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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/>.namespace core_cache;use core\exception\coding_exception;use stdClass;/*** The main cache class.** This class if the first class that any end developer will interact with.* In order to create an instance of a cache that they can work with they must call one of the static make methods belonging* to this class.** @package core_cache* @category cache* @copyright 2012 Sam Hemelryk* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later*/class cache implements loader_interface {/*** @var int Constant for cache entries that do not have a version number*/const VERSION_NONE = -1;/*** We need a timestamp to use within the cache API.* This stamp needs to be used for all ttl and time based operations to ensure that we don't end up with* timing issues.* @var int*/protected static $now;/*** A purge token used to distinguish between multiple cache purges in the same second.* This is in the format <microtime>-<random string>.** @var string*/protected static $purgetoken;/*** The definition used when loading this cache if there was one.* @var definition*/private $definition = false;/*** The cache store that this loader will make use of.* @var store*/private $store;/*** The next cache loader in the chain if there is one.* If a cache request misses for the store belonging to this loader then the loader* stored here will be checked next.* If there is a loader here then $datasource must be false.* @var loader_interface|false*/private $loader = false;/*** The data source to use if we need to load data (because if doesn't exist in the cache store).* If there is a data source here then $loader above must be false.* @var data_source_interface|false*/private $datasource = false;/*** Used to quickly check if the store supports key awareness.* This is set when the cache is initialised and is used to speed up processing.* @var bool*/private $supportskeyawareness = null;/*** Used to quickly check if the store supports ttl natively.* This is set when the cache is initialised and is used to speed up processing.* @var bool*/private $supportsnativettl = null;/*** Gets set to true if the cache is going to be using a static array for acceleration.* The array statically caches items used during the lifetime of the request. This greatly speeds up interaction* with the cache in areas where it will be repetitively hit for the same information such as with strings.* There are several other variables to control how this static acceleration array works.* @var bool*/private $staticacceleration = false;/*** The static acceleration array.* Items will be stored in this cache as they were provided. This ensure there is no unnecessary processing taking place.* @var array*/private $staticaccelerationarray = [];/*** The number of items in the static acceleration array. Avoids count calls like you wouldn't believe.* @var int*/private $staticaccelerationcount = 0;/*** An array containing just the keys being used in the static acceleration array.* This seems redundant perhaps but is used when managing the size of the static acceleration array.* Items are added to the end of the array and the when we need to reduce the size of the cache we use the* key that is first on this array.* @var array*/private $staticaccelerationkeys = [];/*** The maximum size of the static acceleration array.** If set to false there is no max size.* Caches that make use of static acceleration should seriously consider setting this to something reasonably small, but* still large enough to offset repetitive calls.** @var int|false*/private $staticaccelerationsize = false;/*** Gets set to true during initialisation if the definition is making use of a ttl.* Used to speed up processing.* @var bool*/private $hasattl = false;/*** Gets set to the class name of the store during initialisation. This is used several times in the cache class internally* and having it here helps speed up processing.* @var strubg*/protected $storetype = 'unknown';/*** Gets set to true if we want to collect performance information about the cache API.* @var bool*/protected $perfdebug = false;/*** Determines if this loader is a sub loader, not the top of the chain.* @var bool*/protected $subloader = false;/*** Gets set to true if the cache writes (set|delete) must have a manual lock created first.* @var bool*/protected $requirelockingbeforewrite = false;/*** Gets set to true if the cache's primary store natively supports locking.* If it does then we use that, otherwise we need to instantiate a second store to use for locking.* @var store|null*/protected $nativelocking = null;/*** Creates a new cache instance for a pre-defined definition.** @param string $component The component for the definition* @param string $area The area for the definition* @param array $identifiers Any additional identifiers that should be provided to the definition.* @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.* @return application_cache|session_cache|store*/public static function make($component, $area, array $identifiers = [], $unused = null) {$factory = factory::instance();return $factory->create_cache_from_definition($component, $area, $identifiers);}/*** Creates a new cache instance based upon the given params.** @param int $mode One of store::MODE_** @param string $component The component this cache relates to.* @param string $area The area this cache relates to.* @param array $identifiers Any additional identifiers that should be provided to the definition.* @param array $options An array of options, available options are:* - simplekeys : Set to true if the keys you will use are a-zA-Z0-9_* - simpledata : Set to true if the type of the data you are going to store is scalar, or an array of scalar vars* - staticacceleration : If set to true the cache will hold onto data passing through it.* - staticaccelerationsize : The max size for the static acceleration array.