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| 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_N_SEGMENT_H |
| 10 | #define _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H |
| 11 | |
| 12 | #include <__config> |
| 13 | #include <__iterator/iterator_traits.h> |
| 14 | #include <__iterator/segmented_iterator.h> |
| 15 | |
| 16 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 17 | # pragma GCC system_header |
| 18 | #endif |
| 19 | |
| 20 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 21 | |
| 22 | // __for_each_n_segment optimizes linear iteration over segmented iterators. It processes a segmented |
| 23 | // input range [__first, __first + __n) by applying the functor __func to each element within the segment. |
| 24 | // The return value of __func is ignored, and the function returns an iterator pointing to one past the |
| 25 | // last processed element in the input range. |
| 26 | |
| 27 | template <class _SegmentedIterator, class _Size, class _Functor> |
| 28 | _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator |
| 29 | __for_each_n_segment(_SegmentedIterator __first, _Size __orig_n, _Functor __func) { |
| 30 | static_assert(__is_segmented_iterator<_SegmentedIterator>::value && |
| 31 | __has_random_access_iterator_category< |
| 32 | typename __segmented_iterator_traits<_SegmentedIterator>::__local_iterator>::value, |
| 33 | "__for_each_n_segment only works with segmented iterators with random-access local iterators"); |
| 34 | if (__orig_n <= 0) |
| 35 | return __first; |
| 36 | |
| 37 | using _Traits = __segmented_iterator_traits<_SegmentedIterator>; |
| 38 | using __local_iter_t = typename _Traits::__local_iterator; |
| 39 | using __difference_t = typename std::iterator_traits<__local_iter_t>::difference_type; |
| 40 | __difference_t __n = __orig_n; |
| 41 | auto __seg = _Traits::__segment(__first); |
| 42 | auto __local_first = _Traits::__local(__first); |
| 43 | __local_iter_t __local_last; |
| 44 | |
| 45 | while (__n > 0) { |
| 46 | __local_last = _Traits::__end(__seg); |
| 47 | auto __seg_size = __local_last - __local_first; |
| 48 | if (__n <= __seg_size) { |
| 49 | __local_last = __local_first + __n; |
| 50 | __func(__local_first, __local_last); |
| 51 | break; |
| 52 | } |
| 53 | __func(__local_first, __local_last); |
| 54 | __n -= __seg_size; |
| 55 | __local_first = _Traits::__begin(++__seg); |
| 56 | } |
| 57 | |
| 58 | return _Traits::__compose(__seg, __local_last); |
| 59 | } |
| 60 | |
| 61 | _LIBCPP_END_NAMESPACE_STD |
| 62 | |
| 63 | #endif // _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H |
| 64 |
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