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1// -*- C++ -*-2//===----------------------------------------------------------------------===//3//4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.5// See https://llvm.org/LICENSE.txt for license information.6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception7//8//===----------------------------------------------------------------------===//9 10#ifndef _LIBCPP___NUMERIC_MIDPOINT_H11#define _LIBCPP___NUMERIC_MIDPOINT_H12 13#include <__config>14#include <__cstddef/ptrdiff_t.h>15#include <__type_traits/enable_if.h>16#include <__type_traits/is_floating_point.h>17#include <__type_traits/is_integral.h>18#include <__type_traits/is_null_pointer.h>19#include <__type_traits/is_object.h>20#include <__type_traits/is_pointer.h>21#include <__type_traits/is_same.h>22#include <__type_traits/is_void.h>23#include <__type_traits/make_unsigned.h>24#include <__type_traits/remove_pointer.h>25#include <limits>26 27#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)28# pragma GCC system_header29#endif30 31_LIBCPP_PUSH_MACROS32#include <__undef_macros>33 34_LIBCPP_BEGIN_NAMESPACE_STD35 36#if _LIBCPP_STD_VER >= 2037template <class _Tp>38_LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp>39midpoint(_Tp __a, _Tp __b) noexcept _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK {40 using _Up = make_unsigned_t<_Tp>;41 constexpr _Up __bitshift = numeric_limits<_Up>::digits - 1;42 43 _Up __diff = _Up(__b) - _Up(__a);44 _Up __sign_bit = __b < __a;45 46 _Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);47 48 return __a + __half_diff;49}50 51template <class _Tp, enable_if_t<is_object_v<_Tp> && !is_void_v<_Tp> && (sizeof(_Tp) > 0), int> = 0>52_LIBCPP_HIDE_FROM_ABI constexpr _Tp* midpoint(_Tp* __a, _Tp* __b) noexcept {53 return __a + std::midpoint(ptrdiff_t(0), __b - __a);54}55 56template <typename _Tp>57_LIBCPP_HIDE_FROM_ABI constexpr int __sign(_Tp __val) {58 return (_Tp(0) < __val) - (__val < _Tp(0));59}60 61template <typename _Fp>62_LIBCPP_HIDE_FROM_ABI constexpr _Fp __fp_abs(_Fp __f) {63 return __f >= 0 ? __f : -__f;64}65 66template <class _Fp>67_LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_floating_point_v<_Fp>, _Fp> midpoint(_Fp __a, _Fp __b) noexcept {68 constexpr _Fp __lo = numeric_limits<_Fp>::min() * 2;69 constexpr _Fp __hi = numeric_limits<_Fp>::max() / 2;70 71 // typical case: overflow is impossible72 if (std::__fp_abs(__a) <= __hi && std::__fp_abs(__b) <= __hi)73 return (__a + __b) / 2; // always correctly rounded74 if (std::__fp_abs(__a) < __lo)75 return __a + __b / 2; // not safe to halve a76 if (std::__fp_abs(__b) < __lo)77 return __a / 2 + __b; // not safe to halve b78 79 return __a / 2 + __b / 2; // otherwise correctly rounded80}81 82#endif // _LIBCPP_STD_VER >= 2083 84_LIBCPP_END_NAMESPACE_STD85 86_LIBCPP_POP_MACROS87 88#endif // _LIBCPP___NUMERIC_MIDPOINT_H89