<?php

// $Id: cache.inc,v 1.17.2.2 2009/05/26 08:10:33 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_'. $table, 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_'. $table, 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_'. $table, 0);

      if ($cache_flush == 0) {

        // This is the first request to clear the cache, start a timer.

        variable_set('cache_flush_'. $table, time());

      }

      else if (time() > ($cache_flush + variable_get('cache_lifetime', 0))) {

        // Clear the cache for everyone, cache_lifetime 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_'. $table, 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);

    }

  }

}