cache/lib.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * The core cache API.
  19  *
  20  * Pretty much just includes the mandatory classes and contains the misc classes that arn't worth separating into individual files.
  21  *
  22  * This file is part of Moodle's cache API, affectionately called MUC.
  23  * It contains the components that are requried in order to use caching.
  24  *
  25  * @package    core
  26  * @category   cache
  27  * @copyright  2012 Sam Hemelryk
  28  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  29  */
  30
  31 defined('MOODLE_INTERNAL') || die();
  32
  33 // Include the required classes.
  34 require_once($CFG->dirroot.'/cache/classes/interfaces.php');
  35 require_once($CFG->dirroot.'/cache/classes/config.php');
  36 require_once($CFG->dirroot.'/cache/classes/helper.php');
  37 require_once($CFG->dirroot.'/cache/classes/factory.php');
  38 require_once($CFG->dirroot.'/cache/classes/loaders.php');
  39 require_once($CFG->dirroot.'/cache/classes/store.php');
  40 require_once($CFG->dirroot.'/cache/classes/definition.php');
  41
  42 /**
  43  * A cached object wrapper.
  44  *
  45  * This class gets used when the data is an object that has implemented the cacheable_object interface.
  46  *
  47  * @package    core
  48  * @category   cache
  49  * @copyright  2012 Sam Hemelryk
  50  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  51  */
  52 class cache_cached_object {
  53
  54     /**
  55      * The class of the cacheable object
  56      * @var string
  57      */
  58     protected $class;
  59
  60     /**
  61      * The data returned by the cacheable_object prepare_to_cache method.
  62      * @var mixed
  63      */
  64     protected $data;
  65
  66     /**
  67      * Constructs a cached object wrapper.
  68      * @param cacheable_object $obj
  69      */
  70     public function __construct(cacheable_object $obj) {
  71         $this->class = get_class($obj);
  72         $this->data = $obj->prepare_to_cache();
  73     }
  74
  75     /**
  76      * Restores the data as an instance of the cacheable_object class.
  77      * @return object
  78      */
  79     public function restore_object() {
  80         $class = $this->class;
  81         return $class::wake_from_cache($this->data);
  82     }
  83 }
  84
  85 /**
  86  * A wrapper class used to handle ttl when the cache store doesn't natively support it.
  87  *
  88  * This class is exactly why you should use event driving invalidation of cache data rather than relying on ttl.
  89  *
  90  * @package    core
  91  * @category   cache
  92  * @copyright  2012 Sam Hemelryk
  93  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  94  */
  95 class cache_ttl_wrapper {
  96
  97     /**
  98      * The data being stored.
  99      * @var mixed
 100      */
 101     public $data;
 102
 103     /**
 104      * When the cache data expires as a timestamp.
 105      * @var int
 106      */
 107     public $expires;
 108
 109     /**
 110      * Constructs a ttl cache wrapper.
 111      *
 112      * @param mixed $data
 113      * @param int $ttl The time to live in seconds.
 114      */
 115     public function __construct($data, $ttl) {
 116         $this->data = $data;
 117         $this->expires = cache::now() + (int)$ttl;
 118     }
 119
 120     /**
 121      * Returns true if the data has expired.
 122      * @return int
 123      */
 124     public function has_expired() {
 125         return ($this->expires < cache::now());
 126     }
 127 }
 128
 129 /**
 130  * A cache exception class. Just allows people to catch cache exceptions.
 131  *
 132  * @package    core
 133  * @category   cache
 134  * @copyright  2012 Sam Hemelryk
 135  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 136  */
 137 class cache_exception extends moodle_exception {
 138     /**
 139      * Constructs a new exception
 140      *
 141      * @param string $errorcode
 142      * @param string $module
 143      * @param string $link
 144      * @param mixed $a
 145      * @param mixed $debuginfo
 146      */
 147     public function __construct($errorcode, $module = 'cache', $link = '', $a = null, $debuginfo = null) {
 148         // This may appear like a useless override but you will notice that we have set a MUCH more useful default for $module.
 149         parent::__construct($errorcode, $module, $link, $a, $debuginfo);
 150     }
 151 }
 152
 153 /**
 154  * An array of cacheable objects.
 155  *
 156  * This class allows a developer to create an array of cacheable objects and store that.
 157  * 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
 158  * arrays using cacheable object and those that don't.
 159  * Instead the developer must explicitly use a cacheable_object_array instance.
 160  *
 161  * The following is one example of how this class can be used.
 162  * <code>
 163  * $data = array();
 164  * $data[] = new cacheable_object('one');
 165  * $data[] = new cacheable_object('two');
 166  * $data[] = new cacheable_object('three');
 167  * $cache->set(new cacheable_object_array($data));
 168  * </code>
 169  * Another example would be
 170  * <code>
 171  * $data = new cacheable_object_array();
 172  * $data[] = new cacheable_object('one');
 173  * $data[] = new cacheable_object('two');
 174  * $data[] = new cacheable_object('three');
 175  * $cache->set($data);
 176  * </code>
 177  *
 178  * @copyright  2012 Sam Hemelryk
 179  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 180  */
 181 class cacheable_object_array extends ArrayObject implements cacheable_object {
 182
 183     /**
 184      * Constructs a new array object instance.
 185      * @param array $items
 186      */
 187     final public function __construct(array $items = array()) {
 188         parent::__construct($items, ArrayObject::STD_PROP_LIST);
 189     }
 190
 191     /**
 192      * Returns the data to cache for this object.
 193      *
 194      * @return array An array of cache_cached_object instances.
 195      * @throws coding_exception
 196      */
 197     final public function prepare_to_cache() {
 198         $result = array();
 199         foreach ($this as $key => $value) {
 200             if ($value instanceof cacheable_object) {
 201                 $value = new cache_cached_object($value);
 202             } else {
 203                 throw new coding_exception('Only cacheable_object instances can be added to a cacheable_array');
 204             }
 205             $result[$key] = $value;
 206         }
 207         return $result;
 208     }
 209
 210     /**
 211      * Returns the cacheable_object_array that was originally sent to the cache.
 212      *
 213      * @param array $data
 214      * @return cacheable_object_array
 215      * @throws coding_exception
 216      */
 217     final static public function wake_from_cache($data) {
 218         if (!is_array($data)) {
 219             throw new coding_exception('Invalid data type when reviving cacheable_array data');
 220         }
 221         $result = array();
 222         foreach ($data as $key => $value) {
 223             $result[$key] = $value->restore_object();
 224         }
 225         $class = __CLASS__;
 226         return new $class($result);
 227     }
 228 }