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524 lines
22 KiB
524 lines
22 KiB
<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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/**
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* Cache API interfaces
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*
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* This file is part of Moodle's cache API, affectionately called MUC.
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* It contains the components that are requried in order to use caching.
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*
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* @package core
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* @category cache
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* @copyright 2012 Sam Hemelryk
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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defined('MOODLE_INTERNAL') || die();
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/**
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* Cache Loader.
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*
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* This cache loader interface provides the required structure for classes that wish to be interacted with as a
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* means of accessing and interacting with a cache.
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*
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* Can be implemented by any class wishing to be a cache loader.
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*/
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interface cache_loader {
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/**
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* Retrieves the value for the given key from the cache.
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*
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* @param string|int $key The key for the data being requested.
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* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
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* @return mixed The data retrieved from the cache, or false if the key did not exist within the cache.
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* If MUST_EXIST was used then an exception will be thrown if the key does not exist within the cache.
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*/
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public function get($key, $strictness = IGNORE_MISSING);
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/**
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* Retrieves an array of values for an array of keys.
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*
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* Using this function comes with potential performance implications.
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* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
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* the equivalent singular method for each item provided.
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* This should not deter you from using this function as there is a performance benefit in situations where the cache
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* store does support it, but you should be aware of this fact.
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*
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* @param array $keys The keys of the data being requested.
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* @param int $strictness One of IGNORE_MISSING or MUST_EXIST.
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* @return array An array of key value pairs for the items that could be retrieved from the cache.
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* If MUST_EXIST was used and not all keys existed within the cache then an exception will be thrown.
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* Otherwise any key that did not exist will have a data value of false within the results.
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*/
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public function get_many(array $keys, $strictness = IGNORE_MISSING);
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/**
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* Sends a key => value pair to the cache.
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*
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* <code>
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* // This code will add four entries to the cache, one for each url.
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* $cache->set('main', 'http://moodle.org');
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* $cache->set('docs', 'http://docs.moodle.org');
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* $cache->set('tracker', 'http://tracker.moodle.org');
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* $cache->set('qa', 'http://qa.moodle.net');
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* </code>
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*
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* @param string|int $key The key for the data being requested.
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* @param mixed $data The data to set against the key.
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* @return bool True on success, false otherwise.
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*/
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public function set($key, $data);
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/**
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* Sends several key => value pairs to the cache.
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*
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* Using this function comes with potential performance implications.
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* Not all cache stores will support get_many/set_many operations and in order to replicate this functionality will call
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* the equivalent singular method for each item provided.
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* This should not deter you from using this function as there is a performance benefit in situations where the cache store
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* does support it, but you should be aware of this fact.
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*
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* <code>
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* // This code will add four entries to the cache, one for each url.
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* $cache->set_many(array(
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* 'main' => 'http://moodle.org',
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* 'docs' => 'http://docs.moodle.org',
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* 'tracker' => 'http://tracker.moodle.org',
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* 'qa' => ''http://qa.moodle.net'
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* ));
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* </code>
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*
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* @param array $keyvaluearray An array of key => value pairs to send to the cache.
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* @return int The number of items successfully set. It is up to the developer to check this matches the number of items.
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* ... if they care that is.
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*/
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public function set_many(array $keyvaluearray);
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/**
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* Test is a cache has a key.
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*
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* The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the
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* test and any subsequent action (get, set, delete etc).
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* Instead it is recommended to write your code in such a way they it performs the following steps:
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* <ol>
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* <li>Attempt to retrieve the information.</li>
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* <li>Generate the information.</li>
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* <li>Attempt to set the information</li>
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* </ol>
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*
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* Its also worth mentioning that not all stores support key tests.
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* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
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* Just one more reason you should not use these methods unless you have a very good reason to do so.
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*
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* @param string|int $key
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* @return bool True if the cache has the requested key, false otherwise.
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*/
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public function has($key);
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/**
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* Test if a cache has at least one of the given keys.
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*
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* It is strongly recommended to avoid the use of this function if not absolutely required.
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* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
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*
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* Its also worth mentioning that not all stores support key tests.
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* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
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* Just one more reason you should not use these methods unless you have a very good reason to do so.
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*
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* @param array $keys
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* @return bool True if the cache has at least one of the given keys
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*/
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public function has_any(array $keys);
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/**
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* Test is a cache has all of the given keys.
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*
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* It is strongly recommended to avoid the use of this function if not absolutely required.
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* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
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*
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* Its also worth mentioning that not all stores support key tests.
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* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
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* Just one more reason you should not use these methods unless you have a very good reason to do so.
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*
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* @param array $keys
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* @return bool True if the cache has all of the given keys, false otherwise.
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*/
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public function has_all(array $keys);
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/**
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* Delete the given key from the cache.
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*
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* @param string|int $key The key to delete.
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* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
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* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
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* @return bool True of success, false otherwise.
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*/
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public function delete($key, $recurse = true);
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/**
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* Delete all of the given keys from the cache.
