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// <bit> -*- C++ -*- |
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|
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// Copyright (C) 2018-2021 Free Software Foundation, Inc. |
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// |
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// This file is part of the GNU ISO C++ Library. This library is free |
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// software; you can redistribute it and/or modify it under the |
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// terms of the GNU General Public License as published by the |
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// Free Software Foundation; either version 3, or (at your option) |
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// any later version. |
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|
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// This library is distributed in the hope that it will be useful, |
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// but WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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// GNU General Public License for more details. |
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|
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// Under Section 7 of GPL version 3, you are granted additional |
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// permissions described in the GCC Runtime Library Exception, version |
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// 3.1, as published by the Free Software Foundation. |
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|
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// You should have received a copy of the GNU General Public License and |
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// a copy of the GCC Runtime Library Exception along with this program; |
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
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// <http://www.gnu.org/licenses/>. |
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|
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/** @file include/bit |
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* This is a Standard C++ Library header. |
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*/ |
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|
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#ifndef _GLIBCXX_BIT |
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#define _GLIBCXX_BIT 1 |
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|
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#pragma GCC system_header |
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|
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#if __cplusplus >= 201402L |
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|
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#include <type_traits> |
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|
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#if _GLIBCXX_HOSTED |
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# include <ext/numeric_traits.h> |
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#else |
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# include <limits> |
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/// @cond undocumented |
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namespace __gnu_cxx |
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{ |
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template<typename _Tp> |
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struct __int_traits |
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{ |
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static constexpr int __digits = std::numeric_limits<_Tp>::digits; |
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static constexpr _Tp __max = std::numeric_limits<_Tp>::max(); |
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}; |
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} |
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/// @endcond |
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#endif |
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|
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namespace std _GLIBCXX_VISIBILITY(default) |
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{ |
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_GLIBCXX_BEGIN_NAMESPACE_VERSION |
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|
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/** |
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* @defgroup bit_manip Bit manipulation |
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* @ingroup numerics |
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* |
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* Utilities for examining and manipulating individual bits. |
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* |
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* @{ |
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*/ |
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|
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#if __cplusplus > 201703l && __has_builtin(__builtin_bit_cast) |
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#define __cpp_lib_bit_cast 201806L |
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|
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/// Create a value of type `To` from the bits of `from`. |
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template<typename _To, typename _From> |
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[[nodiscard]] |
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constexpr _To |
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bit_cast(const _From& __from) noexcept |
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{ |
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return __builtin_bit_cast(_To, __from); |
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} |
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#endif |
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|
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/// @cond undoc |
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|
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template<typename _Tp> |
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constexpr _Tp |
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__rotl(_Tp __x, int __s) noexcept |
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{ |
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constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
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if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0) |
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{ |
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// Variant for power of two _Nd which the compiler can |
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// easily pattern match. |
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constexpr unsigned __uNd = _Nd; |
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const unsigned __r = __s; |
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return (__x << (__r % __uNd)) | (__x >> ((-__r) % __uNd)); |
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} |
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const int __r = __s % _Nd; |
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if (__r == 0) |
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return __x; |
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else if (__r > 0) |
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return (__x << __r) | (__x >> ((_Nd - __r) % _Nd)); |
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else |
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return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r) |
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} |
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|
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template<typename _Tp> |
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constexpr _Tp |
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__rotr(_Tp __x, int __s) noexcept |
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{ |
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constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
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if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0) |
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{ |
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// Variant for power of two _Nd which the compiler can |
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// easily pattern match. |
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constexpr unsigned __uNd = _Nd; |
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const unsigned __r = __s; |
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return (__x >> (__r % __uNd)) | (__x << ((-__r) % __uNd)); |
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} |
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const int __r = __s % _Nd; |
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if (__r == 0) |
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return __x; |
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else if (__r > 0) |
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return (__x >> __r) | (__x << ((_Nd - __r) % _Nd)); |
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else |
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return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r) |
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} |
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|
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template<typename _Tp> |
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constexpr int |
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__countl_zero(_Tp __x) noexcept |
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{ |
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using __gnu_cxx::__int_traits; |
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constexpr auto _Nd = __int_traits<_Tp>::__digits; |
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|
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if (__x == 0) |
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return _Nd; |
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|
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constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; |
