1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___ALGORITHM_FOR_EACH_SEGMENT_H
10#define _LIBCPP___ALGORITHM_FOR_EACH_SEGMENT_H
11
12#include <__config>
13#include <__iterator/segmented_iterator.h>
14
15#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
16#  pragma GCC system_header
17#endif
18
19_LIBCPP_BEGIN_NAMESPACE_STD
20
21// __for_each_segment is a utility function for optimizing iterating over segmented iterators linearly.
22// __first and __last are expected to be a segmented range. __func is expected to take a range of local iterators.
23// Anything that is returned from __func is ignored.
24
25template <class _SegmentedIterator, class _Functor>
26_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
27__for_each_segment(_SegmentedIterator __first, _SegmentedIterator __last, _Functor __func) {
28  using _Traits = __segmented_iterator_traits<_SegmentedIterator>;
29
30  auto __sfirst = _Traits::__segment(__first);
31  auto __slast  = _Traits::__segment(__last);
32
33  // We are in a single segment, so we might not be at the beginning or end
34  if (__sfirst == __slast) {
35    __func(_Traits::__local(__first), _Traits::__local(__last));
36    return;
37  }
38
39  // We have more than one segment. Iterate over the first segment, since we might not start at the beginning
40  __func(_Traits::__local(__first), _Traits::__end(__sfirst));
41  ++__sfirst;
42  // iterate over the segments which are guaranteed to be completely in the range
43  while (__sfirst != __slast) {
44    __func(_Traits::__begin(__sfirst), _Traits::__end(__sfirst));
45    ++__sfirst;
46  }
47  // iterate over the last segment
48  __func(_Traits::__begin(__sfirst), _Traits::__local(__last));
49}
50
51_LIBCPP_END_NAMESPACE_STD
52
53#endif // _LIBCPP___ALGORITHM_FOR_EACH_SEGMENT_H
54