[Summary view] [Print] [Text view]

   1  <?php
   2  
   3  /**
   4   * Return data from the persistent cache. Data may be stored as either plain text or as serialized data.
   5   * cache_get will automatically return unserialized objects and arrays.
   6   *
   7   * @param $cid
   8   *   The cache ID of the data to retrieve.
   9   * @param $table
  10   *   The table $table to store the data in. Valid core values are 'cache_filter',
  11   *   'cache_menu', 'cache_page', or 'cache' for the default cache.
  12   */
  13  function cache_get($cid, $table = 'cache') {
  14    global $user;
  15  
  16    // Garbage collection necessary when enforcing a minimum cache lifetime
  17    $cache_flush = variable_get('cache_flush_'. $table, 0);
  18    if ($cache_flush && ($cache_flush + variable_get('cache_lifetime', 0) <= time())) {
  19      // Reset the variable immediately to prevent a meltdown in heavy load situations.
  20      variable_set('cache_flush_'. $table, 0);
  21      // Time to flush old cache data
  22      db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire <= %d", CACHE_PERMANENT, $cache_flush);
  23    }
  24  
  25    $cache = db_fetch_object(db_query("SELECT data, created, headers, expire, serialized FROM {". $table ."} WHERE cid = '%s'", $cid));
  26    if (isset($cache->data)) {
  27      // If the data is permanent or we're not enforcing a minimum cache lifetime
  28      // always return the cached data.
  29      if ($cache->expire == CACHE_PERMANENT || !variable_get('cache_lifetime', 0)) {
  30        $cache->data = db_decode_blob($cache->data);
  31        if ($cache->serialized) {
  32          $cache->data = unserialize($cache->data);
  33        }
  34      }
  35      // If enforcing a minimum cache lifetime, validate that the data is
  36      // currently valid for this user before we return it by making sure the
  37      // cache entry was created before the timestamp in the current session's
  38      // cache timer. The cache variable is loaded into the $user object by
  39      // sess_read() in session.inc.
  40      else {
  41        if (isset($user->cache) && $user->cache > $cache->created) {
  42          // This cache data is too old and thus not valid for us, ignore it.
  43          return 0;
  44        }
  45        else {
  46          $cache->data = db_decode_blob($cache->data);
  47          if ($cache->serialized) {
  48            $cache->data = unserialize($cache->data);
  49          }
  50        }
  51      }
  52      return $cache;
  53    }
  54    return 0;
  55  }
  56  
  57  /**
  58   * Store data in the persistent cache.
  59   *
  60   * The persistent cache is split up into four database
  61   * tables. Contributed modules can add additional tables.
  62   *
  63   * 'cache_page': This table stores generated pages for anonymous
  64   * users. This is the only table affected by the page cache setting on
  65   * the administrator panel.
  66   *
  67   * 'cache_menu': Stores the cachable part of the users' menus.
  68   *
  69   * 'cache_filter': Stores filtered pieces of content. This table is
  70   * periodically cleared of stale entries by cron.
  71   *
  72   * 'cache': Generic cache storage table.
  73   *
  74   * The reasons for having several tables are as follows:
  75   *
  76   * - smaller tables allow for faster selects and inserts
  77   * - we try to put fast changing cache items and rather static
  78   *   ones into different tables. The effect is that only the fast
  79   *   changing tables will need a lot of writes to disk. The more
  80   *   static tables will also be better cachable with MySQL's query cache
  81   *
  82   * @param $cid
  83   *   The cache ID of the data to store.
  84   * @param $data
  85   *   The data to store in the cache. Complex data types will be automatically serialized before insertion.
  86   *   Strings will be stored as plain text and not serialized.
  87   * @param $table
  88   *   The table $table to store the data in. Valid core values are 'cache_filter',
  89   *   'cache_menu', 'cache_page', or 'cache'.
