libcxx/include/bit

// -*- 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 T 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 <__bit/bit_cast.h>
#include <__bit/byteswap.h>
#include <__bits> // __libcpp_clz
#include <__config>
#include <__debug>
#include <limits>
#include <type_traits>
#include <version>

#if defined(__IBMCPP__)
#include "__support/ibm/support.h"
#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_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
_Tp __rotl(_Tp __t, unsigned int __cnt) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__rotl 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_INLINE_VISIBILITY _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_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
int __countr_zero(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countr_zero requires an unsigned integer type");
    if (__t == 0)
        return numeric_limits<_Tp>::digits;

    if      (sizeof(_Tp) <= sizeof(unsigned int))
        return __libcpp_ctz(static_cast<unsigned int>(__t));
    else if (sizeof(_Tp) <= sizeof(unsigned long))
        return __libcpp_ctz(static_cast<unsigned long>(__t));
    else if (sizeof(_Tp) <= sizeof(unsigned long long))
        return __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 + __libcpp_ctz(static_cast<unsigned long long>(__t));
    }
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY _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 __libcpp_clz(static_cast<unsigned int>(__t))
              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
    else if (sizeof(_Tp) <= sizeof(unsigned long))
        return __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 __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 = __rotr(__t, __ulldigits);
            if ((__iter = __countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
                break;
            __ret += __iter;
            }
        return __ret + __iter;
    }
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
int __countl_one(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countl_one requires an unsigned integer type");
    return __t != numeric_limits<_Tp>::max()
        ? __countl_zero(static_cast<_Tp>(~__t))
        : numeric_limits<_Tp>::digits;
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
int __countr_one(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__countr_one requires an unsigned integer type");
    return __t != numeric_limits<_Tp>::max()
        ? __countr_zero(static_cast<_Tp>(~__t))
        : numeric_limits<_Tp>::digits;
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
int __popcount(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__popcount requires an unsigned integer type");
    if      (sizeof(_Tp) <= sizeof(unsigned int))
        return __libcpp_popcount(static_cast<unsigned int>(__t));
    else if (sizeof(_Tp) <= sizeof(unsigned long))
        return __libcpp_popcount(static_cast<unsigned long>(__t));
    else if (sizeof(_Tp) <= sizeof(unsigned long long))
        return __libcpp_popcount(static_cast<unsigned long long>(__t));
    else
    {
        int __ret = 0;
        while (__t != 0)
        {
            __ret += __libcpp_popcount(static_cast<unsigned long long>(__t));
            __t >>= numeric_limits<unsigned long long>::digits;
        }
        return __ret;
    }
}

// integral log base 2
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
unsigned __bit_log2(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__bit_log2 requires an unsigned integer type");
    return numeric_limits<_Tp>::digits - 1 - __countl_zero(__t);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
bool __has_single_bit(_Tp __t) _NOEXCEPT
{
    static_assert(__libcpp_is_unsigned_integer<_Tp>::value, "__has_single_bit requires an unsigned integer type");
    return __t != 0 && (((__t & (__t - 1)) == 0));
}

#if _LIBCPP_STD_VER > 17

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
rotl(_Tp __t, unsigned int __cnt) noexcept
{
    return __rotl(__t, __cnt);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
rotr(_Tp __t, unsigned int __cnt) noexcept
{
    return __rotr(__t, __cnt);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
countl_zero(_Tp __t) noexcept
{
    return __countl_zero(__t);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
countl_one(_Tp __t) noexcept
{
    return __countl_one(__t);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
countr_zero(_Tp __t) noexcept
{
    return __countr_zero(__t);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
countr_one(_Tp __t) noexcept
{
    return __countr_one(__t);
}

template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, int>
popcount(_Tp __t) noexcept
{
    return __popcount(__t);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, bool>
has_single_bit(_Tp __t) noexcept
{
    return __has_single_bit(__t);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
bit_floor(_Tp __t) noexcept
{
    return __t == 0 ? 0 : _Tp{1} << __bit_log2(__t);
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
bit_ceil(_Tp __t) noexcept
{
    if (__t < 2) return 1;
    const unsigned __n = numeric_limits<_Tp>::digits - countl_zero((_Tp)(__t - 1u));
    _LIBCPP_DEBUG_ASSERT(__libcpp_is_constant_evaluated() || __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 <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__libcpp_is_unsigned_integer<_Tp>::value, _Tp>
bit_width(_Tp __t) noexcept
{
    return __t == 0 ? 0 : __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