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_FIND_SEGMENT_IF_H
10#define _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_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// __find_segment_if is a utility function for optimizing iteration over segmented iterators linearly.
22// [__first, __last) has to be a segmented range. __pred is expected to take a range of local iterators and the __proj.
23// It returns an iterator to the first element that satisfies the predicate, or a one-past-the-end iterator if there was
24// no match. __proj may be anything that should be passed to __pred, but is expected to be a projection to support
25// ranges algorithms, or __identity for classic algorithms.
26
27template <class _SegmentedIterator, class _Pred, class _Proj>
28_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator
29__find_segment_if(_SegmentedIterator __first, _SegmentedIterator __last, _Pred __pred, _Proj& __proj) {
30  using _Traits = __segmented_iterator_traits<_SegmentedIterator>;
31
32  auto __sfirst = _Traits::__segment(__first);
33  auto __slast  = _Traits::__segment(__last);
34
35  // We are in a single segment, so we might not be at the beginning or end
36  if (__sfirst == __slast)
37    return _Traits::__compose(__sfirst, __pred(_Traits::__local(__first), _Traits::__local(__last), __proj));
38
39  { // We have more than one segment. Iterate over the first segment, since we might not start at the beginning
40    auto __llast = _Traits::__end(__sfirst);
41    auto __liter = __pred(_Traits::__local(__first), __llast, __proj);
42    if (__liter != __llast)
43      return _Traits::__compose(__sfirst, __liter);
44  }
45  ++__sfirst;
46
47  // Iterate over the segments which are guaranteed to be completely in the range
48  while (__sfirst != __slast) {
49    auto __llast = _Traits::__end(__sfirst);
50    auto __liter = __pred(_Traits::__begin(__sfirst), _Traits::__end(__sfirst), __proj);
51    if (__liter != __llast)
52      return _Traits::__compose(__sfirst, __liter);
53    ++__sfirst;
54  }
55
56  // Iterate over the last segment
57  return _Traits::__compose(__sfirst, __pred(_Traits::__begin(__sfirst), _Traits::__local(__last), __proj));
58}
59
60_LIBCPP_END_NAMESPACE_STD
61
62#endif // _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H
63