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_METAPROGRAMMING_ISDERIVED_HPP 26 #define SHARE_VM_METAPROGRAMMING_ISDERIVED_HPP 27 28 #include "memory/allocation.hpp" 29 #include "metaprogramming/integralConstant.hpp" 30 #include "metaprogramming/isSame.hpp" 31 32 // The IsDerived metafunction checks if a DerivedType is derived from a BaseType 33 // or not. This will return false when used on a forward declared class. 34 // Note that due to the ODR rule of C++, this metafunction must be used with care 35 // in contexts where the DerivedType is guaranteed to be fully known. 36 37 template <typename DerivedType, typename BaseType> 38 struct IsDerivedHelper: public StackObj { 39 operator BaseType* () const; 40 operator DerivedType* (); 41 }; 42 43 template <typename DerivedType, typename BaseType> 44 struct IsDerivedImpl: public AllStatic { 45 typedef char yes[1]; 46 typedef char no[2]; 47 48 template <typename T> 49 static yes& test(DerivedType*, T); 50 static no& test(BaseType*, int); 51 52 static const bool value = IsSame<DerivedType, BaseType>::value || 53 sizeof(test(IsDerivedHelper<DerivedType, BaseType>(), 0)) == sizeof(yes); 54 }; 55 56 template <typename DerivedType, typename BaseType> 57 struct IsDerived: public IntegralConstant<bool, IsDerivedImpl<DerivedType, BaseType>::value> {}; 58 59 #endif // SHARE_VM_METAPROGRAMMING_ISDERIVED_HPP