libcxx/include/__algorithm/swap_ranges.h

//===----------------------------------------------------------------------===//
//
// 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_SWAP_RANGES_H
#define _LIBCPP___ALGORITHM_SWAP_RANGES_H

#include <__algorithm/iterator_operations.h>
#include <__algorithm/min.h>
#include <__config>
#include <__fwd/bit_reference.h>
#include <__utility/move.h>
#include <__utility/pair.h>
#include <__utility/swap.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _Cl, class _Cr>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cr, false> __swap_ranges_aligned(
    __bit_iterator<_Cl, false> __first, __bit_iterator<_Cl, false> __last, __bit_iterator<_Cr, false> __result) {
  using _I1             = __bit_iterator<_Cl, false>;
  using difference_type = typename _I1::difference_type;
  using __storage_type  = typename _I1::__storage_type;

  const int __bits_per_word = _I1::__bits_per_word;
  difference_type __n       = __last - __first;
  if (__n > 0) {
    // do first word
    if (__first.__ctz_ != 0) {
      unsigned __clz       = __bits_per_word - __first.__ctz_;
      difference_type __dn = std::min(static_cast<difference_type>(__clz), __n);
      __n -= __dn;
      __storage_type __m  = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
      __storage_type __b1 = *__first.__seg_ & __m;
      *__first.__seg_ &= ~__m;
      __storage_type __b2 = *__result.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b1;
      *__first.__seg_ |= __b2;
      __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
      __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_) % __bits_per_word);
      ++__first.__seg_;
      // __first.__ctz_ = 0;
    }
    // __first.__ctz_ == 0;
    // do middle words
    for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_, ++__result.__seg_)
      swap(*__first.__seg_, *__result.__seg_);
    // do last word
    if (__n > 0) {
      __storage_type __m  = ~__storage_type(0) >> (__bits_per_word - __n);
      __storage_type __b1 = *__first.__seg_ & __m;
      *__first.__seg_ &= ~__m;
      __storage_type __b2 = *__result.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b1;
      *__first.__seg_ |= __b2;
      __result.__ctz_ = static_cast<unsigned>(__n);
    }
  }
  return __result;
}

template <class _Cl, class _Cr>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __bit_iterator<_Cr, false> __swap_ranges_unaligned(
    __bit_iterator<_Cl, false> __first, __bit_iterator<_Cl, false> __last, __bit_iterator<_Cr, false> __result) {
  using _I1             = __bit_iterator<_Cl, false>;
  using difference_type = typename _I1::difference_type;
  using __storage_type  = typename _I1::__storage_type;

  const int __bits_per_word = _I1::__bits_per_word;
  difference_type __n       = __last - __first;
  if (__n > 0) {
    // do first word
    if (__first.__ctz_ != 0) {
      unsigned __clz_f     = __bits_per_word - __first.__ctz_;
      difference_type __dn = std::min(static_cast<difference_type>(__clz_f), __n);
      __n -= __dn;
      __storage_type __m  = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
      __storage_type __b1 = *__first.__seg_ & __m;
      *__first.__seg_ &= ~__m;
      unsigned __clz_r     = __bits_per_word - __result.__ctz_;
      __storage_type __ddn = std::min<__storage_type>(__dn, __clz_r);
      __m                  = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
      __storage_type __b2  = *__result.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      if (__result.__ctz_ > __first.__ctz_) {
        unsigned __s = __result.__ctz_ - __first.__ctz_;
        *__result.__seg_ |= __b1 << __s;
        *__first.__seg_ |= __b2 >> __s;
      } else {
        unsigned __s = __first.__ctz_ - __result.__ctz_;
        *__result.__seg_ |= __b1 >> __s;
        *__first.__seg_ |= __b2 << __s;
      }
      __result.__seg_ += (__ddn + __result.__ctz_) / __bits_per_word;
      __result.__ctz_ = static_cast<unsigned>((__ddn + __result.__ctz_) % __bits_per_word);
      __dn -= __ddn;
      if (__dn > 0) {
        __m  = ~__storage_type(0) >> (__bits_per_word - __dn);
        __b2 = *__result.__seg_ & __m;
        *__result.__seg_ &= ~__m;
        unsigned __s = __first.__ctz_ + __ddn;
        *__result.__seg_ |= __b1 >> __s;
        *__first.__seg_ |= __b2 << __s;
        __result.__ctz_ = static_cast<unsigned>(__dn);
      }
      ++__first.__seg_;
      // __first.__ctz_ = 0;
    }
    // __first.__ctz_ == 0;
    // do middle words
    __storage_type __m = ~__storage_type(0) << __result.__ctz_;
    unsigned __clz_r   = __bits_per_word - __result.__ctz_;
    for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_) {
      __storage_type __b1 = *__first.__seg_;
      __storage_type __b2 = *__result.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b1 << __result.__ctz_;
      *__first.__seg_ = __b2 >> __result.__ctz_;
      ++__result.__seg_;
      __b2 = *__result.__seg_ & ~__m;
      *__result.__seg_ &= __m;
      *__result.__seg_ |= __b1 >> __clz_r;
      *__first.__seg_ |= __b2 << __clz_r;
    }
    // do last word
    if (__n > 0) {
      __m                 = ~__storage_type(0) >> (__bits_per_word - __n);
      __storage_type __b1 = *__first.__seg_ & __m;
      *__first.__seg_ &= ~__m;
      __storage_type __dn = std::min<__storage_type>(__n, __clz_r);
      __m                 = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
      __storage_type __b2 = *__result.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b1 << __result.__ctz_;
      *__first.__seg_ |= __b2 >> __result.__ctz_;
      __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
      __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_) % __bits_per_word);
      __n -= __dn;
      if (__n > 0) {
        __m  = ~__storage_type(0) >> (__bits_per_word - __n);
        __b2 = *__result.__seg_ & __m;
        *__result.__seg_ &= ~__m;
        *__result.__seg_ |= __b1 >> __dn;
        *__first.__seg_ |= __b2 << __dn;
        __result.__ctz_ = static_cast<unsigned>(__n);
      }
    }
  }
  return __result;
}

