1// <bit> -*- C++ -*- 2 3// Copyright (C) 2018-2020 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 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 <type_traits> 37#include <ext/numeric_traits.h> 38 39namespace std _GLIBCXX_VISIBILITY(default) 40{ 41_GLIBCXX_BEGIN_NAMESPACE_VERSION 42 43 /** 44 * @defgroup bit_manip Bit manipulation 45 * @ingroup numerics 46 * 47 * Utilities for examining and manipulating individual bits. 48 * 49 * @{ 50 */ 51 52 /// @cond undoc 53 54 template<typename _Tp> 55 constexpr _Tp 56 __rotl(_Tp __x, int __s) noexcept 57 { 58 constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; 59 const int __r = __s % _Nd; 60 if (__r == 0) 61 return __x; 62 else if (__r > 0) 63 return (__x << __r) | (__x >> ((_Nd - __r) % _Nd)); 64 else 65 return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r) 66 } 67 68 template<typename _Tp> 69 constexpr _Tp 70 __rotr(_Tp __x, int __s) noexcept 71 { 72 constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; 73 const int __r = __s % _Nd; 74 if (__r == 0) 75 return __x; 76 else if (__r > 0) 77 return (__x >> __r) | (__x << ((_Nd - __r) % _Nd)); 78 else 79 return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r) 80 } 81 82 template<typename _Tp> 83 constexpr int 84 __countl_zero(_Tp __x) noexcept 85 { 86 using __gnu_cxx::__int_traits; 87 constexpr auto _Nd = __int_traits<_Tp>::__digits; 88 89 if (__x == 0) 90 return _Nd; 91 92 constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; 93 constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; 94 constexpr auto _Nd_u = __int_traits<unsigned>::__digits; 95 96 if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) 97 { 98 constexpr int __diff = _Nd_u - _Nd; 99 return __builtin_clz(__x) - __diff; 100 } 101 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) 102 { 103 constexpr int __diff = _Nd_ul - _Nd; 104 return __builtin_clzl(__x) - __diff; 105 } 106 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) 107 { 108 constexpr int __diff = _Nd_ull - _Nd; 109 return __builtin_clzll(__x) - __diff; 110 } 111 else // (_Nd > _Nd_ull) 112 { 113 static_assert(_Nd <= (2 * _Nd_ull), 114 "Maximum supported integer size is 128-bit"); 115 116 unsigned long long __high = __x >> _Nd_ull; 117 if (__high != 0) 118 { 119 constexpr int __diff = (2 * _Nd_ull) - _Nd; 120 return __builtin_clzll(__high) - __diff; 121 } 122 constexpr auto __max_ull = __int_traits<unsigned long long>::__max; 123 unsigned long long __low = __x & __max_ull; 124 return (_Nd - _Nd_ull) + __builtin_clzll(__low); 125 } 126 } 127 128 template<typename _Tp> 129 constexpr int 130 __countl_one(_Tp __x) noexcept 131 { 132 return std::__countl_zero<_Tp>((_Tp)~__x); 133 } 134 135 template<typename _Tp> 136 constexpr int 137 __countr_zero(_Tp __x) noexcept 138 { 139 using __gnu_cxx::__int_traits; 140 constexpr auto _Nd = __int_traits<_Tp>::__digits; 141 142 if (__x == 0) 143 return _Nd; 144 145 constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; 146 constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; 147 constexpr auto _Nd_u = __int_traits<unsigned>::__digits; 148 149 if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) 150 return __builtin_ctz(__x); 151 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) 152 return __builtin_ctzl(__x); 153 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) 154 return __builtin_ctzll(__x); 155 else // (_Nd > _Nd_ull) 156 { 157 static_assert(_Nd <= (2 * _Nd_ull), 158 "Maximum supported integer size is 128-bit"); 159 160 constexpr auto __max_ull = __int_traits<unsigned long long>::__max; 161 unsigned long long __low = __x & __max_ull; 162 if (__low != 0) 163 return __builtin_ctzll(__low); 164 unsigned long long __high = __x >> _Nd_ull; 165 return __builtin_ctzll(__high) + _Nd_ull; 166 } 167 } 168 169 template<typename _Tp> 170 constexpr int 171 __countr_one(_Tp __x) noexcept 172 { 173 return std::__countr_zero((_Tp)~__x); 174 } 175 176 template<typename _Tp> 177 constexpr int 178 __popcount(_Tp __x) noexcept 179 { 180 using __gnu_cxx::__int_traits; 181 constexpr auto _Nd = __int_traits<_Tp>::__digits; 182 183 constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; 184 constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; 185 constexpr auto _Nd_u = __int_traits<unsigned>::__digits; 186 187 if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) 188 return __builtin_popcount(__x); 189 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) 190 return __builtin_popcountl(__x); 191 else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) 192 return __builtin_popcountll(__x); 193 else // (_Nd > _Nd_ull) 194 { 195 static_assert(_Nd <= (2 * _Nd_ull), 196 "Maximum supported integer size is 128-bit"); 197 198 constexpr auto __max_ull = __int_traits<unsigned long long>::__max; 199 unsigned long long __low = __x & __max_ull; 200 unsigned long long __high = __x >> _Nd_ull; 201 return __builtin_popcountll(__low) + __builtin_popcountll(__high); 202 } 203 } 204 205 template<typename _Tp> 206 constexpr bool 207 __has_single_bit(_Tp __x) noexcept 208 { return std::__popcount(__x) == 1; } 209 210 template<typename _Tp> 211 constexpr _Tp 212 __bit_ceil(_Tp __x) noexcept 213 { 214 using __gnu_cxx::__int_traits; 215 constexpr auto _Nd = __int_traits<_Tp>::__digits; 216 if (__x == 0 || __x == 1) 217 return 1; 218 auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u)); 219 // If the shift exponent equals _Nd then the correct result is not 220 // representable as a value of _Tp, and so the result is undefined. 