gecko-dev/xpcom/base/nscore.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 */
#ifndef nscore_h___
#define nscore_h___

#ifdef _WIN32
#define NS_WIN32 1
#endif

#if defined(__unix)
#define NS_UNIX 1
#endif

#include "prtypes.h"

#ifdef __cplusplus
#include "nsDebug.h"
#endif

#ifndef __PRUNICHAR__
#define __PRUNICHAR__
typedef PRUint16 PRUnichar;
#endif

/* The preferred symbol for null. */
#define nsnull 0

/* Define brackets for protecting C code from C++ */
#ifdef __cplusplus
#define NS_BEGIN_EXTERN_C extern "C" {
#define NS_END_EXTERN_C }
#else
#define NS_BEGIN_EXTERN_C
#define NS_END_EXTERN_C
#endif

/*----------------------------------------------------------------------*/
/* Import/export defines */

#ifdef NS_WIN32
#define NS_IMPORT _declspec(dllimport)
#define NS_IMPORT_(type) type _declspec(dllimport) __stdcall
#define NS_EXPORT _declspec(dllexport)
/* XXX NS_EXPORT_ defined in nsCOm.h (xpcom) differs in where the __declspec
   is placed. It needs to be done this way to make the 4.x compiler happy... */
#undef NS_EXPORT_
#define NS_EXPORT_(type) type _declspec(dllexport) __stdcall
#elif defined(XP_MAC)

#define NS_IMPORT
#define NS_IMPORT_(type) type

/* XXX NS_EXPORT_ defined in nsCom.h actually does an export. Here it's just sugar. */
#undef NS_EXPORT
#undef NS_EXPORT_

#define NS_EXPORT __declspec(export)
#define NS_EXPORT_(type) __declspec(export) type

#else
/* XXX do something useful? */
#define NS_IMPORT
#define NS_IMPORT_(type) type
#define NS_EXPORT
#define NS_EXPORT_(type) type
#endif

#ifdef _IMPL_NS_BASE
#define NS_BASE NS_EXPORT
#else
#define NS_BASE NS_IMPORT
#endif

#ifdef _IMPL_NS_NET
#define NS_NET NS_EXPORT
#else
#define NS_NET NS_IMPORT
#endif

#ifdef _IMPL_NS_DOM
#define NS_DOM NS_EXPORT
#else
#define NS_DOM NS_IMPORT
#endif

#ifdef _IMPL_NS_WIDGET
#define NS_WIDGET NS_EXPORT
#else
#define NS_WIDGET NS_IMPORT
#endif

#ifdef _IMPL_NS_VIEW
#define NS_VIEW NS_EXPORT
#else
#define NS_VIEW NS_IMPORT
#endif

#ifdef _IMPL_NS_GFXNONXP
#define NS_GFXNONXP NS_EXPORT
#define NS_GFXNONXP_(type) NS_EXPORT_(type)
#else
#define NS_GFXNONXP NS_IMPORT
#define NS_GFXNONXP_(type) NS_IMPORT_(type)
#endif

#ifdef _IMPL_NS_GFX
#define NS_GFX NS_EXPORT
#define NS_GFX_(type) NS_EXPORT_(type)
#else
#define NS_GFX NS_IMPORT
#define NS_GFX_(type) NS_IMPORT_(type)
#endif

#ifdef _IMPL_NS_PLUGIN
#define NS_PLUGIN NS_EXPORT
#else
#define NS_PLUGIN NS_IMPORT
#endif

#ifdef _IMPL_NS_APPSHELL
#define NS_APPSHELL NS_EXPORT
#else
#define NS_APPSHELL NS_IMPORT
#endif


/* ------------------------------------------------------------------------ */
/* Casting macros for hiding C++ features from older compilers */

/* unix and beos now determine this automatically */
#if ! defined XP_UNIX && ! defined XP_BEOS
#define HAVE_CPP_NEW_CASTS /* we'll be optimistic. */
#endif

#if defined(HAVE_CPP_NEW_CASTS)
#define NS_STATIC_CAST(__type, __ptr)      static_cast<__type>(__ptr)
#define NS_CONST_CAST(__type, __ptr)       const_cast<__type>(__ptr)
#define NS_REINTERPRET_CAST(__type, __ptr) reinterpret_cast<__type>(__ptr)
#else
#define NS_STATIC_CAST(__type, __ptr)      ((__type)(__ptr))
#define NS_CONST_CAST(__type, __ptr)       ((__type)(__ptr))

  /* Note: the following is only appropriate for pointers. */
#define NS_REINTERPRET_CAST(__type, __ptr) ((__type)((void*)(__ptr)))
  /*
  	Why cast to a |void*| first?  Well, when old-style casting from
  	a pointer to a base to a pointer to a derived class, the cast will be
  	ambiguous if the source pointer type appears multiple times in the
  	destination, e.g.,
  	
  	  class Base {};
  	  class Derived : public Base, public Base {};
  	  
  	  void foo( Base* b )
  	    {
  	      ((Derived*)b)->some_deried_member ... // Error: Ambiguous, expand from which |Base|?
  	    }

		an old-style cast (like |static_cast|) will change the pointer, but
		here, doesn't know how.  The cast to |void*| prevents it from thinking
		it needs to expand the original pointer.

    The cost is, |NS_REINTERPRET_CAST| is no longer appropriate for non-pointer
    conversions.  Also, mis-applying |NS_REINTERPRET_CAST| to cast |this| to something
    will still expand the pointer to the outer object in standards complying compilers.
  */
#endif

/* No sense in making an NS_DYNAMIC_CAST() macro: you can't duplicate
   the semantics. So if you want to dynamic_cast, then just use it
   "straight", no macro. */

#endif /* nscore_h___ */