// 2+1 iterators: size2 >= size1; used by std::swap_ranges.
template <class, class _Cl, class _Cr>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cl, false>, __bit_iterator<_Cr, false> >
__swap_ranges(__bit_iterator<_Cl, false> __first1,
              __bit_iterator<_Cl, false> __last1,
              __bit_iterator<_Cr, false> __first2) {
  if (__first1.__ctz_ == __first2.__ctz_)
    return std::make_pair(__last1, std::__swap_ranges_aligned(__first1, __last1, __first2));
  return std::make_pair(__last1, std::__swap_ranges_unaligned(__first1, __last1, __first2));
}

// 2+2 iterators: used by std::ranges::swap_ranges.
template <class _AlgPolicy, class _Cl, class _Cr>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cl, false>, __bit_iterator<_Cr, false> >
__swap_ranges(__bit_iterator<_Cl, false> __first1,
              __bit_iterator<_Cl, false> __last1,
              __bit_iterator<_Cr, false> __first2,
              __bit_iterator<_Cr, false> __last2) {
  if (__last1 - __first1 < __last2 - __first2)
    return std::make_pair(__last1, std::__swap_ranges<_AlgPolicy>(__first1, __last1, __first2).second);
  return std::make_pair(std::__swap_ranges<_AlgPolicy>(__first2, __last2, __first1).second, __last2);
}

// 2+2 iterators: the shorter size will be used.
template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2, class _Sentinel2>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator1, _ForwardIterator2>
__swap_ranges(_ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2, _Sentinel2 __last2) {
  while (__first1 != __last1 && __first2 != __last2) {
    _IterOps<_AlgPolicy>::iter_swap(__first1, __first2);
    ++__first1;
    ++__first2;
  }

  return pair<_ForwardIterator1, _ForwardIterator2>(std::move(__first1), std::move(__first2));
}

// 2+1 iterators: size2 >= size1.
template <class _AlgPolicy, class _ForwardIterator1, class _Sentinel1, class _ForwardIterator2>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator1, _ForwardIterator2>
__swap_ranges(_ForwardIterator1 __first1, _Sentinel1 __last1, _ForwardIterator2 __first2) {
  while (__first1 != __last1) {
    _IterOps<_AlgPolicy>::iter_swap(__first1, __first2);
    ++__first1;
    ++__first2;
  }

  return pair<_ForwardIterator1, _ForwardIterator2>(std::move(__first1), std::move(__first2));
}

template <class _ForwardIterator1, class _ForwardIterator2>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator2
swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
  return std::__swap_ranges<_ClassicAlgPolicy>(std::move(__first1), std::move(__last1), std::move(__first2)).second;
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_SWAP_RANGES_H