libstdc++-v3/include/std/bit

// <bit> -*- C++ -*-

// Copyright (C) 2018-2019 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>
#include <limits>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  template<typename _Tp>
    constexpr _Tp
    __rotl(_Tp __x, unsigned int __s) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;
      const unsigned __sN = __s % _Nd;
      return (__x << __sN) | (__x >> ((_Nd - __sN) % _Nd));
    }

  template<typename _Tp>
    constexpr _Tp
    __rotr(_Tp __x, unsigned int __s) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;
      const unsigned __sN = __s % _Nd;
      return (__x >> __sN) | (__x << ((_Nd - __sN) % _Nd));
    }

  template<typename _Tp>
    constexpr int
    __countl_zero(_Tp __x) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;

      if (__x == 0)
        return _Nd;

      constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
      constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
      constexpr auto _Nd_u = numeric_limits<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 = numeric_limits<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
    {
      if (__x == numeric_limits<_Tp>::max())
        return numeric_limits<_Tp>::digits;
      return std::__countl_zero<_Tp>((_Tp)~__x);
    }

  template<typename _Tp>
    constexpr int
    __countr_zero(_Tp __x) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;

      if (__x == 0)
        return _Nd;

      constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
      constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
      constexpr auto _Nd_u = numeric_limits<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 = numeric_limits<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
    {
      if (__x == numeric_limits<_Tp>::max())
        return numeric_limits<_Tp>::digits;
      return std::__countr_zero((_Tp)~__x);
    }

  template<typename _Tp>
    constexpr int
    __popcount(_Tp __x) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;

      if (__x == 0)
        return 0;

      constexpr auto _Nd_ull = numeric_limits<unsigned long long>::digits;
      constexpr auto _Nd_ul = numeric_limits<unsigned long>::digits;
      constexpr auto _Nd_u = numeric_limits<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 = numeric_limits<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
    __ispow2(_Tp __x) noexcept
    { return std::__popcount(__x) == 1; }

  template<typename _Tp>
    constexpr _Tp
    __ceil2(_Tp __x) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;
      if (__x == 0 || __x == 1)
        return 1;
      const unsigned __n = _Nd - std::__countl_zero((_Tp)(__x - 1u));
      const _Tp __y_2 = (_Tp)1u << (__n - 1u);
      return __y_2 << 1u;
    }

  template<typename _Tp>
    constexpr _Tp
    __floor2(_Tp __x) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;
      if (__x == 0)
        return 0;
      return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1)));
    }

  template<typename _Tp>
    constexpr _Tp
    __log2p1(_Tp __x) noexcept
    {
      constexpr auto _Nd = numeric_limits<_Tp>::digits;
      return _Nd - std::__countl_zero(__x);
    }

#if __cplusplus > 201703L

  template<typename _Tp, typename _Up, bool = is_integral_v<_Tp>>
    struct _If_is_unsigned_integer_type { };

  template<typename _Up>
    struct _If_is_unsigned_integer_type<bool, _Up, true> { };

  template<typename _Tp, typename _Up>
    struct _If_is_unsigned_integer_type<_Tp, _Up, true>
    : enable_if<is_same_v<_Tp, make_unsigned_t<_Tp>>, _Up> { };

  template<typename _Tp, typename _Up = _Tp>
    using _If_is_unsigned_integer
      = typename _If_is_unsigned_integer_type<remove_cv_t<_Tp>, _Up>::type;

#if ! __STRICT_ANSI__
  // [bitops.rot], rotating

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    rotl(_Tp __x, unsigned int __s) noexcept
    { return std::__rotl(__x, __s); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    rotr(_Tp __x, unsigned int __s) noexcept
    { return std::__rotr(__x, __s); }

  // [bitops.count], counting

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countl_zero(_Tp __x) noexcept
    { return std::__countl_zero(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countl_one(_Tp __x) noexcept
    { return std::__countl_one(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countr_zero(_Tp __x) noexcept
    { return std::__countr_zero(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countr_one(_Tp __x) noexcept
    { return std::__countr_one(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    popcount(_Tp __x) noexcept
    { return std::__popcount(__x); }
#endif

  // Integral power-of-two operations

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, bool>
    ispow2(_Tp __x) noexcept
    { return std::__ispow2(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    ceil2(_Tp __x) noexcept
    { return std::__ceil2(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    floor2(_Tp __x) noexcept
    { return std::__floor2(__x); }

  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    log2p1(_Tp __x) noexcept
    { return std::__log2p1(__x); }

#if ! __STRICT_ANSI__
  enum class byte : unsigned char;

  constexpr byte
  rotl(byte __x, unsigned int __s) noexcept
  { return (byte)std::__rotl((unsigned char)__x, __s); }

  constexpr byte
  rotr(byte __x, unsigned int __s) noexcept
  { return (byte)std::__rotr((unsigned char)__x, __s); }

  constexpr int
  countl_zero(byte __x) noexcept
  { return std::__countl_zero((unsigned char)__x); }

  constexpr int
  countl_one(byte __x) noexcept
  { return std::__countl_one((unsigned char)__x); }

  constexpr int
  countr_zero(byte __x) noexcept
  { return std::__countr_zero((unsigned char)__x); }

  constexpr int
  countr_one(byte __x) noexcept
  { return std::__countr_one((unsigned char)__x); }

  constexpr int
  popcount(byte __x) noexcept
  { return std::__popcount((unsigned char)__x); }

  constexpr bool
  ispow2(byte __x) noexcept
  { return std::__ispow2((unsigned char)__x); }

  constexpr byte
  ceil2(byte __x) noexcept
  { return (byte)std::__ceil2((unsigned char)__x); }

  constexpr byte
  floor2(byte __x) noexcept
  { return (byte)std::__floor2((unsigned char)__x); }

  constexpr byte
  log2p1(byte __x) noexcept
  { return (byte)std::__log2p1((unsigned char)__x); }
#endif

#endif // C++2a

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // C++14
#endif // _GLIBCXX_BIT