1 | // <bit> -*- C++ -*- |
2 | |
3 | // Copyright (C) 2018-2024 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 include/bit |
26 | * This is a Standard C++ Library header. |
27 | */ |
28 | |
29 | #ifndef _GLIBCXX_BIT |
30 | #define _GLIBCXX_BIT 1 |
31 | |
32 | #pragma GCC system_header |
33 | |
34 | #if __cplusplus >= 201402L |
35 | |
36 | #include <concepts> // for std::integral |
37 | #include <type_traits> |
38 | |
39 | #if _GLIBCXX_HOSTED || __has_include(<ext/numeric_traits.h>) |
40 | # include <ext/numeric_traits.h> |
41 | #else |
42 | # include <limits> |
43 | /// @cond undocumented |
44 | namespace __gnu_cxx |
45 | { |
46 | template<typename _Tp> |
47 | struct __int_traits |
48 | { |
49 | static constexpr int __digits = std::numeric_limits<_Tp>::digits; |
50 | static constexpr _Tp __max = std::numeric_limits<_Tp>::max(); |
51 | }; |
52 | } |
53 | /// @endcond |
54 | #endif |
55 | |
56 | #define __glibcxx_want_bit_cast |
57 | #define __glibcxx_want_byteswap |
58 | #define __glibcxx_want_bitops |
59 | #define __glibcxx_want_int_pow2 |
60 | #define __glibcxx_want_endian |
61 | #include <bits/version.h> |
62 | |
63 | namespace std _GLIBCXX_VISIBILITY(default) |
64 | { |
65 | _GLIBCXX_BEGIN_NAMESPACE_VERSION |
66 | |
67 | /** |
68 | * @defgroup bit_manip Bit manipulation |
69 | * @ingroup numerics |
70 | * |
71 | * Utilities for examining and manipulating individual bits. |
72 | * |
73 | * @{ |
74 | */ |
75 | |
76 | #ifdef __cpp_lib_bit_cast // C++ >= 20 |
77 | |
78 | /// Create a value of type `To` from the bits of `from`. |
79 | /** |
80 | * @tparam _To A trivially-copyable type. |
81 | * @param __from A trivially-copyable object of the same size as `_To`. |
82 | * @return An object of type `_To`. |
83 | * @since C++20 |
84 | */ |
85 | template<typename _To, typename _From> |
86 | [[nodiscard]] |
87 | constexpr _To |
88 | bit_cast(const _From& __from) noexcept |
89 | #ifdef __cpp_concepts |
90 | requires (sizeof(_To) == sizeof(_From)) |
91 | && is_trivially_copyable_v<_To> && is_trivially_copyable_v<_From> |
92 | #endif |
93 | { |
94 | return __builtin_bit_cast(_To, __from); |
95 | } |
96 | #endif // __cpp_lib_bit_cast |
97 | |
98 | #ifdef __cpp_lib_byteswap // C++ >= 23 |
99 | |
100 | /// Reverse order of bytes in the object representation of `value`. |
101 | /** |
102 | * @tparam _Tp An integral type. |
103 | * @param __value An object of integer type. |
104 | * @return An object of the same type, with the bytes reversed. |
105 | * @since C++23 |
106 | */ |
107 | template<integral _Tp> |
108 | [[nodiscard]] |
109 | constexpr _Tp |
110 | byteswap(_Tp __value) noexcept |
111 | { |
112 | if constexpr (sizeof(_Tp) == 1) |
113 | return __value; |
114 | #if __cpp_if_consteval >= 202106L && __CHAR_BIT__ == 8 |
115 | if !consteval |
116 | { |
117 | if constexpr (sizeof(_Tp) == 2) |
118 | return __builtin_bswap16(__value); |
119 | if constexpr (sizeof(_Tp) == 4) |
120 | return __builtin_bswap32(__value); |
121 | if constexpr (sizeof(_Tp) == 8) |
122 | return __builtin_bswap64(__value); |
123 | if constexpr (sizeof(_Tp) == 16) |
124 | #if __has_builtin(__builtin_bswap128) |
125 | return __builtin_bswap128(__value); |
126 | #else |
127 | return (__builtin_bswap64(__value >> 64) |
128 | | (static_cast<_Tp>(__builtin_bswap64(__value)) << 64)); |
129 | #endif |
130 | } |
131 | #endif |
132 | |
133 | // Fallback implementation that handles even __int24 etc. |
134 | using _Up = typename __make_unsigned<__remove_cv_t<_Tp>>::__type; |
135 | size_t __diff = __CHAR_BIT__ * (sizeof(_Tp) - 1); |
136 | _Up __mask1 = static_cast<unsigned char>(~0); |
137 | _Up __mask2 = __mask1 << __diff; |
138 | _Up __val = __value; |
139 | for (size_t __i = 0; __i < sizeof(_Tp) / 2; ++__i) |
140 | { |
141 | _Up __byte1 = __val & __mask1; |
142 | _Up __byte2 = __val & __mask2; |
143 | __val = (__val ^ __byte1 ^ __byte2 |
144 | ^ (__byte1 << __diff) ^ (__byte2 >> __diff)); |