* @return application_cache|session_cache|request_cache*/public static function make_from_params($mode, $component, $area, array $identifiers = [], array $options = []) {$factory = factory::instance();return $factory->create_cache_from_params($mode, $component, $area, $identifiers, $options);}/*** Constructs a new cache instance.** You should not call this method from your code, instead you should use the cache::make methods.** This method is public so that the factory is able to instantiate cache instances.* Ideally we would make this method protected and expose its construction to the factory method internally somehow.* The factory class is responsible for this in order to centralise the storage of instances once created. This way if needed* we can force a reset of the cache API (used during unit testing).** @param definition $definition The definition for the cache instance.* @param store $store The store that cache should use.* @param loader_interface|data_source_interface $loader The next loader in the chain or the data source if there is one* and there are no other loader_interfaces in the chain.*/public function __construct(definition $definition, store $store, $loader = null) {global $CFG;$this->definition = $definition;$this->store = $store;$this->storetype = get_class($store);$this->perfdebug = (!empty($CFG->perfdebug) and $CFG->perfdebug > 7);if ($loader instanceof loader_interface) {$this->set_loader($loader);} else if ($loader instanceof data_source_interface) {$this->set_data_source($loader);}$this->definition->generate_definition_hash();$this->staticacceleration = $this->definition->use_static_acceleration();if ($this->staticacceleration) {$this->staticaccelerationsize = $this->definition->get_static_acceleration_size();}$this->hasattl = ($this->definition->get_ttl() > 0);}/*** Set the loader for this cache.** @param loader_interface $loader*/protected function set_loader(loader_interface $loader): void {$this->loader = $loader;// Mark the loader as a sub (chained) loader.$this->loader->set_is_sub_loader(true);}/*** Set the data source for this cache.** @param data_source_interface $datasource*/protected function set_data_source(data_source_interface $datasource): void {$this->datasource = $datasource;}/*** Used to inform the loader of its state as a sub loader, or as the top of the chain.** This is important as it ensures that we do not have more than one loader keeping static acceleration data.* Subloaders need to be "pure" loaders in the sense that they are used to store and retrieve information from stores or the* next loader/data source in the chain.* Nothing fancy, nothing flash.** @param bool $setting*/protected function set_is_sub_loader($setting = true) {if ($setting) {$this->subloader = true;// Subloaders should not keep static acceleration data.$this->staticacceleration = false;$this->staticaccelerationsize = false;} else {$this->subloader = true;$this->staticacceleration = $this->definition->use_static_acceleration();if ($this->staticacceleration) {$this->staticaccelerationsize = $this->definition->get_static_acceleration_size();}}}/*** Alters the identifiers that have been provided to the definition.** This is an advanced method and should not be used unless really needed.* It allows the developer to slightly alter the definition without having to re-establish the cache.* It will cause more processing as the definition will need to clear and reprepare some of its properties.** @param array $identifiers*/public function set_identifiers(array $identifiers) {if ($this->definition->set_identifiers($identifiers)) {// As static acceleration uses input keys and not parsed keys// it much be cleared when the identifier set is changed.$this->staticaccelerationarray = [];if ($this->staticaccelerationsize !== false) {$this->staticaccelerationkeys = [];$this->staticaccelerationcount = 0;}}}/*** Process any outstanding invalidation events for the cache we are registering,** Identifiers and event invalidation are not compatible with each other at this time.* As a result the cache does not need to consider identifiers when working out what to invalidate.*/protected function handle_invalidation_events() {if (!$this->definition->has_invalidation_events()) {return;}// Each cache stores the current 'lastinvalidation' value within the cache itself.$lastinvalidation = $this->get('lastinvalidation');if ($lastinvalidation === false) {// There is currently no value for the lastinvalidation token, therefore the token is not set, and there// can be nothing to invalidate.// Set the lastinvalidation value to the current purge token and return early.$this->set('lastinvalidation', self::get_purge_token());return;} else if ($lastinvalidation == self::get_purge_token()) {// The current purge request has already been fully handled by this cache.return;}/** Now that the whole cache check is complete, we check the meaning of any specific cache invalidation events.* These are stored in the core/eventinvalidation cache as an multi-dimensinoal array in the form:* [* eventname => [* keyname => purgetoken,* ]* ]** The 'keyname' value is used to delete a specific key in the cache.* If the keyname is set to the special value 'purged', then the whole cache is purged instead.** The 'purgetoken' is the token that this key was last purged.* a) If the purgetoken matches the last invalidation, then the key/cache is not purged.* b) If the purgetoken is newer than the last invalidation, then the key/cache is not purged.* c) If the purge token is older than the last invalidation, or it has a different token component, then the* cache is purged.** Option b should not happen under normal operation, but may happen in race condition whereby a long-running* request's cache is cleared in another process during that request, and prior to that long-running request* creating the cache. In such a condition, it would be incorrect to clear that cache.