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 #ifdef _GLIBCXX_SYSHDR
34 #pragma GCC system_header
35 #endif
36 
37 #include <bits/version.h>
38 
39 #ifdef __glibcxx_saturation_arithmetic // C++ >= 26
40 
41 #include <concepts>
42 #include <ext/numeric_traits.h>
43 
44 namespace std _GLIBCXX_VISIBILITY(default)
45 {
46 _GLIBCXX_BEGIN_NAMESPACE_VERSION
47 
48  /// Add two integers, with saturation in case of overflow.
49  template<typename _Tp> requires __is_standard_integer<_Tp>::value
50  constexpr _Tp
51  add_sat(_Tp __x, _Tp __y) noexcept
52  {
53  _Tp __z;
54  if (!__builtin_add_overflow(__x, __y, &__z))
55  return __z;
56  if constexpr (is_unsigned_v<_Tp>)
58  else if (__x < 0)
60  else
62  }
63 
64  /// Subtract one integer from another, with saturation in case of overflow.
65  template<typename _Tp> requires __is_standard_integer<_Tp>::value
66  constexpr _Tp
67  sub_sat(_Tp __x, _Tp __y) noexcept
68  {
69  _Tp __z;
70  if (!__builtin_sub_overflow(__x, __y, &__z))
71  return __z;
72  if constexpr (is_unsigned_v<_Tp>)
74  else if (__x < 0)
76  else
78  }
79 
80  /// Multiply two integers, with saturation in case of overflow.
81  template<typename _Tp> requires __is_standard_integer<_Tp>::value
82  constexpr _Tp
83  mul_sat(_Tp __x, _Tp __y) noexcept
84  {
85  _Tp __z;
86  if (!__builtin_mul_overflow(__x, __y, &__z))
87  return __z;
88  if constexpr (is_unsigned_v<_Tp>)
90  else if (__x < 0 != __y < 0)
92  else
94  }
95 
96  /// Divide one integer by another, with saturation in case of overflow.
97  template<typename _Tp> requires __is_standard_integer<_Tp>::value
98  constexpr _Tp
99  div_sat(_Tp __x, _Tp __y) noexcept
100  {
101  __glibcxx_assert(__y != 0);
102  if constexpr (is_signed_v<_Tp>)
103  if (__x == __gnu_cxx::__int_traits<_Tp>::__min && __y == _Tp(-1))
105  return __x / __y;
106  }
107 
108  /// Divide one integer by another, with saturation in case of overflow.
109  template<typename _Res, typename _Tp>
110  requires __is_standard_integer<_Res>::value
111  && __is_standard_integer<_Tp>::value
112  constexpr _Res
113  saturate_cast(_Tp __x) noexcept
114  {
115  constexpr int __digits_R = __gnu_cxx::__int_traits<_Res>::__digits;
116  constexpr int __digits_T = __gnu_cxx::__int_traits<_Tp>::__digits;
117  constexpr _Res __max_Res = __gnu_cxx::__int_traits<_Res>::__max;
118 
119  if constexpr (is_signed_v<_Res> == is_signed_v<_Tp>)
120  {
121  if constexpr (__digits_R < __digits_T)
122  {
123  constexpr _Res __min_Res = __gnu_cxx::__int_traits<_Res>::__min;
124 
125  if (__x < static_cast<_Tp>(__min_Res))
126  return __min_Res;
127  else if (__x > static_cast<_Tp>(__max_Res))
128  return __max_Res;
129  }
130  }
131  else if constexpr (is_signed_v<_Tp>) // Res is unsigned
132  {
133  if (__x < 0)
134  return 0;
135  else if (make_unsigned_t<_Tp>(__x) > __max_Res)
137  }
138  else // Tp is unsigned, Res is signed
139  {
140  if (__x > make_unsigned_t<_Res>(__max_Res))
141  return __max_Res;
142  }
143  return static_cast<_Res>(__x);
144  }
145 
146 _GLIBCXX_END_NAMESPACE_VERSION
147 } // namespace
148 
149 #endif // __glibcxx_saturation_arithmetic
150 #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>.