145 | __mask1 <<= __CHAR_BIT__; |
146 | __mask2 >>= __CHAR_BIT__; |
147 | __diff -= 2 * __CHAR_BIT__; |
148 | } |
149 | return __val; |
150 | } |
151 | #endif // __cpp_lib_byteswap |
152 | |
153 | /// @cond undocumented |
154 | |
155 | template<typename _Tp> |
156 | constexpr _Tp |
157 | __rotl(_Tp __x, int __s) noexcept |
158 | { |
159 | constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
160 | if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0) |
161 | { |
162 | // Variant for power of two _Nd which the compiler can |
163 | // easily pattern match. |
164 | constexpr unsigned __uNd = _Nd; |
165 | const unsigned __r = __s; |
166 | return (__x << (__r % __uNd)) | (__x >> ((-__r) % __uNd)); |
167 | } |
168 | const int __r = __s % _Nd; |
169 | if (__r == 0) |
170 | return __x; |
171 | else if (__r > 0) |
172 | return (__x << __r) | (__x >> ((_Nd - __r) % _Nd)); |
173 | else |
174 | return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r) |
175 | } |
176 | |
177 | template<typename _Tp> |
178 | constexpr _Tp |
179 | __rotr(_Tp __x, int __s) noexcept |
180 | { |
181 | constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
182 | if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0) |
183 | { |
184 | // Variant for power of two _Nd which the compiler can |
185 | // easily pattern match. |
186 | constexpr unsigned __uNd = _Nd; |
187 | const unsigned __r = __s; |
188 | return (__x >> (__r % __uNd)) | (__x << ((-__r) % __uNd)); |
189 | } |
190 | const int __r = __s % _Nd; |
191 | if (__r == 0) |
192 | return __x; |
193 | else if (__r > 0) |
194 | return (__x >> __r) | (__x << ((_Nd - __r) % _Nd)); |
195 | else |
196 | return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r) |
197 | } |
198 | |
199 | template<typename _Tp> |
200 | constexpr int |
201 | __countl_zero(_Tp __x) noexcept |
202 | { |
203 | using __gnu_cxx::__int_traits; |
204 | constexpr auto _Nd = __int_traits<_Tp>::__digits; |
205 | |
206 | if (__x == 0) |
207 | return _Nd; |
208 | |
209 | constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; |
210 | constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; |
211 | constexpr auto _Nd_u = __int_traits<unsigned>::__digits; |
212 | |
213 | if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) |
214 | { |
215 | constexpr int __diff = _Nd_u - _Nd; |
216 | return __builtin_clz(__x) - __diff; |
217 | } |
218 | else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) |
219 | { |
220 | constexpr int __diff = _Nd_ul - _Nd; |
221 | return __builtin_clzl(__x) - __diff; |
222 | } |
223 | else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) |
224 | { |
225 | constexpr int __diff = _Nd_ull - _Nd; |
226 | return __builtin_clzll(__x) - __diff; |
227 | } |
228 | else // (_Nd > _Nd_ull) |
229 | { |
230 | static_assert(_Nd <= (2 * _Nd_ull), |
231 | "Maximum supported integer size is 128-bit" ); |
232 | |
233 | unsigned long long __high = __x >> _Nd_ull; |
234 | if (__high != 0) |
235 | { |
236 | constexpr int __diff = (2 * _Nd_ull) - _Nd; |
237 | return __builtin_clzll(__high) - __diff; |
238 | } |
239 | constexpr auto __max_ull = __int_traits<unsigned long long>::__max; |
240 | unsigned long long __low = __x & __max_ull; |
241 | return (_Nd - _Nd_ull) + __builtin_clzll(__low); |
242 | } |
243 | } |
244 | |
245 | template<typename _Tp> |
246 | constexpr int |
247 | __countl_one(_Tp __x) noexcept |
248 | { |
249 | return std::__countl_zero<_Tp>((_Tp)~__x); |
250 | } |
251 | |
252 | template<typename _Tp> |
253 | constexpr int |
254 | __countr_zero(_Tp __x) noexcept |
255 | { |
256 | using __gnu_cxx::__int_traits; |
257 | constexpr auto _Nd = __int_traits<_Tp>::__digits; |
258 | |
259 | if (__x == 0) |
260 | return _Nd; |
261 | |
262 | constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; |
263 | constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; |
264 | constexpr auto _Nd_u = __int_traits<unsigned>::__digits; |
265 | |
