14824e7fdSDimitry Andric // -*- C++ -*- 24824e7fdSDimitry Andric //===----------------------------------------------------------------------===// 34824e7fdSDimitry Andric // 44824e7fdSDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 54824e7fdSDimitry Andric // See https://llvm.org/LICENSE.txt for license information. 64824e7fdSDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 74824e7fdSDimitry Andric // 84824e7fdSDimitry Andric //===----------------------------------------------------------------------===// 94824e7fdSDimitry Andric 104824e7fdSDimitry Andric #ifndef _LIBCPP___NUMERIC_MIDPOINT_H 114824e7fdSDimitry Andric #define _LIBCPP___NUMERIC_MIDPOINT_H 124824e7fdSDimitry Andric 134824e7fdSDimitry Andric #include <__config> 14bdd1243dSDimitry Andric #include <__type_traits/enable_if.h> 15bdd1243dSDimitry Andric #include <__type_traits/is_floating_point.h> 16bdd1243dSDimitry Andric #include <__type_traits/is_integral.h> 17bdd1243dSDimitry Andric #include <__type_traits/is_null_pointer.h> 18bdd1243dSDimitry Andric #include <__type_traits/is_object.h> 19bdd1243dSDimitry Andric #include <__type_traits/is_pointer.h> 20bdd1243dSDimitry Andric #include <__type_traits/is_same.h> 21bdd1243dSDimitry Andric #include <__type_traits/is_void.h> 22bdd1243dSDimitry Andric #include <__type_traits/make_unsigned.h> 23bdd1243dSDimitry Andric #include <__type_traits/remove_pointer.h> 24bdd1243dSDimitry Andric #include <cstddef> 254824e7fdSDimitry Andric #include <limits> 264824e7fdSDimitry Andric 274824e7fdSDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 284824e7fdSDimitry Andric # pragma GCC system_header 294824e7fdSDimitry Andric #endif 304824e7fdSDimitry Andric 314824e7fdSDimitry Andric _LIBCPP_PUSH_MACROS 324824e7fdSDimitry Andric #include <__undef_macros> 334824e7fdSDimitry Andric 344824e7fdSDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD 354824e7fdSDimitry Andric 3606c3fb27SDimitry Andric #if _LIBCPP_STD_VER >= 20 374824e7fdSDimitry Andric template <class _Tp> 38cb14a3feSDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp> 39cb14a3feSDimitry Andric midpoint(_Tp __a, _Tp __b) noexcept _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK { 404824e7fdSDimitry Andric using _Up = make_unsigned_t<_Tp>; 414824e7fdSDimitry Andric constexpr _Up __bitshift = numeric_limits<_Up>::digits - 1; 424824e7fdSDimitry Andric 434824e7fdSDimitry Andric _Up __diff = _Up(__b) - _Up(__a); 444824e7fdSDimitry Andric _Up __sign_bit = __b < __a; 454824e7fdSDimitry Andric 464824e7fdSDimitry Andric _Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff); 474824e7fdSDimitry Andric 484824e7fdSDimitry Andric return __a + __half_diff; 494824e7fdSDimitry Andric } 504824e7fdSDimitry Andric 51cb14a3feSDimitry Andric template <class _Tp, enable_if_t<is_object_v<_Tp> && !is_void_v<_Tp> && (sizeof(_Tp) > 0), int> = 0> 52cb14a3feSDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr _Tp* midpoint(_Tp* __a, _Tp* __b) noexcept { 535f757f3fSDimitry Andric return __a + std::midpoint(ptrdiff_t(0), __b - __a); 544824e7fdSDimitry Andric } 554824e7fdSDimitry Andric 564824e7fdSDimitry Andric template <typename _Tp> 57bdd1243dSDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr int __sign(_Tp __val) { 584824e7fdSDimitry Andric return (_Tp(0) < __val) - (__val < _Tp(0)); 594824e7fdSDimitry Andric } 604824e7fdSDimitry Andric 614824e7fdSDimitry Andric template <typename _Fp> 62cb14a3feSDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr _Fp __fp_abs(_Fp __f) { 63cb14a3feSDimitry Andric return __f >= 0 ? __f : -__f; 64cb14a3feSDimitry Andric } 654824e7fdSDimitry Andric 664824e7fdSDimitry Andric template <class _Fp> 67cb14a3feSDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_floating_point_v<_Fp>, _Fp> midpoint(_Fp __a, _Fp __b) noexcept { 684824e7fdSDimitry Andric constexpr _Fp __lo = numeric_limits<_Fp>::min() * 2; 694824e7fdSDimitry Andric constexpr _Fp __hi = numeric_limits<_Fp>::max() / 2; 70*0fca6ea1SDimitry Andric 71*0fca6ea1SDimitry Andric // typical case: overflow is impossible 72*0fca6ea1SDimitry Andric if (std::__fp_abs(__a) <= __hi && std::__fp_abs(__b) <= __hi) 73*0fca6ea1SDimitry Andric return (__a + __b) / 2; // always correctly rounded 74*0fca6ea1SDimitry Andric if (std::__fp_abs(__a) < __lo) 75*0fca6ea1SDimitry Andric return __a + __b / 2; // not safe to halve a 76*0fca6ea1SDimitry Andric if (std::__fp_abs(__b) < __lo) 77*0fca6ea1SDimitry Andric return __a / 2 + __b; // not safe to halve b 78*0fca6ea1SDimitry Andric 79*0fca6ea1SDimitry Andric return __a / 2 + __b / 2; // otherwise correctly rounded 804824e7fdSDimitry Andric } 814824e7fdSDimitry Andric 8206c3fb27SDimitry Andric #endif // _LIBCPP_STD_VER >= 20 834824e7fdSDimitry Andric 844824e7fdSDimitry Andric _LIBCPP_END_NAMESPACE_STD 854824e7fdSDimitry Andric 864824e7fdSDimitry Andric _LIBCPP_POP_MACROS 874824e7fdSDimitry Andric 884824e7fdSDimitry Andric #endif // _LIBCPP___NUMERIC_MIDPOINT_H 89