boost.module

<?php
// $Id$

/**
 * @file
 * Caches text as static files
 */

define('BOOST_CACHEABILITY_PAGES', '');
define('BOOST_COOKIE', 'DRUPAL_UID');

/**
 * Implementation of hook_menu().
 */
function boost_menu() {
  $items['admin/config/development/performance/default'] = array(
    'title' => 'Performance',
    'type' => MENU_DEFAULT_LOCAL_TASK,
  );

  $items['admin/config/development/performance/boost'] = array(
    'title' => 'Boost Settings',
    'description' => 'Configuration for Boost.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('boost_admin_settings'),
    'access arguments' => array('administer site configuration'),
    'type' => MENU_LOCAL_TASK,
    'file' => 'boost.admin.inc',
    'weight' => 0,
  );

  return $items;
}

/**
 * Implementation of hook_init(). Performs page setup tasks if page not cached.
 */
function boost_init() {
  global $user, $_boost;

  // Check if Drupal is started from index.php - could cause problems with other
  // contrib modules like ad module.
  $uid = isset($user->uid) ? $user->uid : 0;
  if (strpos($_SERVER['SCRIPT_FILENAME'], 'index.php') !== FALSE) {
    // Remove Boost cookie at logout if it still exists
    if (isset($_COOKIE[BOOST_COOKIE]) && $uid == 0) {
      boost_set_cookie($uid, REQUEST_TIME - 86400);
    }
    // Remove Boost cookie if set to -1
    elseif (isset($_COOKIE[BOOST_COOKIE]) && $_COOKIE[BOOST_COOKIE] == '-1') {
      boost_set_cookie($uid, REQUEST_TIME - 86400);
    }
    // Set Boost cookie if it doesn't exists and user is logged in
    elseif (!isset($_COOKIE[BOOST_COOKIE]) && $uid != 0) {
      boost_set_cookie($uid);
    }
  }

  $_boost = boost_transform_url();
  // Make sure the page is/should be cached according to our current configuration
  if (   strpos($_SERVER['SCRIPT_FILENAME'], 'index.php') === FALSE
      || variable_get('site_offline', 0)
      || ($_SERVER['REQUEST_METHOD'] != 'GET' && $_SERVER['REQUEST_METHOD'] != 'HEAD')
      || $_SERVER['SERVER_SOFTWARE'] === 'PHP CLI'
      || isset($_GET['nocache'])
      || $uid != 0
      ) {
    $_boost['cache_this'] = FALSE;
  }
}

/**
 * Implementation of boost_exit().
 */
function boost_exit() {
  global $_boost;
  // Bail out of caching
  if (!isset($_boost['cache_this'])) {
    if (!isset($_boost['is_cacheable'])) {
      return;
    }
    elseif (!$_boost['is_cacheable']) {
      return;
    }
  }
  elseif ($_boost['cache_this'] == FALSE) {
    return;
  }
  elseif (!$_boost['is_cacheable']) {
    return;
  }

  // Get the important data
  $data = ob_get_contents();
  $header_info = boost_get_header_info();

  // Get cache info
  $info = boost_match_header_attributes($header_info);
  if ($info['enabled'] === FALSE) {
    return;
  }

  // attach extension to filename
  $_boost['filename'] .= '.' . $info['extension'];
  // Add note to bottom of content
  if ($info['commment_start'] && $info['commment_end']) {
    $expire = $info['lifetime_max'];
    $cached_at = date('Y-m-d H:i:s', REQUEST_TIME);
    $expires_at = date('Y-m-d H:i:s', REQUEST_TIME + $expire);
    $note = "\n" . $info['commment_start'] . 'Page cached by Boost @ ' . $cached_at . ', expires @ ' . $expires_at . ', lifetime ' . format_interval($expire) . $info['commment_end'];
    $data .= $note;
  }
  // Write Info
  if ($_boost['filename'] && !is_file($_boost['filename'])) {
    if(!is_dir($_boost['directory'])) {
      mkdir($_boost['directory'], 0777, TRUE);
    }
    file_put_contents($_boost['filename'], $data, LOCK_EX);
  }
}

/**
 * Implementation of hook_cron(). Performs periodic actions.
 */
function boost_cron() {
  // Remove expired files from the cache
  global $_boost;
  if (isset($_boost['base_dir'])) {
    _boost_rmdir($_boost['base_dir'], FALSE);
  }
}

