86 lines
2.6 KiB
C++
86 lines
2.6 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___NUMERIC_MIDPOINT_H
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#define _LIBCPP___NUMERIC_MIDPOINT_H
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#include <__config>
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#include <limits>
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#include <type_traits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER > 17
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template <class _Tp>
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_LIBCPP_INLINE_VISIBILITY constexpr
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enable_if_t<is_integral_v<_Tp> && !is_same_v<bool, _Tp> && !is_null_pointer_v<_Tp>, _Tp>
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midpoint(_Tp __a, _Tp __b) noexcept
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_LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
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{
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using _Up = make_unsigned_t<_Tp>;
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constexpr _Up __bitshift = numeric_limits<_Up>::digits - 1;
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_Up __diff = _Up(__b) - _Up(__a);
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_Up __sign_bit = __b < __a;
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_Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);
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return __a + __half_diff;
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}
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template <class _TPtr>
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_LIBCPP_INLINE_VISIBILITY constexpr
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enable_if_t<is_pointer_v<_TPtr>
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&& is_object_v<remove_pointer_t<_TPtr>>
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&& ! is_void_v<remove_pointer_t<_TPtr>>
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&& (sizeof(remove_pointer_t<_TPtr>) > 0), _TPtr>
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midpoint(_TPtr __a, _TPtr __b) noexcept
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{
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return __a + _VSTD::midpoint(ptrdiff_t(0), __b - __a);
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}
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template <typename _Tp>
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constexpr int __sign(_Tp __val) {
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return (_Tp(0) < __val) - (__val < _Tp(0));
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}
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template <typename _Fp>
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constexpr _Fp __fp_abs(_Fp __f) { return __f >= 0 ? __f : -__f; }
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template <class _Fp>
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_LIBCPP_INLINE_VISIBILITY constexpr
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enable_if_t<is_floating_point_v<_Fp>, _Fp>
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midpoint(_Fp __a, _Fp __b) noexcept
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{
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constexpr _Fp __lo = numeric_limits<_Fp>::min()*2;
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constexpr _Fp __hi = numeric_limits<_Fp>::max()/2;
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return __fp_abs(__a) <= __hi && __fp_abs(__b) <= __hi ? // typical case: overflow is impossible
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(__a + __b)/2 : // always correctly rounded
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__fp_abs(__a) < __lo ? __a + __b/2 : // not safe to halve a
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__fp_abs(__b) < __lo ? __a/2 + __b : // not safe to halve b
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__a/2 + __b/2; // otherwise correctly rounded
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}
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#endif // _LIBCPP_STD_VER > 17
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___NUMERIC_MIDPOINT_H
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