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Diffstat (limited to 'libcxx/include/__iterator/segmented_iterator.h')
| -rw-r--r-- | libcxx/include/__iterator/segmented_iterator.h | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/libcxx/include/__iterator/segmented_iterator.h b/libcxx/include/__iterator/segmented_iterator.h new file mode 100644 index 000000000000..f3cd1e5fa1f5 --- /dev/null +++ b/libcxx/include/__iterator/segmented_iterator.h @@ -0,0 +1,79 @@ +//===----------------------------------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#ifndef _LIBCPP___SEGMENTED_ITERATOR_H +#define _LIBCPP___SEGMENTED_ITERATOR_H + +// Segmented iterators are iterators over (not necessarily contiguous) sub-ranges. +// +// For example, std::deque stores its data into multiple blocks of contiguous memory, +// which are not stored contiguously themselves. The concept of segmented iterators +// allows algorithms to operate over these multi-level iterators natively, opening the +// door to various optimizations. See http://lafstern.org/matt/segmented.pdf for details. +// +// If __segmented_iterator_traits can be instantiated, the following functions and associated types must be provided: +// - Traits::__local_iterator +// The type of iterators used to iterate inside a segment. +// +// - Traits::__segment_iterator +// The type of iterators used to iterate over segments. +// Segment iterators can be forward iterators or bidirectional iterators, depending on the +// underlying data structure. +// +// - static __segment_iterator Traits::__segment(It __it) +// Returns an iterator to the segment that the provided iterator is in. +// +// - static __local_iterator Traits::__local(It __it) +// Returns the local iterator pointing to the element that the provided iterator points to. +// +// - static __local_iterator Traits::__begin(__segment_iterator __it) +// Returns the local iterator to the beginning of the segment that the provided iterator is pointing into. +// +// - static __local_iterator Traits::__end(__segment_iterator __it) +// Returns the one-past-the-end local iterator to the segment that the provided iterator is pointing into. +// +// - static It Traits::__compose(__segment_iterator, __local_iterator) +// Returns the iterator composed of the segment iterator and local iterator. + +#include <__config> +#include <__type_traits/integral_constant.h> +#include <cstddef> + +#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) +# pragma GCC system_header +#endif + +_LIBCPP_BEGIN_NAMESPACE_STD + +template <class _Iterator> +struct __segmented_iterator_traits; +/* exposition-only: +{ + using __segment_iterator = ...; + using __local_iterator = ...; + + static __segment_iterator __segment(_Iterator); + static __local_iterator __local(_Iterator); + static __local_iterator __begin(__segment_iterator); + static __local_iterator __end(__segment_iterator); + static _Iterator __compose(__segment_iterator, __local_iterator); +}; +*/ + +template <class _Tp, size_t = 0> +struct __has_specialization : false_type {}; + +template <class _Tp> +struct __has_specialization<_Tp, sizeof(_Tp) * 0> : true_type {}; + +template <class _Iterator> +using __is_segmented_iterator = __has_specialization<__segmented_iterator_traits<_Iterator> >; + +_LIBCPP_END_NAMESPACE_STD + +#endif // _LIBCPP___SEGMENTED_ITERATOR_H |