uuid_file.module

<?php
/**
 * @file
 * UUID Files module file.
 */

/**
 * Implements hook_menu().
 */
function uuid_file_menu() {
  $items = array();
  
  $items['file-uuid'] = array(
    'title' => 'File download',
    'page callback' => 'uuid_file_stream_download',
    'page arguments' => array(1),
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
  
  return $items;
}

/**
 * Implements hook_stream_wrappers(). 
 */
function uuid_file_stream_wrappers() {
  return array(
    'uuid' => array(
      'name' => t('UUID File Stream'),
      'class' => 'UuidFileStreamWrapper',
      'description' => t('Local Files which are using their UUID as resource locator.'),
      'type' => STREAM_WRAPPERS_LOCAL_NORMAL,
    ),
  );
}

/**
 * Menu callback for UUID file stream. 
 */
function uuid_file_stream_download($pseudo) {
  $pieces = explode('.', $pseudo);
  $uuid = array_shift($pieces);
  
  $uri = db_select('file_managed', 'f')
  ->fields('f', array('uri'))
  ->condition('f.uuid', $uuid)
  ->execute()->fetchField();
  
  if ($uri) {
    $scheme = file_uri_scheme($uri);
    $target = file_uri_target($uri);
    $args = explode('/', $target);
    array_unshift($args, $scheme);
    
    if (isset($_GET['style']) && ($style = image_style_load($_GET['style']))) {
      array_unshift($args, $style);
      call_user_func_array('image_style_deliver', $args);
    }
    else {
      call_user_func_array('file_download', $args);
    }
  }
  
  return MENU_NOT_FOUND;
}

/**
 * Returns a file object by a given uri.
 * 
 * @param $uri
 *  A string containing a valid uri.
 * 
 * @return
 *  A file entity object, FALSE when there's no file for the given uri.
 */
function uuid_file_by_uri($uri) {
  $files = &drupal_static(__FUNCTION__, array());
  if (isset($files[$uri])) {
    return $files[$uri];
  }
  
  if (strpos($uri, '://styles/')) {
    // Obviously this is an image style uri.
    // We have to manually extract the file's uri.
    $scheme = file_uri_scheme($uri);
    $target = file_uri_target($uri);
    $pieces = explode('/' . $scheme . '/', $target);
    // This should be the file target.
    $target = !empty($pieces[1]) ? $pieces[1] : $target;
    // Try to re-construct the source uri.
    $uri = $scheme . '://' . $target;
  }
  
  $files[$uri] = FALSE;
  $query = new EntityFieldQuery();
  $query->entityCondition('entity_type', 'file');
  $query->propertyCondition('uri', $uri);
  $result = $query->execute();
  if (!empty($result['file'])) {
    $stub = reset($result['file']);
    $files[$uri] = file_load($stub->fid);
  }
  
  return $files[$uri];
}

/**
 * Returns a possible file extension for a given MIME type.
 * 
 * @param $mime
 *  A valid MIME type as string.
 * 
 * @return
 *  When found, a possible file extension as string.
 *  Otherwise, the return value is an empty string.
 */
function uuid_file_extension_by_mime($mime) {
  $mapping = &drupal_static(__FUNCTION__, array());
  if (!isset($mapping[$mime])) {
    $mapping[$mime] = '';
    require_once 'includes/file.mimetypes.inc';
    $mimetype_mapping = file_mimetype_mapping();
    foreach ($mimetype_mapping['extensions'] as $extension => $mapkey) {
      $mapping[$mimetype_mapping['mimetypes'][$mapkey]] = $extension;
    }
  }
  return $mapping[$mime];
}