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   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   * Cache definition class
  19   *
  20   * This file is part of Moodle's cache API, affectionately called MUC.
  21   * It contains the components that are requried in order to use caching.
  22   *
  23   * @package    core
  24   * @category   cache
  25   * @copyright  2012 Sam Hemelryk
  26   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  27   */
  28  
  29  defined('MOODLE_INTERNAL') || die();
  30  
  31  /**
  32   * The cache definition class.
  33   *
  34   * Cache definitions need to be defined in db/caches.php files.
  35   * They can be constructed with the following options.
  36   *
  37   * Required settings:
  38   *     + mode
  39   *          [int] Sets the mode for the definition. Must be one of cache_store::MODE_*
  40   *
  41   * Optional settings:
  42   *     + simplekeys
  43   *          [bool] Set to true if your cache will only use simple keys for its items.
  44   *          Simple keys consist of digits, underscores and the 26 chars of the english language. a-zA-Z0-9_
  45   *          If true the keys won't be hashed before being passed to the cache store for gets/sets/deletes. It will be
  46   *          better for performance and possible only becase we know the keys are safe.
  47   *     + simpledata
  48   *          [bool] If set to true we know that the data is scalar or array of scalar.
  49   *     + requireidentifiers
  50   *          [array] An array of identifiers that must be provided to the cache when it is created.
  51   *     + requiredataguarantee
  52   *          [bool] If set to true then only stores that can guarantee data will remain available once set will be used.
  53   *     + requiremultipleidentifiers
  54   *          [bool] If set to true then only stores that support multiple identifiers will be used.
  55   *     + requirelockingread
  56   *          [bool] If set to true then a lock will be gained before reading from the cache store. It is recommended not to use
  57   *          this setting unless 100% absolutely positively required. Remember 99.9% of caches will NOT need this setting.
  58   *          This setting will only be used for application caches presently.
  59   *     + requirelockingwrite
  60   *          [bool] If set to true then a lock will be gained before writing to the cache store. As above this is not recommended
  61   *          unless truly needed. Please think about the order of your code and deal with race conditions there first.
  62   *          This setting will only be used for application caches presently.
  63   *     + maxsize
  64   *          [int] If set this will be used as the maximum number of entries within the cache store for this definition.
  65   *          Its important to note that cache stores don't actually have to acknowledge this setting or maintain it as a hard limit.
  66   *     + overrideclass
  67   *          [string] A class to use as the loader for this cache. This is an advanced setting and will allow the developer of the
  68   *          definition to take 100% control of the caching solution.
  69   *          Any class used here must inherit the cache_loader interface and must extend default cache loader for the mode they are
  70   *          using.
  71   *     + overrideclassfile
  72   *          [string] Suplements the above setting indicated the file containing the class to be used. This file is included when
  73   *          required.
  74   *     + datasource
  75   *          [string] A class to use as the data loader for this definition.
  76   *          Any class used here must inherit the cache_data_loader interface.
  77   *     + datasourcefile
  78   *          [string] Supplements the above setting indicating the file containing the class to be used. This file is included when
  79   *          required.
  80   *     + staticacceleration
  81   *          The cache loader will keep an array of the items set and retrieved to the cache during the request.
  82   *          Consider using this setting when you know that there are going to be many calls to the cache for the same information.
  83   *          Requests for data in this array will be ultra fast, but it will cost memory.
  84   *     + staticaccelerationsize
  85   *          [int] This supplements the above setting by limiting the number of items in the static acceleration array.
  86   *          Tweaking this setting lower will allow you to minimise the memory implications above while hopefully still managing to
  87   *          offset calls to the cache store.
  88   *     + ttl
  89   *          [int] A time to live for the data (in seconds). It is strongly recommended that you don't make use of this and
  90   *          instead try to create an event driven invalidation system.
  91   *          Not all cache stores will support this natively and there are undesired performance impacts if the cache store does not.
  92   *     + mappingsonly
  93   *          [bool] If set to true only the mapped cache store(s) will be used and the default mode store will not. This is a super
  94   *          advanced setting and should not be used unless absolutely required. It allows you to avoid the default stores for one
  95   *          reason or another.
  96   *     + invalidationevents
  97   *          [array] An array of events that should cause this cache to invalidate some or all of the items within it.
  98   *     + sharingoptions
  99   *          [int] The sharing options that are appropriate for this definition. Should be the sum of the possible options.
 100   *     + defaultsharing
 101   *          [int] The default sharing option to use. It's highly recommended that you don't set this unless there is a very
 102   *          specific reason not to use the system default.