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constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; |
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constexpr auto _Nd_u = __int_traits<unsigned>::__digits; |
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|
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if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) |
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{ |
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constexpr int __diff = _Nd_u - _Nd; |
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return __builtin_clz(__x) - __diff; |
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} |
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else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) |
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{ |
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constexpr int __diff = _Nd_ul - _Nd; |
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return __builtin_clzl(__x) - __diff; |
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} |
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else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) |
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{ |
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constexpr int __diff = _Nd_ull - _Nd; |
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return __builtin_clzll(__x) - __diff; |
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} |
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else // (_Nd > _Nd_ull) |
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{ |
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static_assert(_Nd <= (2 * _Nd_ull), |
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"Maximum supported integer size is 128-bit"); |
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|
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unsigned long long __high = __x >> _Nd_ull; |
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if (__high != 0) |
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{ |
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constexpr int __diff = (2 * _Nd_ull) - _Nd; |
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return __builtin_clzll(__high) - __diff; |
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} |
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constexpr auto __max_ull = __int_traits<unsigned long long>::__max; |
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unsigned long long __low = __x & __max_ull; |
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return (_Nd - _Nd_ull) + __builtin_clzll(__low); |
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} |
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} |
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|
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template<typename _Tp> |
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constexpr int |
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__countl_one(_Tp __x) noexcept |
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{ |
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return std::__countl_zero<_Tp>((_Tp)~__x); |
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} |
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|
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template<typename _Tp> |
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constexpr int |
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__countr_zero(_Tp __x) noexcept |
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{ |
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using __gnu_cxx::__int_traits; |
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constexpr auto _Nd = __int_traits<_Tp>::__digits; |
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|
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if (__x == 0) |
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return _Nd; |
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|
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constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; |
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constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; |
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constexpr auto _Nd_u = __int_traits<unsigned>::__digits; |
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|
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if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) |
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return __builtin_ctz(__x); |
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else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) |
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return __builtin_ctzl(__x); |
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else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) |
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return __builtin_ctzll(__x); |
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else // (_Nd > _Nd_ull) |
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{ |
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static_assert(_Nd <= (2 * _Nd_ull), |
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"Maximum supported integer size is 128-bit"); |
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|
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constexpr auto __max_ull = __int_traits<unsigned long long>::__max; |
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unsigned long long __low = __x & __max_ull; |
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if (__low != 0) |
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return __builtin_ctzll(__low); |
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unsigned long long __high = __x >> _Nd_ull; |
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return __builtin_ctzll(__high) + _Nd_ull; |
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} |
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} |
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|
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template<typename _Tp> |
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constexpr int |
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__countr_one(_Tp __x) noexcept |
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{ |
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return std::__countr_zero((_Tp)~__x); |
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} |
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|
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template<typename _Tp> |
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constexpr int |
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__popcount(_Tp __x) noexcept |
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{ |
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using __gnu_cxx::__int_traits; |
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constexpr auto _Nd = __int_traits<_Tp>::__digits; |
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|
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constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits; |
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constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits; |
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constexpr auto _Nd_u = __int_traits<unsigned>::__digits; |
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|
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if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u) |
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return __builtin_popcount(__x); |
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else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul) |
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return __builtin_popcountl(__x); |
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else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull) |
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return __builtin_popcountll(__x); |
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else // (_Nd > _Nd_ull) |
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{ |
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static_assert(_Nd <= (2 * _Nd_ull), |
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"Maximum supported integer size is 128-bit"); |
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|
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constexpr auto __max_ull = __int_traits<unsigned long long>::__max; |
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unsigned long long __low = __x & __max_ull; |
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unsigned long long __high = __x >> _Nd_ull; |
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return __builtin_popcountll(__low) + __builtin_popcountll(__high); |
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} |
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} |
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|
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template<typename _Tp> |
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constexpr bool |
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__has_single_bit(_Tp __x) noexcept |
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{ return std::__popcount(__x) == 1; } |
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|
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template<typename _Tp> |
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constexpr _Tp |
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__bit_ceil(_Tp __x) noexcept |
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{ |
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using __gnu_cxx::__int_traits; |
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constexpr auto _Nd = __int_traits<_Tp>::__digits; |
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if (__x == 0 || __x == 1) |
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return 1; |
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auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u)); |
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// If the shift exponent equals _Nd then the correct result is not |
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// representable as a value of _Tp, and so the result is undefined. |
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// Want that undefined behaviour to be detected in constant expressions, |
