/**
* Finds the region in which block content is being rendered.
* Caches node regions by url. Could cause problems if a node
* is on a page twice
* @param int $nid is a node id
* return string of node region location
*/
function tnt_get_region_for_block_content($nid) {
  static $control;
  
  // create the cache name, be safe
  $cache_name = 'theme_regions_'. check_plain($_GET['q']);

  // retrieve cache object
  // $data = cache_get($cache_name, 'cache');

  // get array data from the cache object
  $data = unserialize($data->data);

  // we don't have region data for this node 
  // or we do, but it is the same node in a different region
  if ((!$data[$nid]) || ($control[$nid])) {

    if (! $control[$nid]) {
      $control[$nid] = TRUE;
    }

    // Get the function call stack and search it for block_list().
    // Reverse it for speed-efficiency.
    //   - There are usually only about 5 fns between block_list() and the bottom of the stack.
    //   - With views there can be 20 fns between block_list() the top of the stack.
    // DON'T MODIFY $stack.  Treat it as read-only.
    $stack = array_reverse(debug_backtrace());
  
    // Search for block_list().
    foreach ($stack as $i => $fn) {
      if ($fn['function'] == 'block_list') {
        // Unfortunately the first argument of block_list() is not the correct region,
        // because block_list() renders and stores all the blocks on it's first invocation.
        // So this doesn't work:
        //$vars['region'] = $fn['args'][0];
  
        // block_list() calls module_invoke() to invoke hook_block() in each module.
        // So module_invoke() is the next function UP in the reversed stack.
        // ($i is 0 for the bottom of the reversed stack.)
        // Store the parameters that module_invoke() was called with.
        $module_invoke_args = $stack[$i + 1]['args'];
  
        // Precautionary measure to save on memory consumption.
        // Probably unnecessary.
        // DON'T MODIFY $stack.
        unset($stack);
  
        // The 1st parameter is the block's module.  4th (last) parameter is the block's delta.
        // Search block_list() for 'module_invoke'.
        // See http://api.drupal.org/api/function/block_list/5
        $module = $module_invoke_args[0];
        $delta = $module_invoke_args[3];
  
        // Get and store the block regions from the database.
        // We'll reuse this data each time, so only do this on the first invocation.
        static $blocks;
        if (!isset($blocks)) {
          $blocks = array();
          $result = db_query("SELECT module, delta, region FROM blocks WHERE theme = '%s'", $GLOBALS['theme_key']);
          while ($row = db_fetch_object($result)) {
            // Store region by module then delta.
            $blocks[$row->module][$row->delta] = $row->region;
          }
        }
  
        // Set the region, from the stored regions.
        $return_region =  $blocks[$module][$delta];
      }
    }
  
    // now join the region to the data
    $data = $data ? array_merge($data, array($nid => $return_region)) : array($nid => $return_region);
    // now cache the data
    cache_set($cache_name, 'cache', serialize($data), CACHE_TEMPORARY);
  }
        return $data[$nid];
}