 103   *     + canuselocalstore
 104   *          [bool] The cache is able to safely run with multiple copies on different webservers without any need for administrator
 105   *                 intervention to ensure that data stays in sync across nodes.  This is usually managed by a revision
 106   *                 system as seen in modinfo cache or language cache.  Requiring purge on upgrade is not sufficient as
 107   *                 it requires administrator intervention on each node to make it work.
 108   *
 109   * For examples take a look at lib/db/caches.php
 110   *
 111   * @package    core
 112   * @category   cache
 113   * @copyright  2012 Sam Hemelryk
 114   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 115   */
 116  class cache_definition {
 117  
 118      /** The cache can be shared with everyone */
 119      const SHARING_ALL = 1;
 120      /** The cache can be shared with other sites using the same siteid. */
 121      const SHARING_SITEID = 2;
 122      /** The cache can be shared with other sites of the same version. */
 123      const SHARING_VERSION = 4;
 124      /** The cache can be shared with other sites using the same key */
 125      const SHARING_INPUT = 8;
 126  
 127      /**
 128       * The default sharing options available.
 129       * All + SiteID + Version + Input.
 130       */
 131      const SHARING_DEFAULTOPTIONS = 15;
 132      /**
 133       * The default sharing option that gets used if none have been selected.
 134       * SiteID. It is the most restrictive.
 135       */
 136      const SHARING_DEFAULT = 2;
 137  
 138      /**
 139       * The identifier for the definition
 140       * @var string
 141       */
 142      protected $id;
 143  
 144      /**
 145       * The mode for the defintion. One of cache_store::MODE_*
 146       * @var int
 147       */
 148      protected $mode;
 149  
 150      /**
 151       * The component this definition is associated with.
 152       * @var string
 153       */
 154      protected $component;
 155  
 156      /**
 157       * The area this definition is associated with.
 158       * @var string
 159       */
 160      protected $area;
 161  
 162      /**
 163       * If set to true we know the keys are simple. a-zA-Z0-9_
 164       * @var bool
 165       */
 166      protected $simplekeys = false;
 167  
 168      /**
 169       * Set to true if we know the data is scalar or array of scalar.
 170       * @var bool
 171       */
 172      protected $simpledata = false;
 173  
 174      /**
 175       * An array of identifiers that must be provided when the definition is used to create a cache.
 176       * @var array
 177       */
 178      protected $requireidentifiers = array();
 179  
 180      /**
 181       * If set to true then only stores that guarantee data may be used with this definition.
 182       * @var bool
 183       */
 184      protected $requiredataguarantee = false;
 185  
 186      /**
 187       * If set to true then only stores that support multple identifiers may be used with this definition.
 188       * @var bool
 189       */
 190      protected $requiremultipleidentifiers = false;
 191  
 192      /**
 193       * If set to true then we know that this definition requires the locking functionality.
 194       * This gets set during construction based upon the settings requirelockingread and requirelockingwrite.
 195       * @var bool
 196       */
 197      protected $requirelocking = false;
 198  
 199      /**
 200       * Set to true if this definition requires read locking.
 201       * @var bool
 202       */
 203      protected $requirelockingread = false;
 204  
 205      /**
 206       * Gets set to true if this definition requires write locking.
 207       * @var bool
 208       */
 209      protected $requirelockingwrite = false;
 210  
 211      /**
 212       * Gets set to true if this definition requires searchable stores.
 213       * @since Moodle 2.4.4
 214       * @var bool
 215       */
 216      protected $requiresearchable = false;
 217  
 218      /**
 219       * Sets the maximum number of items that can exist in the cache.
 220       * Please note this isn't a hard limit, and doesn't need to be enforced by the caches. They can choose to do so optionally.
 221       * @var int
 222       */
 223      protected $maxsize = null;
 224  
 225      /**
 226       * The class to use as the cache loader for this definition.
 227       * @var string
 228       */
 229      protected $overrideclass = null;
 230  
 231      /**
 232       * The file in which the override class exists. This will be included if required.
 233       * @var string Absolute path
 234       */
 235      protected $overrideclassfile = null;
 236  
 237      /**
 238       * The data source class to use with this definition.
 239       * @var string
 240       */
 241      protected $datasource = null;
 242  
 243      /**
 244       * The file in which the data source class exists. This will be included if required.
 245       * @var string
 246       */
 247      protected $datasourcefile = null;
 248  
 249      /**
 250       * Deprecated - this is completely unused.
 251       * @deprecated since 2.9
 252       * @todo MDL-55267 This will be deleted in Moodle 3.3.
 253       * @var string
 254       */
 255      protected $datasourceaggregate = null;
 256  
 257      /**
 258       * Set to true if the cache should hold onto items passing through it to speed up subsequent requests.
