1// -*- C++ -*- 2 3// Copyright (C) 2007-2020 Free Software Foundation, Inc. 4// 5// This file is part of the GNU ISO C++ Library. This library is free 6// software; you can redistribute it and/or modify it under the terms 7// of the GNU General Public License as published by the Free Software 8// Foundation; either version 3, or (at your option) any later 9// version. 10 11// This library is distributed in the hope that it will be useful, but 12// WITHOUT ANY WARRANTY; without even the implied warranty of 13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14// General Public License for more details. 15 16// Under Section 7 of GPL version 3, you are granted additional 17// permissions described in the GCC Runtime Library Exception, version 18// 3.1, as published by the Free Software Foundation. 19 20// You should have received a copy of the GNU General Public License and 21// a copy of the GCC Runtime Library Exception along with this program; 22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23// <http://www.gnu.org/licenses/>. 24 25/** @file ext/numeric_traits.h 26 * This file is a GNU extension to the Standard C++ Library. 27 */ 28 29#ifndef _EXT_NUMERIC_TRAITS 30#define _EXT_NUMERIC_TRAITS 1 31 32#pragma GCC system_header 33 34#include <bits/cpp_type_traits.h> 35#include <ext/type_traits.h> 36 37namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 38{ 39_GLIBCXX_BEGIN_NAMESPACE_VERSION 40 41 // Compile time constants for builtin types. 42 // In C++98 std::numeric_limits member functions are not constant expressions 43 // (that changed in C++11 with the addition of 'constexpr'). 44 // Even for C++11, this header is smaller than <limits> and can be used 45 // when only is_signed, digits, min, or max values are needed for integers, 46 // or is_signed, digits10, max_digits10, or max_exponent10 for floats. 47 48 // Unlike __is_integer (and std::is_integral) this trait is true for 49 // non-standard built-in integer types such as __int128 and __int20. 50 template<typename _Tp> 51 struct __is_integer_nonstrict 52 : public std::__is_integer<_Tp> 53 { 54 using std::__is_integer<_Tp>::__value; 55 56 // The number of bits in the value representation. 57 enum { __width = __value ? sizeof(_Tp) * __CHAR_BIT__ : 0 }; 58 }; 59 60 template<typename _Value> 61 struct __numeric_traits_integer 62 { 63#if __cplusplus >= 201103L 64 static_assert(__is_integer_nonstrict<_Value>::__value, 65 "invalid specialization"); 66#endif 67 68 // NB: these two are also available in std::numeric_limits as compile 69 // time constants, but <limits> is big and we can avoid including it. 70 static const bool __is_signed_val = (_Value)(-1) < 0; 71 static const int __digits 72 = __is_integer_nonstrict<_Value>::__width - __is_signed_val; 73 74 // The initializers must be constants so that __max and __min are too. 75 static const _Value __max = __is_signed_val 76 ? (((((_Value)1 << (__digits - 1)) - 1) << 1) + 1) 77 : ~(_Value)0; 78 static const _Value __min = __is_signed_val ? -__max - 1 : (_Value)0; 79 }; 80 81 template<typename _Value> 82 const _Value __numeric_traits_integer<_Value>::__min; 83 84 template<typename _Value> 85 const _Value __numeric_traits_integer<_Value>::__max; 86 87 template<typename _Value> 88 const bool __numeric_traits_integer<_Value>::__is_signed_val; 89 90 template<typename _Value> 91 const int __numeric_traits_integer<_Value>::__digits; 92 93 // Enable __numeric_traits_integer for types where the __is_integer_nonstrict 94 // primary template doesn't give the right answer. 