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// <bit> -*- C++ -*- // Copyright (C) 2018-2022 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file include/bit * This is a Standard C++ Library header. */ #ifndef _GLIBCXX_BIT #define _GLIBCXX_BIT 1 #pragma GCC system_header #if __cplusplus >= 201402L #include <type_traits> #if _GLIBCXX_HOSTED # include <ext/numeric_traits.h> #else # include <limits> /// @cond undocumented namespace __gnu_cxx { template<typename _Tp> struct __int_traits { static constexpr int __digits = std::numeric_limits<_Tp>::digits; static constexpr _Tp __max = std::numeric_limits<_Tp>::max(); }; } /// @endcond #endif namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION /** * @defgroup bit_manip Bit manipulation * @ingroup numerics * * Utilities for examining and manipulating individual bits. * * @{ */ #if __cplusplus > 201703l && __has_builtin(__builtin_bit_cast) #define __cpp_lib_bit_cast 201806L /// Create a value of type `To` from the bits of `from`. /** * @tparam _To A trivially-copyable type. * @param __from A trivially-copyable object of the same size as `_To`. * @return An object of type `_To`. * @since C++20 */ template<typename _To, typename _From> [[nodiscard]] constexpr _To bit_cast(const _From& __from) noexcept #ifdef __cpp_concepts requires (sizeof(_To) == sizeof(_From)) && __is_trivially_copyable(_To) && __is_trivially_copyable(_From) #endif { return __builtin_bit_cast(_To, __from); } #endif #if __cplusplus > 202002L #define __cpp_lib_byteswap 202110L /// Reverse order of bytes in the object representation of `value`. /** * @tparam _Tp An integral type. * @param __value An object of integer type. * @return An object of the same type, with the bytes reversed. * @since C++23 */ template<typename _Tp> [[nodiscard]] constexpr enable_if_t<is_integral<_Tp>::value, _Tp> byteswap(_Tp __value) noexcept { if constexpr (sizeof(_Tp) == 1) return __value; #if __cpp_if_consteval >= 202106L && __CHAR_BIT__ == 8 if !consteval { if constexpr (sizeof(_Tp) == 2) return __builtin_bswap16(__value); if constexpr (sizeof(_Tp) == 4) return __builtin_bswap32(__value); if constexpr (sizeof(_Tp) == 8) return __builtin_bswap64(__value); if constexpr (sizeof(_Tp) == 16) #if __has_builtin(__builtin_bswap128) return __builtin_bswap128(__value); #else return (__builtin_bswap64(__value >> 64) | (static_cast<_Tp>(__builtin_bswap64(__value)) << 64)); #endif } #endif // Fallback implementation that handles even __int24 etc. using _Up = typename __make_unsigned<__remove_cv_t<_Tp>>::__type; size_t __diff = __CHAR_BIT__ * (sizeof(_Tp) - 1); _Up __mask1 = static_cast<unsigned char>(~0); _Up __mask2 = __mask1 << __diff; _Up __val = __value; for (size_t __i = 0; __i < sizeof(_Tp) / 2; ++__i) { _Up __byte1 = __val & __mask1; _Up __byte2 = __val & __mask2; __val = (__val ^ __byte1 ^ __byte2 ^ (__byte1 << __diff) ^ (__byte2 >> __diff)); __mask1 <<= __CHAR_BIT__; __mask2 >>= __CHAR_BIT__; __diff -= 2 * __CHAR_BIT__; } return __val; } #endif /// @cond undoc template<typename _Tp> constexpr _Tp __rotl(_Tp __x, int __s) noexcept { constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0) { // Variant for power of two _Nd which the compiler can // easily pattern match. constexpr unsigned __uNd = _Nd; const unsigned __r = __s; return (__x << (__r % __uNd)) | (__x >> ((-__r) % __uNd)); } const int __r = __s % _Nd; if (__r == 0) return __x; else if (__r > 0) return (__x << __r) | (__x >> ((_Nd - __r) % _Nd)); else return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r) } template<typename _Tp> constexpr _Tp __rotr(_Tp __x, int __s) noexcept { constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0) { // Variant for power of two _Nd which the compiler can // easily pattern match. constexpr unsigned __uNd = _Nd; const unsigned __r = __s; return (__x >> (__r % __uNd)) | (__x << ((-__r) % __uNd)); } const int __r = __s % _Nd; if (__r == 0) return __x; else if (__r > 0) return (__x >> __r) | (__x << ((_Nd - __r) % _Nd)); else return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r) } template<typename _Tp> constexpr int __countl_zero(_Tp __x) noexcept { using __gnu_cxx::__int_traits; constexpr auto _Nd = __int_traits<_Tp>::__digits; if (__x == 0) return _Nd; constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; constexpr auto _Nd_u = __int_traits<unsigned>::__digits; if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) { constexpr int __diff = _Nd_u - _Nd; return __builtin_clz(__x) - __diff; } else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) { constexpr int __diff = _Nd_ul - _Nd; return __builtin_clzl(__x) - __diff; } else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) { constexpr int __diff = _Nd_ull - _Nd; return __builtin_clzll(__x) - __diff; } else // (_Nd > _Nd_ull) { static_assert(_Nd <= (2 * _Nd_ull), "Maximum supported integer size is 128-bit"); unsigned long long __high = __x >> _Nd_ull; if (__high != 0) { constexpr int __diff = (2 * _Nd_ull) - _Nd; return __builtin_clzll(__high) - __diff; } constexpr auto __max_ull = __int_traits<unsigned long long>::__max; unsigned long long __low = __x & __max_ull; return (_Nd - _Nd_ull) + __builtin_clzll(__low); } } template<typename _Tp> constexpr int __countl_one(_Tp __x) noexcept { return std::__countl_zero<_Tp>((_Tp)~__x); } template<typename _Tp> constexpr int __countr_zero(_Tp __x) noexcept { using __gnu_cxx::__int_traits; constexpr auto _Nd = __int_traits<_Tp>::__digits; if (__x == 0) return _Nd; constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; constexpr auto _Nd_u = __int_traits<unsigned>::__digits; if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) return __builtin_ctz(__x); else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) return __builtin_ctzl(__x); else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) return __builtin_ctzll(__x); else // (_Nd > _Nd_ull) { static_assert(_Nd <= (2 * _Nd_ull), "Maximum supported integer size is 128-bit"); constexpr auto __max_ull = __int_traits<unsigned long long>::__max; unsigned long long __low = __x & __max_ull; if (__low != 0) return __builtin_ctzll(__low); unsigned long long __high = __x >> _Nd_ull; return __builtin_ctzll(__high) + _Nd_ull; } } template<typename _Tp> constexpr int __countr_one(_Tp __x) noexcept { return std::__countr_zero((_Tp)~__x); } template<typename _Tp> constexpr int __popcount(_Tp __x) noexcept { using __gnu_cxx::__int_traits; constexpr auto _Nd = __int_traits<_Tp>::__digits; constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; constexpr auto _Nd_u = __int_traits<unsigned>::__digits; if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) return __builtin_popcount(__x); else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) return __builtin_popcountl(__x); else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) return __builtin_popcountll(__x); else // (_Nd > _Nd_ull) { static_assert(_Nd <= (2 * _Nd_ull), "Maximum supported integer size is 128-bit"); constexpr auto __max_ull = __int_traits<unsigned long long>::__max; unsigned long long __low = __x & __max_ull; unsigned long long __high = __x >> _Nd_ull; return __builtin_popcountll(__low) + __builtin_popcountll(__high); } } template<typename _Tp> constexpr bool __has_single_bit(_Tp __x) noexcept { return std::__popcount(__x) == 1; } template<typename _Tp> constexpr _Tp __bit_ceil(_Tp __x) noexcept { using __gnu_cxx::__int_traits; constexpr auto _Nd = __int_traits<_Tp>::__digits; if (__x == 0 || __x == 1) return 1; auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u)); // If the shift exponent equals _Nd then the correct result is not // representable as a value of _Tp, and so the result is undefined. // Want that undefined behaviour to be detected in constant expressions, // by UBSan, and by debug assertions. if (!std::__is_constant_evaluated()) { __glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits ); } using __promoted_type = decltype(__x << 1); if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value) { // If __x undergoes integral promotion then shifting by _Nd is // not undefined. In order to make the shift undefined, so that // it is diagnosed in constant expressions and by UBsan, we also // need to "promote" the shift exponent to be too large for the // promoted type. const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2; __shift_exponent |= (__shift_exponent & _Nd) << __extra_exp; } return (_Tp)1u << __shift_exponent; } template<typename _Tp> constexpr _Tp __bit_floor(_Tp __x) noexcept { constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; if (__x == 0) return 0; return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1))); } template<typename _Tp> constexpr _Tp __bit_width(_Tp __x) noexcept { constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; return _Nd - std::__countl_zero(__x); } /// @endcond #if __cplusplus > 201703L #define __cpp_lib_bitops 201907L /// @cond undoc template<typename _Tp, typename _Up = _Tp> using _If_is_unsigned_integer = enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>; /// @endcond // [bit.rot], rotating /// Rotate `x` to the left by `s` bits. template<typename _Tp> [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp> rotl(_Tp __x, int __s) noexcept { return std::__rotl(__x, __s); } /// Rotate `x` to the right by `s` bits. template<typename _Tp> [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp> rotr(_Tp __x, int __s) noexcept { return std::__rotr(__x, __s); } // [bit.count], counting /// The number of contiguous zero bits, starting from the highest bit. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp, int> countl_zero(_Tp __x) noexcept { return std::__countl_zero(__x); } /// The number of contiguous one bits, starting from the highest bit. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp, int> countl_one(_Tp __x) noexcept { return std::__countl_one(__x); } /// The number of contiguous zero bits, starting from the lowest bit. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp, int> countr_zero(_Tp __x) noexcept { return std::__countr_zero(__x); } /// The number of contiguous one bits, starting from the lowest bit. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp, int> countr_one(_Tp __x) noexcept { return std::__countr_one(__x); } /// The number of bits set in `x`. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp, int> popcount(_Tp __x) noexcept { return std::__popcount(__x); } // [bit.pow.two], integral powers of 2 #define __cpp_lib_int_pow2 202002L /// True if `x` is a power of two, false otherwise. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp, bool> has_single_bit(_Tp __x) noexcept { return std::__has_single_bit(__x); } /// The smallest power-of-two not less than `x`. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp> bit_ceil(_Tp __x) noexcept { return std::__bit_ceil(__x); } /// The largest power-of-two not greater than `x`. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp> bit_floor(_Tp __x) noexcept { return std::__bit_floor(__x); } /// The smallest integer greater than the base-2 logarithm of `x`. template<typename _Tp> constexpr _If_is_unsigned_integer<_Tp> bit_width(_Tp __x) noexcept { return std::__bit_width(__x); } #define __cpp_lib_endian 201907L /// Byte order constants /** * The platform endianness can be checked by comparing `std::endian::native` * to one of `std::endian::big` or `std::endian::little`. * * @since C++20 */ enum class endian { little = __ORDER_LITTLE_ENDIAN__, big = __ORDER_BIG_ENDIAN__, native = __BYTE_ORDER__ }; #endif // C++2a /// @} _GLIBCXX_END_NAMESPACE_VERSION } // namespace std #endif // C++14 #endif // _GLIBCXX_BIT
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