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
25 template <class _SegmentedIterator, class _Functor>
26 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
__for_each_segment(_SegmentedIterator __first,_SegmentedIterator __last,_Functor __func)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