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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H10#define _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H11 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_header18#endif19 20_LIBCPP_BEGIN_NAMESPACE_STD21 22// __for_each_n_segment optimizes linear iteration over segmented iterators. It processes a segmented23// 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 the25// last processed element in the input range.26 27template <class _SegmentedIterator, class _Size, class _Functor>28_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator29__for_each_n_segment(_SegmentedIterator __first, _Size __orig_n, _Functor __func) {30 static_assert(__is_segmented_iterator_v<_SegmentedIterator> &&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_STD62 63#endif // _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H64