266 | if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) |
267 | return __builtin_ctz(__x); |
268 | else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) |
269 | return __builtin_ctzl(__x); |
270 | else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) |
271 | return __builtin_ctzll(__x); |
272 | else // (_Nd > _Nd_ull) |
273 | { |
274 | static_assert(_Nd <= (2 * _Nd_ull), |
275 | "Maximum supported integer size is 128-bit" ); |
276 | |
277 | constexpr auto __max_ull = __int_traits<unsigned long long>::__max; |
278 | unsigned long long __low = __x & __max_ull; |
279 | if (__low != 0) |
280 | return __builtin_ctzll(__low); |
281 | unsigned long long __high = __x >> _Nd_ull; |
282 | return __builtin_ctzll(__high) + _Nd_ull; |
283 | } |
284 | } |
285 | |
286 | template<typename _Tp> |
287 | constexpr int |
288 | __countr_one(_Tp __x) noexcept |
289 | { |
290 | return std::__countr_zero((_Tp)~__x); |
291 | } |
292 | |
293 | template<typename _Tp> |
294 | constexpr int |
295 | __popcount(_Tp __x) noexcept |
296 | { |
297 | using __gnu_cxx::__int_traits; |
298 | constexpr auto _Nd = __int_traits<_Tp>::__digits; |
299 | |
300 | constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; |
301 | constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; |
302 | constexpr auto _Nd_u = __int_traits<unsigned>::__digits; |
303 | |
304 | if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) |
305 | return __builtin_popcount(__x); |
306 | else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) |
307 | return __builtin_popcountl(__x); |
308 | else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) |
309 | return __builtin_popcountll(__x); |
310 | else // (_Nd > _Nd_ull) |
311 | { |
312 | static_assert(_Nd <= (2 * _Nd_ull), |
313 | "Maximum supported integer size is 128-bit" ); |
314 | |
315 | constexpr auto __max_ull = __int_traits<unsigned long long>::__max; |
316 | unsigned long long __low = __x & __max_ull; |
317 | unsigned long long __high = __x >> _Nd_ull; |
318 | return __builtin_popcountll(__low) + __builtin_popcountll(__high); |
319 | } |
320 | } |
321 | |
322 | template<typename _Tp> |
323 | constexpr bool |
324 | __has_single_bit(_Tp __x) noexcept |
325 | { return std::__popcount(__x) == 1; } |
326 | |
327 | template<typename _Tp> |
328 | constexpr _Tp |
329 | __bit_ceil(_Tp __x) noexcept |
330 | { |
331 | using __gnu_cxx::__int_traits; |
332 | constexpr auto _Nd = __int_traits<_Tp>::__digits; |
333 | if (__x == 0 || __x == 1) |
334 | return 1; |
335 | auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u)); |
336 | // If the shift exponent equals _Nd then the correct result is not |
337 | // representable as a value of _Tp, and so the result is undefined. |
338 | // Want that undefined behaviour to be detected in constant expressions, |
339 | // by UBSan, and by debug assertions. |
340 | if (!std::__is_constant_evaluated()) |
341 | { |
342 | __glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits ); |
343 | } |
344 | |
345 | using __promoted_type = decltype(__x << 1); |
346 | if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value) |
347 | { |
348 | // If __x undergoes integral promotion then shifting by _Nd is |
349 | // not undefined. In order to make the shift undefined, so that |
350 | // it is diagnosed in constant expressions and by UBsan, we also |
351 | // need to "promote" the shift exponent to be too large for the |
352 | // promoted type. |
353 | const int = sizeof(__promoted_type) / sizeof(_Tp) / 2; |
354 | __shift_exponent |= (__shift_exponent & _Nd) << __extra_exp; |
355 | } |
356 | return (_Tp)1u << __shift_exponent; |
357 | } |
358 | |
359 | template<typename _Tp> |
360 | constexpr _Tp |
361 | __bit_floor(_Tp __x) noexcept |
362 | { |
363 | constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
364 | if (__x == 0) |
365 | return 0; |
366 | return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1))); |
