source: trunk/www.guidonia.net/wp/wp-includes/cache.php@ 44

<?php
/**
 * Object Cache API
 *
 * @link http://codex.wordpress.org/Function_Reference/WP_Cache
 *
 * @package WordPress
 * @subpackage Cache
 */

/**
 * Adds data to the cache, if the cache key doesn't aleady exist.
 *
 * @since 2.0.0
 * @uses $wp_object_cache Object Cache Class
 * @see WP_Object_Cache::add()
 *
 * @param int|string $key The cache ID to use for retrieval later
 * @param mixed $data The data to add to the cache store
 * @param string $flag The group to add the cache to
 * @param int $expire When the cache data should be expired
 * @return unknown
 */
function wp_cache_add($key, $data, $flag = '', $expire = 0) {
        global $wp_object_cache;

        return $wp_object_cache->add($key, $data, $flag, $expire);
}

/**
 * Closes the cache.
 *
 * This function has ceased to do anything since WordPress 2.5. The
 * functionality was removed along with the rest of the persistant cache. This
 * does not mean that plugins can't implement this function when they need to
 * make sure that the cache is cleaned up after WordPress no longer needs it.
 *
 * @since 2.0.0
 *
 * @return bool Always returns True
 */
function wp_cache_close() {
        return true;
}

/**
 * Removes the cache contents matching ID and flag.
 *
 * @since 2.0.0
 * @uses $wp_object_cache Object Cache Class
 * @see WP_Object_Cache::delete()
 *
 * @param int|string $id What the contents in the cache are called
 * @param string $flag Where the cache contents are grouped
 * @return bool True on successful removal, false on failure
 */
function wp_cache_delete($id, $flag = '') {
        global $wp_object_cache;

        return $wp_object_cache->delete($id, $flag);
}

/**
 * Removes all cache items.
 *
 * @since 2.0.0
 * @uses $wp_object_cache Object Cache Class
 * @see WP_Object_Cache::flush()
 *
 * @return bool Always returns true
 */
function wp_cache_flush() {
        global $wp_object_cache;

        return $wp_object_cache->flush();
}

/**
 * Retrieves the cache contents from the cache by ID and flag.
 *
 * @since 2.0.0
 * @uses $wp_object_cache Object Cache Class
 * @see WP_Object_Cache::get()
 *
 * @param int|string $id What the contents in the cache are called
 * @param string $flag Where the cache contents are grouped
 * @return bool|mixed False on failure to retrieve contents or the cache
 *              contents on success
 */
function wp_cache_get($id, $flag = '') {
        global $wp_object_cache;

        return $wp_object_cache->get($id, $flag);
}

/**
 * Sets up Object Cache Global and assigns it.
 *
 * @since 2.0.0
 * @global WP_Object_Cache $wp_object_cache WordPress Object Cache
 */
function wp_cache_init() {
        $GLOBALS['wp_object_cache'] =& new WP_Object_Cache();
}

/**
 * Replaces the contents of the cache with new data.
 *
 * @since 2.0.0
 * @uses $wp_object_cache Object Cache Class
 * @see WP_Object_Cache::replace()
 *
 * @param int|string $id What to call the contents in the cache
 * @param mixed $data The contents to store in the cache
 * @param string $flag Where to group the cache contents
 * @param int $expire When to expire the cache contents
 * @return bool False if cache ID and group already exists, true on success
 */
function wp_cache_replace($key, $data, $flag = '', $expire = 0) {
        global $wp_object_cache;

        return $wp_object_cache->replace($key, $data, $flag, $expire);
}

/**
 * Saves the data to the cache.
 *
 * @since 2.0
 * @uses $wp_object_cache Object Cache Class
 * @see WP_Object_Cache::set()
 *
 * @param int|string $id What to call the contents in the cache
 * @param mixed $data The contents to store in the cache
 * @param string $flag Where to group the cache contents
 * @param int $expire When to expire the cache contents
 * @return bool False if cache ID and group already exists, true on success
 */
function wp_cache_set($key, $data, $flag = '', $expire = 0) {
        global $wp_object_cache;

        return $wp_object_cache->set($key, $data, $flag, $expire);
}

/**
 * Adds a group or set of groups to the list of global groups.
 *
 * @since 2.6.0
 *
 * @param string|array $groups A group or an array of groups to add
 */
function wp_cache_add_global_groups( $groups ) {
        // Default cache doesn't persist so nothing to do here.
        return;
}

