home *** CD-ROM | disk | FTP | other *** search
- /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
- /* vim:set ts=2 sw=2 sts=2 et cindent: */
- /* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla 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/MPL/
- *
- * 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.
- *
- * The Initial Developer of the Original Code is IBM Corporation.
- * Portions created by IBM Corporation are Copyright (C) 2003
- * IBM Corporation. All Rights Reserved.
- *
- * Contributor(s):
- * Darin Fisher <darin@meer.net>
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
-
- #ifndef nsObsoleteAString_h___
- #define nsObsoleteAString_h___
-
- /*
- STRING INTERNALS
-
- This file defines nsObsoleteAString and nsObsoleteACString. These are
- abstract classes (interfaces), containing only virtual functions
- corresponding to the FROZEN nsA[C]String classes. They exist to provide
- the new non-abstract nsA[C]String classes with a mechanism to maintain
- backwards binary compatability.
-
- From a binary point-of-view, the new nsA[C]String classes appear to have a
- vtable pointer to the vtable of nsObsoleteA[C]StringThunk.
- nsObsoleteA[C]StringThunk is a subclass of nsObsoleteA[C]String that serves
- as a simple bridge between the virtual functions that make up the FROZEN
- nsA[C]String contract and the new ns[C]Substring, which is now our only
- subclass of nsA[C]String.
-
- The methods on the new nsA[C]String are now all non-virtual. This reduces
- codesize at the callsite, and reduces the number of memory dereferences and
- jumps required to invoke a method on nsA[C]String. The result is improved
- performance and reduced codesize. However, to maintain binary
- compatibility, each method on nsA[C]String must check the value of its
- vtable to determine if it corresponds to the built-in implementation of
- nsObsoleteA[C]String (i.e., the address of the canonical vtable). If it
- does, then the vtable can be ignored, and the nsA[C]String object (i.e.,
- |this|) can be cast to ns[C]Substring directly. In which case, the
- nsA[C]String methods can be satisfied by invoking the corresponding methods
- directly on ns[C]Substring. If the vtable address does not correspond to
- the built-in implementation, then the virtual functions on
- nsObsoleteA[C]String must be invoked instead.
-
- So, if a nsA[C]String reference corresponds to an external implementation
- (such as the old nsEmbed[C]String that shipped with previous versions of
- Mozilla), then methods invoked on that nsA[C]String will still act like
- virtual function calls. This ensures binary compatibility while avoiding
- virtual function calls in most cases.
-
- Finally, nsObsoleteA[C]String (i.e., the FROZEN nsA[C]String vtable) is
- now a DEPRECATED interface. See nsStringAPI.h and nsEmbedString.h for
- the new preferred way to access nsA[C]String references in an external
- component or Gecko embedding application.
- */
-
- #ifndef nsStringFwd_h___
- #include "nsStringFwd.h"
- #endif
-
- #ifndef nscore_h___
- #include "nscore.h"
- #endif
-
- // declare nsObsoleteAString
- #include "string-template-def-unichar.h"
- #include "nsTObsoleteAString.h"
- #include "string-template-undef.h"
-
- // declare nsObsoleteACString
- #include "string-template-def-char.h"
- #include "nsTObsoleteAString.h"
- #include "string-template-undef.h"
-
- #endif // !defined(nsObsoleteAString_h___)
-