1*4bdff4beSrobert //===----------------------------------------------------------------------===// 2*4bdff4beSrobert // 3*4bdff4beSrobert // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4*4bdff4beSrobert // See https://llvm.org/LICENSE.txt for license information. 5*4bdff4beSrobert // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6*4bdff4beSrobert // 7*4bdff4beSrobert //===----------------------------------------------------------------------===// 8*4bdff4beSrobert 9*4bdff4beSrobert #ifndef _LIBCPP___SEGMENTED_ITERATOR_H 10*4bdff4beSrobert #define _LIBCPP___SEGMENTED_ITERATOR_H 11*4bdff4beSrobert 12*4bdff4beSrobert // Segmented iterators are iterators over (not necessarily contiguous) sub-ranges. 13*4bdff4beSrobert // 14*4bdff4beSrobert // For example, std::deque stores its data into multiple blocks of contiguous memory, 15*4bdff4beSrobert // which are not stored contiguously themselves. The concept of segmented iterators 16*4bdff4beSrobert // allows algorithms to operate over these multi-level iterators natively, opening the 17*4bdff4beSrobert // door to various optimizations. See http://lafstern.org/matt/segmented.pdf for details. 18*4bdff4beSrobert // 19*4bdff4beSrobert // If __segmented_iterator_traits can be instantiated, the following functions and associated types must be provided: 20*4bdff4beSrobert // - Traits::__local_iterator 21*4bdff4beSrobert // The type of iterators used to iterate inside a segment. 22*4bdff4beSrobert // 23*4bdff4beSrobert // - Traits::__segment_iterator 24*4bdff4beSrobert // The type of iterators used to iterate over segments. 25*4bdff4beSrobert // Segment iterators can be forward iterators or bidirectional iterators, depending on the 26*4bdff4beSrobert // underlying data structure. 27*4bdff4beSrobert // 28*4bdff4beSrobert // - static __segment_iterator Traits::__segment(It __it) 29*4bdff4beSrobert // Returns an iterator to the segment that the provided iterator is in. 30*4bdff4beSrobert // 31*4bdff4beSrobert // - static __local_iterator Traits::__local(It __it) 32*4bdff4beSrobert // Returns the local iterator pointing to the element that the provided iterator points to. 33*4bdff4beSrobert // 34*4bdff4beSrobert // - static __local_iterator Traits::__begin(__segment_iterator __it) 35*4bdff4beSrobert // Returns the local iterator to the beginning of the segment that the provided iterator is pointing into. 36*4bdff4beSrobert // 37*4bdff4beSrobert // - static __local_iterator Traits::__end(__segment_iterator __it) 38*4bdff4beSrobert // Returns the one-past-the-end local iterator to the segment that the provided iterator is pointing into. 39*4bdff4beSrobert // 40*4bdff4beSrobert // - static It Traits::__compose(__segment_iterator, __local_iterator) 41*4bdff4beSrobert // Returns the iterator composed of the segment iterator and local iterator. 42*4bdff4beSrobert 43*4bdff4beSrobert #include <__config> 44*4bdff4beSrobert #include <__type_traits/integral_constant.h> 45*4bdff4beSrobert #include <cstddef> 46*4bdff4beSrobert 47*4bdff4beSrobert #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 48*4bdff4beSrobert # pragma GCC system_header 49*4bdff4beSrobert #endif 50*4bdff4beSrobert 51*4bdff4beSrobert _LIBCPP_BEGIN_NAMESPACE_STD 52*4bdff4beSrobert 53*4bdff4beSrobert template <class _Iterator> 54*4bdff4beSrobert struct __segmented_iterator_traits; 55*4bdff4beSrobert /* exposition-only: 56*4bdff4beSrobert { 57*4bdff4beSrobert using __segment_iterator = ...; 58*4bdff4beSrobert using __local_iterator = ...; 59*4bdff4beSrobert 60*4bdff4beSrobert static __segment_iterator __segment(_Iterator); 61*4bdff4beSrobert static __local_iterator __local(_Iterator); 62*4bdff4beSrobert static __local_iterator __begin(__segment_iterator); 63*4bdff4beSrobert static __local_iterator __end(__segment_iterator); 64*4bdff4beSrobert static _Iterator __compose(__segment_iterator, __local_iterator); 65*4bdff4beSrobert }; 66*4bdff4beSrobert */ 67*4bdff4beSrobert 68*4bdff4beSrobert template <class _Tp, size_t = 0> 69*4bdff4beSrobert struct __has_specialization : false_type {}; 70*4bdff4beSrobert 71*4bdff4beSrobert template <class _Tp> 72*4bdff4beSrobert struct __has_specialization<_Tp, sizeof(_Tp) * 0> : true_type {}; 73*4bdff4beSrobert 74*4bdff4beSrobert template <class _Iterator> 75*4bdff4beSrobert using __is_segmented_iterator = __has_specialization<__segmented_iterator_traits<_Iterator> >; 76*4bdff4beSrobert 77*4bdff4beSrobert _LIBCPP_END_NAMESPACE_STD 78*4bdff4beSrobert 79*4bdff4beSrobert #endif // _LIBCPP___SEGMENTED_ITERATOR_H 80