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<?php
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/**
 * @file
 * API for the Drupal menu system.
 */

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/**
 * @defgroup menu Menu system
 * @{
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 * Define the navigation menus, and route page requests to code based on URLs.
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 *
 * The Drupal menu system drives both the navigation system from a user
 * perspective and the callback system that Drupal uses to respond to URLs
 * passed from the browser. For this reason, a good understanding of the
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 * menu system is fundamental to the creation of complex modules. As a note,
 * this is related to, but separate from menu.module, which allows menus
 * (which in this context are hierarchical lists of links) to be customized from
 * the Drupal administrative interface.
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 *
 * Drupal's menu system follows a simple hierarchy defined by paths.
 * Implementations of hook_menu() define menu items and assign them to
 * paths (which should be unique). The menu system aggregates these items
 * and determines the menu hierarchy from the paths. For example, if the
 * paths defined were a, a/b, e, a/b/c/d, f/g, and a/b/h, the menu system
 * would form the structure:
 * - a
 *   - a/b
 *     - a/b/c/d
 *     - a/b/h
 * - e
 * - f/g
 * Note that the number of elements in the path does not necessarily
 * determine the depth of the menu item in the tree.
 *
 * When responding to a page request, the menu system looks to see if the
 * path requested by the browser is registered as a menu item with a
 * callback. If not, the system searches up the menu tree for the most
 * complete match with a callback it can find. If the path a/b/i is
 * requested in the tree above, the callback for a/b would be used.
 *
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 * The found callback function is called with any arguments specified
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 * in the "page arguments" attribute of its menu item. The
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 * attribute must be an array. After these arguments, any remaining
 * components of the path are appended as further arguments. In this
 * way, the callback for a/b above could respond to a request for
 * a/b/i differently than a request for a/b/j.
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 *
 * For an illustration of this process, see page_example.module.
 *
 * Access to the callback functions is also protected by the menu system.
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 * The "access callback" with an optional "access arguments" of each menu
 * item is called before the page callback proceeds. If this returns TRUE,
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 * then access is granted; if FALSE, then access is denied. Default local task
 * menu items (see next paragraph) may omit this attribute to use the value
 * provided by the parent item.
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 *
 * In the default Drupal interface, you will notice many links rendered as
 * tabs. These are known in the menu system as "local tasks", and they are
 * rendered as tabs by default, though other presentations are possible.
 * Local tasks function just as other menu items in most respects. It is
 * convention that the names of these tasks should be short verbs if
 * possible. In addition, a "default" local task should be provided for
 * each set. When visiting a local task's parent menu item, the default
 * local task will be rendered as if it is selected; this provides for a
 * normal tab user experience. This default task is special in that it
 * links not to its provided path, but to its parent item's path instead.
 * The default task's path is only used to place it appropriately in the
 * menu hierarchy.
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 *
 * Everything described so far is stored in the menu_router table. The
 * menu_links table holds the visible menu links. By default these are
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 * derived from the same hook_menu definitions, however you are free to
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 * add more with menu_link_save().
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 */

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/**
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 * @defgroup menu_flags Menu flags
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 * @{
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 * Flags for use in the "type" attribute of menu items.
 */
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/**
 * Internal menu flag -- menu item is the root of the menu tree.
 */
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const MENU_IS_ROOT = 0x0001;
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/**
 * Internal menu flag -- menu item is visible in the menu tree.
 */
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const MENU_VISIBLE_IN_TREE = 0x0002;
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/**
 * Internal menu flag -- menu item is visible in the breadcrumb.
 */
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const MENU_VISIBLE_IN_BREADCRUMB = 0x0004;
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/**
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 * Internal menu flag -- menu item links back to its parent.
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 */
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const MENU_LINKS_TO_PARENT = 0x0008;
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/**
 * Internal menu flag -- menu item can be modified by administrator.
 */
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const MENU_MODIFIED_BY_ADMIN = 0x0020;
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/**
 * Internal menu flag -- menu item was created by administrator.
 */
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const MENU_CREATED_BY_ADMIN = 0x0040;
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/**
 * Internal menu flag -- menu item is a local task.
 */
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const MENU_IS_LOCAL_TASK = 0x0080;
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/**
 * Internal menu flag -- menu item is a local action.
 */
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const MENU_IS_LOCAL_ACTION = 0x0100;
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/**
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 * @} End of "Menu flags".
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 */

