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1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___ALGORITHM_UNWRAP_ITER_H10#define _LIBCPP___ALGORITHM_UNWRAP_ITER_H11 12#include <__config>13#include <__iterator/iterator_traits.h>14#include <__memory/pointer_traits.h>15#include <__type_traits/enable_if.h>16#include <__type_traits/is_constructible.h>17#include <__utility/declval.h>18#include <__utility/move.h>19 20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)21# pragma GCC system_header22#endif23 24_LIBCPP_PUSH_MACROS25#include <__undef_macros>26 27_LIBCPP_BEGIN_NAMESPACE_STD28 29// TODO: Change the name of __unwrap_iter_impl to something more appropriate30// The job of __unwrap_iter is to remove iterator wrappers (like reverse_iterator or __wrap_iter),31// to reduce the number of template instantiations and to enable pointer-based optimizations e.g. in std::copy.32//33// Some algorithms (e.g. std::copy, but not std::sort) need to convert an34// "unwrapped" result back into the original iterator type. Doing that is the job of __rewrap_iter.35 36// Default case - we can't unwrap anything37template <class _Iter, bool = __libcpp_is_contiguous_iterator<_Iter>::value>38struct __unwrap_iter_impl {39 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter, _Iter __iter) { return __iter; }40 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __unwrap(_Iter __i) _NOEXCEPT { return __i; }41};42 43// TODO(hardening): make sure that the following unwrapping doesn't unexpectedly turn hardened iterators into raw44// pointers.45 46// It's a contiguous iterator, so we can use a raw pointer instead47template <class _Iter>48struct __unwrap_iter_impl<_Iter, true> {49 using _ToAddressT _LIBCPP_NODEBUG = decltype(std::__to_address(std::declval<_Iter>()));50 51 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter __orig_iter, _ToAddressT __unwrapped_iter) {52 return __orig_iter + (__unwrapped_iter - std::__to_address(__orig_iter));53 }54 55 static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ToAddressT __unwrap(_Iter __i) _NOEXCEPT {56 return std::__to_address(__i);57 }58};59 60template <class _Iter,61 class _Impl = __unwrap_iter_impl<_Iter>,62 __enable_if_t<is_copy_constructible<_Iter>::value, int> = 0>63inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 decltype(_Impl::__unwrap(std::declval<_Iter>()))64__unwrap_iter(_Iter __i) _NOEXCEPT {65 return _Impl::__unwrap(__i);66}67 68// Allow input_iterators to be passed to __unwrap_iter (but not __rewrap_iter)69#if _LIBCPP_STD_VER >= 2070template <class _Iter, __enable_if_t<!is_copy_constructible<_Iter>::value, int> = 0>71inline _LIBCPP_HIDE_FROM_ABI constexpr _Iter __unwrap_iter(_Iter __i) noexcept {72 return __i;73}74#endif75 76template <class _OrigIter, class _Iter, class _Impl = __unwrap_iter_impl<_OrigIter> >77_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _OrigIter __rewrap_iter(_OrigIter __orig_iter, _Iter __iter) _NOEXCEPT {78 return _Impl::__rewrap(std::move(__orig_iter), std::move(__iter));79}80 81_LIBCPP_END_NAMESPACE_STD82 83_LIBCPP_POP_MACROS84 85#endif // _LIBCPP___ALGORITHM_UNWRAP_ITER_H86