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<?php
// $Id$

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/**
 * @file
 * API for loading and interacting with Drupal modules.
 */

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/**
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 * Load all the modules that have been enabled in the system table.
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 */
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function module_load_all() {
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  foreach (module_list(TRUE, FALSE) as $module) {
    drupal_load('module', $module);
  }
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}

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/**
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 * Collect a list of all loaded modules. During the bootstrap, return only
 * vital modules. See bootstrap.inc
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 *
 * @param $refresh
 *   Whether to force the module list to be regenerated (such as after the
 *   administrator has changed the system settings).
 * @param $bootstrap
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 *   Whether to return the reduced set of modules loaded in "bootstrap mode"
 *   for cached pages. See bootstrap.inc.
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 * @param $sort
 *   By default, modules are ordered by weight and filename, settings this option
 *   to TRUE, module list will be ordered by module name.
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 * @param $fixed_list
 *   (Optional) Override the module list with the given modules. Stays until the
 *   next call with $refresh = TRUE.
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 * @return
 *   An associative array whose keys and values are the names of all loaded
 *   modules.
 */
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function module_list($refresh = FALSE, $bootstrap = TRUE, $sort = FALSE, $fixed_list = NULL) {
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  static $list = array(), $sorted_list;
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  if (empty($list) || $refresh || $fixed_list) {
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    unset($sorted_list);
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    $list = array();
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    if ($fixed_list) {
      foreach ($fixed_list as $name => $module) {
        drupal_get_filename('module', $name, $module['filename']);
        $list[$name] = $name;
      }
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    }
    else {
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      if ($bootstrap) {
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        $result = db_query("SELECT name, filename FROM {system} WHERE type = 'module' AND status = 1 AND bootstrap = 1 ORDER BY weight ASC, filename ASC");
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      }
      else {
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        $result = db_query("SELECT name, filename FROM {system} WHERE type = 'module' AND status = 1 ORDER BY weight ASC, filename ASC");
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      }
      while ($module = db_fetch_object($result)) {
        if (file_exists($module->filename)) {
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          drupal_get_filename('module', $module->name, $module->filename);
          $list[$module->name] = $module->name;
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        }
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      }
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    }
  }
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  if ($sort) {
    if (!isset($sorted_list)) {
      $sorted_list = $list;
      ksort($sorted_list);
    }
    return $sorted_list;
  }
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  return $list;
}

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/**
 * Rebuild the database cache of module files.
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 *
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 * @return
 *   The array of filesystem objects used to rebuild the cache.
 */
function module_rebuild_cache() {
  // Get current list of modules
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  $files = drupal_system_listing('/\.module$/', 'modules', 'name', 0);
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  // Extract current files from database.
  system_get_files_database($files, 'module');

  ksort($files);

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  // Set defaults for module info
  $defaults = array(
    'dependencies' => array(),
    'dependents' => array(),
    'description' => '',
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    'version' => NULL,
    'php' => DRUPAL_MINIMUM_PHP,
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  );

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  foreach ($files as $filename => $file) {
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    // Look for the info file.
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    $file->info = drupal_parse_info_file(dirname($file->filename) . '/' . $file->name . '.info');
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    // Skip modules that don't provide info.
    if (empty($file->info)) {
      unset($files[$filename]);
      continue;
    }
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    // Merge in defaults and save.
    $files[$filename]->info = $file->info + $defaults;
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    // Invoke hook_system_info_alter() to give installed modules a chance to
    // modify the data in the .info files if necessary.
    drupal_alter('system_info', $files[$filename]->info, $files[$filename]);

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    // Log the critical hooks implemented by this module.
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    $bootstrap = 0;
    foreach (bootstrap_hooks() as $hook) {
      if (module_hook($file->name, $hook)) {
        $bootstrap = 1;
        break;
      }
    }