/**
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 * @defgroup menu_item_types Menu item types
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 * @{
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 * Definitions for various menu item types.
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 *
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 * Menu item definitions provide one of these constants, which are shortcuts for
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 * combinations of @link menu_flags Menu flags @endlink.
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 */
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/**
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 * Menu type -- A "normal" menu item that's shown in menu and breadcrumbs.
 *
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 * Normal menu items show up in the menu tree and can be moved/hidden by
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 * the administrator. Use this for most menu items. It is the default value if
 * no menu item type is specified.
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 */
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define('MENU_NORMAL_ITEM', MENU_VISIBLE_IN_TREE | MENU_VISIBLE_IN_BREADCRUMB);
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/**
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 * Menu type -- A hidden, internal callback, typically used for API calls.
 *
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 * Callbacks simply register a path so that the correct function is fired
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 * when the URL is accessed. They do not appear in menus or breadcrumbs.
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 */
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const MENU_CALLBACK = 0x0000;
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/**
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 * Menu type -- A normal menu item, hidden until enabled by an administrator.
 *
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 * Modules may "suggest" menu items that the administrator may enable. They act
 * just as callbacks do until enabled, at which time they act like normal items.
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 * Note for the value: 0x0010 was a flag which is no longer used, but this way
 * the values of MENU_CALLBACK and MENU_SUGGESTED_ITEM are separate.
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 */
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define('MENU_SUGGESTED_ITEM', MENU_VISIBLE_IN_BREADCRUMB | 0x0010);
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/**
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 * Menu type -- A task specific to the parent item, usually rendered as a tab.
 *
 * Local tasks are menu items that describe actions to be performed on their
 * parent item. An example is the path "node/52/edit", which performs the
 * "edit" task on "node/52".
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 */
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define('MENU_LOCAL_TASK', MENU_IS_LOCAL_TASK | MENU_VISIBLE_IN_BREADCRUMB);
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/**
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 * Menu type -- The "default" local task, which is initially active.
 *
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 * Every set of local tasks should provide one "default" task, that links to the
 * same path as its parent when clicked.
 */
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define('MENU_DEFAULT_LOCAL_TASK', MENU_IS_LOCAL_TASK | MENU_LINKS_TO_PARENT | MENU_VISIBLE_IN_BREADCRUMB);
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/**
 * Menu type -- An action specific to the parent, usually rendered as a link.
 *
 * Local actions are menu items that describe actions on the parent item such
 * as adding a new user, taxonomy term, etc.
 */
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define('MENU_LOCAL_ACTION', MENU_IS_LOCAL_TASK | MENU_IS_LOCAL_ACTION | MENU_VISIBLE_IN_BREADCRUMB);
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/**
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 * @} End of "Menu item types".
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 */

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/**
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 * @defgroup menu_context_types Menu context types
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 * @{
 * Flags for use in the "context" attribute of menu router items.
 */

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/**
 * Internal menu flag: Invisible local task.
 *
 * This flag may be used for local tasks like "Delete", so custom modules and
 * themes can alter the default context and expose the task by altering menu.
 */
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const MENU_CONTEXT_NONE = 0x0000;
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/**
 * Internal menu flag: Local task should be displayed in page context.
 */
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const MENU_CONTEXT_PAGE = 0x0001;
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/**
 * Internal menu flag: Local task should be displayed inline.
 */
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const MENU_CONTEXT_INLINE = 0x0002;
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/**
 * @} End of "Menu context types".
 */

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/**
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 * @defgroup menu_status_codes Menu status codes
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 * @{
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 * Status codes for menu callbacks.
 */
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/**
 * Internal menu status code -- Menu item was found.
 */
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const MENU_FOUND = 1;
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/**
 * Internal menu status code -- Menu item was not found.
 */
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const MENU_NOT_FOUND = 2;
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/**
 * Internal menu status code -- Menu item access is denied.
 */
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const MENU_ACCESS_DENIED = 3;
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/**
 * Internal menu status code -- Menu item inaccessible because site is offline.
 */
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const MENU_SITE_OFFLINE = 4;
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/**
 * Internal menu status code -- Everything is working fine.
 */
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const MENU_SITE_ONLINE = 5;
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/**
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 * @} End of "Menu status codes".
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 */
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/**
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 * @defgroup menu_tree_parameters Menu tree parameters
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 * @{
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 * Parameters for a menu tree.
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 */

