// <bit> -*- C++ -*-
-// Copyright (C) 2018 Free Software Foundation, Inc.
+// Copyright (C) 2018-2020 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
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
+ /**
+ * @defgroup bit_manip Bit manipulation
+ * @ingroup numerics
+ *
+ * Utilities for examining and manipulating individual bits.
+ *
+ * @{
+ */
+
+ /// @cond undoc
+
template<typename _Tp>
constexpr _Tp
- __rotl(_Tp __x, unsigned int __s) noexcept
+ __rotl(_Tp __x, int __s) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
- const unsigned __sN = __s % _Nd;
- return (__x << __sN) | (__x >> ((_Nd - __sN) % _Nd));
+ 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, unsigned int __s) noexcept
+ __rotr(_Tp __x, int __s) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
- const unsigned __sN = __s % _Nd;
- return (__x >> __sN) | (__x << ((_Nd - __sN) % _Nd));
+ 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 __limits = numeric_limits<_Tp>;
+ constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
- return __limits::digits;
+ return _Nd;
- using __limits_ull = numeric_limits<unsigned long long>;
- using __limits_ul = numeric_limits<unsigned long>;
- using __limits_u = numeric_limits<unsigned>;
+ 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 (__limits::digits <= __limits_u::digits)
+ if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
{
- constexpr int __diff = __limits_u::digits - __limits::digits;
+ constexpr int __diff = _Nd_u - _Nd;
return __builtin_clz(__x) - __diff;
}
- else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ul::digits)
+ else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
{
- constexpr int __diff = __limits_ul::digits - __limits::digits;
+ constexpr int __diff = _Nd_ul - _Nd;
return __builtin_clzl(__x) - __diff;
}
- else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ull::digits)
+ else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
{
- constexpr int __diff = __limits_ull::digits - __limits::digits;
+ constexpr int __diff = _Nd_ull - _Nd;
return __builtin_clzll(__x) - __diff;
}
- else // (__limits::digits > __limits_ull::digits)
+ else // (_Nd > _Nd_ull)
{
- static_assert(__limits::digits <= (2 * __limits_ull::digits),
+ static_assert(_Nd <= (2 * _Nd_ull),
"Maximum supported integer size is 128-bit");
- unsigned long long __high = __x >> __limits_ull::digits;
+ unsigned long long __high = __x >> _Nd_ull;
if (__high != 0)
{
- constexpr int __diff
- = (2 * __limits_ull::digits) - __limits::digits;
+ constexpr int __diff = (2 * _Nd_ull) - _Nd;
return __builtin_clzll(__high) - __diff;
}
- unsigned long long __low = __x & __limits_ull::max();
- return (__limits::digits - __limits_ull::digits)
- + __builtin_clzll(__low);
+ constexpr auto __max_ull = numeric_limits<unsigned long long>::max();
+ unsigned long long __low = __x & __max_ull;
+ return (_Nd - _Nd_ull) + __builtin_clzll(__low);
}
}
constexpr int
__countr_zero(_Tp __x) noexcept
{
- using __limits = numeric_limits<_Tp>;
+ constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
- return __limits::digits;
+ return _Nd;
- using __limits_ull = numeric_limits<unsigned long long>;
- using __limits_ul = numeric_limits<unsigned long>;
- using __limits_u = numeric_limits<unsigned>;
+ 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 (__limits::digits <= __limits_u::digits)
+ if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
return __builtin_ctz(__x);
- else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ul::digits)
+ else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
return __builtin_ctzl(__x);
- else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ull::digits)
+ else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
return __builtin_ctzll(__x);
- else // (__limits::digits > __limits_ull::digits)
+ else // (_Nd > _Nd_ull)
{
- static_assert(__limits::digits <= (2 * __limits_ull::digits),
+ static_assert(_Nd <= (2 * _Nd_ull),
"Maximum supported integer size is 128-bit");
- unsigned long long __low = __x & __limits_ull::max();
+ 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 >> __limits_ull::digits;
