mirror of
https://github.com/llvm/llvm-project.git
synced 2025-04-28 18:26:06 +00:00
c90801457f
This has multiple benefits: - The optimizations are also performed for the `ranges::` versions of the algorithms - Code duplication is reduced - it is simpler to add this optimization for other segmented iterators, like `ranges::join_view::iterator` - Algorithm code is removed from `<deque>` Reviewed By: ldionne, huixie90, #libc Spies: mstorsjo, sstefan1, EricWF, libcxx-commits, mgorny Differential Revision: https://reviews.llvm.org/D132505
80 lines
3.0 KiB
C++
80 lines
3.0 KiB
C++
//===----------------------------------------------------------------------===//
|
|
//
|
|
// 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
|