xref: /llvm-project-15.0.7/libcxx/include/bit (revision a83004f4)

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===---------------------------------------------------------------------===//

#ifndef _LIBCPP_BIT
#define _LIBCPP_BIT

/*
    bit synopsis

namespace std {
  // [bit.cast], bit_cast
  template<class To, class From>
    constexpr To bit_cast(const From& from) noexcept; // C++20

  // [bit.byteswap], byteswap
  template<class T>
    constexpr T byteswap(T value) noexcept;      // C++23

  // [bit.pow.two], integral powers of 2
  template <class T>
    constexpr bool has_single_bit(T x) noexcept; // C++20
  template <class T>
    constexpr T bit_ceil(T x);                   // C++20
  template <class T>
    constexpr T bit_floor(T x) noexcept;         // C++20
  template <class T>
    constexpr int bit_width(T x) noexcept;       // C++20

  // [bit.rotate], rotating
  template<class T>
    constexpr T rotl(T x, unsigned int s) noexcept; // C++20
  template<class T>
    constexpr T rotr(T x, unsigned int s) noexcept; // C++20

  // [bit.count], counting
  template<class T>
    constexpr int countl_zero(T x) noexcept;  // C++20
  template<class T>
    constexpr int countl_one(T x) noexcept;   // C++20
  template<class T>
    constexpr int countr_zero(T x) noexcept;  // C++20
  template<class T>
    constexpr int countr_one(T x) noexcept;   // C++20
  template<class T>
    constexpr int popcount(T x) noexcept;     // C++20

  // [bit.endian], endian
  enum class endian {
    little = see below,        // C++20
    big = see below,           // C++20
    native = see below         // C++20
  };

} // namespace std

*/

#include <__assert> // all public C++ headers provide the assertion handler
#include <__bit/bit_cast.h>
#include <__bit/byteswap.h>
#include <__bits> // __libcpp_clz
#include <__concepts/arithmetic.h>
#include <__config>
#include <limits>
#include <type_traits>
#include <version>

#ifndef _LIBCPP_REMOVE_TRANSITIVE_INCLUDES
#  include <iosfwd>
#endif

#if defined(_LIBCPP_COMPILER_MSVC)
#  include <intrin.h>
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template<class _Tp>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
_Tp __rotr(_Tp __t, unsigned int __cnt) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotr requires an unsigned integer type");
    const unsigned int __dig = numeric_limits<_Tp>::digits;
    if ((__cnt % __dig) == 0)
        return __t;
    return (__t >> (__cnt % __dig)) | (__t << (__dig - (__cnt % __dig)));
}

template<class _Tp>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
int __countl_zero(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countl_zero requires an unsigned integer type");
    if (__t == 0)
        return numeric_limits<_Tp>::digits;

    if      (sizeof(_Tp) <= sizeof(unsigned int))
        return std::__libcpp_clz(static_cast<unsigned int>(__t))
              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
    else if (sizeof(_Tp) <= sizeof(unsigned long))
        return std::__libcpp_clz(static_cast<unsigned long>(__t))
              - (numeric_limits<unsigned long>::digits - numeric_limits<_Tp>::digits);
    else if (sizeof(_Tp) <= sizeof(unsigned long long))
        return std::__libcpp_clz(static_cast<unsigned long long>(__t))
              - (numeric_limits<unsigned long long>::digits - numeric_limits<_Tp>::digits);
    else
    {
        int __ret = 0;
        int __iter = 0;
        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
        while (true) {
            __t = std::__rotr(__t, __ulldigits);
            if ((__iter = std::__countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
                break;
            __ret += __iter;
            }
        return __ret + __iter;
    }
}

#if _LIBCPP_STD_VER > 17

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp rotl(_Tp __t, unsigned int __cnt) noexcept {
  const unsigned int __dig = numeric_limits<_Tp>::digits;
  if ((__cnt % __dig) == 0)
    return __t;
  return (__t << (__cnt % __dig)) | (__t >> (__dig - (__cnt % __dig)));
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp rotr(_Tp __t, unsigned int __cnt) noexcept {
  return std::__rotr(__t, __cnt);
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int countl_zero(_Tp __t) noexcept {
  return std::__countl_zero(__t);
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int countl_one(_Tp __t) noexcept {
  return __t != numeric_limits<_Tp>::max() ? std::countl_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int countr_zero(_Tp __t) noexcept {
  if (__t == 0)
    return numeric_limits<_Tp>::digits;

  if (sizeof(_Tp) <= sizeof(unsigned int))
    return std::__libcpp_ctz(static_cast<unsigned int>(__t));
  else if (sizeof(_Tp) <= sizeof(unsigned long))
    return std::__libcpp_ctz(static_cast<unsigned long>(__t));
  else if (sizeof(_Tp) <= sizeof(unsigned long long))
    return std::__libcpp_ctz(static_cast<unsigned long long>(__t));
  else {
    int __ret = 0;
    const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
    while (static_cast<unsigned long long>(__t) == 0uLL) {
      __ret += __ulldigits;
      __t >>= __ulldigits;
    }
    return __ret + std::__libcpp_ctz(static_cast<unsigned long long>(__t));
  }
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int countr_one(_Tp __t) noexcept {
  return __t != numeric_limits<_Tp>::max() ? std::countr_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int popcount(_Tp __t) noexcept {
  if (sizeof(_Tp) <= sizeof(unsigned int))
    return std::__libcpp_popcount(static_cast<unsigned int>(__t));
  else if (sizeof(_Tp) <= sizeof(unsigned long))
    return std::__libcpp_popcount(static_cast<unsigned long>(__t));
  else if (sizeof(_Tp) <= sizeof(unsigned long long))
    return std::__libcpp_popcount(static_cast<unsigned long long>(__t));
  else {
    int __ret = 0;
    while (__t != 0) {
      __ret += std::__libcpp_popcount(static_cast<unsigned long long>(__t));
      __t >>= numeric_limits<unsigned long long>::digits;
    }
    return __ret;
  }
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr bool has_single_bit(_Tp __t) noexcept {
  return __t != 0 && (((__t & (__t - 1)) == 0));
}

// integral log base 2
template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp __bit_log2(_Tp __t) noexcept {
  return numeric_limits<_Tp>::digits - 1 - std::countl_zero(__t);
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp bit_floor(_Tp __t) noexcept {
  return __t == 0 ? 0 : _Tp{1} << std::__bit_log2(__t);
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp bit_ceil(_Tp __t) noexcept {
  if (__t < 2)
    return 1;
  const unsigned __n = numeric_limits<_Tp>::digits - std::countl_zero((_Tp)(__t - 1u));
  _LIBCPP_ASSERT(__n != numeric_limits<_Tp>::digits, "Bad input to bit_ceil");

  if constexpr (sizeof(_Tp) >= sizeof(unsigned))
    return _Tp{1} << __n;
  else {
    const unsigned __extra = numeric_limits<unsigned>::digits - numeric_limits<_Tp>::digits;
    const unsigned __retVal = 1u << (__n + __extra);
    return (_Tp)(__retVal >> __extra);
  }
}

template <__libcpp_unsigned_integer _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int bit_width(_Tp __t) noexcept {
  return __t == 0 ? 0 : std::__bit_log2(__t) + 1;
}

enum class endian {
  little = 0xDEAD,
  big = 0xFACE,
#  if defined(_LIBCPP_LITTLE_ENDIAN)
  native = little
#  elif defined(_LIBCPP_BIG_ENDIAN)
  native = big
#  else
  native = 0xCAFE
#  endif
};

#endif // _LIBCPP_STD_VER > 17

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP_BIT