63 lines · c
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_FIND_SEGMENT_IF_H10#define _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H11 12#include <__config>13#include <__iterator/segmented_iterator.h>14 15#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)16# pragma GCC system_header17#endif18 19_LIBCPP_BEGIN_NAMESPACE_STD20 21// __find_segment_if is a utility function for optimizing iteration over segmented iterators linearly.22// [__first, __last) has to be a segmented range. __pred is expected to take a range of local iterators and the __proj.23// It returns an iterator to the first element that satisfies the predicate, or a one-past-the-end iterator if there was24// no match. __proj may be anything that should be passed to __pred, but is expected to be a projection to support25// ranges algorithms, or __identity for classic algorithms.26 27template <class _SegmentedIterator, class _Pred, class _Proj>28_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _SegmentedIterator29__find_segment_if(_SegmentedIterator __first, _SegmentedIterator __last, _Pred __pred, _Proj& __proj) {30 using _Traits = __segmented_iterator_traits<_SegmentedIterator>;31 32 auto __sfirst = _Traits::__segment(__first);33 auto __slast = _Traits::__segment(__last);34 35 // We are in a single segment, so we might not be at the beginning or end36 if (__sfirst == __slast)37 return _Traits::__compose(__sfirst, __pred(_Traits::__local(__first), _Traits::__local(__last), __proj));38 39 { // We have more than one segment. Iterate over the first segment, since we might not start at the beginning40 auto __llast = _Traits::__end(__sfirst);41 auto __liter = __pred(_Traits::__local(__first), __llast, __proj);42 if (__liter != __llast)43 return _Traits::__compose(__sfirst, __liter);44 }45 ++__sfirst;46 47 // Iterate over the segments which are guaranteed to be completely in the range48 while (__sfirst != __slast) {49 auto __llast = _Traits::__end(__sfirst);50 auto __liter = __pred(_Traits::__begin(__sfirst), _Traits::__end(__sfirst), __proj);51 if (__liter != __llast)52 return _Traits::__compose(__sfirst, __liter);53 ++__sfirst;54 }55 56 // Iterate over the last segment57 return _Traits::__compose(__sfirst, __pred(_Traits::__begin(__sfirst), _Traits::__local(__last), __proj));58}59 60_LIBCPP_END_NAMESPACE_STD61 62#endif // _LIBCPP___ALGORITHM_FIND_SEGMENT_IF_H63