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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-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef _LIBCPP___CXX03___ALGORITHM_UNWRAP_ITER_H |
| 10 | #define _LIBCPP___CXX03___ALGORITHM_UNWRAP_ITER_H |
| 11 | |
| 12 | #include <__cxx03/__config> |
| 13 | #include <__cxx03/__iterator/iterator_traits.h> |
| 14 | #include <__cxx03/__memory/pointer_traits.h> |
| 15 | #include <__cxx03/__type_traits/enable_if.h> |
| 16 | #include <__cxx03/__type_traits/is_constructible.h> |
| 17 | #include <__cxx03/__utility/declval.h> |
| 18 | #include <__cxx03/__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 <__cxx03/__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 |
| 37 | template <class _Iter, bool = __libcpp_is_contiguous_iterator<_Iter>::value> |
| 38 | struct __unwrap_iter_impl { |
| 39 | static _LIBCPP_HIDE_FROM_ABI _Iter __rewrap(_Iter, _Iter __iter) { return __iter; } |
| 40 | static _LIBCPP_HIDE_FROM_ABI _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 |
| 47 | template <class _Iter> |
| 48 | struct __unwrap_iter_impl<_Iter, true> { |
| 49 | using _ToAddressT = decltype(std::__to_address(std::declval<_Iter>())); |
| 50 | |
| 51 | static _LIBCPP_HIDE_FROM_ABI _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 _ToAddressT __unwrap(_Iter __i) _NOEXCEPT { return std::__to_address(__i); } |
| 56 | }; |
| 57 | |
| 58 | template <class _Iter, |
| 59 | class _Impl = __unwrap_iter_impl<_Iter>, |
| 60 | __enable_if_t<is_copy_constructible<_Iter>::value, int> = 0> |
| 61 | inline _LIBCPP_HIDE_FROM_ABI decltype(_Impl::__unwrap(std::declval<_Iter>())) __unwrap_iter(_Iter __i) _NOEXCEPT { |
| 62 | return _Impl::__unwrap(__i); |
| 63 | } |
| 64 | |
| 65 | template <class _OrigIter, class _Iter, class _Impl = __unwrap_iter_impl<_OrigIter> > |
| 66 | _LIBCPP_HIDE_FROM_ABI _OrigIter __rewrap_iter(_OrigIter __orig_iter, _Iter __iter) _NOEXCEPT { |
| 67 | return _Impl::__rewrap(std::move(__orig_iter), std::move(__iter)); |
| 68 | } |
| 69 | |
| 70 | _LIBCPP_END_NAMESPACE_STD |
| 71 | |
| 72 | _LIBCPP_POP_MACROS |
| 73 | |
| 74 | #endif // _LIBCPP___CXX03___ALGORITHM_UNWRAP_ITER_H |
| 75 |
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