367 | } |
368 | |
369 | template<typename _Tp> |
370 | constexpr int |
371 | __bit_width(_Tp __x) noexcept |
372 | { |
373 | constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
374 | return _Nd - std::__countl_zero(__x); |
375 | } |
376 | |
377 | /// @endcond |
378 | |
379 | #ifdef __cpp_lib_bitops // C++ >= 20 |
380 | |
381 | /// @cond undocumented |
382 | template<typename _Tp> |
383 | concept __unsigned_integer = __is_unsigned_integer<_Tp>::value; |
384 | /// @endcond |
385 | |
386 | // [bit.rot], rotating |
387 | |
388 | /// Rotate `x` to the left by `s` bits. |
389 | template<__unsigned_integer _Tp> |
390 | [[nodiscard]] constexpr _Tp |
391 | rotl(_Tp __x, int __s) noexcept |
392 | { return std::__rotl(__x, __s); } |
393 | |
394 | /// Rotate `x` to the right by `s` bits. |
395 | template<__unsigned_integer _Tp> |
396 | [[nodiscard]] constexpr _Tp |
397 | rotr(_Tp __x, int __s) noexcept |
398 | { return std::__rotr(__x, __s); } |
399 | |
400 | // [bit.count], counting |
401 | |
402 | /// The number of contiguous zero bits, starting from the highest bit. |
403 | template<__unsigned_integer _Tp> |
404 | constexpr int |
405 | countl_zero(_Tp __x) noexcept |
406 | { return std::__countl_zero(__x); } |
407 | |
408 | /// The number of contiguous one bits, starting from the highest bit. |
409 | template<__unsigned_integer _Tp> |
410 | constexpr int |
411 | countl_one(_Tp __x) noexcept |
412 | { return std::__countl_one(__x); } |
413 | |
414 | /// The number of contiguous zero bits, starting from the lowest bit. |
415 | template<__unsigned_integer _Tp> |
416 | constexpr int |
417 | countr_zero(_Tp __x) noexcept |
418 | { return std::__countr_zero(__x); } |
419 | |
420 | /// The number of contiguous one bits, starting from the lowest bit. |
421 | template<__unsigned_integer _Tp> |
422 | constexpr int |
423 | countr_one(_Tp __x) noexcept |
424 | { return std::__countr_one(__x); } |
425 | |
426 | /// The number of bits set in `x`. |
427 | template<__unsigned_integer _Tp> |
428 | constexpr int |
429 | popcount(_Tp __x) noexcept |
430 | { return std::__popcount(__x); } |
431 | #endif // __cpp_lib_bitops |
432 | |
433 | #ifdef __cpp_lib_int_pow2 // C++ >= 20 |
434 | // [bit.pow.two], integral powers of 2 |
435 | |
436 | /// True if `x` is a power of two, false otherwise. |
437 | template<__unsigned_integer _Tp> |
438 | constexpr bool |
439 | has_single_bit(_Tp __x) noexcept |
440 | { return std::__has_single_bit(__x); } |
441 | |
442 | /// The smallest power-of-two not less than `x`. |
443 | template<__unsigned_integer _Tp> |
444 | constexpr _Tp |
445 | bit_ceil(_Tp __x) noexcept |
446 | { return std::__bit_ceil(__x); } |
447 | |
448 | /// The largest power-of-two not greater than `x`. |
449 | template<__unsigned_integer _Tp> |
450 | constexpr _Tp |
451 | bit_floor(_Tp __x) noexcept |
452 | { return std::__bit_floor(__x); } |
453 | |
454 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
455 | // 3656. Inconsistent bit operations returning a count |
456 | /// The smallest integer greater than the base-2 logarithm of `x`. |
457 | template<__unsigned_integer _Tp> |
458 | constexpr int |
459 | bit_width(_Tp __x) noexcept |
460 | { return std::__bit_width(__x); } |
461 | #endif // defined (__cpp_lib_int_pow2) |
462 | |
463 | #ifdef __cpp_lib_endian // C++ >= 20 |
464 | |
465 | /// Byte order constants |
466 | /** |
467 | * The platform endianness can be checked by comparing `std::endian::native` |
468 | * to one of `std::endian::big` or `std::endian::little`. |
469 | * |
470 | * @since C++20 |
471 | */ |
472 | enum class endian |
473 | { |
474 | little = __ORDER_LITTLE_ENDIAN__, |
475 | big = __ORDER_BIG_ENDIAN__, |
476 | native = __BYTE_ORDER__ |
477 | }; |
478 | #endif // __cpp_lib_endian |
479 | |
480 | /// @} |
481 | |
482 | _GLIBCXX_END_NAMESPACE_VERSION |
483 | } // namespace std |
484 | |
485 | #endif // C++14 |
486 | #endif // _GLIBCXX_BIT |
487 | |