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 /**
 * The maximum number of path elements for a menu callback
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 */
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const MENU_MAX_PARTS = 9;
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/**
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 * The maximum depth of a menu links tree - matches the number of p columns.
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 */
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const MENU_MAX_DEPTH = 9;
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/**
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 * @} End of "Menu tree parameters".
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 */

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/**
 * Reserved key to identify the most specific menu link for a given path.
 *
 * The value of this constant is a hash of the constant name. We use the hash
 * so that the reserved key is over 32 characters in length and will not
 * collide with allowed menu names:
 * @code
 * sha1('MENU_PREFERRED_LINK') = 1cf698d64d1aa4b83907cf6ed55db3a7f8e92c91
 * @endcode
 *
 * @see menu_link_get_preferred()
 */
const MENU_PREFERRED_LINK = '1cf698d64d1aa4b83907cf6ed55db3a7f8e92c91';

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/**
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 * Returns the ancestors (and relevant placeholders) for any given path.
 *
 * For example, the ancestors of node/12345/edit are:
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 * - node/12345/edit
 * - node/12345/%
 * - node/%/edit
 * - node/%/%
 * - node/12345
 * - node/%
 * - node
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 *
 * To generate these, we will use binary numbers. Each bit represents a
 * part of the path. If the bit is 1, then it represents the original
 * value while 0 means wildcard. If the path is node/12/edit/foo
 * then the 1011 bitstring represents node/%/edit/foo where % means that
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 * any argument matches that part. We limit ourselves to using binary
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 * numbers that correspond the patterns of wildcards of router items that
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 * actually exists. This list of 'masks' is built in menu_rebuild().
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 *
 * @param $parts
 *   An array of path parts, for the above example
 *   array('node', '12345', 'edit').
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 *
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 * @return
 *   An array which contains the ancestors and placeholders. Placeholders
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 *   simply contain as many '%s' as the ancestors.
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 */
function menu_get_ancestors($parts) {
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  $number_parts = count($parts);
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  $ancestors = array();
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  $length =  $number_parts - 1;
  $end = (1 << $number_parts) - 1;
  $masks = variable_get('menu_masks', array());
  // Only examine patterns that actually exist as router items (the masks).
  foreach ($masks as $i) {
    if ($i > $end) {
      // Only look at masks that are not longer than the path of interest.
      continue;
    }
    elseif ($i < (1 << $length)) {
      // We have exhausted the masks of a given length, so decrease the length.
      --$length;
    }
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    $current = '';
    for ($j = $length; $j >= 0; $j--) {
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      // Check the bit on the $j offset.
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      if ($i & (1 << $j)) {
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        // Bit one means the original value.
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        $current .= $parts[$length - $j];
      }
      else {
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        // Bit zero means means wildcard.
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        $current .= '%';
      }
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      // Unless we are at offset 0, add a slash.
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      if ($j) {
        $current .= '/';
      }
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    }
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    $ancestors[] = $current;
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  }
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  return $ancestors;
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}

/**
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 * Unserializes menu data, using a map to replace path elements.
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 *
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 * The menu system stores various path-related information (such as the 'page
 * arguments' and 'access arguments' components of a menu item) in the database
 * using serialized arrays, where integer values in the arrays represent
 * arguments to be replaced by values from the path. This function first
 * unserializes such menu information arrays, and then does the path
 * replacement.
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 *
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 * The path replacement acts on each integer-valued element of the unserialized
 * menu data array ($data) using a map array ($map, which is typically an array
 * of path arguments) as a list of replacements. For instance, if there is an
 * element of $data whose value is the number 2, then it is replaced in $data
 * with $map[2]; non-integer values in $data are left alone.
 *
 * As an example, an unserialized $data array with elements ('node_load', 1)
 * represents instructions for calling the node_load() function. Specifically,
 * this instruction says to use the path component at index 1 as the input
 * parameter to node_load(). If the path is 'node/123', then $map will be the
 * array ('node', 123), and the returned array from this function will have
 * elements ('node_load', 123), since $map[1] is 123. This return value will
 * indicate specifically that node_load(123) is to be called to load the node
 * whose ID is 123 for this menu item.
 *
 * @param $data
 *   A serialized array of menu data, as read from the database.
 * @param $map
 *   A path argument array, used to replace integer values in $data; an integer
 *   value N in $data will be replaced by value $map[N]. Typically, the $map
 *   array is generated from a call to the arg() function.
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 *
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 * @return
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 *   The unserialized $data array, with path arguments replaced.
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 */
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function menu_unserialize($data, $map) {
  if ($data = unserialize($data)) {
    foreach ($data as $k => $v) {
      if (is_int($v)) {
        $data[$k] = isset($map[$v]) ? $map[$v] : '';
      }
    }
    return $data;
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  }
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  else {
    return array();
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  }
}

