/src/LPM/external.protobuf/include/absl/numeric/bits.h
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1 | | // Copyright 2020 The Abseil Authors |
2 | | // |
3 | | // Licensed under the Apache License, Version 2.0 (the "License"); |
4 | | // you may not use this file except in compliance with the License. |
5 | | // You may obtain a copy of the License at |
6 | | // |
7 | | // https://www.apache.org/licenses/LICENSE-2.0 |
8 | | // |
9 | | // Unless required by applicable law or agreed to in writing, software |
10 | | // distributed under the License is distributed on an "AS IS" BASIS, |
11 | | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
12 | | // See the License for the specific language governing permissions and |
13 | | // limitations under the License. |
14 | | // |
15 | | // ----------------------------------------------------------------------------- |
16 | | // File: bits.h |
17 | | // ----------------------------------------------------------------------------- |
18 | | // |
19 | | // This file contains implementations of C++20's bitwise math functions, as |
20 | | // defined by: |
21 | | // |
22 | | // P0553R4: |
23 | | // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0553r4.html |
24 | | // P0556R3: |
25 | | // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0556r3.html |
26 | | // P1355R2: |
27 | | // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1355r2.html |
28 | | // P1956R1: |
29 | | // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1956r1.pdf |
30 | | // |
31 | | // When using a standard library that implements these functions, we use the |
32 | | // standard library's implementation. |
33 | | |
34 | | #ifndef ABSL_NUMERIC_BITS_H_ |
35 | | #define ABSL_NUMERIC_BITS_H_ |
36 | | |
37 | | #include <cstdint> |
38 | | #include <limits> |
39 | | #include <type_traits> |
40 | | |
41 | | #if (defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L) || \ |
42 | | (defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L) |
43 | | #include <bit> |
44 | | #endif |
45 | | |
46 | | #include "absl/base/attributes.h" |
47 | | #include "absl/base/config.h" |
48 | | #include "absl/numeric/internal/bits.h" |
49 | | |
50 | | namespace absl { |
51 | | ABSL_NAMESPACE_BEGIN |
52 | | |
53 | | #if !(defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L) |
54 | | // rotating |
55 | | template <class T> |
56 | | ABSL_MUST_USE_RESULT constexpr |
57 | | typename std::enable_if<std::is_unsigned<T>::value, T>::type |
58 | | rotl(T x, int s) noexcept { |
59 | | return numeric_internal::RotateLeft(x, s); |
60 | | } |
61 | | |
62 | | template <class T> |
63 | | ABSL_MUST_USE_RESULT constexpr |
64 | | typename std::enable_if<std::is_unsigned<T>::value, T>::type |
65 | 0 | rotr(T x, int s) noexcept { |
66 | 0 | return numeric_internal::RotateRight(x, s); |
67 | 0 | } |
68 | | |
69 | | // Counting functions |
70 | | // |
71 | | // While these functions are typically constexpr, on some platforms, they may |
72 | | // not be marked as constexpr due to constraints of the compiler/available |
73 | | // intrinsics. |
74 | | template <class T> |
75 | | ABSL_INTERNAL_CONSTEXPR_CLZ inline |
76 | | typename std::enable_if<std::is_unsigned<T>::value, int>::type |
77 | 0 | countl_zero(T x) noexcept { |
78 | 0 | return numeric_internal::CountLeadingZeroes(x); |
79 | 0 | } Unexecuted instantiation: _ZN4absl12lts_2023012511countl_zeroImEENSt3__19enable_ifIXsr3std11is_unsignedIT_EE5valueEiE4typeES4_ Unexecuted instantiation: _ZN4absl12lts_2023012511countl_zeroIjEENSt3__19enable_ifIXsr3std11is_unsignedIT_EE5valueEiE4typeES4_ |
80 | | |
81 | | template <class T> |
82 | | ABSL_INTERNAL_CONSTEXPR_CLZ inline |
83 | | typename std::enable_if<std::is_unsigned<T>::value, int>::type |
84 | | countl_one(T x) noexcept { |
85 | | // Avoid integer promotion to a wider type |
86 | | return countl_zero(static_cast<T>(~x)); |