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*
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* @param array $keys The key to delete.
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* @param bool $recurse When set to true the key will also be deleted from all stacked cache loaders and their stores.
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* This happens by default and ensure that all the caches are consistent. It is NOT recommended to change this.
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* @return int The number of items successfully deleted.
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*/
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public function delete_many(array $keys, $recurse = true);
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}
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/**
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* Cache Loader supporting locking.
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*
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* This interface should be given to classes already implementing cache_loader that also wish to support locking.
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* It outlines the required structure for utilising locking functionality when using a cache.
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*
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* Can be implemented by any class already implementing the cache_loader interface.
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*/
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interface cache_loader_with_locking {
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/**
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* Acquires a lock for the given key.
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*
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* Please note that this happens automatically if the cache definition requires locking.
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* it is still made a public method so that adhoc caches can use it if they choose.
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* However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure
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* locks are acquired, checked, and released.
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*
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* @param string|int $key
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* @return bool True if the lock could be acquired, false otherwise.
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*/
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public function acquire_lock($key);
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/**
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* Checks if the cache loader owns the lock for the given key.
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*
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* Please note that this happens automatically if the cache definition requires locking.
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* it is still made a public method so that adhoc caches can use it if they choose.
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* However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure
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* locks are acquired, checked, and released.
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*
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* @param string|int $key
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* @return bool True if this code has the lock, false if there is a lock but this code doesn't have it,
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* null if there is no lock.
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*/
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public function check_lock_state($key);
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/**
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* Releases the lock for the given key.
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*
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* Please note that this happens automatically if the cache definition requires locking.
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* it is still made a public method so that adhoc caches can use it if they choose.
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* However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure
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* locks are acquired, checked, and released.
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*
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* @param string|int $key
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* @return bool True if the lock has been released, false if there was a problem releasing the lock.
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*/
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public function release_lock($key);
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}
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/**
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* Cache store feature: locking
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*
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* This is a feature that cache stores can implement if they wish to support locking themselves rather
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* than having the cache loader handle it for them.
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*
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* Can be implemented by classes already implementing cache_store.
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*/
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interface cache_is_lockable {
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/**
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* Acquires a lock on the given key for the given identifier.
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*
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* @param string $key The key we are locking.
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* @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
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* The use of this property is entirely optional and implementations can act as they like upon it.
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* @return bool True if the lock could be acquired, false otherwise.
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*/
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public function acquire_lock($key, $ownerid);
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/**
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* Test if there is already a lock for the given key and if there is whether it belongs to the calling code.
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*
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* @param string $key The key we are locking.
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* @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
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* @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there
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* is no lock.
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*/
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public function check_lock_state($key, $ownerid);
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/**
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* Releases the lock on the given key.
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*
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* @param string $key The key we are locking.
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* @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
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* The use of this property is entirely optional and implementations can act as they like upon it.
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* @return bool True if the lock has been released, false if there was a problem releasing the lock.
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*/
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public function release_lock($key, $ownerid);
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}
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/**
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* Cache store feature: key awareness.
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*
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* This is a feature that cache stores and cache loaders can both choose to implement.
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* If a cache store implements this then it will be made responsible for tests for items within the cache.
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* If the cache store being used doesn't implement this then it will be the responsibility of the cache loader to use the
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* equivalent get methods to mimick the functionality of these tests.
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*
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* Cache stores should only override these methods if they natively support such features or if they have a better performing
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* means of performing these tests than the handling that would otherwise take place in the cache_loader.
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*
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* Can be implemented by classes already implementing cache_store.
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*/
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interface cache_is_key_aware {
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/**
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* Test is a cache has a key.
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*
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* The use of the has methods is strongly discouraged. In a high load environment the cache may well change between the
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* test and any subsequent action (get, set, delete etc).
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* Instead it is recommended to write your code in such a way they it performs the following steps:
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* <ol>
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* <li>Attempt to retrieve the information.</li>
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* <li>Generate the information.</li>
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* <li>Attempt to set the information</li>
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* </ol>
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*
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* Its also worth mentioning that not all stores support key tests.
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* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
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* Just one more reason you should not use these methods unless you have a very good reason to do so.
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*
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* @param string|int $key
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* @return bool True if the cache has the requested key, false otherwise.
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*/
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public function has($key);
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/**
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* Test if a cache has at least one of the given keys.
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*
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* It is strongly recommended to avoid the use of this function if not absolutely required.
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* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
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*
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* Its also worth mentioning that not all stores support key tests.
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* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
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* Just one more reason you should not use these methods unless you have a very good reason to do so.
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*
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* @param array $keys
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* @return bool True if the cache has at least one of the given keys
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*/
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public function has_any(array $keys);
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/**
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* Test is a cache has all of the given keys.
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*
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* It is strongly recommended to avoid the use of this function if not absolutely required.
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* In a high load environment the cache may well change between the test and any subsequent action (get, set, delete etc).