 259       * @var bool
 260       */
 261      protected $staticacceleration = false;
 262  
 263      /**
 264       * The maximum number of items that static acceleration cache should hold onto.
 265       * @var int
 266       */
 267      protected $staticaccelerationsize = false;
 268  
 269      /**
 270       * The TTL for data in this cache. Please don't use this, instead use event driven invalidation.
 271       * @var int
 272       */
 273      protected $ttl = 0;
 274  
 275      /**
 276       * Set to true if this cache should only use mapped cache stores and not the default mode cache store.
 277       * @var bool
 278       */
 279      protected $mappingsonly = false;
 280  
 281      /**
 282       * An array of events that should cause this cache to invalidate.
 283       * @var array
 284       */
 285      protected $invalidationevents = array();
 286  
 287      /**
 288       * An array of identifiers provided to this cache when it was initialised.
 289       * @var array
 290       */
 291      protected $identifiers = null;
 292  
 293      /**
 294       * Key prefix for use with single key cache stores
 295       * @var string
 296       */
 297      protected $keyprefixsingle = null;
 298  
 299      /**
 300       * Key prefix to use with cache stores that support multi keys.
 301       * @var array
 302       */
 303      protected $keyprefixmulti = null;
 304  
 305      /**
 306       * A hash identifier of this definition.
 307       * @var string
 308       */
 309      protected $definitionhash = null;
 310  
 311      /**
 312       * The selected sharing mode for this definition.
 313       * @var int
 314       */
 315      protected $sharingoptions;
 316  
 317      /**
 318       * Whether this cache supports local storages.
 319       * @var bool
 320       */
 321      protected $canuselocalstore = false;
 322  
 323      /**
 324       * The selected sharing option.
 325       * @var int One of self::SHARING_*
 326       */
 327      protected $selectedsharingoption = self::SHARING_DEFAULT;
 328  
 329      /**
 330       * The user input key to use if the SHARING_INPUT option has been selected.
 331       * @var string Must be ALPHANUMEXT
 332       */
 333      protected $userinputsharingkey = '';
 334  
 335      /**
 336       * Creates a cache definition given a definition from the cache configuration or from a caches.php file.
 337       *
 338       * @param string $id
 339       * @param array $definition
 340       * @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.
 341       * @return cache_definition
 342       * @throws coding_exception
 343       */
 344      public static function load($id, array $definition, $unused = null) {
 345          global $CFG;
 346  
 347          if (!array_key_exists('mode', $definition)) {
 348              throw new coding_exception('You must provide a mode when creating a cache definition');
 349          }
 350          if (!array_key_exists('component', $definition)) {
 351              throw new coding_exception('You must provide a component when creating a cache definition');
 352          }
 353          if (!array_key_exists('area', $definition)) {
 354              throw new coding_exception('You must provide an area when creating a cache definition');
 355          }
 356          $mode = (int)$definition['mode'];
 357          $component = (string)$definition['component'];
 358          $area = (string)$definition['area'];
 359  
 360          // Set the defaults.
 361          $simplekeys = false;
 362          $simpledata = false;
 363          $requireidentifiers = array();
 364          $requiredataguarantee = false;
 365          $requiremultipleidentifiers = false;
 366          $requirelockingread = false;
 367          $requirelockingwrite = false;
 368          $requiresearchable = ($mode === cache_store::MODE_SESSION) ? true : false;
 369          $maxsize = null;
 370          $overrideclass = null;
 371          $overrideclassfile = null;
 372          $datasource = null;
 373          $datasourcefile = null;
 374          $staticacceleration = false;
 375          $staticaccelerationsize = false;
 376          $ttl = 0;
 377          $mappingsonly = false;
 378          $invalidationevents = array();
 379          $sharingoptions = self::SHARING_DEFAULT;
 380          $selectedsharingoption = self::SHARING_DEFAULT;
 381          $userinputsharingkey = '';
 382          $canuselocalstore = false;
 383  
 384          if (array_key_exists('simplekeys', $definition)) {
 385              $simplekeys = (bool)$definition['simplekeys'];
 386          }
 387          if (array_key_exists('simpledata', $definition)) {
 388              $simpledata = (bool)$definition['simpledata'];
 389          }
 390          if (array_key_exists('requireidentifiers', $definition)) {
 391              $requireidentifiers = (array)$definition['requireidentifiers'];
 392          }
 393          if (array_key_exists('requiredataguarantee', $definition)) {
 394              $requiredataguarantee = (bool)$definition['requiredataguarantee'];
 395          }
