| // -*- 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 <limits> |
| #include <type_traits> |
| |
| #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 > 17 |
| template <class _Tp> |
| _LIBCPP_INLINE_VISIBILITY 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 _TPtr> |
| _LIBCPP_INLINE_VISIBILITY constexpr |
| enable_if_t<is_pointer_v<_TPtr> |
| && is_object_v<remove_pointer_t<_TPtr>> |
| && ! is_void_v<remove_pointer_t<_TPtr>> |
| && (sizeof(remove_pointer_t<_TPtr>) > 0), _TPtr> |
| midpoint(_TPtr __a, _TPtr __b) noexcept |
| { |
| return __a + _VSTD::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_INLINE_VISIBILITY 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 > 17 |
| |
| _LIBCPP_END_NAMESPACE_STD |
| |
| _LIBCPP_POP_MACROS |
| |
| #endif // _LIBCPP___NUMERIC_MIDPOINT_H |