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*
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* Its also worth mentioning that not all stores support key tests.
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* For stores that don't support key tests this functionality is mimicked by using the equivalent get method.
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* Just one more reason you should not use these methods unless you have a very good reason to do so.
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*
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* @param array $keys
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* @return bool True if the cache has all of the given keys, false otherwise.
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*/
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public function has_all(array $keys);
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}
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/**
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* Cache store feature: keys are searchable.
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*
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* Cache stores can choose to implement this interface.
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* In order for a store to be usable as a session cache it must implement this interface.
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*
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* @since Moodle 2.4.4
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*/
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interface cache_is_searchable {
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/**
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* Finds all of the keys being used by the cache store.
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*
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* @return array.
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*/
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public function find_all();
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/**
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* Finds all of the keys whose keys start with the given prefix.
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*
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* @param string $prefix
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*/
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public function find_by_prefix($prefix);
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}
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/**
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* Cache store feature: configurable.
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*
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* This feature should be implemented by all cache stores that are configurable when adding an instance.
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* It requires the implementation of methods required to convert form data into the a configuration array for the
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* store instance, and then the reverse converting configuration data into an array that can be used to set the
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* data for the edit form.
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*
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* Can be implemented by classes already implementing cache_store.
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*/
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interface cache_is_configurable {
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/**
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* Given the data from the add instance form this function creates a configuration array.
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*
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* @param stdClass $data
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* @return array
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*/
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public static function config_get_configuration_array($data);
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/**
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* Allows the cache store to set its data against the edit form before it is shown to the user.
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*
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* @param moodleform $editform
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* @param array $config
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*/
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public static function config_set_edit_form_data(moodleform $editform, array $config);
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}
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/**
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* Cache Data Source.
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*
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* The cache data source interface can be implemented by any class within Moodle.
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* If implemented then the class can be reference in a cache definition and will be used to load information that cannot be
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* retrieved from the cache. As part of its retrieval that information will also be loaded into the cache.
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*
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* This allows developers to created a complete cache solution that can be used through code ensuring consistent cache
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* interaction and loading. Allowing them in turn to centralise code and help keeps things more easily maintainable.
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*
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* Can be implemented by any class.
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*
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* @package core
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* @category cache
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* @copyright 2012 Sam Hemelryk
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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interface cache_data_source {
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/**
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* Returns an instance of the data source class that the cache can use for loading data using the other methods
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* specified by this interface.
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*
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* @param cache_definition $definition
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* @return object
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*/
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public static function get_instance_for_cache(cache_definition $definition);
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/**
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* Loads the data for the key provided ready formatted for caching.
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*
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* @param string|int $key The key to load.
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* @return mixed What ever data should be returned, or false if it can't be loaded.
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*/
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public function load_for_cache($key);
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/**
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* Loads several keys for the cache.
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*
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* @param array $keys An array of keys each of which will be string|int.
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* @return array An array of matching data items.
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*/
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public function load_many_for_cache(array $keys);
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}
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/**
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* Cacheable object.
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*
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* 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
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* structure and the information about to be cached, as well as how to deal with it when it is retrieved from a cache.
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* Think of it like serialisation and the __sleep and __wakeup methods.
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* This is used because cache stores are responsible for how they interact with data and what they do when storing it. This
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* interface ensures there is always a guaranteed action.
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*/
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interface cacheable_object {
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/**
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* Prepares the object for caching. Works like the __sleep method.
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*
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* @return mixed The data to cache, can be anything except a class that implements the cacheable_object... that would
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* be dumb.
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*/
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public function prepare_to_cache();
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/**
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* Takes the data provided by prepare_to_cache and reinitialises an instance of the associated from it.
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*
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* @param mixed $data
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* @return object The instance for the given data.
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*/
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public static function wake_from_cache($data);
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}
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/**
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* Cache lock interface
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*
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* This interface needs to be inherited by all cache lock plugins.
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*/
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interface cache_lock_interface {
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/**
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* Constructs an instance of the cache lock given its name and its configuration data
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*
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* @param string $name The unique name of the lock instance
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* @param array $configuration
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*/
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public function __construct($name, array $configuration = array());
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/**
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* Acquires a lock on a given key.
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*
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* @param string $key The key to acquire a lock for.
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* @param string $ownerid An unique identifier for the owner of this lock. It is entirely optional for the cache lock plugin
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* to use this. Each implementation can decide for themselves.
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* @param bool $block If set to true the application will wait until a lock can be acquired
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* @return bool True if the lock can be acquired false otherwise.
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*/
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public function lock($key, $ownerid, $block = false);
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|
|
|
/**
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|
* Releases the lock held on a certain key.
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|
*
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|
* @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 $forceunlock If set to true the lock will be removed if it exists regardless of whether or not we own it.
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|
*/
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|
public function unlock($key, $ownerid, $forceunlock = false);
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|
|
|
/**
|
|
* 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);
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|
|
|
/**
|
|
* 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();
|
|
}
|