1 // -*- C++ -*-
2
3 // Copyright (C) 2007-2019 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
_GLIBCXX_VISIBILITY(default)37 namespace __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 = (_Value)(-1) < 0;
71 static const int __digits
72 = __is_integer_nonstrict<_Value>::__width - __is_signed;
73
74 // The initializers must be constants so that __max and __min are too.
75 static const _Value __max = __is_signed
76 ? (((((_Value)1 << (__digits - 1)) - 1) << 1) + 1)
77 : ~(_Value)0;
78 static const _Value __min = __is_signed ? -__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;
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 = 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;
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<std::__is_integer<_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