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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* The core cache API.
*
* Pretty much just includes the mandatory classes and contains the misc classes that arn't worth separating into individual files.
*
* This file is part of Moodle's cache API, affectionately called MUC.
* It contains the components that are requried in order to use caching.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
defined('MOODLE_INTERNAL') || die();
// Include the required classes.
require_once($CFG->dirroot.'/cache/classes/interfaces.php');
require_once($CFG->dirroot.'/cache/classes/config.php');
require_once($CFG->dirroot.'/cache/classes/helper.php');
require_once($CFG->dirroot.'/cache/classes/factory.php');
require_once($CFG->dirroot.'/cache/classes/loaders.php');
require_once($CFG->dirroot.'/cache/classes/store.php');
require_once($CFG->dirroot.'/cache/classes/definition.php');
/**
* A cached object wrapper.
*
* This class gets used when the data is an object that has implemented the cacheable_object interface.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache_cached_object {
/**
* The class of the cacheable object
* @var string
*/
protected $class;
/**
* The data returned by the cacheable_object prepare_to_cache method.
* @var mixed
*/
protected $data;
/**
* Constructs a cached object wrapper.
* @param cacheable_object $obj
*/
public function __construct(cacheable_object $obj) {
$this->class = get_class($obj);
$this->data = $obj->prepare_to_cache();
}
/**
* Restores the data as an instance of the cacheable_object class.
* @return object
*/
public function restore_object() {
$class = $this->class;
return $class::wake_from_cache($this->data);
}
}
/**
* A wrapper class used to handle ttl when the cache store doesn't natively support it.
*
* This class is exactly why you should use event driving invalidation of cache data rather than relying on ttl.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache_ttl_wrapper {
/**
* The data being stored.
* @var mixed
*/
public $data;
/**
* When the cache data expires as a timestamp.
* @var int
*/
public $expires;
/**
* Constructs a ttl cache wrapper.
*
* @param mixed $data
* @param int $ttl The time to live in seconds.
*/
public function __construct($data, $ttl) {
$this->data = $data;
$this->expires = cache::now() + (int)$ttl;
}
/**
* Returns true if the data has expired.
* @return int
*/
public function has_expired() {
return ($this->expires < cache::now());
}
}
/**
* A cache exception class. Just allows people to catch cache exceptions.
*
* @package core
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cache_exception extends moodle_exception {
/**
* Constructs a new exception
*
* @param string $errorcode
* @param string $module
* @param string $link
* @param mixed $a
* @param mixed $debuginfo
*/
public function __construct($errorcode, $module = 'cache', $link = '', $a = null, $debuginfo = null) {
// This may appear like a useless override but you will notice that we have set a MUCH more useful default for $module.
parent::__construct($errorcode, $module, $link, $a, $debuginfo);
}
}
/**
* An array of cacheable objects.
*
* This class allows a developer to create an array of cacheable objects and store that.
* The cache API doesn't check items within an array to see whether they are cacheable. Such a check would be very costly to both
* arrays using cacheable object and those that don't.
* Instead the developer must explicitly use a cacheable_object_array instance.
*
* The following is one example of how this class can be used.
* <code>
* $data = array();
* $data[] = new cacheable_object('one');
* $data[] = new cacheable_object('two');
* $data[] = new cacheable_object('three');
* $cache->set(new cacheable_object_array($data));
* </code>
* Another example would be
* <code>
* $data = new cacheable_object_array();
* $data[] = new cacheable_object('one');
* $data[] = new cacheable_object('two');
* $data[] = new cacheable_object('three');
* $cache->set($data);
* </code>
*
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cacheable_object_array extends ArrayObject implements cacheable_object {
/**
* Constructs a new array object instance.
* @param array $items
*/
final public function __construct(array $items = array()) {
parent::__construct($items, ArrayObject::STD_PROP_LIST);
}
/**
* Returns the data to cache for this object.
*
* @return array An array of cache_cached_object instances.
* @throws coding_exception
*/
final public function prepare_to_cache() {
$result = array();
foreach ($this as $key => $value) {
if ($value instanceof cacheable_object) {
$value = new cache_cached_object($value);
} else {
throw new coding_exception('Only cacheable_object instances can be added to a cacheable_array');
}
$result[$key] = $value;
}
return $result;
}
/**
* Returns the cacheable_object_array that was originally sent to the cache.
*
* @param array $data
* @return cacheable_object_array
* @throws coding_exception
*/
final static public function wake_from_cache($data) {
if (!is_array($data)) {
throw new coding_exception('Invalid data type when reviving cacheable_array data');
}
$result = array();
foreach ($data as $key => $value) {
$result[$key] = $value->restore_object();
}
$class = __CLASS__;
return new $class($result);
}
}