87 | | } |
88 | | |
89 | | template <class T> |
90 | | ABSL_INTERNAL_CONSTEXPR_CTZ inline |
91 | | typename std::enable_if<std::is_unsigned<T>::value, int>::type |
92 | 0 | countr_zero(T x) noexcept { |
93 | 0 | return numeric_internal::CountTrailingZeroes(x); |
94 | 0 | } Unexecuted instantiation: _ZN4absl12lts_2023012511countr_zeroImEENSt3__19enable_ifIXsr3std11is_unsignedIT_EE5valueEiE4typeES4_ Unexecuted instantiation: _ZN4absl12lts_2023012511countr_zeroIjEENSt3__19enable_ifIXsr3std11is_unsignedIT_EE5valueEiE4typeES4_ |
95 | | |
96 | | template <class T> |
97 | | ABSL_INTERNAL_CONSTEXPR_CTZ inline |
98 | | typename std::enable_if<std::is_unsigned<T>::value, int>::type |
99 | | countr_one(T x) noexcept { |
100 | | // Avoid integer promotion to a wider type |
101 | | return countr_zero(static_cast<T>(~x)); |
102 | | } |
103 | | |
104 | | template <class T> |
105 | | ABSL_INTERNAL_CONSTEXPR_POPCOUNT inline |
106 | | typename std::enable_if<std::is_unsigned<T>::value, int>::type |
107 | | popcount(T x) noexcept { |
108 | | return numeric_internal::Popcount(x); |
109 | | } |
110 | | #else // defined(__cpp_lib_bitops) && __cpp_lib_bitops >= 201907L |
111 | | |
112 | | using std::countl_one; |
113 | | using std::countl_zero; |
114 | | using std::countr_one; |
115 | | using std::countr_zero; |
116 | | using std::popcount; |
117 | | using std::rotl; |
118 | | using std::rotr; |
119 | | |
120 | | #endif |
121 | | |
122 | | #if !(defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L) |
123 | | // Returns: true if x is an integral power of two; false otherwise. |
124 | | template <class T> |
125 | | constexpr inline typename std::enable_if<std::is_unsigned<T>::value, bool>::type |
126 | 0 | has_single_bit(T x) noexcept { |
127 | 0 | return x != 0 && (x & (x - 1)) == 0; |
128 | 0 | } |
129 | | |
130 | | // Returns: If x == 0, 0; otherwise one plus the base-2 logarithm of x, with any |
131 | | // fractional part discarded. |
132 | | template <class T> |
133 | | ABSL_INTERNAL_CONSTEXPR_CLZ inline |
134 | | typename std::enable_if<std::is_unsigned<T>::value, int>::type |
135 | 0 | bit_width(T x) noexcept { |
136 | 0 | return std::numeric_limits<T>::digits - countl_zero(x); |
137 | 0 | } |
138 | | |
139 | | // Returns: If x == 0, 0; otherwise the maximal value y such that |
140 | | // has_single_bit(y) is true and y <= x. |
141 | | template <class T> |
142 | | ABSL_INTERNAL_CONSTEXPR_CLZ inline |
143 | | typename std::enable_if<std::is_unsigned<T>::value, T>::type |
144 | | bit_floor(T x) noexcept { |
145 | | return x == 0 ? 0 : T{1} << (bit_width(x) - 1); |
146 | | } |
147 | | |
148 | | // Returns: N, where N is the smallest power of 2 greater than or equal to x. |
149 | | // |
150 | | // Preconditions: N is representable as a value of type T. |
151 | | template <class T> |
152 | | ABSL_INTERNAL_CONSTEXPR_CLZ inline |
153 | | typename std::enable_if<std::is_unsigned<T>::value, T>::type |
154 | | bit_ceil(T x) { |
155 | | // If T is narrower than unsigned, T{1} << bit_width will be promoted. We |
156 | | // want to force it to wraparound so that bit_ceil of an invalid value are not |
157 | | // core constant expressions. |
158 | | // |
159 | | // BitCeilNonPowerOf2 triggers an overflow in constexpr contexts if we would |
160 | | // undergo promotion to unsigned but not fit the result into T without |
161 | | // truncation. |
162 | | return has_single_bit(x) ? T{1} << (bit_width(x) - 1) |
163 | | : numeric_internal::BitCeilNonPowerOf2(x); |
164 | | } |
165 | | #else // defined(__cpp_lib_int_pow2) && __cpp_lib_int_pow2 >= 202002L |
166 | | |
167 | | using std::bit_ceil; |
168 | | using std::bit_floor; |
169 | | using std::bit_width; |
170 | | using std::has_single_bit; |
171 | | |
172 | | #endif |
173 | | |
174 | | ABSL_NAMESPACE_END |
175 | | } // namespace absl |
176 | | |
177 | | #endif // ABSL_NUMERIC_BITS_H_ |