  90   * @param $expire
  91   *   One of the following values:
  92   *   - CACHE_PERMANENT: Indicates that the item should never be removed unless
  93   *     explicitly told to using cache_clear_all() with a cache ID.
  94   *   - CACHE_TEMPORARY: Indicates that the item should be removed at the next
  95   *     general cache wipe.
  96   *   - A Unix timestamp: Indicates that the item should be kept at least until
  97   *     the given time, after which it behaves like CACHE_TEMPORARY.
  98   * @param $headers
  99   *   A string containing HTTP header information for cached pages.
 100   */
 101  function cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $headers = NULL) {
 102    $serialized = 0;
 103    if (is_object($data) || is_array($data)) {
 104      $data = serialize($data);
 105      $serialized = 1;
 106    }
 107    $created = time();
 108    db_query("UPDATE {". $table ."} SET data = %b, created = %d, expire = %d, headers = '%s', serialized = %d WHERE cid = '%s'", $data, $created, $expire, $headers, $serialized, $cid);
 109    if (!db_affected_rows()) {
 110      @db_query("INSERT INTO {". $table ."} (cid, data, created, expire, headers, serialized) VALUES ('%s', %b, %d, %d, '%s', %d)", $cid, $data, $created, $expire, $headers, $serialized);
 111    }
 112  }
 113  
 114  /**
 115   *
 116   * Expire data from the cache. If called without arguments, expirable
 117   * entries will be cleared from the cache_page and cache_block tables.
 118   *
 119   * @param $cid
 120   *   If set, the cache ID to delete. Otherwise, all cache entries that can
 121   *   expire are deleted.
 122   *
 123   * @param $table
 124   *   If set, the table $table to delete from. Mandatory
 125   *   argument if $cid is set.
 126   *
 127   * @param $wildcard
 128   *   If $wildcard is TRUE, cache IDs starting with $cid are deleted in
 129   *   addition to the exact cache ID specified by $cid.  If $wildcard is
 130   *   TRUE and $cid is '*' then the entire table $table is emptied.
 131   */
 132  function cache_clear_all($cid = NULL, $table = NULL, $wildcard = FALSE) {
 133    global $user;
 134  
 135    if (!isset($cid) && !isset($table)) {
 136      // Clear the block cache first, so stale data will
 137      // not end up in the page cache.
 138      cache_clear_all(NULL, 'cache_block');
 139      cache_clear_all(NULL, 'cache_page');
 140      return;
 141    }
 142  
 143    if (empty($cid)) {
 144      if (variable_get('cache_lifetime', 0)) {
 145        // We store the time in the current user's $user->cache variable which
 146        // will be saved into the sessions table by sess_write(). We then
 147        // simulate that the cache was flushed for this user by not returning
 148        // cached data that was cached before the timestamp.
 149        $user->cache = time();
 150  
 151        $cache_flush = variable_get('cache_flush_'. $table, 0);
 152        if ($cache_flush == 0) {
 153          // This is the first request to clear the cache, start a timer.
 154          variable_set('cache_flush_'. $table, time());
 155        }
 156        else if (time() > ($cache_flush + variable_get('cache_lifetime', 0))) {
 157          // Clear the cache for everyone, cache_lifetime seconds have
 158          // passed since the first request to clear the cache.
 159          db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
 160          variable_set('cache_flush_'. $table, 0);
 161        }
 162      }
 163      else {
 164        // No minimum cache lifetime, flush all temporary cache entries now.
 165        db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
 166      }
 167    }
 168    else {
 169      if ($wildcard) {
 170        if ($cid == '*') {
 171          db_query("TRUNCATE TABLE {". $table ."}");
 172        }
 173        else {
 174          db_query("DELETE FROM {". $table ."} WHERE cid LIKE '%s%%'", $cid);
 175        }
 176      }
 177      else {
 178        db_query("DELETE FROM {". $table ."} WHERE cid = '%s'", $cid);
 179      }
 180    }
 181  }
 182