/**
 * Adds a group or set of groups to the list of non-persistent groups.
 *
 * @since 2.6.0
 *
 * @param string|array $groups A group or an array of groups to add
 */
function wp_cache_add_non_persistent_groups( $groups ) {
        // Default cache doesn't persist so nothing to do here.
        return;
}

/**
 * WordPress Object Cache
 *
 * The WordPress Object Cache is used to save on trips to the database. The
 * Object Cache stores all of the cache data to memory and makes the cache
 * contents available by using a key, which is used to name and later retrieve
 * the cache contents.
 *
 * The Object Cache can be replaced by other caching mechanisms by placing files
 * in the wp-content folder which is looked at in wp-settings. If that file
 * exists, then this file will not be included.
 *
 * @package WordPress
 * @subpackage Cache
 * @since 2.0
 */
class WP_Object_Cache {

        /**
         * Holds the cached objects
         *
         * @var array
         * @access private
         * @since 2.0.0
         */
        var $cache = array ();

        /**
         * Cache objects that do not exist in the cache
         *
         * @var array
         * @access private
         * @since 2.0.0
         */
        var $non_existant_objects = array ();

        /**
         * The amount of times the cache data was already stored in the cache.
         *
         * @since 2.5.0
         * @access private
         * @var int
         */
        var $cache_hits = 0;

        /**
         * Amount of times the cache did not have the request in cache
         *
         * @var int
         * @access public
         * @since 2.0.0
         */
        var $cache_misses = 0;

        /**
         * Adds data to the cache if it doesn't already exist.
         *
         * @uses WP_Object_Cache::get Checks to see if the cache already has data.
         * @uses WP_Object_Cache::set Sets the data after the checking the cache
         *              contents existance.
         *
         * @since 2.0.0
         *
         * @param int|string $id What to call the contents in the cache
         * @param mixed $data The contents to store in the cache
         * @param string $group Where to group the cache contents
         * @param int $expire When to expire the cache contents
         * @return bool False if cache ID and group already exists, true on success
         */
        function add($id, $data, $group = 'default', $expire = '') {
                if (empty ($group))
                        $group = 'default';

                if (false !== $this->get($id, $group, false))
                        return false;

                return $this->set($id, $data, $group, $expire);
        }

        /**
         * Remove the contents of the cache ID in the group
         *
         * If the cache ID does not exist in the group and $force parameter is set
         * to false, then nothing will happen. The $force parameter is set to false
         * by default.
         *
         * On success the group and the id will be added to the
         * $non_existant_objects property in the class.
         *
         * @since 2.0.0
         *
         * @param int|string $id What the contents in the cache are called
         * @param string $group Where the cache contents are grouped
         * @param bool $force Optional. Whether to force the unsetting of the cache
         *              ID in the group
         * @return bool False if the contents weren't deleted and true on success
         */
        function delete($id, $group = 'default', $force = false) {
                if (empty ($group))
                        $group = 'default';

                if (!$force && false === $this->get($id, $group, false))
                        return false;

                unset ($this->cache[$group][$id]);
                $this->non_existant_objects[$group][$id] = true;
                return true;
        }

        /**
         * Clears the object cache of all data
         *
         * @since 2.0.0
         *
         * @return bool Always returns true
         */
        function flush() {
                $this->cache = array ();

                return true;
        }

        /**
         * Retrieves the cache contents, if it exists
         *
         * The contents will be first attempted to be retrieved by searching by the
         * ID in the cache group. If the cache is hit (success) then the contents
         * are returned.
         *
         * On failure, the $non_existant_objects property is checked and if the
         * cache group and ID exist in there the cache misses will not be
         * incremented. If not in the nonexistant objects property, then the cache
         * misses will be incremented and the cache group and ID will be added to
         * the nonexistant objects.
         *
         * @since 2.0.0
         *
         * @param int|string $id What the contents in the cache are called
         * @param string $group Where the cache contents are grouped
         * @return bool|mixed False on failure to retrieve contents or the cache
         *              contents on success
         */
        function get($id, $group = 'default') {
                if (empty ($group))
                        $group = 'default';