 396          if (array_key_exists('requiremultipleidentifiers', $definition)) {
 397              $requiremultipleidentifiers = (bool)$definition['requiremultipleidentifiers'];
 398          }
 399  
 400          if (array_key_exists('requirelockingread', $definition)) {
 401              $requirelockingread = (bool)$definition['requirelockingread'];
 402          }
 403          if (array_key_exists('requirelockingwrite', $definition)) {
 404              $requirelockingwrite = (bool)$definition['requirelockingwrite'];
 405          }
 406          $requirelocking = $requirelockingwrite || $requirelockingread;
 407  
 408          if (array_key_exists('requiresearchable', $definition)) {
 409              $requiresearchable = (bool)$definition['requiresearchable'];
 410          }
 411  
 412          if (array_key_exists('maxsize', $definition)) {
 413              $maxsize = (int)$definition['maxsize'];
 414          }
 415  
 416          if (array_key_exists('overrideclass', $definition)) {
 417              $overrideclass = $definition['overrideclass'];
 418          }
 419          if (array_key_exists('overrideclassfile', $definition)) {
 420              $overrideclassfile = $definition['overrideclassfile'];
 421          }
 422  
 423          if (array_key_exists('datasource', $definition)) {
 424              $datasource = $definition['datasource'];
 425          }
 426          if (array_key_exists('datasourcefile', $definition)) {
 427              $datasourcefile = $definition['datasourcefile'];
 428          }
 429  
 430          if (array_key_exists('persistent', $definition)) {
 431              // Ahhh this is the legacy persistent option.
 432              $staticacceleration = (bool)$definition['persistent'];
 433          }
 434          if (array_key_exists('staticacceleration', $definition)) {
 435              $staticacceleration = (bool)$definition['staticacceleration'];
 436          }
 437          if (array_key_exists('persistentmaxsize', $definition)) {
 438              // Ahhh this is the legacy persistentmaxsize option.
 439              $staticaccelerationsize = (int)$definition['persistentmaxsize'];
 440          }
 441          if (array_key_exists('staticaccelerationsize', $definition)) {
 442              $staticaccelerationsize = (int)$definition['staticaccelerationsize'];
 443          }
 444          if (array_key_exists('ttl', $definition)) {
 445              $ttl = (int)$definition['ttl'];
 446          }
 447          if (array_key_exists('mappingsonly', $definition)) {
 448              $mappingsonly = (bool)$definition['mappingsonly'];
 449          }
 450          if (array_key_exists('invalidationevents', $definition)) {
 451              $invalidationevents = (array)$definition['invalidationevents'];
 452          }
 453          if (array_key_exists('sharingoptions', $definition)) {
 454              $sharingoptions = (int)$definition['sharingoptions'];
 455          }
 456          if (array_key_exists('selectedsharingoption', $definition)) {
 457              $selectedsharingoption = (int)$definition['selectedsharingoption'];
 458          } else if (array_key_exists('defaultsharing', $definition)) {
 459              $selectedsharingoption = (int)$definition['defaultsharing'];
 460          } else if ($sharingoptions ^ $selectedsharingoption) {
 461              if ($sharingoptions & self::SHARING_SITEID) {
 462                  $selectedsharingoption = self::SHARING_SITEID;
 463              } else if ($sharingoptions & self::SHARING_VERSION) {
 464                  $selectedsharingoption = self::SHARING_VERSION;
 465              } else {
 466                  $selectedsharingoption = self::SHARING_ALL;
 467              }
 468          }
 469          if (array_key_exists('canuselocalstore', $definition)) {
 470              $canuselocalstore = (bool)$definition['canuselocalstore'];
 471          }
 472  
 473          if (array_key_exists('userinputsharingkey', $definition) && !empty($definition['userinputsharingkey'])) {
 474              $userinputsharingkey = (string)$definition['userinputsharingkey'];
 475          }
 476  
 477          if (!is_null($overrideclass)) {
 478              if (!is_null($overrideclassfile)) {
 479                  if (strpos($overrideclassfile, $CFG->dirroot) !== 0) {
 480                      $overrideclassfile = $CFG->dirroot.'/'.$overrideclassfile;
 481                  }
 482                  if (strpos($overrideclassfile, '../') !== false) {
 483                      throw new coding_exception('No path craziness allowed within override class file path.');
 484                  }
 485                  if (!file_exists($overrideclassfile)) {
 486                      throw new coding_exception('The override class file does not exist.');
 487                  }
 488                  require_once($overrideclassfile);
 489              }
 490              if (!class_exists($overrideclass)) {
 491                  throw new coding_exception('The override class does not exist.');
 492              }
 493  
 494              // Make sure that the provided class extends the default class for the mode.