/*
 * Implementation of hook_flush_caches(). Deletes all static files.
 */
function boost_flush_caches() {
  // Remove all files from the cache
  global $_boost;
  if (isset($_boost['base_dir'])) {
    _boost_rmdir($_boost['base_dir'], TRUE);
  }
  return;
}

/**
 * Given a URL give back eveything we know
 *
 * @param $url
 *   Full URL
 * @param $b_path
 *   Base Path
 */
function boost_transform_url($url = NULL, $b_path = NULL) {
  global $base_root, $base_path;
  $items = &drupal_static(__FUNCTION__);

  // Set defaults if none passed in
  if ($url === NULL) {
    $url = $base_root . request_uri();
  }
  if ($b_path == NULL) {
    $b_path = $base_path;
  }
  $hash = $url . ' ' . $b_path;

  if (!isset($items[$hash])) {
    $parts = boost_parse_url($url, $b_path);
    if (!$parts) {
      $items[$hash] = array('cache_this' => FALSE);
      return $items[$hash];
    }
    $parts['base_dir'] = 'cache/normal/' . $parts['host'] . $b_path;
    $parts['filename'] = $parts['base_dir'] . $parts['path'] . '_' . $parts['query'];
    $parts['directory'] = dirname($parts['filename']);

    // Get the internal path (node/8)
    if (drupal_is_front_page()) {
      $parts['normal_path'] = variable_get('site_frontpage', 'node');
    }
    else {
      $parts['normal_path'] = drupal_get_normal_path($parts['path']);
    }
    // Get the alias (content/about-us)
    $parts['path_alias'] = drupal_get_path_alias($parts['normal_path']);
    // Get all args
    $args = arg(NULL, $parts['normal_path']);
    // Prevent array warnings
    $args[0] = empty($args[0]) ? '' : $args[0];
    $args[1] = empty($args[1]) ? '' : $args[1];
    $args[2] = empty($args[2]) ? '' : $args[2];
    $parts['args'] = $args;

    // Get content type
    $parts = _boost_get_menu_router($parts);
    // See if url is cacheable
    $parts = boost_is_cacheable($parts);
    $items[$hash] = $parts;
  }

  return $items[$hash];
}

/**
 * parse_url that takes into account the base_path
 *
 * @param $url
 *   Full URL
 * @param $b_path
 *   Base Path
 */
function boost_parse_url($url = NULL, $b_path = NULL) {
  global $base_root, $base_path;
  // Set defaults
  if ($url === NULL) {
    $url = $base_root . request_uri();
  }
  if ($b_path == NULL) {
    $b_path = $base_path;
  }

  // parse url
  $parts = parse_url($url);
  if (empty($parts['host']) || empty($parts['path'])) {
    return FALSE;
  }
  if (!isset($parts['query'])) {
    $parts['query'] = '';
  }
  $parts['path'] = str_replace($b_path, '', $parts['path']);
  $parts['base_path'] = $b_path;
  $parts['query_array'] = array();
  parse_str($parts['query'], $parts['query_array']);

  // get page number and simple query for DB
  if (!empty($parts['query_array'])) {
    $query = array();
    foreach ($parts['query_array'] as $key => $val) {
      if ($key != 'q' && $key != 'destination' && $key != 'page' && !empty($val)) {
        $query[$key] = $val;
      }
      if ($key == 'page' && is_numeric($val)) {
        $parts['page_number'] = $val;
      }
    }
    ksort($query);
    $parts['query_db'] = str_replace('&amp;', '&', urldecode(http_build_query($query)));
  }

  // Get fully decoded URL
  $decoded1 = urldecode($parts['base_path'] . $parts['path'] . '_' . $parts['query']);
  $decoded2 = urldecode($decoded1);
  while ($decoded1 != $decoded2) {
    $decoded1 = urldecode($decoded2);
    $decoded2 = urldecode($decoded1);
  }
  $decoded = $decoded2;
  unset($decoded2);
  unset($decoded1);

  $parts['url_full'] = $parts['host'] . $parts['base_path'] . $parts['path'] . '_' . $parts['query'];
  $parts['url'] = $url;
  $parts['url_decoded'] = $decoded;
  return $parts;
}