*/$cache = self::make('core', 'eventinvalidation');$events = $cache->get_many($this->definition->get_invalidation_events());$todelete = [];$purgeall = false;// Iterate the returned data for the events.foreach ($events as $event => $keys) {if ($keys === false) {// No data to be invalidated yet.continue;}// Look at each key and check the timestamp.foreach ($keys as $key => $purgetoken) {// If the timestamp of the event is more than or equal to the last invalidation (happened between the last// invalidation and now), then we need to invaliate the key.if (self::compare_purge_tokens($purgetoken, $lastinvalidation) > 0) {if ($key === 'purged') {$purgeall = true;break;} else {$todelete[] = $key;}}}}if ($purgeall) {$this->purge();} else if (!empty($todelete)) {$todelete = array_unique($todelete);$this->delete_many($todelete);}// Set the time of the last invalidation.if ($purgeall || !empty($todelete)) {$this->set('lastinvalidation', self::get_purge_token(true));}}/*** Retrieves the value for the given key from the cache.** @param string|int $key The key for the data being requested.* It can be any structure although using a scalar string or int is recommended in the interests of performance.* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.* @param int $strictness One of IGNORE_MISSING | MUST_EXIST* @return mixed|false The data from the cache or false if the key did not exist within the cache.* @throws coding_exception*/public function get($key, $strictness = IGNORE_MISSING) {return $this->get_implementation($key, self::VERSION_NONE, $strictness);}/*** Retrieves the value and actual version for the given key, with at least the required version.** If there is no value for the key, or there is a value but it doesn't have the required* version, then this function will return null (or throw an exception if you set strictness* to MUST_EXIST).** This function can be used to make it easier to support localisable caches (where the cache* could be stored on a local server as well as a shared cache). Specifying the version means* that it will automatically retrieve the correct version if available, either from the local* server or [if that has an older version] from the shared server.** If the cached version is newer than specified version, it will be returned regardless. For* example, if you request version 4, but the locally cached version is 5, it will be returned.* If you request version 6, and the locally cached version is 5, then the system will look in* higher-level caches (if any); if there still isn't a version 6 or greater, it will return* null.** You must use this function if you use set_versioned.** @param string|int $key The key for the data being requested.* @param int $requiredversion Minimum required version of the data* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.* @param mixed $actualversion If specified, will be set to the actual version number retrieved* @return mixed Data from the cache, or false if the key did not exist or was too old* @throws \coding_exception If you call get_versioned on a non-versioned cache key*/public function get_versioned($key, int $requiredversion, int $strictness = IGNORE_MISSING, &$actualversion = null) {return $this->get_implementation($key, $requiredversion, $strictness, $actualversion);}/*** Checks returned data to see if it matches the specified version number.** For versioned data, this returns the version_wrapper object (or false). For other* data, it returns the actual data (or false).** @param mixed $result Result data* @param int $requiredversion Required version number or VERSION_NONE if there must be no version* @return bool True if version is current, false if not (or if result is false)* @throws \coding_exception If unexpected type of data (versioned vs non-versioned) is found*/protected static function check_version($result, int $requiredversion): bool {if ($requiredversion === self::VERSION_NONE) {if ($result instanceof \core_cache\version_wrapper) {throw new \coding_exception('Unexpectedly found versioned cache entry');} else {// No version checks, so version is always correct.return true;}} else {// If there's no result, obviously it doesn't meet the required version.if (!helper::result_found($result)) {return false;}if (!($result instanceof \core_cache\version_wrapper)) {throw new \coding_exception('Unexpectedly found non-versioned cache entry');}// If the result doesn't match the required version tag, return false.if ($result->version < $requiredversion) {return false;}// The version meets the requirement.return true;}}/*** Retrieves the value for the given key from the cache.** @param string|int $key The key for the data being requested.* It can be any structure although using a scalar string or int is recommended in the interests of performance.* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.* @param int $requiredversion Minimum required version of the data or cache::VERSION_NONE* @param int $strictness One of IGNORE_MISSING | MUST_EXIST* @param mixed $actualversion If specified, will be set to the actual version number retrieved* @return mixed|false The data from the cache or false if the key did not exist within the cache.* @throws coding_exception*/protected function get_implementation($key, int $requiredversion, int $strictness, &$actualversion = null) {// 1. Get it from the static acceleration array if we can (only when it is enabled and it has already been requested/set).$usesstaticacceleration = $this->use_static_acceleration();if ($usesstaticacceleration) {$result = $this->static_acceleration_get($key);if (helper::result_found($result) && self::check_version($result, $requiredversion)) {if ($requiredversion === self::VERSION_NONE) {return $result;} else {$actualversion = $result->version;return $result->data;}}}// 2. Parse the key.$parsedkey = $this->parse_key($key);// 3. Get it from the store. Obviously wasn't in the static acceleration array.$result = $this->store->get($parsedkey);if (helper::result_found($result)) {// Check the result has at least the required version.try {$validversion = self::check_version($result, $requiredversion);} catch (\coding_exception $e) {// In certain circumstances this could happen before users are taken to the upgrade// screen when upgrading from an earlier Moodle version that didn't use a versioned// cache for this item, so redirect instead of showing error if that's the case.redirect_if_major_upgrade_required();// If we still get an exception because there is incorrect data in the cache (not// versioned when it ought to be), delete it so this exception goes away next time.