 495              if (get_parent_class($overrideclass) !== cache_helper::get_class_for_mode($mode)) {
 496                  throw new coding_exception('The override class does not immediately extend the relevant cache class.');
 497              }
 498          }
 499  
 500          if (!is_null($datasource)) {
 501              if (!is_null($datasourcefile)) {
 502                  if (strpos($datasourcefile, $CFG->dirroot) !== 0) {
 503                      $datasourcefile = $CFG->dirroot.'/'.$datasourcefile;
 504                  }
 505                  if (strpos($datasourcefile, '../') !== false) {
 506                      throw new coding_exception('No path craziness allowed within data source file path.');
 507                  }
 508                  if (!file_exists($datasourcefile)) {
 509                      throw new coding_exception('The data source class file does not exist.');
 510                  }
 511                  require_once($datasourcefile);
 512              }
 513              if (!class_exists($datasource)) {
 514                  throw new coding_exception('The data source class does not exist.');
 515              }
 516              if (!array_key_exists('cache_data_source', class_implements($datasource))) {
 517                  throw new coding_exception('Cache data source classes must implement the cache_data_source interface');
 518              }
 519          }
 520  
 521          $cachedefinition = new cache_definition();
 522          $cachedefinition->id = $id;
 523          $cachedefinition->mode = $mode;
 524          $cachedefinition->component = $component;
 525          $cachedefinition->area = $area;
 526          $cachedefinition->simplekeys = $simplekeys;
 527          $cachedefinition->simpledata = $simpledata;
 528          $cachedefinition->requireidentifiers = $requireidentifiers;
 529          $cachedefinition->requiredataguarantee = $requiredataguarantee;
 530          $cachedefinition->requiremultipleidentifiers = $requiremultipleidentifiers;
 531          $cachedefinition->requirelocking = $requirelocking;
 532          $cachedefinition->requirelockingread = $requirelockingread;
 533          $cachedefinition->requirelockingwrite = $requirelockingwrite;
 534          $cachedefinition->requiresearchable = $requiresearchable;
 535          $cachedefinition->maxsize = $maxsize;
 536          $cachedefinition->overrideclass = $overrideclass;
 537          $cachedefinition->overrideclassfile = $overrideclassfile;
 538          $cachedefinition->datasource = $datasource;
 539          $cachedefinition->datasourcefile = $datasourcefile;
 540          $cachedefinition->staticacceleration = $staticacceleration;
 541          $cachedefinition->staticaccelerationsize = $staticaccelerationsize;
 542          $cachedefinition->ttl = $ttl;
 543          $cachedefinition->mappingsonly = $mappingsonly;
 544          $cachedefinition->invalidationevents = $invalidationevents;
 545          $cachedefinition->sharingoptions = $sharingoptions;
 546          $cachedefinition->selectedsharingoption = $selectedsharingoption;
 547          $cachedefinition->userinputsharingkey = $userinputsharingkey;
 548          $cachedefinition->canuselocalstore = $canuselocalstore;
 549  
 550          return $cachedefinition;
 551      }
 552  
 553      /**
 554       * Creates an ah-hoc cache definition given the required params.
 555       *
 556       * Please note that when using an adhoc definition you cannot set any of the optional params.
 557       * This is because we cannot guarantee consistent access and we don't want to mislead people into thinking that.
 558       *
 559       * @param int $mode One of cache_store::MODE_*
 560       * @param string $component The component this definition relates to.
 561       * @param string $area The area this definition relates to.
 562       * @param array $options An array of options, available options are:
 563       *   - simplekeys : Set to true if the keys you will use are a-zA-Z0-9_
 564       *   - simpledata : Set to true if the type of the data you are going to store is scalar, or an array of scalar vars
 565       *   - overrideclass : The class to use as the loader.
 566       *   - staticacceleration : If set to true the cache will hold onto data passing through it.
 567       *   - staticaccelerationsize : Set it to an int to limit the size of the staticacceleration cache.
 568       * @return cache_application|cache_session|cache_request
 569       */
 570      public static function load_adhoc($mode, $component, $area, array $options = array()) {
 571          $id = 'adhoc/'.$component.'_'.$area;
 572          $definition = array(
 573              'mode' => $mode,
 574              'component' => $component,
 575              'area' => $area,
 576          );
 577          if (!empty($options['simplekeys'])) {
 578              $definition['simplekeys'] = $options['simplekeys'];
 579          }
 580          if (!empty($options['simpledata'])) {
 581              $definition['simpledata'] = $options['simpledata'];
 582          }
 583          if (!empty($options['persistent'])) {
 584              // Ahhh this is the legacy persistent option.
