Proyectos de Subversion Moodle

<?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/>.

/**

 * Cache API interfaces

 *

 * This file is part of Moodle's cache API, affectionately called MUC.

 * It contains the components that are requried in order to use caching.

 *

 * @package    core

 * @category   cache

 * @copyright  2012 Sam Hemelryk

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

defined('MOODLE_INTERNAL') || die();

/**

 * Cache Loader.

 *

 * This cache loader interface provides the required structure for classes that wish to be interacted with as a

 * means of accessing and interacting with a cache.

 *

 * Can be implemented by any class wishing to be a cache loader.

 */

interface cache_loader {

    /**

     * Retrieves the value for the given key from the cache.

     *

     * @param string|int $key The key for the data being requested.

     * @param int $strictness One of IGNORE_MISSING or MUST_EXIST.

     * @return mixed The data retrieved from the cache, or false if the key did not exist within the cache.

     *      If MUST_EXIST was used then an exception will be thrown if the key does not exist within the cache.

     */

    public function get($key, $strictness = IGNORE_MISSING);

    /**

     * 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 false (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

     */

    public function get_versioned($key, int $requiredversion, int $strictness = IGNORE_MISSING, &$actualversion = null);

    /**

     * 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.

     * @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.

     */

    public function get_many(array $keys, $strictness = IGNORE_MISSING);

    /**

     * 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.

     * @param mixed $data The data to set against the key.

     * @return bool True on success, false otherwise.

     */

    public function set($key, $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;

    /**

     * 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);

    /**

     * 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

     * @return bool True if the cache has the requested key, false otherwise.

     */

    public function has($key);

    /**

     * 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);

    /**

     * 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);

    /**

     * 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);

    /**

     * 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);

}

/**

 * Cache Loader supporting locking.

 *

 * This interface should be given to classes already implementing cache_loader that also wish to support locking.

 * It outlines the required structure for utilising locking functionality when using a cache.

 *

 * Can be implemented by any class already implementing the cache_loader interface.

 */

interface cache_loader_with_locking {

    /**

     * Acquires a lock for the given key.

     *

     * Please note that this happens automatically if the cache definition requires locking.

     * it is still made a public method so that adhoc caches can use it if they choose.

     * However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure

     * locks are acquired, checked, and released.

     *

     * Prior to Moodle 4,3 this function used to return false if the lock cannot be obtained. It

     * now always returns true, and throws an exception if the lock cannot be obtained.

     *

     * @param string|int $key

     * @return bool Always returns true (for backwards compatibility)

     * @throws moodle_exception If the lock cannot be obtained after a timeout

     */

    public function acquire_lock($key);

    /**

     * Checks if the cache loader owns the lock for the given key.

     *

     * Please note that this happens automatically if the cache definition requires locking.

     * it is still made a public method so that adhoc caches can use it if they choose.

     * However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure

     * locks are acquired, checked, and released.

     *

     * @param string|int $key

     * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it,

     *      null if there is no lock.

     */

    public function check_lock_state($key);

    /**

     * Releases the lock for the given key.

     *

     * Please note that this happens automatically if the cache definition requires locking.

     * it is still made a public method so that adhoc caches can use it if they choose.

     * However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure

     * locks are acquired, checked, and released.

     *

     * @param string|int $key

     * @return bool True if the lock has been released, false if there was a problem releasing the lock.

     */

    public function release_lock($key);

}

/**

 * Cache store feature: locking

 *

 * This is a feature that cache stores can implement if they wish to support locking themselves rather

 * than having the cache loader handle it for them.

 *

 * Can be implemented by classes already implementing cache_store.

 */

interface cache_is_lockable {

    /**

     * Acquires a lock on the given key for the given identifier.

     *

     * @param string $key The key we are locking.

     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.

     *      The use of this property is entirely optional and implementations can act as they like upon it.

     * @return bool True if the lock could be acquired, false otherwise.

     */

    public function acquire_lock($key, $ownerid);

    /**

     * Test if there is already a lock for the given key and if there is whether it belongs to the calling code.

     *

     * @param string $key The key we are locking.

     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.

     * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there

     *      is no lock.

     */

    public function check_lock_state($key, $ownerid);

    /**

     * Releases the lock on the given key.

     *

     * @param string $key The key we are locking.

     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.

     *      The use of this property is entirely optional and implementations can act as they like upon it.

     * @return bool True if the lock has been released, false if there was a problem releasing the lock.

     */

    public function release_lock($key, $ownerid);

}

/**

 * Cache store feature: key awareness.

 *

 * This is a feature that cache stores and cache loaders can both choose to implement.

 * If a cache store implements this then it will be made responsible for tests for items within the cache.

 * If the cache store being used doesn't implement this then it will be the responsibility of the cache loader to use the

 * equivalent get methods to mimick the functionality of these tests.

 *

 * Cache stores should only override these methods if they natively support such features or if they have a better performing

 * means of performing these tests than the handling that would otherwise take place in the cache_loader.

 *

 * Can be implemented by classes already implementing cache_store.

 */

interface cache_is_key_aware {

    /**

     * 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

     * @return bool True if the cache has the requested key, false otherwise.

     */

    public function has($key);

    /**

     * 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);

    /**

     * 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);

}

/**

 * Cache store feature: keys are searchable.

 *

 * Cache stores can choose to implement this interface.

 * In order for a store to be usable as a session cache it must implement this interface.

 *

 * @since Moodle 2.4.4

 */

interface cache_is_searchable {

    /**

     * Finds all of the keys being used by the cache store.

     *

     * @return array.

     */

    public function find_all();

    /**

     * Finds all of the keys whose keys start with the given prefix.