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/**
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 * Replaces the statically cached item for a given path.
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 *
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 * @param $path
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 *   The path.
 * @param $router_item
 *   The router item. Usually you take a router entry from menu_get_item and
 *   set it back either modified or to a different path. This lets you modify the
 *   navigation block, the page title, the breadcrumb and the page help in one
 *   call.
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 */
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function menu_set_item($path, $router_item) {
  menu_get_item($path, $router_item);
}

/**
 * Get a router item.
 *
 * @param $path
 *   The path, for example node/5. The function will find the corresponding
 *   node/% item and return that.
 * @param $router_item
 *   Internal use only.
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 *
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 * @return
 *   The router item, an associate array corresponding to one row in the
 *   menu_router table. The value of key map holds the loaded objects. The
 *   value of key access is TRUE if the current user can access this page.
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 *   The values for key title, page_arguments, access_arguments, and
 *   theme_arguments will be filled in based on the database values and the
 *   objects loaded.
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 */
function menu_get_item($path = NULL, $router_item = NULL) {
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  $router_items = &drupal_static(__FUNCTION__);
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  if (!isset($path)) {
    $path = $_GET['q'];
  }
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  if (isset($router_item)) {
    $router_items[$path] = $router_item;
  }
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  if (!isset($router_items[$path])) {
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    // Rebuild if we know it's needed, or if the menu masks are missing which
    // occurs rarely, likely due to a race condition of multiple rebuilds.
    if (variable_get('menu_rebuild_needed', FALSE) || !variable_get('menu_masks', array())) {
      menu_rebuild();
    }
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    $original_map = arg(NULL, $path);
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    // Since there is no limit to the length of $path, use a hash to keep it
    // short yet unique.
    $cid = 'menu_item:' . hash('sha256', $path);
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    if ($cached = cache('menu')->get($cid)) {
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      $router_item = $cached->data;
    }
    else {
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      $parts = array_slice($original_map, 0, MENU_MAX_PARTS);
      $ancestors = menu_get_ancestors($parts);
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      $router_item = db_query_range('SELECT * FROM {menu_router} WHERE path IN (:ancestors) ORDER BY fit DESC', 0, 1, array(':ancestors' => $ancestors))->fetchAssoc();
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      cache('menu')->set($cid, $router_item);
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    }
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    if ($router_item) {
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      // Allow modules to alter the router item before it is translated and
      // checked for access.
      drupal_alter('menu_get_item', $router_item, $path, $original_map);

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      $map = _menu_translate($router_item, $original_map);
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      $router_item['original_map'] = $original_map;
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      if ($map === FALSE) {
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        $router_items[$path] = FALSE;
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        return FALSE;
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      }
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      if ($router_item['access']) {
        $router_item['map'] = $map;
        $router_item['page_arguments'] = array_merge(menu_unserialize($router_item['page_arguments'], $map), array_slice($map, $router_item['number_parts']));
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        $router_item['theme_arguments'] = array_merge(menu_unserialize($router_item['theme_arguments'], $map), array_slice($map, $router_item['number_parts']));
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      }
    }
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    $router_items[$path] = $router_item;
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  }
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  return $router_items[$path];
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}

