ding_session_cache.module

<?php
/**
 * @file
 * Implementation of a session ID index cache module to cache infomation that
 * should only be available during a sessions lifespan.
 */

/**
 * Implements hook_form_FORM_ID_alter().
 *
 * Adds configuration options to the system performance page based on the custom
 * hook_ding_session_cache_defaults() module implementations.
 */
function ding_session_cache_form_system_performance_settings_alter(&$form, &$form_state, $form_id) {
  $form['clear_cache']['#weight'] = -30;

  // Add new field-set to display the new cache options.
  $form['ding_session_cache'] = array(
    '#type' => 'fieldset',
    '#title' => t('Ding user cache'),
    '#description' => t('Configure the behaviour of the different elements cached for ding users.'),
    '#weight' => -25,
    '#tree' => TRUE,
  );

  // Calculate the cache time periods.
  $period = drupal_map_assoc(array(60, 180, 300, 600, 900, 1800, 2700, 3600, 10800, 21600, 32400, 43200, 86400), 'format_interval');

  // Get previous store default values.
  $defaults = variable_get('ding_session_cache', array());

  // Find the modules that implements hook_ding_session_cache_defautls() and
  // build the field-set around them.
  $form_elements = array();
  foreach (module_implements('ding_session_cache_defaults') as $module) {
    $function = $module . '_ding_session_cache_defaults';
    if (function_exists($function)) {
      $result = $function();
      $form['ding_session_cache'][$module] = array(
        '#type' => 'fieldset',
        '#title' => $result['titel'],
        'enabled' => array(
          '#type' => 'checkbox',
          '#title' => 'Enabled',
          '#default_value' => isset($defaults[$module]['enabled']) ? $defaults[$module]['enabled'] : $result['enabled'],
        ),
        'expire' => array(
          '#type' => 'select',
          '#title' => t('Maximum cache lifetime'),
          '#default_value' => isset($defaults[$module]['expire']) ? $defaults[$module]['expire'] : $result['enabled'],
          '#options' => $period,
        ),
      );
    }
  }

  // If non one supports this module insert an empty fieldset message.
  if (empty($form_elements)) {
    $form['ding_session_cache']['#description'] = t('There where no modules enabled that implements this cache.');
  }
}

/**
 * Store data into ding user cache.
 *
 * Notice that this function will only have effect if ding user cache have been
 * activated under performance settings in the administration interface.
 *
 * @param string $module
 *   Name of the module to store the data under (perfix).
 * @param string $cid
 *   Index used to store the data under.
 * @param mixed $data
 *   Data to store in the cache.
 */
function ding_session_cache_set($module, $cid, $data) {
  if (_ding_session_cache_enabled($module)) {
    cache_set(_ding_session_cache_get_cid($module, $cid), $data, 'cache_ding_session_cache', _ding_session_cache_get_expire($module));
  }
}

/**
 * Get cached item.
 *
 * @param string $module
 *   Name of the module that the date is stored under (prefix).
 * @param string $cid
 *   Index data is stored under.
 *
 * @return mixed
 *   If data found it's returned else FALSE.
 */
function ding_session_cache_get($module, $cid) {
  if (_ding_session_cache_enabled($module)) {
    $cache = cache_get(_ding_session_cache_get_cid($module, $cid), 'cache_ding_session_cache');
    if (isset($cache->expire) && $cache->expire > REQUEST_TIME) {
      return $cache->data;
    }
  }
  return FALSE;
}

/**
 * Clear cache entry.
 *
 * @param string $module
 *   Name of the module that the date is stored under (prefix).
 * @param string $cid
 *   Index data is stored under.
 */
function ding_session_cache_clear($module, $cid) {
  cache_clear_all(_ding_session_cache_get_cid($module, $cid), 'cache_ding_session_cache', FALSE);
}

/**
 * Implements hook_user_logout().
 *
 * Remove cached data for the user that is logging out.
 */
function ding_session_cache_user_logout($account) {
  cache_clear_all(session_id(), 'cache_ding_session_cache', TRUE);
}

/**
 * Implements hook_flush_cache().
 */
function ding_session_cache_flush_caches() {
  return 'cache_ding_session_cache';
}

/**
 * Checks if caching is activated for the module given as parameter.
 *
 * @param string $module
 *   Name of the module to check.
 *
 * @return bool
 *   TRUE if enabled else FALSE.
 */
function _ding_session_cache_enabled($module) {
  $conf = _ding_session_cache_get_conf($module);
  if (isset($conf['enabled']) && $conf['enabled']) {
    return TRUE;
  }
  return FALSE;
}

/**
 * Get expire timestamp based on the maximum cache lifetime for the module
 * given as parameter.
 *
 * @param string $module
 *   Name of the module to get the expire for.
 *
 * @return string
 *   Unix timestamp with expire date or CACHE_TEMPORARY (-1).
 */
function _ding_session_cache_get_expire($module) {
  $conf = _ding_session_cache_get_conf($module);
  if (isset($conf['expire'])) {
    return REQUEST_TIME + $conf['expire'];
  }
  return CACHE_TEMPORARY;
}

/**
 * Get session cache configuration for a given module.
 *
 * @param string $module
 *   Name of the module to get the expire for.
 *
 * @return array
 *   The configuration or an empty array if not found.
 */
function _ding_session_cache_get_conf($module) {
  // First try to load conf from database.
  $conf = variable_get('ding_session_cache', array());
  if (!isset($conf[$module])) {
    // Configuration not found, try the modules defaults.
    $function = $module . '_ding_session_cache_defaults';
    if (function_exists($function)) {
      return $function();
    }
  }
  else {
    return $conf[$module];
  }

  return array();
}

/**
 * Build cache id based on the session id.
 *
 * @param string $module
 *   Name of the module to prefix result.
 * @param string $cid
 *   Name to postfix the result.
 *
 * @return string
 *   Id that can be used in the cache.
 */
function _ding_session_cache_get_cid($module, $cid) {
  return session_id() . '_' . $module . '_' . $cid;
}