException if the module is already initialized

	 * @throws TConfigurationException if the file is not in proper namespace format

	 */

	public function setDbFile($value)

	{

		if($this->_initialized)

			throw new TInvalidOperationException('sqlitecache_dbfile_unchangeable');

		else if(($this->_file=Prado::getPathOfNamespace($value,self::DB_FILE_EXT))===null)

			throw new TConfigurationException('sqlitecache_dbfile_invalid',$value);

	}

	/**

	 * Retrieves a value from cache with a specified key.

	 * This is the implementation of the method declared in the parent class.

	 * @param string a unique key identifying the cached value

	 * @return string the value stored in cache, false if the value is not in the cache or expired.

	 */

	protected function getValue($key)

	{

		$sql='SELECT value FROM '.self::CACHE_TABLE.' WHERE key=\''.$key.'\' AND (expire=0 OR expire>'.time().') LIMIT 1';

		if(($ret=$this->_db->query($sql))!=false && ($row=$ret->fetch(SQLITE_ASSOC))!==false)

			return $row['value'];

		else

			return false;

	}

	/**

	 * Stores a value identified by a key in cache.

	 * This is the implementation of the method declared in the parent class.

	 *

	 * @param string the key identifying the value to be cached

	 * @param string the value to be cached

	 * @param integer the number of seconds in which the cached value will expire. 0 means never expire.

	 * @return boolean true if the value is successfully stored into cache, false otherwise

	 */

	protected function setValue($key,$value,$expire)

	{

		$expire=($expire<=0)?0:time()+$expire;

		$sql='REPLACE INTO '.self::CACHE_TABLE.' VALUES(\''.$key.'\',\''.sqlite_escape_string($value).'\','.$expire.')';

		return $this->_db->query($sql)!==false;

	}

	/**

	 * Stores a value identified by a key into cache if the cache does not contain this key.

	 * This is the implementation of the method declared in the parent class.

	 *

	 * @param string the key identifying the value to be cached

	 * @param string the value to be cached

	 * @param integer the number of seconds in which the cached value will expire. 0 means never expire.

	 * @return boolean true if the value is successfully stored into cache, false otherwise

	 */

	protected function addValue($key,$value,$expire)

	{

		$expire=($expire<=0)?0:time()+$expire;

		$sql='INSERT INTO '.self::CACHE_TABLE.' VALUES(\''.$key.'\',\''.sqlite_escape_string($value).'\','.$expire.')';

		return @$this->_db->query($sql)!==false;

	}

	/**

	 * Deletes a value with the specified key from cache

	 * This is the implementation of the method declared in the parent class.

	 * @param string the key of the value to be deleted

	 * @return boolean if no error happens during deletion

	 */

	protected function deleteValue($key)

	{

		$sql='DELETE FROM '.self::CACHE_TABLE.' WHERE key=\''.$key.'\'';

		return $this->_db->query($sql)!==false;

	}

	/**

	 * Deletes all values from cache.

	 * Be careful of performing this operation if the cache is shared by multiple applications.

	 */

	public function flush()

	{

		return $this->_db->query('DELETE FROM '.self::CACHE_TABLE)!==false;

	}

}