// The exception should only happen if there is a code bug (which is why we still// throw it) but there are unusual scenarios in development where it might happen// and that would be annoying if it doesn't fix itself.$this->store->delete($parsedkey);throw $e;}if (!$validversion) {// If the result was too old, don't use it.$result = false;// Also delete it immediately. This improves performance in the// case when the cache item is large and there may be multiple clients simultaneously// requesting it - they won't all have to do a megabyte of IO just in order to find// that it's out of date.$this->store->delete($parsedkey);}}if (helper::result_found($result)) {// Look to see if there's a TTL wrapper. It might be inside a version wrapper.if ($requiredversion !== self::VERSION_NONE) {$ttlconsider = $result->data;} else {$ttlconsider = $result;}if ($ttlconsider instanceof ttl_wrapper) {if ($ttlconsider->has_expired()) {$this->store->delete($parsedkey);$result = false;} else if ($requiredversion === self::VERSION_NONE) {// Use the data inside the TTL wrapper as the result.$result = $ttlconsider->data;} else {// Put the data from the TTL wrapper directly inside the version wrapper.$result->data = $ttlconsider->data;}}if ($usesstaticacceleration) {$this->static_acceleration_set($key, $result);}// Remove version wrapper if necessary.if ($requiredversion !== self::VERSION_NONE) {$actualversion = $result->version;$result = $result->data;}if ($result instanceof cached_object) {$result = $result->restore_object();}}// 4. Load if from the loader/datasource if we don't already have it.$setaftervalidation = false;if (!helper::result_found($result)) {if ($this->perfdebug) {helper::record_cache_miss($this->store, $this->definition);}if ($this->loader !== false) {// We must pass the original (unparsed) key to the next loader in the chain.// The next loader will parse the key as it sees fit. It may be parsed differently// depending upon the capabilities of the store associated with the loader.if ($requiredversion === self::VERSION_NONE) {$result = $this->loader->get($key);} else {$result = $this->loader->get_versioned($key, $requiredversion, IGNORE_MISSING, $actualversion);}} else if ($this->datasource !== false) {if ($requiredversion === self::VERSION_NONE) {$result = $this->datasource->load_for_cache($key);} else {if (!$this->datasource instanceof versionable_data_source_interface) {throw new \coding_exception('Data source is not versionable');}$result = $this->datasource->load_for_cache_versioned($key, $requiredversion, $actualversion);if ($result && $actualversion < $requiredversion) {throw new \coding_exception('Data source returned outdated version');}}}$setaftervalidation = (helper::result_found($result));} else if ($this->perfdebug) {$readbytes = $this->store->get_last_io_bytes();helper::record_cache_hit($this->store, $this->definition, 1, $readbytes);}// 5. Validate strictness.if ($strictness === MUST_EXIST && !helper::result_found($result)) {throw new coding_exception('Requested key did not exist in any cache stores and could not be loaded.');}// 6. Set it to the store if we got it from the loader/datasource. Only set to this direct// store; parent method will have set it to all stores if needed.if ($setaftervalidation) {$lock = false;try {// Only try to acquire a lock for this cache if we do not already have one.if (!empty($this->requirelockingbeforewrite) && !$this->check_lock_state($key)) {$this->acquire_lock($key);$lock = true;}if ($requiredversion === self::VERSION_NONE) {$this->set_implementation($key, self::VERSION_NONE, $result, false);} else {$this->set_implementation($key, $actualversion, $result, false);}} finally {if ($lock) {$this->release_lock($key);}}}// 7. Make sure we don't pass back anything that could be a reference.// We don't want people modifying the data in the cache.if (!$this->store->supports_dereferencing_objects() && !is_scalar($result)) {// If data is an object it will be a reference.// If data is an array if may contain references.// We want to break references so that the cache cannot be modified outside of itself.// Call the function to unreference it (in the best way possible).$result = $this->unref($result);}return $result;}/*** Retrieves an array of values for an array of keys.** Using this function comes with potential performance implications.* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call* the equivalent singular method for each item provided.* This should not deter you from using this function as there is a performance benefit in situations where the cache store* does support it, but you should be aware of this fact.** @param array $keys The keys of the data being requested.* Each key can be any structure although using a scalar string or int is recommended in the interests of performance.* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.* @return array An array of key value pairs for the items that could be retrieved from the cache.* If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.* Otherwise any key that did not exist will have a data value of false within the results.* @throws coding_exception*/public function get_many(array $keys, $strictness = IGNORE_MISSING) {$keysparsed = [];$parsedkeys = [];$resultpersist = [];$resultstore = [];$keystofind = [];$readbytes = store::IO_BYTES_NOT_SUPPORTED;// First up check the persist cache for each key.$isusingpersist = $this->use_static_acceleration();foreach ($keys as $key) {$pkey = $this->parse_key($key);if (is_array($pkey)) {$pkey = $pkey['key'];}$keysparsed[$key] = $pkey;$parsedkeys[$pkey] = $key;$keystofind[$pkey] = $key;if ($isusingpersist) {$value = $this->static_acceleration_get($key);if ($value !