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<?php
// $Id: cache.inc,v 1.17 2008/01/29 11:36:06 goba Exp $
/**
* Return data from the persistent cache. Data may be stored as either plain text or as serialized data.
* cache_get will automatically return unserialized objects and arrays.
*
* @param $cid
* The cache ID of the data to retrieve.
* @param $table
* The table $table to store the data in. Valid core values are 'cache_filter',
* 'cache_menu', 'cache_page', or 'cache' for the default cache.
*/
function cache_get($cid, $table = 'cache') {
global $user;
// Garbage collection necessary when enforcing a minimum cache lifetime
$cache_flush = variable_get('cache_flush', 0);
if ($cache_flush && ($cache_flush + variable_get('cache_lifetime', 0) <= time())) {
// Reset the variable immediately to prevent a meltdown in heavy load situations.
variable_set('cache_flush', 0);
// Time to flush old cache data
db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire <= %d", CACHE_PERMANENT, $cache_flush);
}
$cache = db_fetch_object(db_query("SELECT data, created, headers, expire, serialized FROM {". $table ."} WHERE cid = '%s'", $cid));
if (isset($cache->data)) {
// If the data is permanent or we're not enforcing a minimum cache lifetime
// always return the cached data.
if ($cache->expire == CACHE_PERMANENT || !variable_get('cache_lifetime', 0)) {
$cache->data = db_decode_blob($cache->data);
if ($cache->serialized) {
$cache->data = unserialize($cache->data);
}
}
// If enforcing a minimum cache lifetime, validate that the data is
// currently valid for this user before we return it by making sure the
// cache entry was created before the timestamp in the current session's
// cache timer. The cache variable is loaded into the $user object by
// sess_read() in session.inc.
else {
if ($user->cache > $cache->created) {
// This cache data is too old and thus not valid for us, ignore it.
return 0;
}
else {
$cache->data = db_decode_blob($cache->data);
if ($cache->serialized) {
$cache->data = unserialize($cache->data);
}
}
}
return $cache;
}
return 0;
}
/**
* Store data in the persistent cache.
*
* The persistent cache is split up into four database
* tables. Contributed modules can add additional tables.
*
* 'cache_page': This table stores generated pages for anonymous
* users. This is the only table affected by the page cache setting on
* the administrator panel.
*
* 'cache_menu': Stores the cachable part of the users' menus.
*
* 'cache_filter': Stores filtered pieces of content. This table is
* periodically cleared of stale entries by cron.
*
* 'cache': Generic cache storage table.
*
* The reasons for having several tables are as follows:
*
* - smaller tables allow for faster selects and inserts
* - we try to put fast changing cache items and rather static
* ones into different tables. The effect is that only the fast
* changing tables will need a lot of writes to disk. The more
* static tables will also be better cachable with MySQL's query cache
*
* @param $cid
* The cache ID of the data to store.
* @param $data
* The data to store in the cache. Complex data types will be automatically serialized before insertion.
* Strings will be stored as plain text and not serialized.
* @param $table
* The table $table to store the data in. Valid core values are 'cache_filter',
* 'cache_menu', 'cache_page', or 'cache'.
* @param $expire
* One of the following values:
* - CACHE_PERMANENT: Indicates that the item should never be removed unless
* explicitly told to using cache_clear_all() with a cache ID.
* - CACHE_TEMPORARY: Indicates that the item should be removed at the next
* general cache wipe.
* - A Unix timestamp: Indicates that the item should be kept at least until
* the given time, after which it behaves like CACHE_TEMPORARY.
* @param $headers
* A string containing HTTP header information for cached pages.
*/
function cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $headers = NULL) {
$serialized = 0;
if (is_object($data) || is_array($data)) {
$data = serialize($data);
$serialized = 1;
}
$created = time();
db_query("UPDATE {". $table ."} SET data = %b, created = %d, expire = %d, headers = '%s', serialized = %d WHERE cid = '%s'", $data, $created, $expire, $headers, $serialized, $cid);
if (!db_affected_rows()) {
@db_query("INSERT INTO {". $table ."} (cid, data, created, expire, headers, serialized) VALUES ('%s', %b, %d, %d, '%s', %d)", $cid, $data, $created, $expire, $headers, $serialized);
}
}
/**
*
* Expire data from the cache. If called without arguments, expirable
* entries will be cleared from the cache_page and cache_block tables.
*
* @param $cid
* If set, the cache ID to delete. Otherwise, all cache entries that can
* expire are deleted.
*
* @param $table
* If set, the table $table to delete from. Mandatory
* argument if $cid is set.
*
* @param $wildcard
* If set to TRUE, the $cid is treated as a substring
* to match rather than a complete ID. The match is a right hand
* match. If '*' is given as $cid, the table $table will be emptied.
*/
function cache_clear_all($cid = NULL, $table = NULL, $wildcard = FALSE) {
global $user;
if (!isset($cid) && !isset($table)) {
// Clear the block cache first, so stale data will
// not end up in the page cache.
cache_clear_all(NULL, 'cache_block');
cache_clear_all(NULL, 'cache_page');
return;
}
if (empty($cid)) {
if (variable_get('cache_lifetime', 0)) {
// We store the time in the current user's $user->cache variable which
// will be saved into the sessions table by sess_write(). We then
// simulate that the cache was flushed for this user by not returning
// cached data that was cached before the timestamp.
$user->cache = time();
$cache_flush = variable_get('cache_flush', 0);
if ($cache_flush == 0) {
// This is the first request to clear the cache, start a timer.
variable_set('cache_flush', time());
}
else if (time() > ($cache_flush + variable_get('cache_lifetime', 0))) {
// Clear the cache for everyone, cache_flush_delay seconds have
// passed since the first request to clear the cache.
db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
variable_set('cache_flush', 0);
}
}
else {
// No minimum cache lifetime, flush all temporary cache entries now.
db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
}
}
else {
if ($wildcard) {
if ($cid == '*') {
db_query("DELETE FROM {". $table ."}");
}
else {
db_query("DELETE FROM {". $table ."} WHERE cid LIKE '%s%%'", $cid);
}
}
else {
db_query("DELETE FROM {". $table ."} WHERE cid = '%s'", $cid);
}
}
}
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