- return __builtin_ctzll(__high) + __limits_ull::digits;
+ unsigned long long __high = __x >> _Nd_ull;
+ return __builtin_ctzll(__high) + _Nd_ull;
}
}
constexpr int
__popcount(_Tp __x) noexcept
{
- using __limits = numeric_limits<_Tp>;
+ constexpr auto _Nd = numeric_limits<_Tp>::digits;
if (__x == 0)
return 0;
- using __limits_ull = numeric_limits<unsigned long long>;
- using __limits_ul = numeric_limits<unsigned long>;
- using __limits_u = numeric_limits<unsigned>;
+ 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 (__limits::digits <= __limits_u::digits)
+ if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
return __builtin_popcount(__x);
- else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ul::digits)
+ else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
return __builtin_popcountl(__x);
- else if _GLIBCXX17_CONSTEXPR (__limits::digits <= __limits_ull::digits)
+ else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
return __builtin_popcountll(__x);
- else // (__limits::digits > __limits_ull::digits)
+ else // (_Nd > _Nd_ull)
{
- static_assert(__limits::digits <= (2 * __limits_ull::digits),
+ static_assert(_Nd <= (2 * _Nd_ull),
"Maximum supported integer size is 128-bit");
- unsigned long long __low = __x & __limits_ull::max();
- unsigned long long __high = __x >> __limits_ull::digits;
+ 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);
}
}
__ceil2(_Tp __x) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
- if (__x == 0)
+ if (__x == 0 || __x == 1)
return 1;
- return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x - 1u)));
+ 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.
+#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
+ if (!__builtin_is_constant_evaluated())
+ {
+ __glibcxx_assert( __shift_exponent != numeric_limits<_Tp>::digits );
+ }
+#endif
+ 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>
__log2p1(_Tp __x) noexcept
{
constexpr auto _Nd = numeric_limits<_Tp>::digits;
- if (__x == 0)
- return 0;
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 { };
+ /// @endcond
- template<typename _Up>
- struct _If_is_unsigned_integer_type<bool, _Up, true> { };
+#if __cplusplus > 201703L
- 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> { };
+#define __cpp_lib_bitops 201907L
+ /// @cond undoc
template<typename _Tp, typename _Up = _Tp>
using _If_is_unsigned_integer
- = typename _If_is_unsigned_integer_type<remove_cv_t<_Tp>, _Up>::type;
+ = enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>;
+ /// @endcond
-#if ! __STRICT_ANSI__
- // [bitops.rot], rotating
+ // [bit.rot], rotating
+ /// Rotate `x` to the left by `s` bits.
template<typename _Tp>
- constexpr _If_is_unsigned_integer<_Tp>
- rotl(_Tp __x, unsigned int __s) noexcept
+ [[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>
- constexpr _If_is_unsigned_integer<_Tp>
- rotr(_Tp __x, unsigned int __s) noexcept
+ [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
+ rotr(_Tp __x, int __s) noexcept
{ return std::__rotr(__x, __s); }
- // [bitops.count], counting
+ // [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); }
-#endif
- // Integral power-of-two operations
+ // [bit.pow.two], integral powers of 2
+ /// True if `x` is a power of two, false otherwise.
template<typename _Tp>
constexpr _If_is_unsigned_integer<_Tp, bool>
ispow2(_Tp __x) noexcept
{ return std::__ispow2(__x); }
+ /// The smallest power-of-two not less than `x`.
template<typename _Tp>
constexpr _If_is_unsigned_integer<_Tp>
ceil2(_Tp __x) noexcept
{ return std::__ceil2(__x); }
+ /// The largest power-of-two not greater than `x`.
template<typename _Tp>
constexpr _If_is_unsigned_integer<_Tp>
floor2(_Tp __x) noexcept
{ return std::__floor2(__x); }
+ /// The smallest integer greater than the base-2 logarithm of `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
+#define __cpp_lib_endian 201907L
+ /// Byte order
+ enum class endian
+ {
+ little = __ORDER_LITTLE_ENDIAN__,
+ big = __ORDER_BIG_ENDIAN__,
+ native = __BYTE_ORDER__
+ };
#endif // C++2a
+ /// @}
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
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