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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H
#define _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H
#include <__config>
#include <__iterator/iterator_traits.h>
#include <__iterator/segmented_iterator.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
// __for_each_n_segment optimizes linear iteration over segmented iterators. It processes a segmented
// input range [__first, __first + __n) by applying the functor __func to each element within the segment.
// The return value of __func is ignored, and the function returns an iterator pointing to one past the
// last processed element in the input range.
template <class _SegmentedIterator, class _Size, class _Functor>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator
__for_each_n_segment(_SegmentedIterator __first, _Size __orig_n, _Functor __func) {
static_assert(__is_segmented_iterator<_SegmentedIterator>::value &&
__has_random_access_iterator_category<
typename __segmented_iterator_traits<_SegmentedIterator>::__local_iterator>::value,
"__for_each_n_segment only works with segmented iterators with random-access local iterators");
if (__orig_n <= 0)
return __first;
using _Traits = __segmented_iterator_traits<_SegmentedIterator>;
using __local_iter_t = typename _Traits::__local_iterator;
using __difference_t = typename std::iterator_traits<__local_iter_t>::difference_type;
__difference_t __n = __orig_n;
auto __seg = _Traits::__segment(__first);
auto __local_first = _Traits::__local(__first);
__local_iter_t __local_last;
while (__n > 0) {
__local_last = _Traits::__end(__seg);
auto __seg_size = __local_last - __local_first;
if (__n <= __seg_size) {
__local_last = __local_first + __n;
__func(__local_first, __local_last);
break;
}
__func(__local_first, __local_last);
__n -= __seg_size;
__local_first = _Traits::__begin(++__seg);
}
return _Traits::__compose(__seg, __local_last);
}
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ALGORITHM_FOR_EACH_N_SEGMENT_H
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