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82 lines
3.2 KiB
C++
82 lines
3.2 KiB
C++
//===----------------------------------------------------------------------===//
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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___ALGORITHM_UNWRAP_ITER_H
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#define _LIBCPP___ALGORITHM_UNWRAP_ITER_H
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#include <__config>
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#include <__iterator/iterator_traits.h>
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#include <__memory/pointer_traits.h>
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#include <__type_traits/enable_if.h>
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#include <__type_traits/is_copy_constructible.h>
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#include <__utility/declval.h>
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#include <__utility/move.h>
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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_BEGIN_NAMESPACE_STD
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// TODO: Change the name of __unwrap_iter_impl to something more appropriate
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// The job of __unwrap_iter is to remove iterator wrappers (like reverse_iterator or __wrap_iter),
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// to reduce the number of template instantiations and to enable pointer-based optimizations e.g. in std::copy.
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// In debug mode, we don't do this.
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//
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// Some algorithms (e.g. std::copy, but not std::sort) need to convert an
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// "unwrapped" result back into the original iterator type. Doing that is the job of __rewrap_iter.
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// Default case - we can't unwrap anything
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template <class _Iter, bool = __libcpp_is_contiguous_iterator<_Iter>::value>
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struct __unwrap_iter_impl {
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static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter, _Iter __iter) { return __iter; }
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static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __unwrap(_Iter __i) _NOEXCEPT { return __i; }
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};
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#ifndef _LIBCPP_ENABLE_DEBUG_MODE
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// It's a contiguous iterator, so we can use a raw pointer instead
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template <class _Iter>
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struct __unwrap_iter_impl<_Iter, true> {
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using _ToAddressT = decltype(std::__to_address(std::declval<_Iter>()));
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static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter __orig_iter, _ToAddressT __unwrapped_iter) {
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return __orig_iter + (__unwrapped_iter - std::__to_address(__orig_iter));
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}
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static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ToAddressT __unwrap(_Iter __i) _NOEXCEPT {
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return std::__to_address(__i);
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}
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};
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#endif // !_LIBCPP_ENABLE_DEBUG_MODE
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template<class _Iter,
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class _Impl = __unwrap_iter_impl<_Iter>,
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__enable_if_t<is_copy_constructible<_Iter>::value, int> = 0>
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inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
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decltype(_Impl::__unwrap(std::declval<_Iter>())) __unwrap_iter(_Iter __i) _NOEXCEPT {
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return _Impl::__unwrap(__i);
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}
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// Allow input_iterators to be passed to __unwrap_iter (but not __rewrap_iter)
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#if _LIBCPP_STD_VER >= 20
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template <class _Iter, __enable_if_t<!is_copy_constructible<_Iter>::value, int> = 0>
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inline _LIBCPP_HIDE_FROM_ABI constexpr _Iter __unwrap_iter(_Iter __i) noexcept {
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return __i;
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}
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#endif
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template <class _OrigIter, class _Iter, class _Impl = __unwrap_iter_impl<_OrigIter> >
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _OrigIter __rewrap_iter(_OrigIter __orig_iter, _Iter __iter) _NOEXCEPT {
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return _Impl::__rewrap(std::move(__orig_iter), std::move(__iter));
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___ALGORITHM_UNWRAP_ITER_H
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