/**
 * Determines whether a given url can be cached or not by boost.
 *
 * TODO: Add in support for the menu_item
 *
 * @param $parts
 *   $parts
 *
 * @return $parts
 */
function boost_is_cacheable($parts) {
  // Set local variables
  $path = $parts['path'];
  $query = $parts['query'];
  $full = $parts['url_full'];
  $normal_path = $parts['normal_path'];
  $alias = $parts['path_alias'];
  $decoded = $parts['url_decoded'];

  // Never cache
  //  the user autocomplete/login/registration/password/reset/logout pages
  //  any admin pages
  //  comment reply pages
  //  node add page
  //  openid login page
  //  URL variables that contain / or \
  //  if incoming URL contains '..' or null bytes
  //  if decoded URL contains :// outside of the host portion of the url
  //  Limit the maximum directory nesting depth of the path
  //  Do not cache if destination is set
  if (   $normal_path == 'user'
      || preg_match('!^user/(autocomplete|login|register|password|reset|logout)!', $normal_path)
      || preg_match('!^admin!', $normal_path)
      || preg_match('!^comment/reply!', $normal_path)
      || preg_match('!^node/add!', $normal_path)
      || preg_match('!^openid/authenticate!', $normal_path)
      || strpos($query, '/') !== FALSE
      || strpos($query, "\\") !== FALSE
      || strpos($full, '..') !== FALSE
      || strpos($full, "\0") !== FALSE
      || count(explode('/', $path)) > 10
      || strpos($decoded, "://") !== FALSE
      || !empty($query_array['destination'])
    ) {
    $parts['is_cacheable'] = FALSE;
    return $parts;
  }

  // Check for reserved characters if on windows
  // http://en.wikipedia.org/wiki/Filename#Reserved_characters_and_words
  // " * : < > |
  $chars = '"*:<>|';
  if (stristr(PHP_OS, 'WIN') && preg_match("/[" . $chars . "]/", $full)) {
    $parts['is_cacheable'] = FALSE;
    return $parts;
  }

  // Match the user's cacheability settings against the path
  // See http://api.drupal.org/api/function/block_block_list_alter/7
  $visibility = variable_get('boost_cacheability_option', BLOCK_VISIBILITY_NOTLISTED);
  $pages_setting = variable_get('boost_cacheability_pages', BOOST_CACHEABILITY_PAGES);
  if ($pages_setting) {
    // Convert path string to lowercase. This allows comparison of the same path
    // with different case. Ex: /Page, /page, /PAGE.
    $pages = drupal_strtolower($pages_setting);
    if ($visibility < BLOCK_VISIBILITY_PHP) {
      // Convert the alias to lowercase
      $path = drupal_strtolower($alias);
      // Compare the lowercase internal and lowercase path alias (if any).
      $page_match = drupal_match_path($path, $pages);
      if ($path != $normal_path) {
        $page_match = $page_match || drupal_match_path($normal_path, $pages);
      }
      // When 'boost_cacheability_option' has a value of 0 (BLOCK_VISIBILITY_NOTLISTED),
      // Boost will cache all pages except those listed in 'boost_cacheability_pages'.
      // When set to 1 (BLOCK_VISIBILITY_LISTED), Boost will only cache those
      // pages listed in 'boost_cacheability_pages'.
      $page_match = !($visibility xor $page_match);
    }
    elseif (module_exists('php')) {
      $page_match = php_eval($pages_setting);
    }
    else {
      $page_match = FALSE;
    }
  }
  else {
    $page_match = TRUE;
  }
  $parts['is_cacheable'] = $page_match;
  if (!$parts['is_cacheable']) {
    return $parts;
  }

  // Invoke hook_boost_is_cacheable($path)
  $modules = boost_module_implements('boost_is_cacheable', 'boost');
  foreach ($modules as $module) {
    if (($result = module_invoke($module, 'boost_is_cacheable', $parts)) !== NULL) {
      return $result;
    }
  }
}

/**
 * Implementation of hook_boost_is_cacheable().
 *
 * TODO support for node types, etc.
 *
 * @param $parts
 *   info about this request
 *
 * @return $parts
 */
function boost_boost_is_cacheable($parts) {
  $parts['is_cacheable'] = TRUE;
  return $parts;
}

