mirror of
https://github.com/llvm/llvm-project.git
synced 2025-04-25 06:46:05 +00:00
80643d9366
We plan to add concepts for checking that iterators actually provide what they claim to. This is to avoid people thinking that these type traits actually check the iterator requirements in more detail. Reviewed By: ldionne, #libc Spies: Mordante, libcxx-commits, wenlei Differential Revision: https://reviews.llvm.org/D150801
102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
//===----------------------------------------------------------------------===//
|
|
//
|
|
// 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_SHIFT_RIGHT_H
|
|
#define _LIBCPP___ALGORITHM_SHIFT_RIGHT_H
|
|
|
|
#include <__algorithm/move.h>
|
|
#include <__algorithm/move_backward.h>
|
|
#include <__algorithm/swap_ranges.h>
|
|
#include <__config>
|
|
#include <__iterator/iterator_traits.h>
|
|
#include <__utility/swap.h>
|
|
|
|
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
|
|
# pragma GCC system_header
|
|
#endif
|
|
|
|
_LIBCPP_BEGIN_NAMESPACE_STD
|
|
|
|
#if _LIBCPP_STD_VER >= 20
|
|
|
|
template <class _ForwardIterator>
|
|
inline _LIBCPP_INLINE_VISIBILITY constexpr
|
|
_ForwardIterator
|
|
shift_right(_ForwardIterator __first, _ForwardIterator __last,
|
|
typename iterator_traits<_ForwardIterator>::difference_type __n)
|
|
{
|
|
if (__n == 0) {
|
|
return __first;
|
|
}
|
|
|
|
if constexpr (__has_random_access_iterator_category<_ForwardIterator>::value) {
|
|
decltype(__n) __d = __last - __first;
|
|
if (__n >= __d) {
|
|
return __last;
|
|
}
|
|
_ForwardIterator __m = __first + (__d - __n);
|
|
return _VSTD::move_backward(__first, __m, __last);
|
|
} else if constexpr (__has_bidirectional_iterator_category<_ForwardIterator>::value) {
|
|
_ForwardIterator __m = __last;
|
|
for (; __n > 0; --__n) {
|
|
if (__m == __first) {
|
|
return __last;
|
|
}
|
|
--__m;
|
|
}
|
|
return _VSTD::move_backward(__first, __m, __last);
|
|
} else {
|
|
_ForwardIterator __ret = __first;
|
|
for (; __n > 0; --__n) {
|
|
if (__ret == __last) {
|
|
return __last;
|
|
}
|
|
++__ret;
|
|
}
|
|
|
|
// We have an __n-element scratch space from __first to __ret.
|
|
// Slide an __n-element window [__trail, __lead) from left to right.
|
|
// We're essentially doing swap_ranges(__first, __ret, __trail, __lead)
|
|
// over and over; but once __lead reaches __last we needn't bother
|
|
// to save the values of elements [__trail, __last).
|
|
|
|
auto __trail = __first;
|
|
auto __lead = __ret;
|
|
while (__trail != __ret) {
|
|
if (__lead == __last) {
|
|
_VSTD::move(__first, __trail, __ret);
|
|
return __ret;
|
|
}
|
|
++__trail;
|
|
++__lead;
|
|
}
|
|
|
|
_ForwardIterator __mid = __first;
|
|
while (true) {
|
|
if (__lead == __last) {
|
|
__trail = _VSTD::move(__mid, __ret, __trail);
|
|
_VSTD::move(__first, __mid, __trail);
|
|
return __ret;
|
|
}
|
|
swap(*__mid, *__trail);
|
|
++__mid;
|
|
++__trail;
|
|
++__lead;
|
|
if (__mid == __ret) {
|
|
__mid = __first;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
#endif // _LIBCPP_STD_VER >= 20
|
|
|
|
_LIBCPP_END_NAMESPACE_STD
|
|
|
|
#endif // _LIBCPP___ALGORITHM_SHIFT_RIGHT_H
|