1 /*
   2  * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_UTILITIES_TRAITS_SELECT_BASE_CLASS_HPP
  26 #define SHARE_VM_UTILITIES_TRAITS_SELECT_BASE_CLASS_HPP
  27 
  28 #include "utilities/traits/isBaseOf.hpp"
  29 
  30 // The ::type of this struct will be the Desired type if it was defined
  31 // and is a subtype of Fallback, otherwise it will be Fallback.
  32 // This is useful when optionally inheriting from a specialized subtype.
  33 template <class Desired, class Fallback>
  34 class SelectBaseClass {
  35   template <bool, class T, class U>
  36   struct CheckInheritance {
  37       typedef T type;
  38   };
  39   
  40   template <class T, class U>
  41   struct CheckInheritance<true, T, U> {
  42       typedef U type;
  43   };
  44 public:
  45   typedef typename CheckInheritance<IsBaseOf<Fallback, Desired>::value, Fallback, Desired>::type type;
  46 };
  47 
  48 #endif // SHARE_VM_UTILITIES_TRAITS_SELECT_BASE_CLASS_HPP
  49