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-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___ALGORITHM_UNWRAP_ITER_H
10#define _LIBCPP___ALGORITHM_UNWRAP_ITER_H
11
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_header
22#endif
23
24_LIBCPP_PUSH_MACROS
25#include <__undef_macros>
26
27_LIBCPP_BEGIN_NAMESPACE_STD
28
29// TODO: Change the name of __unwrap_iter_impl to something more appropriate
30// 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 an
34// "unwrapped" result back into the original iterator type. Doing that is the job of __rewrap_iter.
35
36// Default case - we can't unwrap anything
37template <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 raw
44// pointers.
45
46// It's a contiguous iterator, so we can use a raw pointer instead
47template <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 >= 20
70template <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#endif
75
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_STD
82
83_LIBCPP_POP_MACROS
84
85#endif // _LIBCPP___ALGORITHM_UNWRAP_ITER_H
86