189 lines
6.7 KiB
PHP
189 lines
6.7 KiB
PHP
<?php
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// $Id$
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/**
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* Return data from the persistent cache. Data may be stored as either plain text or as serialized data.
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* cache_get will automatically return unserialized objects and arrays.
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*
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* @param $cid
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* The cache ID of the data to retrieve.
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* @param $table
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* The table $table to store the data in. Valid core values are 'cache_filter',
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* 'cache_menu', 'cache_page', or 'cache' for the default cache.
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* @return The cache or FALSE on failure.
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*/
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function cache_get($cid, $table = 'cache') {
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global $user;
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// Garbage collection necessary when enforcing a minimum cache lifetime
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$cache_flush = variable_get('cache_flush', 0);
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if ($cache_flush && ($cache_flush + variable_get('cache_lifetime', 0) <= time())) {
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// Reset the variable immediately to prevent a meltdown in heavy load situations.
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variable_set('cache_flush', 0);
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// Time to flush old cache data
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db_query("DELETE FROM {" . $table . "} WHERE expire != %d AND expire <= %d", CACHE_PERMANENT, $cache_flush);
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}
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$cache = db_fetch_object(db_query("SELECT data, created, headers, expire, serialized FROM {" . $table . "} WHERE cid = '%s'", $cid));
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if (isset($cache->data)) {
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// If the data is permanent or we're not enforcing a minimum cache lifetime
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// always return the cached data.
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if ($cache->expire == CACHE_PERMANENT || !variable_get('cache_lifetime', 0)) {
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if ($cache->serialized) {
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$cache->data = unserialize($cache->data);
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}
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}
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// If enforcing a minimum cache lifetime, validate that the data is
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// currently valid for this user before we return it by making sure the
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// cache entry was created before the timestamp in the current session's
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// cache timer. The cache variable is loaded into the $user object by
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// sess_read() in session.inc.
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else {
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if ($user->cache > $cache->created) {
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// This cache data is too old and thus not valid for us, ignore it.
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return FALSE;
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}
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else {
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if ($cache->serialized) {
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$cache->data = unserialize($cache->data);
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}
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}
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}
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return $cache;
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}
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return FALSE;
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}
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/**
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* Store data in the persistent cache.
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*
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* The persistent cache is split up into four database
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* tables. Contributed modules can add additional tables.
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*
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* 'cache_page': This table stores generated pages for anonymous
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* users. This is the only table affected by the page cache setting on
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* the administrator panel.
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*
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* 'cache_menu': Stores the cachable part of the users' menus.
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*
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* 'cache_filter': Stores filtered pieces of content. This table is
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* periodically cleared of stale entries by cron.
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*
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* 'cache': Generic cache storage table.
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*
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* The reasons for having several tables are as follows:
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*
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* - smaller tables allow for faster selects and inserts
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* - we try to put fast changing cache items and rather static
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* ones into different tables. The effect is that only the fast
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* changing tables will need a lot of writes to disk. The more
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* static tables will also be better cachable with MySQL's query cache
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*
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* @param $cid
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* The cache ID of the data to store.
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* @param $data
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* The data to store in the cache. Complex data types will be automatically serialized before insertion.
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* Strings will be stored as plain text and not serialized.
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* @param $table
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* The table $table to store the data in. Valid core values are 'cache_filter',
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* 'cache_menu', 'cache_page', or 'cache'.
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* @param $expire
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* One of the following values:
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* - CACHE_PERMANENT: Indicates that the item should never be removed unless
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* explicitly told to using cache_clear_all() with a cache ID.
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* - CACHE_TEMPORARY: Indicates that the item should be removed at the next
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* general cache wipe.
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* - A Unix timestamp: Indicates that the item should be kept at least until
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* the given time, after which it behaves like CACHE_TEMPORARY.
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* @param $headers
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* A string containing HTTP header information for cached pages.
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*/
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function cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $headers = NULL) {
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$fields = array(
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'serialized' => 0,
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'created' => time(),
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'expire' => $expire,
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'headers' => $headers,
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);
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if (!is_string($data)) {
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$fields['data'] = serialize($data);
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$fields['serialized'] = 1;
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}
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else {
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$fields['data'] = $data;
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$fields['serialized'] = 0;
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}
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db_merge($table)->key(array('cid' => $cid))->fields($fields)->execute();
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}
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/**
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*
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* Expire data from the cache. If called without arguments, expirable
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* entries will be cleared from the cache_page and cache_block tables.
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*
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* @param $cid
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* If set, the cache ID to delete. Otherwise, all cache entries that can
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* expire are deleted.
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*
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* @param $table
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* If set, the table $table to delete from. Mandatory
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* argument if $cid is set.
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*
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* @param $wildcard
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* If set to TRUE, the $cid is treated as a substring
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* to match rather than a complete ID. The match is a right hand
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* match. If '*' is given as $cid, the table $table will be emptied.
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*/
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function cache_clear_all($cid = NULL, $table = NULL, $wildcard = FALSE) {
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global $user;
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if (!isset($cid) && !isset($table)) {
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// Clear the block cache first, so stale data will
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// not end up in the page cache.
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cache_clear_all(NULL, 'cache_block');
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cache_clear_all(NULL, 'cache_page');
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return;
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}
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if (empty($cid)) {
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if (variable_get('cache_lifetime', 0)) {
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// We store the time in the current user's $user->cache variable which
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// will be saved into the sessions table by sess_write(). We then
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// simulate that the cache was flushed for this user by not returning
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// cached data that was cached before the timestamp.
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$user->cache = time();
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$cache_flush = variable_get('cache_flush', 0);
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if ($cache_flush == 0) {
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// This is the first request to clear the cache, start a timer.
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variable_set('cache_flush', time());
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}
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else if (time() > ($cache_flush + variable_get('cache_lifetime', 0))) {
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// Clear the cache for everyone, cache_flush_delay seconds have
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// passed since the first request to clear the cache.
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db_query("DELETE FROM {" . $table . "} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
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variable_set('cache_flush', 0);
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}
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}
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else {
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// No minimum cache lifetime, flush all temporary cache entries now.
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db_query("DELETE FROM {" . $table . "} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
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}
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}
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else {
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if ($wildcard) {
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if ($cid == '*') {
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db_delete($table)->execute();
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}
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else {
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db_delete($table)->condition('cid', $cid .'%', 'LIKE')->execute();
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}
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}
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else {
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db_delete($table)->condition('cid', $cid)->execute();
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}
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}
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}
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