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// -*- 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___NUMERIC_MIDPOINT_H
#define _LIBCPP___NUMERIC_MIDPOINT_H
#include <__config>
#include <__type_traits/enable_if.h>
#include <__type_traits/is_floating_point.h>
#include <__type_traits/is_integral.h>
#include <__type_traits/is_null_pointer.h>
#include <__type_traits/is_object.h>
#include <__type_traits/is_pointer.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_void.h>
#include <__type_traits/make_unsigned.h>
#include <__type_traits/remove_pointer.h>
#include <cstddef>
#include <limits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER >= 20
template <class _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp>
midpoint(_Tp __a, _Tp __b) noexcept _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK {
using _Up = make_unsigned_t<_Tp>;
constexpr _Up __bitshift = numeric_limits<_Up>::digits - 1;
_Up __diff = _Up(__b) - _Up(__a);
_Up __sign_bit = __b < __a;
_Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);
return __a + __half_diff;
}
template <class _Tp, enable_if_t<is_object_v<_Tp> && !is_void_v<_Tp> && (sizeof(_Tp) > 0), int> = 0>
_LIBCPP_HIDE_FROM_ABI constexpr _Tp* midpoint(_Tp* __a, _Tp* __b) noexcept {
return __a + std::midpoint(ptrdiff_t(0), __b - __a);
}
template <typename _Tp>
_LIBCPP_HIDE_FROM_ABI constexpr int __sign(_Tp __val) {
return (_Tp(0) < __val) - (__val < _Tp(0));
}
template <typename _Fp>
_LIBCPP_HIDE_FROM_ABI constexpr _Fp __fp_abs(_Fp __f) {
return __f >= 0 ? __f : -__f;
}
template <class _Fp>
_LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_floating_point_v<_Fp>, _Fp> midpoint(_Fp __a, _Fp __b) noexcept {
constexpr _Fp __lo = numeric_limits<_Fp>::min() * 2;
constexpr _Fp __hi = numeric_limits<_Fp>::max() / 2;
return std::__fp_abs(__a) <= __hi && std::__fp_abs(__b) <= __hi
? // typical case: overflow is impossible
(__a + __b) / 2
: // always correctly rounded
std::__fp_abs(__a) < __lo ? __a + __b / 2 : // not safe to halve a
std::__fp_abs(__b) < __lo ? __a / 2 + __b
: // not safe to halve b
__a / 2 + __b / 2; // otherwise correctly rounded
}
#endif // _LIBCPP_STD_VER >= 20
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // _LIBCPP___NUMERIC_MIDPOINT_H
|