/**
 * Sets a special cookie preventing authenticated users getting served pages
 * from the static page cache.
 *
 * @param $uid
 *   User ID Number
 * @param $expires
 *   Expiration time
 */
function boost_set_cookie($uid, $expires = NULL) {
  if (!$expires) {
    $expires = ini_get('session.cookie_lifetime');
    $expires = (!empty($expires) && is_numeric($expires)) ? REQUEST_TIME + (int)$expires : 0;
    setcookie(BOOST_COOKIE, strval($uid), $expires, ini_get('session.cookie_path'), ini_get('session.cookie_domain'), ini_get('session.cookie_secure') == '1');
  }
  else {
    setcookie(BOOST_COOKIE, '0', $expires, ini_get('session.cookie_path'), ini_get('session.cookie_domain'), ini_get('session.cookie_secure') == '1');
  }
}

/**
 * Gets menu router contex
 *
 * Allows for any content type to have it's own cache expiration among other things.
 *
 * @param $parts
 *
 * @return $parts
 *
 */
function _boost_get_menu_router($parts) {
  // Declare array keys
  $router_item = array();
  $router_item['page_type'] = '';
  $router_item['page_id'] = '';
  // Load the menu item
  $item = menu_get_item($parts['normal_path']);
  if (is_array($item)) {
    $router_item += $item;
  }

  // Get any extra arguments
  $menu_args = arg(NULL, $router_item['path']);
  $diff = array();
  foreach ($parts['args'] as $key => $value) {
    if (!empty($value) && $value !== $menu_args[$key] && $menu_args[$key] !== '%') {
      $diff[] = $value;
    }
  }
  if (!empty($diff)) {
    $router_item['extra_arguments'] = implode('/', $diff);
  }
  else {
    $router_item['extra_arguments'] = '';
  }

  $parts['menu_item'] = $router_item;
  // Invoke hook_boost_menu_router($router_item)
  $modules = boost_module_implements('boost_menu_router', 'boost');
  foreach ($modules as $module) {
    if (($result = module_invoke($module, 'boost_menu_router', $parts)) !== NULL) {
      return $result;
    }
  }
}

/**
 * Implementation of hook_boost_menu_router().
 *
 * TODO Better support for arguments.
 *
 * @param $parts
 *   info about this request
 *
 * @return $parts
 */
function boost_boost_menu_router($parts) {
  $router_item = $parts['menu_item'];
  // Handle nodes
  if ($parts['args'][0] == 'node' && is_numeric($parts['args'][1])) {
    $node = node_load($parts['args'][1]);
    $parts['menu_item']['page_callback'] = 'node';
    $parts['menu_item']['page_id'] = $parts['args'][1];
    if ($node) {
      $parts['menu_item']['page_type'] = $node->type;
    }
    return $parts;
  }
  // Handle taxonomy
  if ($parts['args'][0] == 'taxonomy' && is_numeric($parts['args'][2])) {
    $term = taxonomy_term_load($parts['args'][2]);
    $parts['menu_item']['page_callback'] = 'taxonomy';
    $parts['menu_item']['page_id'] = $parts['args'][2];
    if ($term) {
      $vocab = taxonomy_vocabulary_load($term->vid);
      $parts['menu_item']['page_type'] = $vocab->name;
    }
    return $parts;
  }
  // Handle users
  if ($parts['args'][0] == 'user' && is_numeric($parts['args'][1])) {
    $user = user_load($parts['args'][1]);
    $parts['menu_item']['page_callback'] = 'user';
    $parts['menu_item']['page_id'] = $parts['args'][1];
    if ($user !== FALSE) {
      $parts['menu_item']['page_type'] = implode(', ', $user->roles);
    }
    return $parts;
  }
  // Handle views
  if ($router_item['page_callback'] == 'views_page') {
    $parts['menu_item']['page_callback'] = 'view';
    $parts['menu_item']['page_type'] = array_shift($router_item['page_arguments']);
    $parts['menu_item']['page_id'] = array_shift($router_item['page_arguments']);
    // See http://drupal.org/node/651798 for the reason why this if is needed
    if (is_array($parts['menu_item']['page_id'])) {
      $parts['menu_item']['page_id'] = array_shift($parts['menu_item']['page_id']);
    }
    return $parts;
  }

  // Handle panels
  if ($parts['menu_item']['page_callback'] == 'page_manager_page_execute') {
    $subtask_id = array_shift($parts['menu_item']['page_arguments']);
    $page = page_manager_page_load($subtask_id);
    $task = page_manager_get_task($page->task);
    if ($function = ctools_plugin_get_function($task, 'page callback')) {
      $parts['menu_item']['page_callback'] = $function;
    }
    $parts['menu_item']['page_type'] = $page->task;
    $parts['menu_item']['page_id'] = $page->name;
    return $parts;
  }

