fc5e0c071b
This patch does two things. (1) It replaces SFINAE with `if constexpr`, avoiding some overload resolution and unnecessary boilerplate. (2) It removes an overload from `__for_each_n` to forward to `__for_each`, since `__for_each` doesn't provide any further optimizations.
81 lines
3.1 KiB
C++
81 lines
3.1 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___SEGMENTED_ITERATOR_H
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#define _LIBCPP___SEGMENTED_ITERATOR_H
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// Segmented iterators are iterators over (not necessarily contiguous) sub-ranges.
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//
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// For example, std::deque stores its data into multiple blocks of contiguous memory,
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// which are not stored contiguously themselves. The concept of segmented iterators
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// allows algorithms to operate over these multi-level iterators natively, opening the
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// door to various optimizations. See http://lafstern.org/matt/segmented.pdf for details.
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//
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// If __segmented_iterator_traits can be instantiated, the following functions and associated types must be provided:
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// - Traits::__local_iterator
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// The type of iterators used to iterate inside a segment.
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//
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// - Traits::__segment_iterator
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// The type of iterators used to iterate over segments.
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// Segment iterators can be forward iterators or bidirectional iterators, depending on the
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// underlying data structure.
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//
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// - static __segment_iterator Traits::__segment(It __it)
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// Returns an iterator to the segment that the provided iterator is in.
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//
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// - static __local_iterator Traits::__local(It __it)
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// Returns the local iterator pointing to the element that the provided iterator points to.
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//
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// - static __local_iterator Traits::__begin(__segment_iterator __it)
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// Returns the local iterator to the beginning of the segment that the provided iterator is pointing into.
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//
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// - static __local_iterator Traits::__end(__segment_iterator __it)
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// Returns the one-past-the-end local iterator to the segment that the provided iterator is pointing into.
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//
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// - static It Traits::__compose(__segment_iterator, __local_iterator)
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// Returns the iterator composed of the segment iterator and local iterator.
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#include <__config>
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#include <__cstddef/size_t.h>
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#include <__iterator/iterator_traits.h>
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#include <__type_traits/integral_constant.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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template <class _Iterator>
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struct __segmented_iterator_traits;
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/* exposition-only:
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{
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using __segment_iterator = ...;
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using __local_iterator = ...;
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static __segment_iterator __segment(_Iterator);
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static __local_iterator __local(_Iterator);
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static __local_iterator __begin(__segment_iterator);
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static __local_iterator __end(__segment_iterator);
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static _Iterator __compose(__segment_iterator, __local_iterator);
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};
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*/
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template <class _Tp, size_t = 0>
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inline const bool __has_specialization_v = false;
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template <class _Tp>
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inline const bool __has_specialization_v<_Tp, sizeof(_Tp) * 0> = true;
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template <class _Iterator>
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inline const bool __is_segmented_iterator_v = __has_specialization_v<__segmented_iterator_traits<_Iterator> >;
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___SEGMENTED_ITERATOR_H
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