== false) {$resultpersist[$pkey] = $value;unset($keystofind[$pkey]);}}}// Next assuming we didn't find all of the keys in the persist cache try loading them from the store.if (count($keystofind)) {$resultstore = $this->store->get_many(array_keys($keystofind));if ($this->perfdebug) {$readbytes = $this->store->get_last_io_bytes();}// Process each item in the result to "unwrap" it.foreach ($resultstore as $key => $value) {if ($value instanceof ttl_wrapper) {if ($value->has_expired()) {$value = false;} else {$value = $value->data;}}if ($value !== false && $this->use_static_acceleration()) {$this->static_acceleration_set($keystofind[$key], $value);}if ($value instanceof cached_object) {$value = $value->restore_object();}$resultstore[$key] = $value;}}// Merge the result from the persis cache with the results from the store load.$result = $resultpersist + $resultstore;unset($resultpersist);unset($resultstore);// Next we need to find any missing values and load them from the loader/datasource next in the chain.$usingloader = ($this->loader !== false);$usingsource = (!$usingloader && ($this->datasource !== false));if ($usingloader || $usingsource) {$missingkeys = [];foreach ($result as $key => $value) {if ($value === false) {$missingkeys[] = $parsedkeys[$key];}}if (!empty($missingkeys)) {if ($usingloader) {$resultmissing = $this->loader->get_many($missingkeys);} else {$resultmissing = $this->datasource->load_many_for_cache($missingkeys);}foreach ($resultmissing as $key => $value) {$result[$keysparsed[$key]] = $value;$lock = false;try {if (!empty($this->requirelockingbeforewrite)) {$this->acquire_lock($key);$lock = true;}if ($value !== false) {$this->set($key, $value);}} finally {if ($lock) {$this->release_lock($key);}}}unset($resultmissing);}unset($missingkeys);}// Create an array with the original keys and the found values. This will be what we return.$fullresult = [];foreach ($result as $key => $value) {if (!is_scalar($value)) {// If data is an object it will be a reference.// If data is an array if may contain references.// We want to break references so that the cache cannot be modified outside of itself.// Call the function to unreference it (in the best way possible).$value = $this->unref($value);}$fullresult[$parsedkeys[$key]] = $value;}unset($result);// Final step is to check strictness.if ($strictness === MUST_EXIST) {foreach ($keys as $key) {if (!array_key_exists($key, $fullresult)) {throw new coding_exception('Not all the requested keys existed within the cache stores.');}}}if ($this->perfdebug) {$hits = 0;$misses = 0;foreach ($fullresult as $value) {if ($value === false) {$misses++;} else {$hits++;}}helper::record_cache_hit($this->store, $this->definition, $hits, $readbytes);helper::record_cache_miss($this->store, $this->definition, $misses);}// Return the result. Phew!return $fullresult;}/*** Sends a key => value pair to the cache.** <code>* // This code will add four entries to the cache, one for each url.* $cache->set('main', 'http://moodle.org');* $cache->set('docs', 'http://docs.moodle.org');* $cache->set('tracker', 'http://tracker.moodle.org');* $cache->set('qa', 'http://qa.moodle.net');* </code>** @param string|int $key The key for the data being requested.* It can be any structure although using a scalar string or int is recommended in the interests of performance.* In advanced cases an array may be useful such as in situations requiring the multi-key functionality.* @param mixed $data The data to set against the key.* @return bool True on success, false otherwise.*/public function set($key, $data) {return $this->set_implementation($key, self::VERSION_NONE, $data);}/*** Sets the value for the given key with the given version.** The cache does not store multiple versions - any existing version will be overwritten with* this one. This function should only be used if there is a known 'current version' (e.g.* stored in a database table). It only ensures that the cache does not return outdated data.** This function can be used to help implement localisable caches (where the cache could be* stored on a local server as well as a shared cache). The version will be recorded alongside* the item and get_versioned will always return the correct version.** The version number must be an integer that always increases. This could be based on the* current time, or a stored value that increases by 1 each time it changes, etc.** If you use this function you must use get_versioned to retrieve the data.** @param string|int $key The key for the data being set.* @param int $version Integer for the version of the data* @param mixed $data The data to set against the key.* @return bool True on success, false otherwise.*/public function set_versioned($key, int $version, $data): bool {return $this->set_implementation($key, $version, $data);}/*** Sets the value for the given key, optionally with a version tag.** @param string|int $key The key for the data being set.* @param int $version Version number for the data or cache::VERSION_NONE if none* @param mixed $data The data to set against the key.* @param bool $setparents If true, sets all parent loaders, otherwise only this one* @return bool True on success, false otherwise.*/protected function set_implementation($key, int $version, $data, bool $setparents = true): bool {if ($this->loader !== false && $setparents) {// We have a loader available set it there as well.// We have to let the loader do its own parsing of data as it may be unique.if ($version === self::VERSION_NONE) {$this->loader->set($key, $data);} else {$this->loader->set_versioned($key, $version, $data);}}$usestaticacceleration = $this->use_static_acceleration();if (is_object($data) && $data instanceof cacheable_object_interface) {$data = new cached_object($data);} else if (!$this->store->supports_dereferencing_objects() && !is_scalar($data)) {// If data is an object it will be a reference.// If data is an array if may contain references.// We want to break references so that the cache cannot be modified outside of itself.// Call the function to unreference it (in the best way possible).