  // Try to handle everything else
  elseif (is_array($parts['menu_item']['page_arguments'])) {
    foreach ($parts['menu_item']['page_arguments'] as $string) {
      if (is_string($string) && empty($parts['menu_item']['page_type'])) {
        $parts['menu_item']['page_type'] = $string;
      }
      elseif (is_string($string)) {
        $parts['menu_item']['page_id'] .= $string;
      }
    }
  }
  // If router doesn't hold the the arguments, get them from the URL.
  if (empty($parts['menu_item']['page_type'])) {
    $parts['menu_item']['page_type'] = $parts['menu_item']['extra_arguments'];
  }
  elseif (empty($parts['menu_item']['page_id'])) {
    $parts['menu_item']['page_id'] = $parts['menu_item']['extra_arguments'];
  }

  // Try populating with the query string
  if (empty($parts['menu_item']['page_type']) && !empty($parts['query_db'])) {
    $parts['menu_item']['page_type'] = $parts['query_db'];
  }
  elseif (empty($router_item['page_id']) && !empty($parts['query_db'])) {
    $parts['menu_item']['page_id'] = $parts['query_db'];
  }

  return $parts;
}

/**
 * Alters module_implements to set a hook to fire at the end
 *
 * @param $hook
 *   name of hook
 * @param $name
 *   module name to shift to the end of the array
 *
 * @return array
 */
function boost_module_implements($hook, $name) {
  $modules = module_implements($hook);
  // Make $names built in hook the last one.
  $pos = array_search($name, $modules);
  if ($pos !== FALSE) {
    $temp = $modules[$pos];
    unset($modules[$pos]);
    $modules[] = $temp;
  }
  return $modules;
}

/**
 * Gets and parses the header info.
 *
 * @see drupal_send_headers()
 *
 * @return array
 *   array contains info about the page that is about to be sent
 */
function boost_get_header_info() {
  $headers = drupal_get_http_header();
  $status = '200 OK';
  $status_number = '200';
  $content_type = 'text/html; charset=utf-8';
  $content_type_basic = 'text/html';
  $charset = 'utf-8';

  foreach ($headers as $name_lower => $value) {
    if ($name_lower == 'status') {
      $status = $value;
    }
    elseif ($name_lower == 'content-type') {
      $content_type = $value;
    }
  }

  preg_match('!^(\d+)!', $status, $matches);
  if (isset($matches[1])) {
    $status_number = (int) $matches[1];
  }
  $content_type_info = explode('; charset=', $content_type);
  $content_type_basic = array_shift($content_type_info);
  if (!empty($content_type_info)) {
    $charset = array_shift($content_type_info);
  }

  return array(
    'status' => $status,
    'status-number' => $status_number,
    'content-type' => $content_type,
    'content-type-basic' => $content_type_basic,
    'charset' => $charset,
    'headers_sent' => headers_sent(),
  );
}

/**
 * Given header info, match it to a file extension
 *
 * @param $header_info
 *   array contains header info
 *
 * @return array
 */
function boost_match_header_attributes($header_info) {
  $type = $header_info['content-type-basic'];
  $enabled = variable_get('boost_enabled_' . $type, -1);
  if ($enabled === -1) {
    boost_get_storage_types();
    $enabled = variable_get('boost_enabled_' . $type, -1);
    if ($enabled === -1) {
      variable_set('boost_enabled_' . $type, FALSE);
      $enabled = FALSE;
    }
  }
  if (!$enabled) {
    return array('enabled' => FALSE);
  }

  $keys = array(
    'enabled',
    'extension',
    'lifetime_max',
    'lifetime_min',
    'commment_start',
    'commment_end',
  );
  $info = array();
  foreach ($keys as $key) {
    $info[$key] = variable_get('boost_' . $key . '_' . $type, -1);
    if ($info[$key] === -1) {
      return array('enabled' => FALSE);
    }
  }
  return $info;
}

/**
 * Get the storage types for the boost cache
 *
 * @return $types
 *   array('title' => array('content-type' => $values));
 */
function boost_get_storage_types() {
  $primary_types = array();
  $secondary_types = array();

  // Force boost to be last in the array
  $modules = boost_module_implements('boost_storage_types', 'boost');

