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   1  <?php
   2  // $Id: cache.inc,v 1.17.2.5 2010/11/03 19:07:46 goba Exp $
   3  
   4  /**
   5   * Return data from the persistent cache. Data may be stored as either plain text or as serialized data.
   6   * cache_get will automatically return unserialized objects and arrays.
   7   *
   8   * @param $cid
   9   *   The cache ID of the data to retrieve.
  10   * @param $table
  11   *   The table $table to store the data in. Valid core values are 'cache_filter',
  12   *   'cache_menu', 'cache_page', or 'cache' for the default cache.
  13   */
  14  function cache_get($cid, $table = 'cache') {
  15    global $user;
  16  
  17    // Garbage collection necessary when enforcing a minimum cache lifetime
  18    $cache_flush = variable_get('cache_flush_'. $table, 0);
  19    if ($cache_flush && ($cache_flush + variable_get('cache_lifetime', 0) <= time())) {
  20      // Reset the variable immediately to prevent a meltdown in heavy load situations.
  21      variable_set('cache_flush_'. $table, 0);
  22      // Time to flush old cache data
  23      db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire <= %d", CACHE_PERMANENT, $cache_flush);
  24    }
  25  
  26    $cache = db_fetch_object(db_query("SELECT data, created, headers, expire, serialized FROM {". $table ."} WHERE cid = '%s'", $cid));
  27    if (isset($cache->data)) {
  28      // If the data is permanent or we're not enforcing a minimum cache lifetime
  29      // always return the cached data.
  30      if ($cache->expire == CACHE_PERMANENT || !variable_get('cache_lifetime', 0)) {
  31        $cache->data = db_decode_blob($cache->data);
  32        if ($cache->serialized) {
  33          $cache->data = unserialize($cache->data);
  34        }
  35      }
  36      // If enforcing a minimum cache lifetime, validate that the data is
  37      // currently valid for this user before we return it by making sure the
  38      // cache entry was created before the timestamp in the current session's
  39      // cache timer. The cache variable is loaded into the $user object by
  40      // sess_read() in session.inc.
  41      else {
  42        if (isset($user->cache) && $user->cache > $cache->created) {
  43          // This cache data is too old and thus not valid for us, ignore it.
  44          return 0;
  45        }
  46        else {
  47          $cache->data = db_decode_blob($cache->data);
  48          if ($cache->serialized) {
  49            $cache->data = unserialize($cache->data);
  50          }
  51        }
  52      }
  53      return $cache;
  54    }
  55    return 0;
  56  }
  57  
  58  /**
  59   * Store data in the persistent cache.
  60   *
  61   * The persistent cache is split up into four database
  62   * tables. Contributed modules can add additional tables.
  63   *
  64   * 'cache_page': This table stores generated pages for anonymous
  65   * users. This is the only table affected by the page cache setting on
  66   * the administrator panel.
  67   *
  68   * 'cache_menu': Stores the cachable part of the users' menus.
  69   *
  70   * 'cache_filter': Stores filtered pieces of content. This table is
  71   * periodically cleared of stale entries by cron.
  72   *
  73   * 'cache': Generic cache storage table.
  74   *
  75   * The reasons for having several tables are as follows:
  76   *
  77   * - smaller tables allow for faster selects and inserts
  78   * - we try to put fast changing cache items and rather static
  79   *   ones into different tables. The effect is that only the fast
  80   *   changing tables will need a lot of writes to disk. The more
  81   *   static tables will also be better cachable with MySQL's query cache
  82   *
  83   * @param $cid
  84   *   The cache ID of the data to store.
  85   * @param $data
  86   *   The data to store in the cache. Complex data types will be automatically serialized before insertion.
  87   *   Strings will be stored as plain text and not serialized.
  88   * @param $table
  89   *   The table $table to store the data in. Valid core values are 'cache_filter',
  90   *   'cache_menu', 'cache_page', or 'cache'.
  91   * @param $expire
  92   *   One of the following values:
  93   *   - CACHE_PERMANENT: Indicates that the item should never be removed unless
  94   *     explicitly told to using cache_clear_all() with a cache ID.