 585              $definition['staticacceleration'] = (bool)$options['persistent'];
 586          }
 587          if (!empty($options['staticacceleration'])) {
 588              $definition['staticacceleration'] = (bool)$options['staticacceleration'];
 589          }
 590          if (!empty($options['staticaccelerationsize'])) {
 591              $definition['staticaccelerationsize'] = (int)$options['staticaccelerationsize'];
 592          }
 593          if (!empty($options['overrideclass'])) {
 594              $definition['overrideclass'] = $options['overrideclass'];
 595          }
 596          if (!empty($options['sharingoptions'])) {
 597              $definition['sharingoptions'] = $options['sharingoptions'];
 598          }
 599          return self::load($id, $definition, null);
 600      }
 601  
 602      /**
 603       * Returns the cache loader class that should be used for this definition.
 604       * @return string
 605       */
 606      public function get_cache_class() {
 607          if (!is_null($this->overrideclass)) {
 608              return $this->overrideclass;
 609          }
 610          return cache_helper::get_class_for_mode($this->mode);
 611      }
 612  
 613      /**
 614       * Returns the id of this definition.
 615       * @return string
 616       */
 617      public function get_id() {
 618          return $this->id;
 619      }
 620  
 621      /**
 622       * Returns the name for this definition
 623       * @return string
 624       */
 625      public function get_name() {
 626          $identifier = 'cachedef_'.clean_param($this->area, PARAM_STRINGID);
 627          $component = $this->component;
 628          if ($component === 'core') {
 629              $component = 'cache';
 630          }
 631          return new lang_string($identifier, $component);
 632      }
 633  
 634      /**
 635       * Returns the mode of this definition
 636       * @return int One more cache_store::MODE_
 637       */
 638      public function get_mode() {
 639          return $this->mode;
 640      }
 641  
 642      /**
 643       * Returns the area this definition is associated with.
 644       * @return string
 645       */
 646      public function get_area() {
 647          return $this->area;
 648      }
 649  
 650      /**
 651       * Returns the component this definition is associated with.
 652       * @return string
 653       */
 654      public function get_component() {
 655          return $this->component;
 656      }
 657  
 658      /**
 659       * Returns true if this definition is using simple keys.
 660       *
 661       * Simple keys contain only a-zA-Z0-9_
 662       *
 663       * @return bool
 664       */
 665      public function uses_simple_keys() {
 666          return $this->simplekeys;
 667      }
 668  
 669      /**
 670       * Returns the identifiers that are being used for this definition.
 671       * @return array
 672       */
 673      public function get_identifiers() {
 674          if (!isset($this->identifiers)) {
 675              return array();
 676          }
 677          return $this->identifiers;
 678      }
 679  
 680      /**
 681       * Returns the ttl in seconds for this definition if there is one, or null if not.
 682       * @return int|null
 683       */
 684      public function get_ttl() {
 685          return $this->ttl;
 686      }
 687  
 688      /**
 689       * Returns the maximum number of items allowed in this cache.
 690       * @return int
 691       */
 692      public function get_maxsize() {
 693          return $this->maxsize;
 694      }
 695  
 696      /**
 697       * Returns true if this definition should only be used with mappings.
 698       * @return bool
 699       */
 700      public function is_for_mappings_only() {
 701          return $this->mappingsonly;
 702      }
 703  
 704      /**
 705       * Returns true if the data is known to be scalar or array of scalar.
 706       * @return bool
 707       */
 708      public function uses_simple_data() {
 709          return $this->simpledata;
 710      }
 711  
 712      /**
 713       * Returns true if this definition requires a data guarantee from the cache stores being used.
 714       * @return bool
 715       */
 716      public function require_data_guarantee() {
 717          return $this->requiredataguarantee;
 718      }
 719  
 720      /**
 721       * Returns true if this definition requires that the cache stores support multiple identifiers
 722       * @return bool
 723       */
 724      public function require_multiple_identifiers() {
 725          return $this->requiremultipleidentifiers;
 726      }
 727  
 728      /**
 729       * Returns true if this definition requires locking functionality. Either read or write locking.
 730       * @return bool
 731       */
 732      public function require_locking() {
 733          return $this->requirelocking;
 734      }
 735  
 736      /**
 737       * Returns true if this definition requires read locking.
 738       * @return bool
 739       */
 740      public function require_locking_read() {
 741          return $this->requirelockingread;
 742      }
 743  
 744      /**
 745       * Returns true if this definition requires write locking.
 746       * @return bool
 747       */
 748      public function require_locking_write() {
 749          return $this->requirelockingwrite;
 750      }
 751  
 752      /**
 753       * Returns true if this definition allows local storage to be used for caching.