$data = $this->unref($data);}if ($usestaticacceleration) {// Static acceleration cache should include the cache version wrapper, but not TTL.if ($version === self::VERSION_NONE) {$this->static_acceleration_set($key, $data);} else {$this->static_acceleration_set($key, new \core_cache\version_wrapper($data, $version));}}if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {$data = new ttl_wrapper($data, $this->definition->get_ttl());}$parsedkey = $this->parse_key($key);if ($version !== self::VERSION_NONE) {$data = new \core_cache\version_wrapper($data, $version);}$success = $this->store->set($parsedkey, $data);if ($this->perfdebug) {helper::record_cache_set($this->store,$this->definition,1,$this->store->get_last_io_bytes());}return $success;}/*** Removes references where required.** @param stdClass|array $data* @return mixed What ever was put in but without any references.*/protected function unref($data) {if ($this->definition->uses_simple_data()) {return $data;}// Check if it requires serialisation in order to produce a reference free copy.if ($this->requires_serialisation($data)) {// Damn, its going to have to be serialise.$data = serialize($data);// We unserialise immediately so that we don't have to do it every time on get.$data = unserialize($data);} else if (!is_scalar($data)) {// Its safe to clone, lets do it, its going to beat the pants of serialisation.$data = $this->deep_clone($data);}return $data;}/*** Checks to see if a var requires serialisation.** @param mixed $value The value to check.* @param int $depth Used to ensure we don't enter an endless loop (think recursion).* @return bool Returns true if the value is going to require serialisation in order to ensure a reference free copy* or false if its safe to clone.*/protected function requires_serialisation($value, $depth = 1) {if (is_scalar($value)) {return false;} else if (is_array($value) || $value instanceof stdClass || $value instanceof Traversable) {if ($depth > 5) {// Skrew it, mega-deep object, developer you suck, we're just going to serialise.return true;}foreach ($value as $key => $subvalue) {if ($this->requires_serialisation($subvalue, $depth++)) {return true;}}}// Its not scalar, array, or stdClass so we'll need to serialise.return true;}/*** Creates a reference free clone of the given value.** @param mixed $value* @return mixed*/protected function deep_clone($value) {if (is_object($value)) {// Objects must be cloned to begin with.$value = clone $value;}if (is_array($value) || is_object($value)) {foreach ($value as $key => $subvalue) {$value[$key] = $this->deep_clone($subvalue);}}return $value;}/*** Sends several key => value pairs to the cache.** Using this function comes with potential performance implications.* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call* the equivalent singular method for each item provided.* This should not deter you from using this function as there is a performance benefit in situations where the cache store* does support it, but you should be aware of this fact.** <code>* // This code will add four entries to the cache, one for each url.* $cache->set_many(array(* 'main' => 'http://moodle.org',* 'docs' => 'http://docs.moodle.org',* 'tracker' => 'http://tracker.moodle.org',* 'qa' => ''http://qa.moodle.net'* ));* </code>** @param array $keyvaluearray An array of key => value pairs to send to the cache.* @return int The number of items successfully set. It is up to the developer to check this matches the number of items.* ... if they care that is.*/public function set_many(array $keyvaluearray) {if ($this->loader !== false) {// We have a loader available set it there as well.// We have to let the loader do its own parsing of data as it may be unique.$this->loader->set_many($keyvaluearray);}$data = array();$simulatettl = $this->has_a_ttl() && !$this->store_supports_native_ttl();$usestaticaccelerationarray = $this->use_static_acceleration();$needsdereferencing = !$this->store->supports_dereferencing_objects();foreach ($keyvaluearray as $key => $value) {if (is_object($value) && $value instanceof cacheable_object_interface) {$value = new cached_object($value);} else if ($needsdereferencing && !is_scalar($value)) {// If data is an object it will be a reference.// If data is an array if may contain references.// We want to break references so that the cache cannot be modified outside of itself.// Call the function to unreference it (in the best way possible).$value = $this->unref($value);}if ($usestaticaccelerationarray) {$this->static_acceleration_set($key, $value);}if ($simulatettl) {$value = new ttl_wrapper($value, $this->definition->get_ttl());}$data[$key] = ['key' => $this->parse_key($key),'value' => $value,];}$successfullyset = $this->store->set_many($data);if ($this->perfdebug && $successfullyset) {helper::record_cache_set($this->store,$this->definition,$successfullyset,$this->store->get_last_io_bytes());}return $successfullyset;}/*** Test is a cache has a key.** The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the* test and any subsequent action (get, set, delete etc).* Instead it is recommended to write your code in such a way they it performs the following steps:* <ol>* <li>Attempt to retrieve the information.</li>* <li>Generate the information.</li>* <li>Attempt to set the information</li>* </ol>** Its also worth mentioning that not all stores support key tests.* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.* Just one more reason you should not use these methods unless you have a very good reason to do so.** @param string|int $key* @param bool $tryloadifpossible If set to true, the cache doesn't contain the key, and there is another cache loader or* data source then the code will try load the key value from the next item in the chain.* @return bool True if the cache has the requested key, false otherwise.*/public function has($key, $tryloadifpossible = false) {if ($this->static_acceleration_has($key)) {// Hoorah, that was easy. It exists in the static acceleration array so we definitely have it.return true;}$parsedkey = $this->parse_key($key);if ($this->has_a_ttl() && !$this->store_supports_native_ttl()) {// The data has a TTL and the store doesn't support it natively.