/**
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 * Execute the page callback associated with the current path.
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 *
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 * @param $path
 *   The drupal path whose handler is to be be executed. If set to NULL, then
 *   the current path is used.
 * @param $deliver
 *   (optional) A boolean to indicate whether the content should be sent to the
 *   browser using the appropriate delivery callback (TRUE) or whether to return
 *   the result to the caller (FALSE).
 */
function menu_execute_active_handler($path = NULL, $deliver = TRUE) {
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  // Check if site is offline.
  $page_callback_result = _menu_site_is_offline() ? MENU_SITE_OFFLINE : MENU_SITE_ONLINE;

  // Allow other modules to change the site status but not the path because that
  // would not change the global variable. hook_url_inbound_alter() can be used
  // to change the path. Code later will not use the $read_only_path variable.
  $read_only_path = !empty($path) ? $path : $_GET['q'];
  drupal_alter('menu_site_status', $page_callback_result, $read_only_path);

  // Only continue if the site status is not set.
  if ($page_callback_result == MENU_SITE_ONLINE) {
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    if ($router_item = menu_get_item($path)) {
      if ($router_item['access']) {
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        if ($router_item['include_file']) {
          require_once DRUPAL_ROOT . '/' . $router_item['include_file'];
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        }
        $page_callback_result = call_user_func_array($router_item['page_callback'], $router_item['page_arguments']);
      }
      else {
        $page_callback_result = MENU_ACCESS_DENIED;
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      }
    }
    else {
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      $page_callback_result = MENU_NOT_FOUND;
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    }
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  }
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  // Deliver the result of the page callback to the browser, or if requested,
  // return it raw, so calling code can do more processing.
  if ($deliver) {
    $default_delivery_callback = (isset($router_item) && $router_item) ? $router_item['delivery_callback'] : NULL;
    drupal_deliver_page($page_callback_result, $default_delivery_callback);
  }
  else {
    return $page_callback_result;
  }
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}
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/**
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 * Loads objects into the map as defined in the $item['load_functions'].
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 *
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 * @param $item
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 *   A menu router or menu link item
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 * @param $map
 *   An array of path arguments (ex: array('node', '5'))
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 *
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 * @return
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 *   Returns TRUE for success, FALSE if an object cannot be loaded.
 *   Names of object loading functions are placed in $item['load_functions'].
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 *   Loaded objects are placed in $map[]; keys are the same as keys in the
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 *   $item['load_functions'] array.
 *   $item['access'] is set to FALSE if an object cannot be loaded.
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 */
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function _menu_load_objects(&$item, &$map) {
  if ($load_functions = $item['load_functions']) {
    // If someone calls this function twice, then unserialize will fail.
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    if (!is_array($load_functions)) {
      $load_functions = unserialize($load_functions);
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    }
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    $path_map = $map;
    foreach ($load_functions as $index => $function) {
      if ($function) {
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        $value = isset($path_map[$index]) ? $path_map[$index] : '';
        if (is_array($function)) {
          // Set up arguments for the load function. These were pulled from
          // 'load arguments' in the hook_menu() entry, but they need
          // some processing. In this case the $function is the key to the
          // load_function array, and the value is the list of arguments.
          list($function, $args) = each($function);
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          $load_functions[$index] = $function;
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          // Some arguments are placeholders for dynamic items to process.
          foreach ($args as $i => $arg) {
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            if ($arg === '%index') {
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              // Pass on argument index to the load function, so multiple
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              // occurrences of the same placeholder can be identified.
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              $args[$i] = $index;
            }
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            if ($arg === '%map') {
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              // Pass on menu map by reference. The accepting function must
              // also declare this as a reference if it wants to modify
              // the map.
              $args[$i] = &$map;
            }
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            if (is_int($arg)) {
              $args[$i] = isset($path_map[$arg]) ? $path_map[$arg] : '';
            }
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          }
          array_unshift($args, $value);
          $return = call_user_func_array($function, $args);
        }
        else {
          $return = $function($value);
        }
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        // If callback returned an error or there is no callback, trigger 404.
        if ($return === FALSE) {
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          $item['access'] = FALSE;
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          $map = FALSE;
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          return FALSE;
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        }
        $map[$index] = $return;
      }
    }
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    $item['load_functions'] = $load_functions;
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  }
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  return TRUE;
}