 754       * @since Moodle 3.1.0
 755       * @return bool
 756       */
 757      public function can_use_localstore() {
 758          return $this->canuselocalstore;
 759      }
 760  
 761      /**
 762       * Returns true if this definition requires a searchable cache.
 763       * @since Moodle 2.4.4
 764       * @return bool
 765       */
 766      public function require_searchable() {
 767          return $this->requiresearchable;
 768      }
 769  
 770      /**
 771       * Returns true if this definition has an associated data source.
 772       * @return bool
 773       */
 774      public function has_data_source() {
 775          return !is_null($this->datasource);
 776      }
 777  
 778      /**
 779       * Returns an instance of the data source class used for this definition.
 780       *
 781       * @return cache_data_source
 782       * @throws coding_exception
 783       */
 784      public function get_data_source() {
 785          if (!$this->has_data_source()) {
 786              throw new coding_exception('This cache does not use a data source.');
 787          }
 788          return forward_static_call(array($this->datasource, 'get_instance_for_cache'), $this);
 789      }
 790  
 791      /**
 792       * Sets the identifiers for this definition, or updates them if they have already been set.
 793       *
 794       * @param array $identifiers
 795       * @return bool false if no identifiers where changed, true otherwise.
 796       * @throws coding_exception
 797       */
 798      public function set_identifiers(array $identifiers = array()) {
 799          // If we are setting the exact same identifiers then just return as nothing really changed.
 800          // We don't care about order as cache::make will use the same definition order all the time.
 801          if ($identifiers === $this->identifiers) {
 802              return false;
 803          }
 804  
 805          foreach ($this->requireidentifiers as $identifier) {
 806              if (!isset($identifiers[$identifier])) {
 807                  throw new coding_exception('Identifier required for cache has not been provided: '.$identifier);
 808              }
 809          }
 810  
 811          if ($this->identifiers === null) {
 812              // Initialize identifiers if they have not been.
 813              $this->identifiers = array();
 814          }
 815          foreach ($identifiers as $name => $value) {
 816              $this->identifiers[$name] = (string)$value;
 817          }
 818          // Reset the key prefix's they need updating now.
 819          $this->keyprefixsingle = null;
 820          $this->keyprefixmulti = null;
 821  
 822          return true;
 823      }
 824  
 825      /**
 826       * Returns the requirements of this definition as a binary flag.
 827       * @return int
 828       */
 829      public function get_requirements_bin() {
 830          $requires = 0;
 831          if ($this->require_data_guarantee()) {
 832              $requires += cache_store::SUPPORTS_DATA_GUARANTEE;
 833          }
 834          if ($this->require_multiple_identifiers()) {
 835              $requires += cache_store::SUPPORTS_MULTIPLE_IDENTIFIERS;
 836          }
 837          if ($this->require_searchable()) {
 838              $requires += cache_store::IS_SEARCHABLE;
 839          }
 840          return $requires;
 841      }
 842  
 843      /**
 844       * Please call {@link cache_definition::use_static_acceleration()} instead.
 845       *
 846       * @see cache_definition::use_static_acceleration()
 847       * @deprecated since 2.6
 848       */
 849      public function should_be_persistent() {
 850          throw new coding_exception('cache_definition::should_be_persistent() can not be used anymore.' .
 851              ' Please use cache_definition::use_static_acceleration() instead.');
 852      }
 853  
 854      /**
 855       * Returns true if we should hold onto the data flowing through the cache.
 856       *
 857       * If set to true data flowing through the cache will be stored in a static variable
 858       * to make subsequent requests for the data much faster.
 859       *
 860       * @return bool
 861       */
 862      public function use_static_acceleration() {
 863          if ($this->mode === cache_store::MODE_REQUEST) {
 864              // Request caches should never use static acceleration - it just doesn't make sense.
 865              return false;
 866          }
 867          return $this->staticacceleration;
 868      }
 869  
 870      /**
 871       * Please call {@link cache_definition::get_static_acceleration_size()} instead.
 872       *
 873       * @see cache_definition::get_static_acceleration_size()
 874       * @deprecated since 2.6
 875       */
 876      public function get_persistent_max_size() {
 877          throw new coding_exception('cache_definition::get_persistent_max_size() can not be used anymore.' .
 878              ' Please use cache_definition::get_static_acceleration_size() instead.');
 879      }
 880  
 881      /**
 882       * Returns the max size for the static acceleration array.
 883       * @return int
 884       */
 885      public function get_static_acceleration_size() {
 886          return $this->staticaccelerationsize;
 887      }
 888  
 889      /**
 890       * Generates a hash of this definition and returns it.