    // Update the contents of the system table:
    if (isset($file->status) || (isset($file->old_filename) && $file->old_filename != $file->filename)) {
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      db_query("UPDATE {system} SET info = '%s', name = '%s', filename = '%s', bootstrap = %d WHERE filename = '%s'", serialize($files[$filename]->info), $file->name, $file->filename, $bootstrap, $file->old_filename);
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    }
    else {
      // This is a new module.
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      $files[$filename]->status = 0;
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      db_query("INSERT INTO {system} (name, info, type, filename, status, bootstrap) VALUES ('%s', '%s', '%s', '%s', %d, %d)", $file->name, serialize($files[$filename]->info), 'module', $file->filename, 0, $bootstrap);
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    }
  }
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  $files = _module_build_dependencies($files);
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  return $files;
}
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/**
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 * Find dependencies any level deep and fill in dependents information too.
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 *
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 * If module A depends on B which in turn depends on C then this function will
 * add C to the list of modules A depends on. This will be repeated until
 * module A has a list of all modules it depends on. If it depends on itself,
 * called a circular dependency, that's marked by adding a nonexistent module,
 * called -circular- to this list of modules. Because this does not exist,
 * it'll be impossible to switch module A on.
 *
 * Also we fill in a dependents array in $file->info. Using the names above,
 * the dependents array of module B lists A.
 *
 * @param $files
 *   The array of filesystem objects used to rebuild the cache.
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 * @return
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 *   The same array with dependencies and dependents added where applicable.
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 */
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function _module_build_dependencies($files) {
  do {
    $new_dependency = FALSE;
    foreach ($files as $filename => $file) {
      // We will modify this object (module A, see doxygen for module A, B, C).
      $file = &$files[$filename];
      if (isset($file->info['dependencies']) && is_array($file->info['dependencies'])) {
        foreach ($file->info['dependencies'] as $dependency_name) {
          // This is a nonexistent module.
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          if ($dependency_name == '-circular-' || !isset($files[$dependency_name])) {
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            continue;
          }
          // $dependency_name is module B (again, see doxygen).
          $files[$dependency_name]->info['dependents'][$filename] = $filename;
          $dependency = $files[$dependency_name];
          if (isset($dependency->info['dependencies']) && is_array($dependency->info['dependencies'])) {
            // Let's find possible C modules.
            foreach ($dependency->info['dependencies'] as $candidate) {
              if (array_search($candidate, $file->info['dependencies']) === FALSE) {
                // Is this a circular dependency?
                if ($candidate == $filename) {
                  // As a module name can not contain dashes, this makes
                  // impossible to switch on the module.
                  $candidate = '-circular-';
                  // Do not display the message or add -circular- more than once.
                  if (array_search($candidate, $file->info['dependencies']) !== FALSE) {
                    continue;
                  }
                  drupal_set_message(t('%module is part of a circular dependency. This is not supported and you will not be able to switch it on.', array('%module' => $file->info['name'])), 'error');
                }
                else {
                  // We added a new dependency to module A. The next loop will
                  // be able to use this as "B module" thus finding even
                  // deeper dependencies.
                  $new_dependency = TRUE;
                }
                $file->info['dependencies'][] = $candidate;
              }
            }
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          }
        }
      }
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      // Don't forget to break the reference.
      unset($file);
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    }
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  } while ($new_dependency);
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  return $files;
}

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/**
 * Determine whether a given module exists.
 *
 * @param $module
 *   The name of the module (without the .module extension).
 * @return
 *   TRUE if the module is both installed and enabled.
 */
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function module_exists($module) {
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  $list = module_list();
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  return isset($list[$module]);
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}

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/**
 * Load a module's installation hooks.
 */
function module_load_install($module) {
  // Make sure the installation API is available
  include_once './includes/install.inc';

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  module_load_include('install', $module);
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}

/**
 * Load a module include file.
 *
 * @param $type
 *   The include file's type (file extension).
 * @param $module
 *   The module to which the include file belongs.
 * @param $name
 *   Optionally, specify the file name. If not set, the module's name is used.
 */
function module_load_include($type, $module, $name = NULL) {
  if (empty($name)) {
    $name = $module;
  }

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  if (drupal_function_exists('drupal_get_path')) {
    $file = './' . drupal_get_path('module', $module) . "/$name.$type";
  }
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  if (is_file($file)) {
    require_once $file;
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    return $file;
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  }
  else {
    return FALSE;
  }
}

/**
 * Load an include file for each of the modules that have been enabled in
 * the system table.
 */
function module_load_all_includes($type, $name = NULL) {
  $modules = module_list();
  foreach ($modules as $module) {
    module_load_include($type, $module, $name);
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  }
}

/**
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 * Enable a given list of modules.
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 *
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 * @param $module_list
 *   An array of module names.
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 */
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function module_enable($module_list) {
  $invoke_modules = array();
  foreach ($module_list as $module) {
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    $existing = db_fetch_object(db_query("SELECT status FROM {system} WHERE type = '%s' AND name = '%s'", 'module', $module));
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    if ($existing->status == 0) {
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      module_load_install($module);
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      db_query("UPDATE {system} SET status = %d WHERE type = '%s' AND name = '%s'", 1, 'module', $module);
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      drupal_load('module', $module);
      $invoke_modules[] = $module;
    }
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  }
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  if (!empty($invoke_modules)) {
    // Refresh the module list to include the new enabled module.
    module_list(TRUE, FALSE);
    // Force to regenerate the stored list of hook implementations.
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    registry_rebuild();
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  }

  foreach ($invoke_modules as $module) {
    module_invoke($module, 'enable');
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    // Check if node_access table needs rebuilding.
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    // We check for the existence of node_access_needs_rebuild() since
    // at install time, module_enable() could be called while node.module
    // is not enabled yet.
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    if (drupal_function_exists('node_access_needs_rebuild') && !node_access_needs_rebuild() && module_hook($module, 'node_grants')) {
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      node_access_needs_rebuild(TRUE);
    }
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  }
}

/**
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 * Disable a given set of modules.
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 *
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 * @param $module_list
 *   An array of module names.
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 */
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function module_disable($module_list) {
  $invoke_modules = array();
  foreach ($module_list as $module) {
    if (module_exists($module)) {
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      // Check if node_access table needs rebuilding.
      if (!node_access_needs_rebuild() && module_hook($module, 'node_grants')) {
        node_access_needs_rebuild(TRUE);
      }

