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llvm-capstone/libcxx/include/__algorithm/stable_partition.h
Louis Dionne 368faacac7 [libc++] Revert "Protect users from relying on detail headers" & related changes 
This commit reverts 5aaefa51 (and also partly 7f285f48e77 and b6d75682f9,
which were related to the original commit). As landed, 5aaefa51 had
unintended consequences on some downstream bots and didn't have proper
coverage upstream due to a few subtle things. Implementing this is
something we should do in libc++, however we'll first need to address
a few issues listed in https://reviews.llvm.org/D106124#3349710.

Differential Revision: https://reviews.llvm.org/D120683
2022-03-01 08:20:24 -05:00

296 lines
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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_STABLE_PARTITION_H
#define _LIBCPP___ALGORITHM_STABLE_PARTITION_H
#include <__algorithm/rotate.h>
#include <__config>
#include <__iterator/iterator_traits.h>
#include <__utility/swap.h>
#include <memory>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
_ForwardIterator
__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
_Distance __len, _Pair __p, forward_iterator_tag __fit)
{
// *__first is known to be false
// __len >= 1
if (__len == 1)
return __first;
if (__len == 2)
{
_ForwardIterator __m = __first;
if (__pred(*++__m))
{
swap(*__first, *__m);
return __m;
}
return __first;
}
if (__len <= __p.second)
{ // The buffer is big enough to use
typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
__destruct_n __d(0);
unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
// Move the falses into the temporary buffer, and the trues to the front of the line
// Update __first to always point to the end of the trues
value_type* __t = __p.first;
::new ((void*)__t) value_type(_VSTD::move(*__first));
__d.template __incr<value_type>();
++__t;
_ForwardIterator __i = __first;
while (++__i != __last)
{
if (__pred(*__i))
{
*__first = _VSTD::move(*__i);
++__first;
}
else
{
::new ((void*)__t) value_type(_VSTD::move(*__i));
__d.template __incr<value_type>();
++__t;
}
}
// All trues now at start of range, all falses in buffer
// Move falses back into range, but don't mess up __first which points to first false
__i = __first;
for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
*__i = _VSTD::move(*__t2);
// __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
return __first;
}
// Else not enough buffer, do in place
// __len >= 3
_ForwardIterator __m = __first;
_Distance __len2 = __len / 2; // __len2 >= 2
_VSTD::advance(__m, __len2);
// recurse on [__first, __m), *__first know to be false
// F?????????????????
// f m l
_ForwardIterator __first_false = _VSTD::__stable_partition<_Predicate&>(__first, __m, __pred, __len2, __p, __fit);
// TTTFFFFF??????????
// f ff m l
// recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
_ForwardIterator __m1 = __m;
_ForwardIterator __second_false = __last;
_Distance __len_half = __len - __len2;
while (__pred(*__m1))
{
if (++__m1 == __last)
goto __second_half_done;
--__len_half;
}
// TTTFFFFFTTTF??????
// f ff m m1 l
__second_false = _VSTD::__stable_partition<_Predicate&>(__m1, __last, __pred, __len_half, __p, __fit);
__second_half_done:
// TTTFFFFFTTTTTFFFFF
// f ff m sf l
return _VSTD::rotate(__first_false, __m, __second_false);
// TTTTTTTTFFFFFFFFFF
// |
}
template <class _Predicate, class _ForwardIterator>
_ForwardIterator
__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
forward_iterator_tag)
{
const unsigned __alloc_limit = 3; // might want to make this a function of trivial assignment
// Either prove all true and return __first or point to first false
while (true)
{
if (__first == __last)
return __first;
if (!__pred(*__first))
break;
++__first;
}
// We now have a reduced range [__first, __last)
// *__first is known to be false
typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
difference_type __len = _VSTD::distance(__first, __last);
pair<value_type*, ptrdiff_t> __p(0, 0);
unique_ptr<value_type, __return_temporary_buffer> __h;
if (__len >= __alloc_limit)
{
__p = _VSTD::get_temporary_buffer<value_type>(__len);
__h.reset(__p.first);
}
return _VSTD::__stable_partition<_Predicate&>(__first, __last, __pred, __len, __p, forward_iterator_tag());
}
template <class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