/**
 * Check access to a menu item using the access callback
 *
 * @param $item
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 *   A menu router or menu link item
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 * @param $map
 *   An array of path arguments (ex: array('node', '5'))
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 *
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 * @return
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 *   $item['access'] becomes TRUE if the item is accessible, FALSE otherwise.
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 */
function _menu_check_access(&$item, $map) {
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  // Determine access callback, which will decide whether or not the current
  // user has access to this path.
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  $callback = empty($item['access_callback']) ? 0 : trim($item['access_callback']);
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  // Check for a TRUE or FALSE value.
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  if (is_numeric($callback)) {
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    $item['access'] = (bool) $callback;
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  }
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  else {
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    $arguments = menu_unserialize($item['access_arguments'], $map);
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    // As call_user_func_array is quite slow and user_access is a very common
    // callback, it is worth making a special case for it.
    if ($callback == 'user_access') {
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      $item['access'] = (count($arguments) == 1) ? user_access($arguments[0]) : user_access($arguments[0], $arguments[1]);
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    }
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    elseif (function_exists($callback)) {
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      $item['access'] = call_user_func_array($callback, $arguments);
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    }
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  }
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}
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/**
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 * Localize the router item title using t() or another callback.
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 *
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 * Translate the title and description to allow storage of English title
 * strings in the database, yet display of them in the language required
 * by the current user.
 *
 * @param $item
 *   A menu router item or a menu link item.
 * @param $map
 *   The path as an array with objects already replaced. E.g., for path
 *   node/123 $map would be array('node', $node) where $node is the node
 *   object for node 123.
 * @param $link_translate
 *   TRUE if we are translating a menu link item; FALSE if we are
 *   translating a menu router item.
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 *
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 * @return
 *   No return value.
 *   $item['title'] is localized according to $item['title_callback'].
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 *   If an item's callback is check_plain(), $item['options']['html'] becomes
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 *   TRUE.
 *   $item['description'] is translated using t().
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 *   When doing link translation and the $item['options']['attributes']['title']
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 *   (link title attribute) matches the description, it is translated as well.
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 */
function _menu_item_localize(&$item, $map, $link_translate = FALSE) {
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  $callback = $item['title_callback'];
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  $item['localized_options'] = $item['options'];
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  // All 'class' attributes are assumed to be an array during rendering, but
  // links stored in the database may use an old string value.
  // @todo In order to remove this code we need to implement a database update
  //   including unserializing all existing link options and running this code
  //   on them, as well as adding validation to menu_link_save().
  if (isset($item['options']['attributes']['class']) && is_string($item['options']['attributes']['class'])) {
    $item['localized_options']['attributes']['class'] = explode(' ', $item['options']['attributes']['class']);
  }
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  // If we are translating the title of a menu link, and its title is the same
  // as the corresponding router item, then we can use the title information
  // from the router. If it's customized, then we need to use the link title
  // itself; can't localize.
  // If we are translating a router item (tabs, page, breadcrumb), then we
  // can always use the information from the router item.
  if (!$link_translate || ($item['title'] == $item['link_title'])) {
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    // t() is a special case. Since it is used very close to all the time,
    // we handle it directly instead of using indirect, slower methods.
    if ($callback == 't') {
      if (empty($item['title_arguments'])) {
        $item['title'] = t($item['title']);
      }
      else {
        $item['title'] = t($item['title'], menu_unserialize($item['title_arguments'], $map));
      }
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    }
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    elseif ($callback && function_exists($callback)) {
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      if (empty($item['title_arguments'])) {
        $item['title'] = $callback($item['title']);
      }
      else {
        $item['title'] = call_user_func_array($callback, menu_unserialize($item['title_arguments'], $map));
      }
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      // Avoid calling check_plain again on l() function.
      if ($callback == 'check_plain') {
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        $item['localized_options']['html'] = TRUE;
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      }
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    }
  }
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  elseif ($link_translate) {
    $item['title'] = $item['link_title'];
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  }

  // Translate description, see the motivation above.
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  if (!empty($item['description'])) {
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    $original_description = $item['description'];
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    $item['description'] = t($item['description']);
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    if ($link_translate && isset($item['options']['attributes']['title']) && $item['options']['attributes']['title'] == $original_description) {
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      $item['localized_options']['attributes']['title'] = $item['description'];
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    }
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  }
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}