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// by UBSan, and by debug assertions. |
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#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED |
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if (!__builtin_is_constant_evaluated()) |
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{ |
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__glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits ); |
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} |
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#endif |
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using __promoted_type = decltype(__x << 1); |
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if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value) |
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{ |
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// If __x undergoes integral promotion then shifting by _Nd is |
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// not undefined. In order to make the shift undefined, so that |
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// it is diagnosed in constant expressions and by UBsan, we also |
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// need to "promote" the shift exponent to be too large for the |
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// promoted type. |
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const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2; |
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__shift_exponent |= (__shift_exponent & _Nd) << __extra_exp; |
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} |
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return (_Tp)1u << __shift_exponent; |
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} |
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|
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template<typename _Tp> |
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constexpr _Tp |
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__bit_floor(_Tp __x) noexcept |
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{ |
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constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
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if (__x == 0) |
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return 0; |
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return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1))); |
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} |
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|
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template<typename _Tp> |
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constexpr _Tp |
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__bit_width(_Tp __x) noexcept |
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{ |
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constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits; |
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return _Nd - std::__countl_zero(__x); |
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} |
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|
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/// @endcond |
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|
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#if __cplusplus > 201703L |
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|
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#define __cpp_lib_bitops 201907L |
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|
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/// @cond undoc |
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template<typename _Tp, typename _Up = _Tp> |
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using _If_is_unsigned_integer |
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= enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>; |
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/// @endcond |
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|
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// [bit.rot], rotating |
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|
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/// Rotate `x` to the left by `s` bits. |
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template<typename _Tp> |
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[[nodiscard]] constexpr _If_is_unsigned_integer<_Tp> |
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rotl(_Tp __x, int __s) noexcept |
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{ return std::__rotl(__x, __s); } |
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|
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/// Rotate `x` to the right by `s` bits. |
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template<typename _Tp> |
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[[nodiscard]] constexpr _If_is_unsigned_integer<_Tp> |
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rotr(_Tp __x, int __s) noexcept |
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{ return std::__rotr(__x, __s); } |
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|
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// [bit.count], counting |
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|
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/// The number of contiguous zero bits, starting from the highest bit. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp, int> |
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countl_zero(_Tp __x) noexcept |
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{ return std::__countl_zero(__x); } |
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|
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/// The number of contiguous one bits, starting from the highest bit. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp, int> |
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countl_one(_Tp __x) noexcept |
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{ return std::__countl_one(__x); } |
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|
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/// The number of contiguous zero bits, starting from the lowest bit. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp, int> |
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countr_zero(_Tp __x) noexcept |
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{ return std::__countr_zero(__x); } |
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|
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/// The number of contiguous one bits, starting from the lowest bit. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp, int> |
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countr_one(_Tp __x) noexcept |
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{ return std::__countr_one(__x); } |
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|
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/// The number of bits set in `x`. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp, int> |
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popcount(_Tp __x) noexcept |
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{ return std::__popcount(__x); } |
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|
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// [bit.pow.two], integral powers of 2 |
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|
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#define __cpp_lib_int_pow2 202002L |
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|
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/// True if `x` is a power of two, false otherwise. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp, bool> |
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has_single_bit(_Tp __x) noexcept |
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{ return std::__has_single_bit(__x); } |
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|
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/// The smallest power-of-two not less than `x`. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp> |
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bit_ceil(_Tp __x) noexcept |
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{ return std::__bit_ceil(__x); } |
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|
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/// The largest power-of-two not greater than `x`. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp> |
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bit_floor(_Tp __x) noexcept |
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{ return std::__bit_floor(__x); } |
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|
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/// The smallest integer greater than the base-2 logarithm of `x`. |
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template<typename _Tp> |
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constexpr _If_is_unsigned_integer<_Tp> |
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bit_width(_Tp __x) noexcept |
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{ return std::__bit_width(__x); } |
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|
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#define __cpp_lib_endian 201907L |
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|
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/// Byte order |
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enum class endian |
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{ |
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little = __ORDER_LITTLE_ENDIAN__, |
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big = __ORDER_BIG_ENDIAN__, |
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native = __BYTE_ORDER__ |
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}; |
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#endif // C++2a |
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|
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/// @} |
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|
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_GLIBCXX_END_NAMESPACE_VERSION |
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} // namespace std |
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|
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#endif // C++14 |
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#endif // _GLIBCXX_BIT |