_BidirectionalIterator
__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
_Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
{
// *__first is known to be false
// *__last is known to be true
// __len >= 2
if (__len == 2)
{
swap(*__first, *__last);
return __last;
}
if (__len == 3)
{
_BidirectionalIterator __m = __first;
if (__pred(*++__m))
{
swap(*__first, *__m);
swap(*__m, *__last);
return __last;
}
swap(*__m, *__last);
swap(*__first, *__m);
return __m;
}
if (__len <= __p.second)
{ // The buffer is big enough to use
typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
__destruct_n __d(0);
unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
// Move the falses into the temporary buffer, and the trues to the front of the line
// Update __first to always point to the end of the trues
value_type* __t = __p.first;
::new ((void*)__t) value_type(_VSTD::move(*__first));
__d.template __incr<value_type>();
++__t;
_BidirectionalIterator __i = __first;
while (++__i != __last)
{
if (__pred(*__i))
{
*__first = _VSTD::move(*__i);
++__first;
}
else
{
::new ((void*)__t) value_type(_VSTD::move(*__i));
__d.template __incr<value_type>();
++__t;
}
}
// move *__last, known to be true
*__first = _VSTD::move(*__i);
__i = ++__first;
// All trues now at start of range, all falses in buffer
// Move falses back into range, but don't mess up __first which points to first false
for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
*__i = _VSTD::move(*__t2);
// __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
return __first;
}
// Else not enough buffer, do in place
// __len >= 4
_BidirectionalIterator __m = __first;
_Distance __len2 = __len / 2; // __len2 >= 2
_VSTD::advance(__m, __len2);
// recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
// F????????????????T
// f m l
_BidirectionalIterator __m1 = __m;
_BidirectionalIterator __first_false = __first;
_Distance __len_half = __len2;
while (!__pred(*--__m1))
{
if (__m1 == __first)
goto __first_half_done;
--__len_half;
}
// F???TFFF?????????T
// f m1 m l
__first_false = _VSTD::__stable_partition<_Predicate&>(__first, __m1, __pred, __len_half, __p, __bit);
__first_half_done:
// TTTFFFFF?????????T
// f ff m l
// recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
__m1 = __m;
_BidirectionalIterator __second_false = __last;
++__second_false;
__len_half = __len - __len2;
while (__pred(*__m1))
{
if (++__m1 == __last)
goto __second_half_done;
--__len_half;
}
// TTTFFFFFTTTF?????T
// f ff m m1 l
__second_false = _VSTD::__stable_partition<_Predicate&>(__m1, __last, __pred, __len_half, __p, __bit);
__second_half_done:
// TTTFFFFFTTTTTFFFFF
// f ff m sf l
return _VSTD::rotate(__first_false, __m, __second_false);
// TTTTTTTTFFFFFFFFFF
// |
}
template <class _Predicate, class _BidirectionalIterator>
_BidirectionalIterator
__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
bidirectional_iterator_tag)
{
typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
const difference_type __alloc_limit = 4; // might want to make this a function of trivial assignment
// Either prove all true and return __first or point to first false
while (true)
{
if (__first == __last)
return __first;
if (!__pred(*__first))
break;
++__first;
}
// __first points to first false, everything prior to __first is already set.
// Either prove [__first, __last) is all false and return __first, or point __last to last true
do
{
if (__first == --__last)
return __first;
} while (!__pred(*__last));
// We now have a reduced range [__first, __last]
// *__first is known to be false
// *__last is known to be true
// __len >= 2
difference_type __len = _VSTD::distance(__first, __last) + 1;
pair<value_type*, ptrdiff_t> __p(0, 0);
unique_ptr<value_type, __return_temporary_buffer> __h;
if (__len >= __alloc_limit)
{
__p = _VSTD::get_temporary_buffer<value_type>(__len);
__h.reset(__p.first);
}
return _VSTD::__stable_partition<_Predicate&>(__first, __last, __pred, __len, __p, bidirectional_iterator_tag());
}
template <class _ForwardIterator, class _Predicate>
inline _LIBCPP_INLINE_VISIBILITY
_ForwardIterator
stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
{
return _VSTD::__stable_partition<_Predicate&>(__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
}
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ALGORITHM_STABLE_PARTITION_H
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