// We must fetch the data and expect a ttl wrapper.$data = $this->store->get($parsedkey);$has = ($data instanceof ttl_wrapper && !$data->has_expired());} else if (!$this->store_supports_key_awareness()) {// The store doesn't support key awareness, get the data and check it manually... puke.// Either no TTL is set of the store supports its handling natively.$data = $this->store->get($parsedkey);$has = ($data !== false);} else {// The store supports key awareness, this is easy!// Either no TTL is set of the store supports its handling natively.$has = $this->store->has($parsedkey);}if (!$has && $tryloadifpossible) {if ($this->loader !== false) {$result = $this->loader->get($parsedkey);} else if ($this->datasource !== null) {$result = $this->datasource->load_for_cache($key);}$has = ($result !== null);if ($has) {$this->set($key, $result);}}return $has;}/*** Test is a cache has all of the given keys.** It is strongly recommended to avoid the use of this function if not absolutely required.* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).** Its also worth mentioning that not all stores support key tests.* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.* Just one more reason you should not use these methods unless you have a very good reason to do so.** @param array $keys* @return bool True if the cache has all of the given keys, false otherwise.*/public function has_all(array $keys) {if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {foreach ($keys as $key) {if (!$this->has($key)) {return false;}}return true;}$parsedkeys = array_map([$this, 'parse_key'], $keys);return $this->store->has_all($parsedkeys);}/*** Test if a cache has at least one of the given keys.** It is strongly recommended to avoid the use of this function if not absolutely required.* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).** Its also worth mentioning that not all stores support key tests.* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.* Just one more reason you should not use these methods unless you have a very good reason to do so.** @param array $keys* @return bool True if the cache has at least one of the given keys*/public function has_any(array $keys) {if (($this->has_a_ttl() && !$this->store_supports_native_ttl()) || !$this->store_supports_key_awareness()) {foreach ($keys as $key) {if ($this->has($key)) {return true;}}return false;}if ($this->use_static_acceleration()) {foreach ($keys as $id => $key) {if ($this->static_acceleration_has($key)) {return true;}}}$parsedkeys = array_map([$this, 'parse_key'], $keys);return $this->store->has_any($parsedkeys);}/*** Delete the given key from the cache.** @param string|int $key The key to delete.* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.* @return bool True of success, false otherwise.*/public function delete($key, $recurse = true) {$this->static_acceleration_delete($key);if ($recurse && $this->loader !== false) {// Delete from the bottom of the stack first.$this->loader->delete($key, $recurse);}$parsedkey = $this->parse_key($key);return $this->store->delete($parsedkey);}/*** Delete all of the given keys from the cache.** @param array $keys The key to delete.* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.* @return int The number of items successfully deleted.*/public function delete_many(array $keys, $recurse = true) {if ($this->use_static_acceleration()) {foreach ($keys as $key) {$this->static_acceleration_delete($key);}}if ($recurse && $this->loader !== false) {// Delete from the bottom of the stack first.$this->loader->delete_many($keys, $recurse);}$parsedkeys = array_map([$this, 'parse_key'], $keys);return $this->store->delete_many($parsedkeys);}/*** Purges the cache store, and loader if there is one.** @return bool True on success, false otherwise*/public function purge() {// 1. Purge the static acceleration array.$this->static_acceleration_purge();// 2. Purge the store.$this->store->purge();// 3. Optionally pruge any stacked loaders.if ($this->loader) {$this->loader->purge();}return true;}/*** Parses the key turning it into a string (or array is required) suitable to be passed to the cache store.** @param string|int $key As passed to get|set|delete etc.* @return string|array String unless the store supports multi-identifiers in which case an array if returned.*/protected function parse_key($key) {// First up if the store supports multiple keys we'll go with that.if ($this->store->supports_multiple_identifiers()) {$result = $this->definition->generate_multi_key_parts();$result['key'] = $key;return $result;}// If not we need to generate a hash and to for that we use the helper.return helper::hash_key($key, $this->definition);}/*** Returns true if the cache is making use of a ttl.* @return bool*/protected function has_a_ttl() {return $this->hasattl;}/*** Returns true if the cache store supports native ttl.* @return bool*/protected function store_supports_native_ttl() {if ($this->supportsnativettl === null) {$this->supportsnativettl = ($this->store->supports_native_ttl());}return $this->supportsnativettl;}/*** Returns the cache definition.** @return definition*/protected function get_definition() {return $this->definition;}/*** Returns the cache store** @return store*/protected function get_store() {return $this->store;}/*** Returns the loader associated with this instance.** @since Moodle 2.4.4* @return cache|false*/protected function get_loader() {return $this->loader;}/*** Returns the data source associated with this cache.** @since Moodle 2.4.4* @return data_source_interface|false*/protected function get_datasource() {return $this->datasource;}/*** Returns true if the store supports key awareness.** @return bool*/protected function store_supports_key_awareness() {if ($this->supportskeyawareness === null) {$this->supportskeyawareness = ($this->store instanceof key_aware_cache_interface);}return $this->supportskeyawareness;}/*** Returns true if the store natively supports locking.