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.
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.
25
26template <class _SegmentedIterator, class _Pred>
27_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator
28__find_segment_if(_SegmentedIterator __first, _SegmentedIterator __last, _Pred __pred) {
29 using _Traits = __segmented_iterator_traits<_SegmentedIterator>;
30
31 auto __sfirst = _Traits::__segment(__first);
32 auto __slast = _Traits::__segment(__last);
33
34 // We are in a single segment, so we might not be at the beginning or end
35 if (__sfirst == __slast)
36 return _Traits::__compose(__sfirst, __pred(_Traits::__local(__first), _Traits::__local(__last)));
37
38 { // We have more than one segment. Iterate over the first segment, since we might not start at the beginning
39 auto __llast = _Traits::__end(__sfirst);
40 auto __liter = __pred(_Traits::__local(__first), __llast);
41 if (__liter != __llast)
42 return _Traits::__compose(__sfirst, __liter);
43 }
44 ++__sfirst;
45
46 // Iterate over the segments which are guaranteed to be completely in the range
47 while (__sfirst != __slast) {
48 auto __llast = _Traits::__end(__sfirst);
49 auto __liter = __pred(_Traits::__begin(__sfirst), _Traits::__end(__sfirst));
50 if (__liter != __llast)
51 return _Traits::__compose(__sfirst, __liter);
52 ++__sfirst;
53 }
54
55 // Iterate over the last segment
56 return _Traits::__compose(__sfirst, __pred(_Traits::__begin(__sfirst), _Traits::__local(__last)));
57}
58
59_LIBCPP_END_NAMESPACE_STD
60
61#endif // _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H
62