gistfile1.aw

<?php

// media_gallery.module

function media_gallery_menu() {
  $items['media-gallery/detail/%node/%file'] = array(
    'page callback' => 'media_gallery_detail_page',
    'page arguments' => array(2, 3),
    'access callback' => 'node_access',
    'access arguments' => array('view', 2),
    'file' => 'media_gallery.pages.inc',
    'expire callback' => 'media_gallery_detail_page_expire',
    'expire arguments' => array('file'),
  );
  return $items;
}

function media_gallery_detail_page_expire($path, $type, $file) {
  switch ($type) {
    case 'file':
      if (isset($file->media_title)) {
        $query = new EntityFieldQuery();
        $query->entityCondition('entity_type', 'node', '=')
          ->entityCondition('bundle', 'media_gallery', '=')
          ->fieldCondition('media_gallery_media', 'fid', $file->fid, '=');

        if ($res = $query->execute()) {
          $expire_paths = array();
          foreach ($res['node'] as $node) {
            $expire_paths[] = str_replace(array('%node', '%file'), array($node->nid, $file->fid), $path);
          }
        }
      }
      break;
  }
  return $expire_paths;
}


// expire.module

function expire_file_update($file) {
  expire_expire_path('file', $file->fid, $file);
}

function expire_node_update($node) {
  expire_expire_path('node', $node->nid, $node);
}

function expire_expire_path($type, $id, $obj) {
  $tag_paths = expire_tag_paths();
  $expire_paths = array();

  if (isset($tag_paths[$type])) {
    foreach ($tag_paths[$type] as $item) {
      if (isset($item['callback'])) {
        $expire_paths[] = $item['callback']($item['path'], $type, $obj);
      }
      else {
        $expire_paths[] = str_replace('%' . $type, $id, $item['path']);
      }
    }
  }
  expire_cache_derivative($expire_paths);
}

function expire_tag_paths() {
  if (!$cache= cache_get('expire_tag_paths')) {
    $menus = module_invoke_all('menu');
    drupal_alter('menu', $menus);
    $tag_paths = array();
    foreach ($menus as $path => $info) {
      if (!empty($info['expire arguments'])) {
        foreach ($info['expire arguments'] as $tag) {
          if (!isset($tag_paths[$tag])) {
            $tag_paths[$tag] = array();
          }

          $path_item = array('path' => $path);
          if (isset($info['expire callback'])) {
            $path_item['callback'] = $info['expire callback'];
          }
          $tag_paths[$tag][] = $path_item;
        }
      }
    }
    cache_set('expire_tag_paths', $tag_paths);
  }
  else {
    $tag_paths = $cache->data;
  }
  return $tag_paths;
}