** @return bool*/protected function store_supports_native_locking() {if ($this->nativelocking === null) {$this->nativelocking = ($this->store instanceof lockable_cache_interface);}return $this->nativelocking;}/*** Returns true if this cache is making use of the static acceleration array.** @return bool*/protected function use_static_acceleration() {return $this->staticacceleration;}/*** Returns true if the requested key exists within the static acceleration array.** @param string $key The parsed key* @return bool*/protected function static_acceleration_has($key) {// This could be written as a single line, however it has been split because the ttl check is faster than the instanceof// and has_expired calls.if (!$this->staticacceleration || !isset($this->staticaccelerationarray[$key])) {return false;}return true;}/*** Returns the item from the static acceleration array if it exists there.** @param string $key The parsed key* @return mixed|false Dereferenced data from the static acceleration array or false if it wasn't there.*/protected function static_acceleration_get($key) {if (!$this->staticacceleration || !isset($this->staticaccelerationarray[$key])) {$result = false;} else {$data = $this->staticaccelerationarray[$key]['data'];if ($data instanceof cached_object) {$result = $data->restore_object();} else if ($this->staticaccelerationarray[$key]['serialized']) {$result = unserialize($data);} else {$result = $data;}}if (helper::result_found($result)) {if ($this->perfdebug) {helper::record_cache_hit(store::STATIC_ACCEL, $this->definition);}if ($this->staticaccelerationsize > 1 && $this->staticaccelerationcount > 1) {// Check to see if this is the last item on the static acceleration keys array.if (end($this->staticaccelerationkeys) !== $key) {// It isn't the last item.// Move the item to the end of the array so that it is last to be removed.unset($this->staticaccelerationkeys[$key]);$this->staticaccelerationkeys[$key] = $key;}}return $result;} else {if ($this->perfdebug) {helper::record_cache_miss(store::STATIC_ACCEL, $this->definition);}return false;}}/*** Sets a key value pair into the static acceleration array.** @param string $key The parsed key* @param mixed $data* @return bool*/protected function static_acceleration_set($key, $data) {if ($this->staticaccelerationsize !== false && isset($this->staticaccelerationkeys[$key])) {$this->staticaccelerationcount--;unset($this->staticaccelerationkeys[$key]);}// We serialize anything that's not;// 1. A known scalar safe value.// 2. A definition that says it's simpledata. We trust it that it doesn't contain dangerous references.// 3. An object that handles dereferencing by itself.if (is_scalar($data) || $this->definition->uses_simple_data()|| $data instanceof cached_object) {$this->staticaccelerationarray[$key]['data'] = $data;$this->staticaccelerationarray[$key]['serialized'] = false;} else {$this->staticaccelerationarray[$key]['data'] = serialize($data);$this->staticaccelerationarray[$key]['serialized'] = true;}if ($this->staticaccelerationsize !== false) {$this->staticaccelerationcount++;$this->staticaccelerationkeys[$key] = $key;if ($this->staticaccelerationcount > $this->staticaccelerationsize) {$dropkey = array_shift($this->staticaccelerationkeys);unset($this->staticaccelerationarray[$dropkey]);$this->staticaccelerationcount--;}}return true;}/*** Deletes an item from the static acceleration array.** @param string|int $key As given to get|set|delete* @return bool True on success, false otherwise.*/protected function static_acceleration_delete($key) {unset($this->staticaccelerationarray[$key]);if ($this->staticaccelerationsize !== false && isset($this->staticaccelerationkeys[$key])) {unset($this->staticaccelerationkeys[$key]);$this->staticaccelerationcount--;}return true;}/*** Purge the static acceleration cache.*/protected function static_acceleration_purge() {$this->staticaccelerationarray = [];if ($this->staticaccelerationsize !== false) {$this->staticaccelerationkeys = [];$this->staticaccelerationcount = 0;}}/*** Returns the timestamp from the first request for the time from the cache API.** This stamp needs to be used for all ttl and time based operations to ensure that we don't end up with* timing issues.** @param bool $float Whether to use floating precision accuracy.* @return int|float*/public static function now($float = false) {if (self::$now === null) {self::$now = microtime(true);}if ($float) {return self::$now;} else {return (int) self::$now;}}/*** Get a 'purge' token used for cache invalidation handling.** Note: This function is intended for use from within the Cache API only and not by plugins, or cache stores.** @param bool $reset Whether to reset the token and generate a new one.* @return string*/public static function get_purge_token($reset = false) {if (self::$purgetoken === null || $reset) {self::$now = null;self::$purgetoken = self::now(true) . '-' . uniqid('', true);}return self::$purgetoken;}/*** Compare a pair of purge tokens.** If the two tokens are identical, then the return value is 0.* If the time component of token A is newer than token B, then a positive value is returned.* If the time component of token B is newer than token A, then a negative value is returned.** Note: This function is intended for use from within the Cache API only and not by plugins, or cache stores.** @param string $tokena* @param string $tokenb* @return int*/public static function compare_purge_tokens($tokena, $tokenb) {if ($tokena === $tokenb) {// There is an exact match.return 0;}// The token for when the cache was last invalidated.[$atime] = explode('-', "{$tokena}-", 2);// The token for this cache.[$btime] = explode('-', "{$tokenb}-", 2);if ($atime >= $btime) {// Token A is newer.return 1;} else {// Token A is older.return -1;}}/*** Subclasses may support purging cache of all data belonging to the* current user.*/public function purge_current_user() {}}// Alias this class to the old name.// This file will be autoloaded by the legacyclasses autoload system.// In future all uses of this class will be corrected and the legacy references will be removed.class_alias(cache::class, \cache::class);