libstdc++
sat_arith.h
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1 // Saturation arithmetic -*- C++ -*-
2 
3 // Copyright The GNU Toolchain Authors.
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
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU 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 include/bits/sat_arith.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{numeric}
28  */
29 
30 #ifndef _GLIBCXX_SAT_ARITH_H
31 #define _GLIBCXX_SAT_ARITH_H 1
32 
33 #pragma GCC system_header
34 
35 #include <bits/version.h>
36 
37 #ifdef __glibcxx_saturation_arithmetic // C++ >= 26
38 
39 #include <concepts>
40 #include <ext/numeric_traits.h>
41 
42 namespace std _GLIBCXX_VISIBILITY(default)
43 {
44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
45 
46  /// Add two integers, with saturation in case of overflow.
47  template<typename _Tp> requires __is_standard_integer<_Tp>::value
48  constexpr _Tp
49  add_sat(_Tp __x, _Tp __y) noexcept
50  {
51  _Tp __z;
52  if (!__builtin_add_overflow(__x, __y, &__z))
53  return __z;
54  if constexpr (is_unsigned_v<_Tp>)
56  else if (__x < 0)
58  else
60  }
61 
62  /// Subtract one integer from another, with saturation in case of overflow.
63  template<typename _Tp> requires __is_standard_integer<_Tp>::value
64  constexpr _Tp
65  sub_sat(_Tp __x, _Tp __y) noexcept
66  {
67  _Tp __z;
68  if (!__builtin_sub_overflow(__x, __y, &__z))
69  return __z;
70  if constexpr (is_unsigned_v<_Tp>)
72  else if (__x < 0)
74  else
76  }
77 
78  /// Multiply two integers, with saturation in case of overflow.
79  template<typename _Tp> requires __is_standard_integer<_Tp>::value
80  constexpr _Tp
81  mul_sat(_Tp __x, _Tp __y) noexcept
82  {
83  _Tp __z;
84  if (!__builtin_mul_overflow(__x, __y, &__z))
85  return __z;
86  if constexpr (is_unsigned_v<_Tp>)
88  else if (__x < 0 != __y < 0)
90  else
92  }
93 
94  /// Divide one integer by another, with saturation in case of overflow.
95  template<typename _Tp> requires __is_standard_integer<_Tp>::value
96  constexpr _Tp
97  div_sat(_Tp __x, _Tp __y) noexcept
98  {
99  __glibcxx_assert(__y != 0);
100  if constexpr (is_signed_v<_Tp>)
101  if (__x == __gnu_cxx::__int_traits<_Tp>::__min && __y == _Tp(-1))
103  return __x / __y;
104  }
105 
106  /// Divide one integer by another, with saturation in case of overflow.
107  template<typename _Res, typename _Tp>
108  requires __is_standard_integer<_Res>::value
109  && __is_standard_integer<_Tp>::value
110  constexpr _Res
111  saturate_cast(_Tp __x) noexcept
112  {
113  constexpr int __digits_R = __gnu_cxx::__int_traits<_Res>::__digits;
114  constexpr int __digits_T = __gnu_cxx::__int_traits<_Tp>::__digits;
115  constexpr _Res __max_Res = __gnu_cxx::__int_traits<_Res>::__max;
116 
117  if constexpr (is_signed_v<_Res> == is_signed_v<_Tp>)
118  {
119  if constexpr (__digits_R < __digits_T)
120  {
121  constexpr _Res __min_Res = __gnu_cxx::__int_traits<_Res>::__min;
122 
123  if (__x < static_cast<_Tp>(__min_Res))
124  return __min_Res;
125  else if (__x > static_cast<_Tp>(__max_Res))
126  return __max_Res;
127  }
128  }
129  else if constexpr (is_signed_v<_Tp>) // Res is unsigned
130  {
131  if (__x < 0)
132  return 0;
133  else if (make_unsigned_t<_Tp>(__x) > __max_Res)
135  }
136  else // Tp is unsigned, Res is signed
137  {
138  if (__x > make_unsigned_t<_Res>(__max_Res))
139  return __max_Res;
140  }
141  return static_cast<_Res>(__x);
142  }
143 
144 _GLIBCXX_END_NAMESPACE_VERSION
145 } // namespace
146 
147 #endif // __glibcxx_saturation_arithmetic
148 #endif /* _GLIBCXX_SAT_ARITH_H */
ISO C++ entities toplevel namespace is std.
__numeric_traits_integer< _Tp > __int_traits
Convenience alias for __numeric_traits<integer-type>.