5aaefa510e
libc++ has started splicing standard library headers into much more fine-grained content for maintainability. It's very likely that outdated and naive tooling (some of which is outside of LLVM's scope) will suggest users include things such as <__ranges/access.h> instead of <ranges>, and Hyrum's law suggests that users will eventually begin to rely on this without the help of tooling. As such, this commit intends to protect users from themselves, by making it a hard error for anyone outside of the standard library to include libc++ detail headers. Differential Revision: https://reviews.llvm.org/D106124
86 lines
2.7 KiB
C++
86 lines
2.7 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 <__memory/pointer_traits.h>
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#include <iterator>
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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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# pragma clang include_instead(<algorithm>)
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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// The job of __unwrap_iter is to lower contiguous iterators (such as
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// vector<T>::iterator) into pointers, to reduce the number of template
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// instantiations and to enable pointer-based optimizations e.g. in std::copy.
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// For iterators that are not contiguous, it must be a no-op.
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// In debug mode, we don't do this.
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//
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// __unwrap_iter is non-constexpr for user-defined iterators whose
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// `to_address` and/or `operator->` is non-constexpr. This is okay; but we
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// try to avoid doing __unwrap_iter in constant-evaluated contexts anyway.
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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 a contiguous iterator. Since contiguous iterators
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// are random-access, we can do this portably using iterator arithmetic; this
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// is the job of __rewrap_iter.
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template <class _Iter, bool = __is_cpp17_contiguous_iterator<_Iter>::value>
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struct __unwrap_iter_impl {
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static _LIBCPP_CONSTEXPR _Iter
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__apply(_Iter __i) _NOEXCEPT {
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return __i;
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}
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};
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#if _LIBCPP_DEBUG_LEVEL < 2
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template <class _Iter>
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struct __unwrap_iter_impl<_Iter, true> {
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static _LIBCPP_CONSTEXPR decltype(_VSTD::__to_address(declval<_Iter>()))
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__apply(_Iter __i) _NOEXCEPT {
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return _VSTD::__to_address(__i);
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}
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};
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#endif // _LIBCPP_DEBUG_LEVEL < 2
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template<class _Iter, class _Impl = __unwrap_iter_impl<_Iter> >
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inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
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decltype(_Impl::__apply(declval<_Iter>()))
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__unwrap_iter(_Iter __i) _NOEXCEPT
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{
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return _Impl::__apply(__i);
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}
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template<class _OrigIter>
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_LIBCPP_HIDE_FROM_ABI
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_OrigIter __rewrap_iter(_OrigIter, _OrigIter __result)
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{
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return __result;
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}
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template<class _OrigIter, class _UnwrappedIter>
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_LIBCPP_HIDE_FROM_ABI
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_OrigIter __rewrap_iter(_OrigIter __first, _UnwrappedIter __result)
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{
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// Precondition: __result is reachable from __first
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// Precondition: _OrigIter is a contiguous iterator
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return __first + (__result - _VSTD::__unwrap_iter(__first));
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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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