 891       * @return string
 892       */
 893      public function generate_definition_hash() {
 894          if ($this->definitionhash === null) {
 895              $this->definitionhash = md5("{$this->mode} {$this->component} {$this->area}");
 896          }
 897          return $this->definitionhash;
 898      }
 899  
 900      /**
 901       * Generates a single key prefix for this definition
 902       *
 903       * @return string
 904       */
 905      public function generate_single_key_prefix() {
 906          if ($this->keyprefixsingle === null) {
 907              $this->keyprefixsingle = $this->mode.'/'.$this->component.'/'.$this->area;
 908              $this->keyprefixsingle .= '/'.$this->get_cache_identifier();
 909              $identifiers = $this->get_identifiers();
 910              if ($identifiers) {
 911                  foreach ($identifiers as $key => $value) {
 912                      $this->keyprefixsingle .= '/'.$key.'='.$value;
 913                  }
 914              }
 915              $this->keyprefixsingle = md5($this->keyprefixsingle);
 916          }
 917          return $this->keyprefixsingle;
 918      }
 919  
 920      /**
 921       * Generates a multi key prefix for this definition
 922       *
 923       * @return array
 924       */
 925      public function generate_multi_key_parts() {
 926          if ($this->keyprefixmulti === null) {
 927              $this->keyprefixmulti = array(
 928                  'mode' => $this->mode,
 929                  'component' => $this->component,
 930                  'area' => $this->area,
 931                  'siteidentifier' => $this->get_cache_identifier()
 932              );
 933              if (isset($this->identifiers) && !empty($this->identifiers)) {
 934                  $identifiers = array();
 935                  foreach ($this->identifiers as $key => $value) {
 936                      $identifiers[] = htmlentities($key, ENT_QUOTES, 'UTF-8').'='.htmlentities($value, ENT_QUOTES, 'UTF-8');
 937                  }
 938                  $this->keyprefixmulti['identifiers'] = join('&', $identifiers);
 939              }
 940          }
 941          return $this->keyprefixmulti;
 942      }
 943  
 944      /**
 945       * Check if this definition should invalidate on the given event.
 946       *
 947       * @param string $event
 948       * @return bool True if the definition should invalidate on the event. False otherwise.
 949       */
 950      public function invalidates_on_event($event) {
 951          return (in_array($event, $this->invalidationevents));
 952      }
 953  
 954      /**
 955       * Check if the definition has any invalidation events.
 956       *
 957       * @return bool True if it does, false otherwise
 958       */
 959      public function has_invalidation_events() {
 960          return !empty($this->invalidationevents);
 961      }
 962  
 963      /**
 964       * Returns all of the invalidation events for this definition.
 965       *
 966       * @return array
 967       */
 968      public function get_invalidation_events() {
 969          return $this->invalidationevents;
 970      }
 971  
 972      /**
 973       * Returns a cache identification string.
 974       *
 975       * @return string A string to be used as part of keys.
 976       */
 977      protected function get_cache_identifier() {
 978          $identifiers = array();
 979          if ($this->selectedsharingoption & self::SHARING_ALL) {
 980              // Nothing to do here.
 981          } else {
 982              if ($this->selectedsharingoption & self::SHARING_SITEID) {
 983                  $identifiers[] = cache_helper::get_site_identifier();
 984              }
 985              if ($this->selectedsharingoption & self::SHARING_VERSION) {
 986                  $identifiers[] = cache_helper::get_site_version();
 987              }
 988              if ($this->selectedsharingoption & self::SHARING_INPUT && !empty($this->userinputsharingkey)) {
 989                  $identifiers[] = $this->userinputsharingkey;
 990              }
 991          }
 992          return join('/', $identifiers);
 993      }
 994  
 995      /**
 996       * Returns true if this definition requires identifiers.
 997       *
 998       * @param bool
 999       */
1000      public function has_required_identifiers() {
1001          return (count($this->requireidentifiers) > 0);
1002      }
1003  
1004      /**
1005       * Returns the possible sharing options that can be used with this defintion.
1006       *
1007       * @return int
1008       */
1009      public function get_sharing_options() {
1010          return $this->sharingoptions;
1011      }
1012  
1013      /**
1014       * Returns the user entered sharing key for this definition.
1015       *
1016       * @return string
1017       */
1018      public function get_user_input_sharing_key() {
1019          return $this->userinputsharingkey;
1020      }
1021  
1022      /**
1023       * Returns the user selected sharing option for this definition.
1024       *
1025       * @return int
1026       */
1027      public function get_selected_sharing_option() {
1028          return $this->selectedsharingoption;
1029      }
1030  }