95#define _GLIBCXX_INT_N_TRAITS(T, WIDTH) \ 96 template<> struct __is_integer_nonstrict<T> \ 97 { \ 98 enum { __value = 1 }; \ 99 typedef std::__true_type __type; \ 100 enum { __width = WIDTH }; \ 101 }; \ 102 template<> struct __is_integer_nonstrict<unsigned T> \ 103 { \ 104 enum { __value = 1 }; \ 105 typedef std::__true_type __type; \ 106 enum { __width = WIDTH }; \ 107 }; 108 109 // We need to specify the width for some __intNN types because they 110 // have padding bits, e.g. the object representation of __int20 has 32 bits, 111 // but its width (number of bits in the value representation) is only 20. 112#if defined __GLIBCXX_TYPE_INT_N_0 && __GLIBCXX_BITSIZE_INT_N_0 % __CHAR_BIT__ 113 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_0, __GLIBCXX_BITSIZE_INT_N_0) 114#endif 115#if defined __GLIBCXX_TYPE_INT_N_1 && __GLIBCXX_BITSIZE_INT_N_1 % __CHAR_BIT__ 116 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_1, __GLIBCXX_BITSIZE_INT_N_1) 117#endif 118#if defined __GLIBCXX_TYPE_INT_N_2 && __GLIBCXX_BITSIZE_INT_N_2 % __CHAR_BIT__ 119 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_2, __GLIBCXX_BITSIZE_INT_N_2) 120#endif 121#if defined __GLIBCXX_TYPE_INT_N_3 && __GLIBCXX_BITSIZE_INT_N_3 % __CHAR_BIT__ 122 _GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_3, __GLIBCXX_BITSIZE_INT_N_3) 123#endif 124 125#if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__ 126 // In strict modes __is_integer<__int128> is false, 127 // but we still want to define __numeric_traits_integer<__int128>. 128 _GLIBCXX_INT_N_TRAITS(__int128, 128) 129#endif 130 131#undef _GLIBCXX_INT_N_TRAITS 132 133#if __cplusplus >= 201103L 134 /// Convenience alias for __numeric_traits<integer-type>. 135 template<typename _Tp> 136 using __int_traits = __numeric_traits_integer<_Tp>; 137#endif 138 139#define __glibcxx_floating(_Tp, _Fval, _Dval, _LDval) \ 140 (std::__are_same<_Tp, float>::__value ? _Fval \ 141 : std::__are_same<_Tp, double>::__value ? _Dval : _LDval) 142 143#define __glibcxx_max_digits10(_Tp) \ 144 (2 + __glibcxx_floating(_Tp, __FLT_MANT_DIG__, __DBL_MANT_DIG__, \ 145 __LDBL_MANT_DIG__) * 643L / 2136) 146 147#define __glibcxx_digits10(_Tp) \ 148 __glibcxx_floating(_Tp, __FLT_DIG__, __DBL_DIG__, __LDBL_DIG__) 149 150#define __glibcxx_max_exponent10(_Tp) \ 151 __glibcxx_floating(_Tp, __FLT_MAX_10_EXP__, __DBL_MAX_10_EXP__, \ 152 __LDBL_MAX_10_EXP__) 153 154 // N.B. this only supports float, double and long double (no __float128 etc.) 155 template<typename _Value> 156 struct __numeric_traits_floating 157 { 158 // Only floating point types. See N1822. 159 static const int __max_digits10 = __glibcxx_max_digits10(_Value); 160 161 // See above comment... 162 static const bool __is_signed_val = true; 163 static const int __digits10 = __glibcxx_digits10(_Value); 164 static const int __max_exponent10 = __glibcxx_max_exponent10(_Value); 165 }; 166 167 template<typename _Value> 168 const int __numeric_traits_floating<_Value>::__max_digits10; 169 170 template<typename _Value> 171 const bool __numeric_traits_floating<_Value>::__is_signed_val; 172 173 template<typename _Value> 174 const int __numeric_traits_floating<_Value>::__digits10; 175 176 template<typename _Value> 177 const int __numeric_traits_floating<_Value>::__max_exponent10; 178 179 template<typename _Value> 180 struct __numeric_traits 181 : public __conditional_type<__is_integer_nonstrict<_Value>::__value, 182 __numeric_traits_integer<_Value>, 183 __numeric_traits_floating<_Value> >::__type 184 { }; 185 186_GLIBCXX_END_NAMESPACE_VERSION 187} // namespace 188 189#undef __glibcxx_floating 190#undef __glibcxx_max_digits10 191#undef __glibcxx_digits10 192#undef __glibcxx_max_exponent10 193 194#endif 195