     *

     * @param string $prefix

     */

    public function find_by_prefix($prefix);

}

/**

 * Cache store feature: configurable.

 *

 * This feature should be implemented by all cache stores that are configurable when adding an instance.

 * It requires the implementation of methods required to convert form data into the a configuration array for the

 * store instance, and then the reverse converting configuration data into an array that can be used to set the

 * data for the edit form.

 *

 * Can be implemented by classes already implementing cache_store.

 */

interface cache_is_configurable {

    /**

     * Given the data from the add instance form this function creates a configuration array.

     *

     * @param stdClass $data

     * @return array

     */

    public static function config_get_configuration_array($data);

    /**

     * Allows the cache store to set its data against the edit form before it is shown to the user.

     *

     * @param moodleform $editform

     * @param array $config

     */

    public static function config_set_edit_form_data(moodleform $editform, array $config);

}

/**

 * Cache Data Source.

 *

 * The cache data source interface can be implemented by any class within Moodle.

 * If implemented then the class can be reference in a cache definition and will be used to load information that cannot be

 * retrieved from the cache. As part of its retrieval that information will also be loaded into the cache.

 *

 * This allows developers to created a complete cache solution that can be used through code ensuring consistent cache

 * interaction and loading. Allowing them in turn to centralise code and help keeps things more easily maintainable.

 *

 * Can be implemented by any class.

 *

 * @package    core

 * @category   cache

 * @copyright  2012 Sam Hemelryk

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

interface cache_data_source {

    /**

     * Returns an instance of the data source class that the cache can use for loading data using the other methods

     * specified by this interface.

     *

     * @param cache_definition $definition

     * @return object

     */

    public static function get_instance_for_cache(cache_definition $definition);

    /**

     * Loads the data for the key provided ready formatted for caching.

     *

     * @param string|int $key The key to load.

     * @return mixed What ever data should be returned, or false if it can't be loaded.

     */

    public function load_for_cache($key);

    /**

     * Loads several keys for the cache.

     *

     * @param array $keys An array of keys each of which will be string|int.

     * @return array An array of matching data items.

     */

    public function load_many_for_cache(array $keys);

}

/**

 * Versionable cache data source.

 *

 * This interface extends the main cache data source interface to add an extra required method if

 * the data source is to be used for a versioned cache.

 *

 * @package core_cache

 */

interface cache_data_source_versionable extends cache_data_source {

    /**

     * Loads the data for the key provided ready formatted for caching.

     *

     * If there is no data for that key, or if the data for the required key has an older version

     * than the specified $requiredversion, then this returns null.

     *

     * If there is data then $actualversion should be set to the actual version number retrieved

     * (may be the same as $requiredversion or newer).

     *

     * @param string|int $key The key to load.

     * @param int $requiredversion Minimum required version

     * @param mixed $actualversion Should be set to the actual version number retrieved

     * @return mixed What ever data should be returned, or false if it can't be loaded.

     */

    public function load_for_cache_versioned($key, int $requiredversion, &$actualversion);

}

/**

 * Cacheable object.

 *

 * This interface can be implemented by any class that is going to be passed into a cache and allows it to take control of the

 * structure and the information about to be cached, as well as how to deal with it when it is retrieved from a cache.

 * Think of it like serialisation and the __sleep and __wakeup methods.

 * This is used because cache stores are responsible for how they interact with data and what they do when storing it. This

 * interface ensures there is always a guaranteed action.

 */

interface cacheable_object {

    /**

     * Prepares the object for caching. Works like the __sleep method.

     *

     * @return mixed The data to cache, can be anything except a class that implements the cacheable_object... that would

     *      be dumb.

     */

    public function prepare_to_cache();

    /**

     * Takes the data provided by prepare_to_cache and reinitialises an instance of the associated from it.

     *

     * @param mixed $data

     * @return object The instance for the given data.

     */

    public static function wake_from_cache($data);

}

/**

 * Cache lock interface

 *

 * This interface needs to be inherited by all cache lock plugins.

 */

interface cache_lock_interface {

    /**

     * Constructs an instance of the cache lock given its name and its configuration data

     *

     * @param string $name The unique name of the lock instance

     * @param array $configuration

     */

    public function __construct($name, array $configuration = array());

    /**

     * Acquires a lock on a given key.

     *

     * @param string $key The key to acquire a lock for.

     * @param string $ownerid An unique identifier for the owner of this lock. It is entirely optional for the cache lock plugin

     *      to use this. Each implementation can decide for themselves.

     * @param bool $block If set to true the application will wait until a lock can be acquired

     * @return bool True if the lock can be acquired false otherwise.

     */

    public function lock($key, $ownerid, $block = false);

    /**

     * Releases the lock held on a certain key.

     *

     * @param string $key The key to release the lock for.

     * @param string $ownerid An unique identifier for the owner of this lock. It is entirely optional for the cache lock plugin

     *      to use this. Each implementation can decide for themselves.

     * @param bool $forceunlock If set to true the lock will be removed if it exists regardless of whether or not we own it.

     */

    public function unlock($key, $ownerid, $forceunlock = false);

    /**

     * Checks the state of the given key.

     *

     * Returns true if the key is locked and belongs to the ownerid.

     * Returns false if the key is locked but does not belong to the ownerid.

     * Returns null if there is no lock

     *

     * @param string $key The key we are checking for.

     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.

     * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there

     *      is no lock.

     */

    public function check_state($key, $ownerid);

    /**

     * Cleans up any left over locks.

     *

     * This function MUST clean up any locks that have been acquired and not released during processing.

     * Although the situation of acquiring a lock and not releasing it should be insanely rare we need to deal with it.

     * Things such as unfortunate timeouts etc could cause this situation.

     */

    public function __destruct();

}