221 // Want that undefined behaviour to be detected in constant expressions, 222 // by UBSan, and by debug assertions. 223#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 224 if (!__builtin_is_constant_evaluated()) 225 { 226 __glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits ); 227 } 228#endif 229 using __promoted_type = decltype(__x << 1); 230 if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value) 231 { 232 // If __x undergoes integral promotion then shifting by _Nd is 233 // not undefined. In order to make the shift undefined, so that 234 // it is diagnosed in constant expressions and by UBsan, we also 235 // need to "promote" the shift exponent to be too large for the 236 // promoted type. 237 const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2; 238 __shift_exponent |= (__shift_exponent & _Nd) << __extra_exp; 239 } 240 return (_Tp)1u << __shift_exponent; 241 } 242 243 template<typename _Tp> 244 constexpr _Tp 245 __bit_floor(_Tp __x) noexcept 246 { 247 constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; 248 if (__x == 0) 249 return 0; 250 return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1))); 251 } 252 253 template<typename _Tp> 254 constexpr _Tp 255 __bit_width(_Tp __x) noexcept 256 { 257 constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; 258 return _Nd - std::__countl_zero(__x); 259 } 260 261 /// @endcond 262 263#if __cplusplus > 201703L 264 265#define __cpp_lib_bitops 201907L 266 267 /// @cond undoc 268 template<typename _Tp, typename _Up = _Tp> 269 using _If_is_unsigned_integer 270 = enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>; 271 /// @endcond 272 273 // [bit.rot], rotating 274 275 /// Rotate `x` to the left by `s` bits. 276 template<typename _Tp> 277 [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp> 278 rotl(_Tp __x, int __s) noexcept 279 { return std::__rotl(__x, __s); } 280 281 /// Rotate `x` to the right by `s` bits. 282 template<typename _Tp> 283 [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp> 284 rotr(_Tp __x, int __s) noexcept 285 { return std::__rotr(__x, __s); } 286 287 // [bit.count], counting 288 289 /// The number of contiguous zero bits, starting from the highest bit. 290 template<typename _Tp> 291 constexpr _If_is_unsigned_integer<_Tp, int> 292 countl_zero(_Tp __x) noexcept 293 { return std::__countl_zero(__x); } 294 295 /// The number of contiguous one bits, starting from the highest bit. 296 template<typename _Tp> 297 constexpr _If_is_unsigned_integer<_Tp, int> 298 countl_one(_Tp __x) noexcept 299 { return std::__countl_one(__x); } 300 301 /// The number of contiguous zero bits, starting from the lowest bit. 302 template<typename _Tp> 303 constexpr _If_is_unsigned_integer<_Tp, int> 304 countr_zero(_Tp __x) noexcept 305 { return std::__countr_zero(__x); } 306 307 /// The number of contiguous one bits, starting from the lowest bit. 308 template<typename _Tp> 309 constexpr _If_is_unsigned_integer<_Tp, int> 310 countr_one(_Tp __x) noexcept 311 { return std::__countr_one(__x); } 312 313 /// The number of bits set in `x`. 314 template<typename _Tp> 315 constexpr _If_is_unsigned_integer<_Tp, int> 316 popcount(_Tp __x) noexcept 317 { return std::__popcount(__x); } 318 319 // [bit.pow.two], integral powers of 2 320 321#define __cpp_lib_int_pow2 202002L 322 323 /// True if `x` is a power of two, false otherwise. 324 template<typename _Tp> 325 constexpr _If_is_unsigned_integer<_Tp, bool> 326 has_single_bit(_Tp __x) noexcept 327 { return std::__has_single_bit(__x); } 328 329 /// The smallest power-of-two not less than `x`. 330 template<typename _Tp> 331 constexpr _If_is_unsigned_integer<_Tp> 332 bit_ceil(_Tp __x) noexcept 333 { return std::__bit_ceil(__x); } 334 335 /// The largest power-of-two not greater than `x`. 336 template<typename _Tp> 337 constexpr _If_is_unsigned_integer<_Tp> 338 bit_floor(_Tp __x) noexcept 339 { return std::__bit_floor(__x); } 340 341 /// The smallest integer greater than the base-2 logarithm of `x`. 342 template<typename _Tp> 343 constexpr _If_is_unsigned_integer<_Tp> 344 bit_width(_Tp __x) noexcept 345 { return std::__bit_width(__x); } 346 347#define __cpp_lib_endian 201907L 348 349 /// Byte order 350 enum class endian 351 { 352 little = __ORDER_LITTLE_ENDIAN__, 353 big = __ORDER_BIG_ENDIAN__, 354 native = __BYTE_ORDER__ 355 }; 356#endif // C++2a 357 358 /// @} 359 360_GLIBCXX_END_NAMESPACE_VERSION 361} // namespace std 362 363#endif // C++14 364#endif // _GLIBCXX_BIT 365