  95   *   - CACHE_TEMPORARY: Indicates that the item should be removed at the next
  96   *     general cache wipe.
  97   *   - A Unix timestamp: Indicates that the item should be kept at least until
  98   *     the given time, after which it behaves like CACHE_TEMPORARY.
  99   * @param $headers
 100   *   A string containing HTTP header information for cached pages.
 101   */
 102  function cache_set($cid, $data, $table = 'cache', $expire = CACHE_PERMANENT, $headers = NULL) {
 103    $serialized = 0;
 104    if (is_object($data) || is_array($data)) {
 105      $data = serialize($data);
 106      $serialized = 1;
 107    }
 108    $created = time();
 109    db_query("UPDATE {". $table ."} SET data = %b, created = %d, expire = %d, headers = '%s', serialized = %d WHERE cid = '%s'", $data, $created, $expire, $headers, $serialized, $cid);
 110    if (!db_affected_rows()) {
 111      @db_query("INSERT INTO {". $table ."} (cid, data, created, expire, headers, serialized) VALUES ('%s', %b, %d, %d, '%s', %d)", $cid, $data, $created, $expire, $headers, $serialized);
 112    }
 113  }
 114  
 115  /**
 116   *
 117   * Expire data from the cache. If called without arguments, expirable
 118   * entries will be cleared from the cache_page and cache_block tables.
 119   *
 120   * @param $cid
 121   *   If set, the cache ID to delete. Otherwise, all cache entries that can
 122   *   expire are deleted.
 123   *
 124   * @param $table
 125   *   If set, the table $table to delete from. Mandatory
 126   *   argument if $cid is set.
 127   *
 128   * @param $wildcard
 129   *   If $wildcard is TRUE, cache IDs starting with $cid are deleted in
 130   *   addition to the exact cache ID specified by $cid.  If $wildcard is
 131   *   TRUE and $cid is '*' then the entire table $table is emptied.
 132   */
 133  function cache_clear_all($cid = NULL, $table = NULL, $wildcard = FALSE) {
 134    global $user;
 135  
 136    if (!isset($cid) && !isset($table)) {
 137      // Clear the block cache first, so stale data will
 138      // not end up in the page cache.
 139      cache_clear_all(NULL, 'cache_block');
 140      cache_clear_all(NULL, 'cache_page');
 141      return;
 142    }
 143  
 144    if (empty($cid)) {
 145      if (variable_get('cache_lifetime', 0)) {
 146        // We store the time in the current user's $user->cache variable which
 147        // will be saved into the sessions table by sess_write(). We then
 148        // simulate that the cache was flushed for this user by not returning
 149        // cached data that was cached before the timestamp.
 150        $user->cache = time();
 151  
 152        $cache_flush = variable_get('cache_flush_'. $table, 0);
 153        if ($cache_flush == 0) {
 154          // This is the first request to clear the cache, start a timer.
 155          variable_set('cache_flush_'. $table, time());
 156        }
 157        else if (time() > ($cache_flush + variable_get('cache_lifetime', 0))) {
 158          // Clear the cache for everyone, cache_lifetime seconds have
 159          // passed since the first request to clear the cache.
 160          db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
 161          variable_set('cache_flush_'. $table, 0);
 162        }
 163      }
 164      else {
 165        // No minimum cache lifetime, flush all temporary cache entries now.
 166        db_query("DELETE FROM {". $table ."} WHERE expire != %d AND expire < %d", CACHE_PERMANENT, time());
 167      }
 168    }
 169    else {
 170      if ($wildcard) {
 171        if ($cid == '*') {
 172          db_query("TRUNCATE TABLE {". $table ."}");
 173        }
 174        else {
 175          db_query("DELETE FROM {". $table ."} WHERE cid LIKE '%s%%'", $cid);
 176        }
 177      }
 178      else {
 179        db_query("DELETE FROM {". $table ."} WHERE cid = '%s'", $cid);
 180      }
 181    }
 182  }
 183