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<?php defined('SYSPATH') or die('No direct script access.');
/**
* Provides a driver-based interface for finding, creating, and deleting cached
* resources. Caches are identified by a unique string. Tagging of caches is
* also supported, and caches can be found and deleted by id or tag.
*
* $Id: Cache.php 1911 2008-02-04 16:13:16Z PugFish $
*
* @package Cache
* @author Kohana Team
* @copyright (c) 2007-2008 Kohana Team
* @license http://kohanaphp.com/license.html
*/
class Cache {

// For garbage collection
protected static $loaded;

// Configuration
protected $config;

// Driver object
protected $driver;

/**
* Loads the configured driver and validates it.
*
* @param array custom configuration
* @return void
*/
public function __construct($config = array())
{
// Load configuration
$this->config = (array) $config + Config::item('cache');

// Set driver name
$driver = 'Cache_'.ucfirst($this->config['driver']).'_Driver';

// Load the driver
if ( ! Kohana::auto_load($driver))
throw new Kohana_Exception('cache.driver_not_supported', $this->config['driver']);

// Initialize the driver
$this->driver = new $driver($this->config['params']);

// Validate the driver
if ( ! ($this->driver instanceof Cache_Driver))
throw new Kohana_Exception('cache.driver_not_supported', 'Cache drivers must use the Cache_Driver interface.');

Log::add('debug', 'Cache Library initialized');

if (self::$loaded != TRUE)
{
if (mt_rand(0, (int) $this->config['requests']) === 1)
{
// Do garbage collection
$this->driver->delete_expired();

Log::add('debug', 'Cache: Expired caches deleted.');
}

// Cache has been loaded once
self::$loaded = TRUE;
}
}

/**
* Fetches a cache by id. Non-string cache items are automatically
* unserialized before the cache is returned. NULL is returned when
* a cache item is not found.
*
* @param string cache id
* @return mixed cached data or NULL
*/
public function get($id)
{
// Change slashes to colons
$id = str_replace(array('/', '\\'), '=', $id);

if ($data = $this->driver->get($id))
{
if (substr($data, 0, 14) === '<{serialized}>')
{
// Data has been serialized, unserialize now
$data = unserialize(substr($data, 14));
}
}

return $data;
}

/**
* Fetches all of the caches for a given tag. An empty array will be
* returned when no matching caches are found.
*
* @param string cache tag
* @return array all cache items matching the tag
*/
public function find($tag)
{
if ($ids = $this->driver->find($tag))
{
$data = array();
foreach($ids as $id)
{
// Load each cache item and add it to the array
if (($cache = $this->get($id)) !== NULL)
{
$data[$id] = $cache;
}
}
return $data;
}

return array();
}

/**
* Set a cache item by id. Tags may also be added and a custom lifetime
* can be set. Non-string data is automatically serialized.
*
* @param string unique cache id
* @param mixed data to cache
* @param array tags for this item
* @param integer number of seconds until the cache expires
* @return bool
*/
function set($id, $data, $tags = NULL, $lifetime = NULL)
{
if (is_resource($data))
throw new Kohana_Exception('cache.resources');

// Change slashes to colons
$id = str_replace(array('/', '\\'), '=', $id);

if ( ! is_string($data))
{
// Serialize all non-string data, so that types can be preserved
$data = '<{serialized}>'.serialize($data);
}

if (empty($tags))
{
$tags = array();
}
else
{
// Make sure that tags is an array
$tags = (array) $tags;
}

if ($lifetime === NULL)
{
// Get the default lifetime
$lifetime = $this->config['lifetime'];
}

if ($lifetime !== 0)
{
// Lifetime is the current timestamp + the lifetime in seconds
$lifetime += time();
}

return $this->driver->set($id, $data, $tags, $lifetime);
}

/**
* Delete a cache item by id.
*
* @param string cache id
* @return bool
*/
public function delete($id)
{
// Change slashes to colons
$id = str_replace(array('/', '\\'), '=', $id);

return $this->driver->delete($id);
}

/**
* Delete all cache items with a given tag.
*
* @param string cache tag name
* @return bool
*/
public function delete_tag($tag)
{
return $this->driver->delete(FALSE, $tag);
}

/**
* Delete ALL cache items items.
*
* @return bool
*/
public function delete_all()
{
return $this->driver->delete(TRUE);
}

} // End Cache
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