                if (isset ($this->cache[$group][$id])) {
                        $this->cache_hits += 1;
                        if ( is_object($this->cache[$group][$id]) )
                                return wp_clone($this->cache[$group][$id]);
                        else
                                return $this->cache[$group][$id];
                }

                if ( isset ($this->non_existant_objects[$group][$id]) )
                        return false;

                $this->non_existant_objects[$group][$id] = true;
                $this->cache_misses += 1;
                return false;
        }

        /**
         * Replace the contents in the cache, if contents already exist
         *
         * @since 2.0.0
         * @see WP_Object_Cache::set()
         *
         * @param int|string $id What to call the contents in the cache
         * @param mixed $data The contents to store in the cache
         * @param string $group Where to group the cache contents
         * @param int $expire When to expire the cache contents
         * @return bool False if not exists, true if contents were replaced
         */
        function replace($id, $data, $group = 'default', $expire = '') {
                if (empty ($group))
                        $group = 'default';

                if (false === $this->get($id, $group, false))
                        return false;

                return $this->set($id, $data, $group, $expire);
        }

        /**
         * Sets the data contents into the cache
         *
         * The cache contents is grouped by the $group parameter followed by the
         * $id. This allows for duplicate ids in unique groups. Therefore, naming of
         * the group should be used with care and should follow normal function
         * naming guidelines outside of core WordPress usage.
         *
         * The $expire parameter is not used, because the cache will automatically
         * expire for each time a page is accessed and PHP finishes. The method is
         * more for cache plugins which use files.
         *
         * @since 2.0.0
         *
         * @param int|string $id What to call the contents in the cache
         * @param mixed $data The contents to store in the cache
         * @param string $group Where to group the cache contents
         * @param int $expire Not Used
         * @return bool Always returns true
         */
        function set($id, $data, $group = 'default', $expire = '') {
                if (empty ($group))
                        $group = 'default';

                if (NULL === $data)
                        $data = '';

                if ( is_object($data) )
                        $data = wp_clone($data);

                $this->cache[$group][$id] = $data;

                if(isset($this->non_existant_objects[$group][$id]))
                        unset ($this->non_existant_objects[$group][$id]);

                return true;
        }

        /**
         * Echos the stats of the caching.
         *
         * Gives the cache hits, and cache misses. Also prints every cached group,
         * key and the data.
         *
         * @since 2.0.0
         */
        function stats() {
                echo "<p>";
                echo "<strong>Cache Hits:</strong> {$this->cache_hits}<br />";
                echo "<strong>Cache Misses:</strong> {$this->cache_misses}<br />";
                echo "</p>";

                foreach ($this->cache as $group => $cache) {
                        echo "<p>";
                        echo "<strong>Group:</strong> $group<br />";
                        echo "<strong>Cache:</strong>";
                        echo "<pre>";
                        print_r($cache);
                        echo "</pre>";
                }
        }

        /**
         * PHP4 constructor; Calls PHP 5 style constructor
         *
         * @since 2.0.0
         *
         * @return WP_Object_Cache
         */
        function WP_Object_Cache() {
                return $this->__construct();
        }

        /**
         * Sets up object properties; PHP 5 style constructor
         *
         * @since 2.0.8
         * @return null|WP_Object_Cache If cache is disabled, returns null.
         */
        function __construct() {
                /**
                 * @todo This should be moved to the PHP4 style constructor, PHP5
                 * already calls __destruct()
                 */
                register_shutdown_function(array(&$this, "__destruct"));
        }

        /**
         * Will save the object cache before object is completely destroyed.
         *
         * Called upon object destruction, which should be when PHP ends.
         *
         * @since  2.0.8
         *
         * @return bool True value. Won't be used by PHP
         */
        function __destruct() {
                return true;
        }
}
?>