/**
 * Handles dynamic path translation and menu access control.
 *
 * When a user arrives on a page such as node/5, this function determines
 * what "5" corresponds to, by inspecting the page's menu path definition,
 * node/%node. This will call node_load(5) to load the corresponding node
 * object.
 *
 * It also works in reverse, to allow the display of tabs and menu items which
 * contain these dynamic arguments, translating node/%node to node/5.
 *
 * Translation of menu item titles and descriptions are done here to
 * allow for storage of English strings in the database, and translation
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 * to the language required to generate the current page.
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 *
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 * @param $router_item
 *   A menu router item
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 * @param $map
 *   An array of path arguments (ex: array('node', '5'))
 * @param $to_arg
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 *   Execute $item['to_arg_functions'] or not. Use only if you want to render a
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 *   path from the menu table, for example tabs.
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 *
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 * @return
 *   Returns the map with objects loaded as defined in the
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 *   $item['load_functions']. $item['access'] becomes TRUE if the item is
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 *   accessible, FALSE otherwise. $item['href'] is set according to the map.
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 *   If an error occurs during calling the load_functions (like trying to load
 *   a non existing node) then this function return FALSE.
 */
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function _menu_translate(&$router_item, $map, $to_arg = FALSE) {
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  if ($to_arg && !empty($router_item['to_arg_functions'])) {
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    // Fill in missing path elements, such as the current uid.
    _menu_link_map_translate($map, $router_item['to_arg_functions']);
  }
  // The $path_map saves the pieces of the path as strings, while elements in
  // $map may be replaced with loaded objects.
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  $path_map = $map;
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  if (!empty($router_item['load_functions']) && !_menu_load_objects($router_item, $map)) {
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    // An error occurred loading an object.
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    $router_item['access'] = FALSE;
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    return FALSE;
  }

  // Generate the link path for the page request or local tasks.
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  $link_map = explode('/', $router_item['path']);
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  if (isset($router_item['tab_root'])) {
    $tab_root_map = explode('/', $router_item['tab_root']);
  }
  if (isset($router_item['tab_parent'])) {
    $tab_parent_map = explode('/', $router_item['tab_parent']);
  }
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  for ($i = 0; $i < $router_item['number_parts']; $i++) {
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    if ($link_map[$i] == '%') {
      $link_map[$i] = $path_map[$i];
    }
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    if (isset($tab_root_map[$i]) && $tab_root_map[$i] == '%') {
      $tab_root_map[$i] = $path_map[$i];
    }
    if (isset($tab_parent_map[$i]) && $tab_parent_map[$i] == '%') {
      $tab_parent_map[$i] = $path_map[$i];
    }
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  }
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  $router_item['href'] = implode('/', $link_map);
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  $router_item['tab_root_href'] = implode('/', $tab_root_map);
  $router_item['tab_parent_href'] = implode('/', $tab_parent_map);
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  $router_item['options'] = array();
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  _menu_check_access($router_item, $map);
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  // For performance, don't localize an item the user can't access.
  if ($router_item['access']) {
    _menu_item_localize($router_item, $map);
  }
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  return $map;
}

/**
 * This function translates the path elements in the map using any to_arg
 * helper function. These functions take an argument and return an object.
 * See http://drupal.org/node/109153 for more information.
 *
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 * @param $map
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 *   An array of path arguments (ex: array('node', '5'))
 * @param $to_arg_functions
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 *   An array of helper function (ex: array(2 => 'menu_tail_to_arg'))
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 */
function _menu_link_map_translate(&$map, $to_arg_functions) {
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  $to_arg_functions = unserialize($to_arg_functions);
  foreach ($to_arg_functions as $index => $function) {
    // Translate place-holders into real values.
    $arg = $function(!empty($map[$index]) ? $map[$index] : '', $map, $index);
    if (!empty($map[$index]) || isset($arg)) {
      $map[$index] = $arg;
    }
    else {
      unset($map[$index]);
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    }
  }
}

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/**
 * Returns path as one string from the argument we are currently at.
 */
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function menu_tail_to_arg($arg, $map, $index) {
  return implode('/', array_slice($map, $index));
}

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/**
 * Loads path as one string from the argument we are currently at.
 *
 * To use this load function, you must specify the load arguments
 * in the router item as:
 * @code
 * $item['load arguments'] = array('%map', '%index');
 * @endcode
 *
 * @see search_menu().
 */
function menu_tail_load($arg, &$map, $index) {
  $arg = implode('/', array_slice($map, $index));
  $map = array_slice($map, 0, $index);
  return $arg;
}

