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+/* -*- 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___)