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
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