libstdc++
int_limits.h
Go to the documentation of this file.
1 // Minimal replacement for numeric_limits of integers. -*- C++ -*-
2 
3 // Copyright (C) 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
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 bits/int_limits.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{limits}
28  */
29 
30 #ifndef _GLIBCXX_INT_LIMITS_H
31 #define _GLIBCXX_INT_LIMITS_H 1
32 
33 #pragma GCC system_header
34 
35 #if __cplusplus >= 201103L
36 #include <bits/c++config.h>
37 
38 namespace std _GLIBCXX_VISIBILITY(default)
39 {
40 _GLIBCXX_BEGIN_NAMESPACE_VERSION
41 namespace __detail
42 {
43  // This template is used for arbitrary signed and unsigned integer types
44  // (by headers <bit> and <charconv>) and for specific integer types
45  // (by <memory_resource> and <string_view>) but also for char (<charconv>).
46  // For simplicity's sake, all integral types except bool are supported.
47 
48  // Lightweight alternative to numeric_limits<signed integer type>.
49  template<typename _Tp, bool = is_signed<_Tp>::value>
50  struct __int_limits
51  {
52  static_assert(is_integral<_Tp>::value, "unsupported specialization");
53  using _Up = typename make_unsigned<_Tp>::type;
54  static constexpr int digits = sizeof(_Tp) * __CHAR_BIT__ - 1;
55  static constexpr _Tp min() noexcept { return _Tp(_Up(1) << digits); }
56  static constexpr _Tp max() noexcept { return _Tp(_Up(~_Up(0)) >> 1); }
57  };
58 
59  // Lightweight alternative to numeric_limits<unsigned integer type>.
60  template<typename _Tp>
61  struct __int_limits<_Tp, false>
62  {
63  static_assert(is_integral<_Tp>::value, "unsupported specialization");
64  static constexpr int digits = sizeof(_Tp) * __CHAR_BIT__;
65  static constexpr _Tp min() noexcept { return 0; }
66  static constexpr _Tp max() noexcept { return _Tp(-1); }
67  };
68 
69  template<> struct __int_limits<bool>; // not defined
70 }
71 _GLIBCXX_END_NAMESPACE_VERSION
72 } // namespace
73 #endif // C++11
74 #endif // _GLIBCXX_INT_LIMITS_H
std::min
constexpr const _Tp & min(const _Tp &, const _Tp &)
This does what you think it does.
Definition: stl_algobase.h:230
std
ISO C++ entities toplevel namespace is std.
c++config.h
std::max
constexpr const _Tp & max(const _Tp &, const _Tp &)
This does what you think it does.
Definition: stl_algobase.h:254