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      module_load_install($module);
      module_invoke($module, 'disable');
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      db_query("UPDATE {system} SET status = %d WHERE type = '%s' AND name = '%s'", 0, 'module', $module);
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      $invoke_modules[] = $module;
    }
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  }
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  if (!empty($invoke_modules)) {
    // Refresh the module list to exclude the disabled modules.
    module_list(TRUE, FALSE);
    // Force to regenerate the stored list of hook implementations.
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    registry_rebuild();
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  }
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  // If there remains no more node_access module, rebuilding will be
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  // straightforward, we can do it right now.
  if (node_access_needs_rebuild() && count(module_implements('node_grants')) == 0) {
    node_access_rebuild();
  }
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}

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/**
 * @defgroup hooks Hooks
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 * @{
 * Allow modules to interact with the Drupal core.
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 *
 * Drupal's module system is based on the concept of "hooks". A hook is a PHP
 * function that is named foo_bar(), where "foo" is the name of the module (whose
 * filename is thus foo.module) and "bar" is the name of the hook. Each hook has
 * a defined set of parameters and a specified result type.
 *
 * To extend Drupal, a module need simply implement a hook. When Drupal wishes to
 * allow intervention from modules, it determines which modules implement a hook
 * and call that hook in all enabled modules that implement it.
 *
 * The available hooks to implement are explained here in the Hooks section of
 * the developer documentation. The string "hook" is used as a placeholder for
 * the module name is the hook definitions. For example, if the module file is
 * called example.module, then hook_help() as implemented by that module would be
 * defined as example_help().
 */

/**
 * Determine whether a module implements a hook.
 *
 * @param $module
 *   The name of the module (without the .module extension).
 * @param $hook
 *   The name of the hook (e.g. "help" or "menu").
 * @return
 *   TRUE if the module is both installed and enabled, and the hook is
 *   implemented in that module.
 */
function module_hook($module, $hook) {
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  $function = $module . '_' . $hook;
  if (defined('MAINTENANCE_MODE')) {
    return function_exists($function);
  }
  else {
    return drupal_function_exists($function);
  }
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}

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/**
 * Determine which modules are implementing a hook.
 *
 * @param $hook
 *   The name of the hook (e.g. "help" or "menu").
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 * @param $sort
 *   By default, modules are ordered by weight and filename, settings this option
 *   to TRUE, module list will be ordered by module name.
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 * @param $refresh
 *   For internal use only: Whether to force the stored list of hook
 *   implementations to be regenerated (such as after enabling a new module,
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 *   before processing hook_enable).  Note that if $refresh is TRUE this function
 *   will always return NULL.
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 * @return
 *   An array with the names of the modules which are implementing this hook.
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 *   If $hook is NULL then it will return the implementation cache.
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 */
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function module_implements($hook = NULL, $sort = FALSE, $refresh = FALSE) {
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  static $implementations = array();
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  if (!isset($hook)) {
    return $implementations;
  }
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  if ($refresh) {
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    $implementations = array();
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  }
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  if (!defined('MAINTENANCE_MODE') && empty($implementations) && ($cache = cache_get('hooks', 'cache_registry'))) {
    $implementations = $cache->data;
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  }

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  if ($hook) {
    if (!isset($implementations[$hook])) {
      $implementations[$hook] = array();
      foreach (module_list() as $module) {
        if (module_hook($module, $hook)) {
          $implementations[$hook][] = $module;
        }
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      }
    }
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    registry_cache_hook_implementations(array('hook' => $hook, 'modules' => $implementations[$hook]));
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    return $implementations[$hook];
  }
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}

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/**
 * Invoke a hook in a particular module.
 *
 * @param $module
 *   The name of the module (without the .module extension).
 * @param $hook
 *   The name of the hook to invoke.
 * @param ...
 *   Arguments to pass to the hook implementation.
 * @return
 *   The return value of the hook implementation.
 */
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function module_invoke() {
  $args = func_get_args();
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  $module = $args[0];
  $hook = $args[1];
  unset($args[0], $args[1]);
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  if (module_hook($module, $hook)) {
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    return call_user_func_array($module . '_' . $hook, $args);
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  }
}
/**
 * Invoke a hook in all enabled modules that implement it.
 *
 * @param $hook
 *   The name of the hook to invoke.
 * @param ...
 *   Arguments to pass to the hook.
 * @return
 *   An array of return values of the hook implementations. If modules return
 *   arrays from their implementations, those are merged into one array.
 */
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function module_invoke_all() {
  $args = func_get_args();
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  $hook = $args[0];
  unset($args[0]);
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  $return = array();
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  foreach (module_implements($hook) as $module) {
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    $function = $module . '_' . $hook;
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    if (drupal_function_exists($function)) {
      $result = call_user_func_array($function, $args);
      if (isset($result) && is_array($result)) {
        $return = array_merge_recursive($return, $result);
      }
      else if (isset($result)) {
        $return[] = $result;
      }
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    }
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  }

  return $return;
}

/**
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 * @} End of "defgroup hooks".
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 */

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/**
 * Array of modules required by core.
 */
function drupal_required_modules() {
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  return array('block', 'filter', 'node', 'system', 'user');
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}