1 /*
   2  * Copyright (c) 2017, 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_ISDERIVED_HPP
  26 #define SHARE_VM_UTILITIES_TRAITS_ISDERIVED_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/traits/isSame.hpp"
  30 
  31 namespace IsDerivedImpl {
  32   template <typename DerivedType, typename BaseType>
  33   struct Helper: public StackObj {
  34     operator BaseType* () const;
  35     operator DerivedType* ();
  36   };
  37 }
  38 
  39 template <typename DerivedType, typename BaseType>
  40 struct IsDerived: AllStatic {
  41   typedef char yes[1];
  42   typedef char no[2];
  43 
  44   template <typename T>
  45   static yes& test(DerivedType*, T);
  46   static no& test(BaseType*, int);
  47 
  48   enum {
  49     value = IsSame<DerivedType, BaseType>::value || sizeof(test(IsDerivedImpl::Helper<DerivedType, BaseType>(), 0)) == sizeof(yes)
  50   };
  51 };
  52 
  53 #endif // SHARE_VM_UTILITIES_TRAITS_ISDERIVED_HPP