// -*- C++ -*-


//=============================================================================
/**
 *  @file    TAO_Singleton_Manager.h
 *
 *  $Id$
 *
 *   Header file for the TAO-specific Singleton Manager.  Based
 *   entirely on ace/Object_Manager.{h,i,cpp}.
 *
 *
 *  @author  Ossama Othman <ossama@uci.edu>
 */
//=============================================================================


#ifndef TAO_OBJECT_MANAGER_H
#define TAO_OBJECT_MANAGER_H

#include "ace/pre.h"

#include "tao/TAO_Export.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

#include "ace/OS.h"

// Forward declarations
class ACE_Recursive_Thread_Mutex;

// Adapter for cleanup, used to register cleanup function with the
// ACE_Object_Manager.
extern "C"
void
TAO_Singleton_Manager_cleanup_destroyer (void *, void *);

/**
 * @class TAO_Singleton_Manager
 *
 * @brief Manager for TAO library services and singleton cleanup.
 *
 * The <TAO_Singleton_Manager> is basically simplified version of
 * the ACE_Object_Manager.  It is designed specifically to
 * manage singletons created by TAO.  For example, Singleton
 * instances created by TAO will be automatically registered
 * with the Singleton instance of this Singleton Manager.
 * This class is necessary to ensure that TAO-specific
 * Singletons are centrally isolated.  The idea is that
 * destruction of the instance of the <TAO_Singleton_Manager>
 * triggers destruction of all objects/services registered with
 * it.
 */
class TAO_Export TAO_Singleton_Manager : public ACE_Object_Manager_Base
{

  friend void TAO_Singleton_Manager_cleanup_destroyer (void *, void *);

public:
  /// Explicitly initialize.
  virtual int init (void);

  /**
   * Explicitly initialize the TAO_Singleton_Manager, in addition to
   * explicitly registering (or not registering) with the
   * ACE_Object_Manager.
   */
  int init (int register_with_object_manager);

  /// Explicitly destroy.
  virtual int fini (void);

  /**
   * Returns 1 before the <TAO_Singleton_Manager> has been
   * constructed.  See <ACE_Object_Manager::starting_up> for more
   * information.
   */
  static int starting_up (void);

  /// Returns 1 after the <TAO_Singleton_Manager> has been destroyed.
  /// See <ACE_Object_Manager::shutting_down> for more information.
  static int shutting_down (void);

  enum Preallocated_Object
    {
# if defined (ACE_MT_SAFE) && (ACE_MT_SAFE != 0)
      // @@ No MT-specific preallocated objects (yet).  Remove the
      //    below dummy enum once a preallocated object is added.
      TAO_EMPTY_PREALLOCATED_OBJECT,
# else
      // Without ACE_MT_SAFE, There are no preallocated objects.  Make
      // sure that the preallocated_array size is at least one by
      // declaring this dummy . . .
      TAO_EMPTY_PREALLOCATED_OBJECT,
# endif /* ACE_MT_SAFE */

      TAO_PREALLOCATED_OBJECTS  // This enum value must be last!
    };
  // Unique identifiers for preallocated objects.

  /// Accesses a default signal set used, for example, in
  /// <ACE_Sig_Guard> methods.
  static sigset_t *default_mask (void);

  /// Returns the current thread hook for the process.
  static ACE_Thread_Hook *thread_hook (void);

  /// Returns the existing thread hook and assign a <new_thread_hook>.
  static ACE_Thread_Hook *thread_hook (ACE_Thread_Hook *new_thread_hook);

  /// Accessor to singleton instance.
  static TAO_Singleton_Manager *instance (void);

  /**
   * Register an ACE_Cleanup object for cleanup at process
   * termination.  The object is deleted via the
   * <ace_cleanup_destroyer>.  If you need more flexiblity, see the
   * <other at_exit> method below.  For OS's that do not have
   * processes, cleanup takes place at the end of <main>.  Returns 0
   * on success.  On failure, returns -1 and sets errno to: EAGAIN if
   * shutting down, ENOMEM if insufficient virtual memory, or EEXIST
   * if the object (or array) had already been registered.
   */
  static int at_exit (ACE_Cleanup *object, void *param = 0);

  /**
   * Register an object (or array) for cleanup at process termination.
   * "cleanup_hook" points to a (global, or static member) function
   * that is called for the object or array when it to be destroyed.
   * It may perform any necessary cleanup specific for that object or
   * its class.  "param" is passed as the second parameter to the
   * "cleanup_hook" function; the first parameter is the object (or
   * array) to be destroyed.  "cleanup_hook", for example, may delete
   * the object (or array).  For OS's that do not have processes, this
   * function is the same as <at_thread_exit>.  Returns 0 on success.
   * On failure, returns -1 and sets errno to: EAGAIN if shutting
   * down, ENOMEM if insufficient virtual memory, or EEXIST if the
   * object (or array) had already been registered.
   */
  static int at_exit (void *object,
                      ACE_CLEANUP_FUNC cleanup_hook,
                      void *param);

private:
  // Force allocation on the heap.
  TAO_Singleton_Manager (void);
  ~TAO_Singleton_Manager (void);

  // Disallow copying by not implementing the following . . .
  TAO_Singleton_Manager (const TAO_Singleton_Manager &);
  TAO_Singleton_Manager &operator= (const TAO_Singleton_Manager &);

  /// Register an object or array for deletion at program termination.
  /// See description of static version above for return values.
  int at_exit_i (void *object, ACE_CLEANUP_FUNC cleanup_hook, void *param);

private:

  /// Singleton instance pointer.
  static TAO_Singleton_Manager *instance_;

  /// Table of preallocated objects.
  static void *preallocated_object[TAO_PREALLOCATED_OBJECTS];

  /// Default signal set used, for example, in ACE_Sig_Guard.
  sigset_t *default_mask_;

  /// Thread hook that's used by this process.
  ACE_Thread_Hook *thread_hook_;

  /// For at_exit support.
  ACE_OS_Exit_Info exit_info_;

  /// Indicates if TAO_Singleton_Manager is registered with the
  /// ACE_Object_Manager.
  int registered_with_object_manager_;

#if defined (ACE_MT_SAFE) && (ACE_MT_SAFE != 0)
  /// Lock that is used to guard internal structures.
  ACE_Recursive_Thread_Mutex *internal_lock_;
#endif /* ACE_MT_SAFE */
};

#if defined (__ACE_INLINE__)
# include "tao/TAO_Singleton_Manager.inl"
#endif /* __ACE_INLINE__ */

#include "ace/post.h"

#endif  /* TAO_OBJECT_MANAGER_H */