  // Module with the lightest weight runs last. They will then be able to change
  // the defaults and modules that are heavier
  $modules = array_reverse($modules);
  foreach ($modules as $module) {
    // Invoke hook_boost_storage_types()
    if (($result = module_invoke($module, 'boost_storage_types')) !== NULL) {
      foreach ($result as $key => $values) {
        if (!empty($values['variants'])) {
          foreach ($values['variants'] as $type) {
            $secondary_types[$type] = $values;
            unset($secondary_types[$type]['variants']);
          }
        }
        unset($values['variants']);
        $primary_types[$key] = $values;
      }
    }
  }

  // Merge it all back together
  $merged = array_merge($secondary_types, $primary_types);
  $types = array();
  foreach ($merged as $type => $values) {
    if ($values['title']) {
      $title = $values['title'];
      unset($values['title']);
      $types[$title][$type] = $values;
    }
  }

  // Apply what's saved in the database
  $keys = array(
    'enabled',
    'extension',
    'lifetime_max',
    'lifetime_min',
    'commment_start',
    'commment_end',
  );
  foreach ($types as $title => $content_types) {
    foreach ($content_types as $type => $values) {
      foreach ($keys as $key) {
        $types[$title][$type][$key] = variable_get('boost_' . $key . '_' . $type, $values[$key]);
        // Set variable in DB if it has never been set before
        if (variable_get('boost_' . $key . '_' . $type, -1) === -1) {
          variable_set('boost_' . $key . '_' . $type, $values[$key]);
        }
      }
    }
  }

  return $types;
}

/**
 * Implementation of hook_boost_storage_types().
 *
 * @return $types
 */
function boost_boost_storage_types() {
  $types = array();

  $types['text/html'] = array(
    'title'           => t('HTML'),
    'description'     => t('HTML output, usually a webpage'),
    'extension'       => 'html',
    'enabled'         => TRUE,
    'lifetime_max'    => 3600,
    'lifetime_min'    => 0,
    'commment_start'  => '<!-- ',
    'commment_end'    => ' -->',
    'variants'        => array(),
  );
  $types['text/xml'] = array(
    'title'           => t('XML'),
    'description'     => t('XML output, usually a feed'),
    'extension'       => 'xml',
    'enabled'         => FALSE,
    'lifetime_max'    => 3600,
    'lifetime_min'    => 0,
    'commment_start'  => '<!-- ',
    'commment_end'    => ' -->',
    'variants'        => array(
      'application/xml',
      'application/rss',
      'application/rss+xml',
    ),
  );
  $types['text/javascript'] = array(
    'title'           => t('AJAX/JSON'),
    'description'     => t('JSON output, usually a response to a AJAX request'),
    'extension'       => 'json',
    'enabled'         => FALSE,
    'lifetime_max'    => 3600,
    'lifetime_min'    => 0,
    'commment_start'  => '/* ',
    'commment_end'    => ' */',
    'variants'        => array(),
  );
  return $types;
}

/**
 * Recursive version of rmdir(); use with extreme caution.
 *
 * @param $dir
 *   the top-level directory that will be recursively removed
 */
function _boost_rmdir($dir, $flush = TRUE) {
  static $lifetimes = array();
  // Map extensions to cache lifetimes
  if (empty($lifetimes)) {
    $types = boost_get_storage_types();
    foreach ($types as $title => $content_types) {
      foreach ($content_types as $type => $values) {
        $lifetimes[$values['extension']] = $values['lifetime_max'];
      }
    }
  }

  if (is_dir($dir)) {
    $objects = scandir($dir);
    foreach ($objects as $object) {
      $empty_dir = TRUE;
      if ($object != "." && $object != "..") {
        $file = $dir . "/" . $object;
        if (is_dir($file)) {
          rrmdir($file);
        }
        elseif ($flush) {
          unlink($file);
        }
        else {
          // Handle gzipped files eventually
          // Need to support multi level cache expiration per content type
          $ext = substr(strrchr($file, '.'), 1);
          $age = boost_file_get_age($file);
          if (isset($lifetimes[$ext]) && $age > $lifetimes[$ext]) {
            unlink($file);
          }
          else {
            $empty_dir = FALSE;
          }
        }
      }
    }
    reset($objects);
    if ($empty_dir) {
      rmdir($dir);
    }
  }
}

/**
 * Returns the age of a cached file, measured in seconds since it was last
 * updated.
 *
 * @param $filename
 *   Name of cached file
 * @return int
 */
function boost_file_get_age($filename) {
  return REQUEST_TIME - filemtime($filename);
}