1 /*
   2  * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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   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
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  24 
  25 #ifndef SHARE_VM_METAPROGRAMMING_INTEGRALCONSTANT_HPP
  26 #define SHARE_VM_METAPROGRAMMING_INTEGRALCONSTANT_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 
  30 // An Integral Constant is a class providing a compile-time value of an
  31 // integral type.  An Integral Constant is also a nullary metafunction,
  32 // returning itself.  An integral constant object is implicitly
  33 // convertible to the associated value.
  34 //
  35 // A type n is a model of Integral Constant if it meets the following
  36 // requirements:
  37 //
  38 // n::ValueType                : The integral type of n::value
  39 // n::value                    : An integral constant expression
  40 // n::type                     : IsSame<n::type, n>::value is true
  41 // n::value_type const c = n() : c == n::value
  42 
  43 // A model of the Integer Constant concept.
  44 // T is an integral type, and is the value_type.
  45 // v is an integral constant, and is the value.
  46 template<typename T, T v>
  47 struct IntegralConstant {
  48   typedef T value_type;
  49   static const value_type value = v;
  50   typedef IntegralConstant<T, v> type;
  51   operator value_type() { return value; }
  52 };
  53 
  54 // A bool valued IntegralConstant whose value is true.
  55 typedef IntegralConstant<bool, true> TrueType;
  56 
  57 // A bool valued IntegralConstant whose value is false.
  58 typedef IntegralConstant<bool, false> FalseType;
  59 
  60 #endif // SHARE_VM_METAPROGRAMMING_INTEGRALCONSTANT_HPP