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/**
 * This function is similar to _menu_translate() but does link-specific
 * preparation such as always calling to_arg functions
 *
 * @param $item
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 *   A menu link.
 * @param $translate
 *   (optional) Whether to try to translate a link containing dynamic path
 *   argument placeholders (%) based on the menu router item of the current
 *   path. Defaults to FALSE. Internally used for breadcrumbs.
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 *
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 * @return
 *   Returns the map of path arguments with objects loaded as defined in the
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 *   $item['load_functions'].
 *   $item['access'] becomes TRUE if the item is accessible, FALSE otherwise.
 *   $item['href'] is generated from link_path, possibly by to_arg functions.
 *   $item['title'] is generated from link_title, and may be localized.
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 *   $item['options'] is unserialized; it is also changed within the call here
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 *   to $item['localized_options'] by _menu_item_localize().
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 */
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function _menu_link_translate(&$item, $translate = FALSE) {
  if (!is_array($item['options'])) {
    $item['options'] = unserialize($item['options']);
  }
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  if ($item['external']) {
    $item['access'] = 1;
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    $map = array();
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    $item['href'] = $item['link_path'];
    $item['title'] = $item['link_title'];
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    $item['localized_options'] = $item['options'];
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  }
  else {
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    // Complete the path of the menu link with elements from the current path,
    // if it contains dynamic placeholders (%).
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    $map = explode('/', $item['link_path']);
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    if (strpos($item['link_path'], '%') !== FALSE) {
      // Invoke registered to_arg callbacks.
      if (!empty($item['to_arg_functions'])) {
        _menu_link_map_translate($map, $item['to_arg_functions']);
      }
      // Or try to derive the path argument map from the current router item,
      // if this $item's path is within the router item's path. This means
      // that if we are on the current path 'foo/%/bar/%/baz', then
      // menu_get_item() will have translated the menu router item for the
      // current path, and we can take over the argument map for a link like
      // 'foo/%/bar'. This inheritance is only valid for breadcrumb links.
      // @see _menu_tree_check_access()
      // @see menu_get_active_breadcrumb()
      elseif ($translate && ($current_router_item = menu_get_item())) {
        // If $translate is TRUE, then this link is in the active trail.
        // Only translate paths within the current path.
        if (strpos($current_router_item['path'], $item['link_path']) === 0) {
          $count = count($map);
          $map = array_slice($current_router_item['original_map'], 0, $count);
          $item['original_map'] = $map;
          if (isset($current_router_item['map'])) {
            $item['map'] = array_slice($current_router_item['map'], 0, $count);
          }
          // Reset access to check it (for the first time).
          unset($item['access']);
        }
      }
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    }
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    $item['href'] = implode('/', $map);
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    // Skip links containing untranslated arguments.
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    if (strpos($item['href'], '%') !== FALSE) {
      $item['access'] = FALSE;
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      return FALSE;
    }
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    // menu_tree_check_access() may set this ahead of time for links to nodes.
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    if (!isset($item['access'])) {
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      if (!empty($item['load_functions']) && !_menu_load_objects($item, $map)) {
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        // An error occurred loading an object.
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        $item['access'] = FALSE;
        return FALSE;
      }
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      _menu_check_access($item, $map);
    }
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    // For performance, don't localize a link the user can't access.
    if ($item['access']) {
      _menu_item_localize($item, $map, TRUE);
    }
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  }
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  // Allow other customizations - e.g. adding a page-specific query string to the
  // options array. For performance reasons we only invoke this hook if the link
  // has the 'alter' flag set in the options array.
  if (!empty($item['options']['alter'])) {
    drupal_alter('translated_menu_link', $item, $map);
  }
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  return $map;
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}

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/**
 * Get a loaded object from a router item.
 *
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 * menu_get_object() provides access to objects loaded by the current router
 * item. For example, on the page node/%node, the router loads the %node object,
 * and calling menu_get_object() will return that. Normally, it is necessary to
 * specify the type of object referenced, however node is the default.
 * The following example tests to see whether the node being displayed is of the
 * "story" content type:
 *