libcxx/include/__algorithm/copy.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_COPY_H
#define _LIBCPP___ALGORITHM_COPY_H

#include <__algorithm/copy_move_common.h>
#include <__algorithm/for_each_segment.h>
#include <__algorithm/min.h>
#include <__config>
#include <__fwd/bit_reference.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/segmented_iterator.h>
#include <__memory/pointer_traits.h>
#include <__type_traits/common_type.h>
#include <__type_traits/enable_if.h>
#include <__utility/move.h>
#include <__utility/pair.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 _InputIterator, class _OutputIterator>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result);

template <class _InIter, class _Sent, class _OutIter>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> __copy(_InIter, _Sent, _OutIter);

template <class _Cp, bool _IsConst>
_LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> __copy_aligned(
    __bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result) {
  using _In             = __bit_iterator<_Cp, _IsConst>;
  using difference_type = typename _In::difference_type;
  using __storage_type  = typename _In::__storage_type;

  const int __bits_per_word = _In::__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 = std::__middle_mask<__storage_type>(__clz - __dn, __first.__ctz_);
      __storage_type __b = *__first.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b;
      __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
    __storage_type __nw = __n / __bits_per_word;
    std::copy(std::__to_address(__first.__seg_),
              std::__to_address(__first.__seg_ + __nw),
              std::__to_address(__result.__seg_));
    __n -= __nw * __bits_per_word;
    __result.__seg_ += __nw;
    // do last word
    if (__n > 0) {
      __first.__seg_ += __nw;
      __storage_type __m = std::__trailing_mask<__storage_type>(__bits_per_word - __n);
      __storage_type __b = *__first.__seg_ & __m;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b;
      __result.__ctz_ = static_cast<unsigned>(__n);
    }
  }
  return __result;
}

template <class _Cp, bool _IsConst>
_LIBCPP_CONSTEXPR_SINCE_CXX20 _LIBCPP_HIDE_FROM_ABI __bit_iterator<_Cp, false> __copy_unaligned(
    __bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result) {
  using _In             = __bit_iterator<_Cp, _IsConst>;
  using difference_type = typename _In::difference_type;
  using __storage_type  = typename _In::__storage_type;

  const int __bits_per_word = _In::__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   = std::__middle_mask<__storage_type>(__clz_f - __dn, __first.__ctz_);
      __storage_type __b   = *__first.__seg_ & __m;
      unsigned __clz_r     = __bits_per_word - __result.__ctz_;
      __storage_type __ddn = std::min<__storage_type>(__dn, __clz_r);
      __m                  = std::__middle_mask<__storage_type>(__clz_r - __ddn, __result.__ctz_);
      *__result.__seg_ &= ~__m;
      if (__result.__ctz_ > __first.__ctz_)
        *__result.__seg_ |= __b << (__result.__ctz_ - __first.__ctz_);
      else
        *__result.__seg_ |= __b >> (__first.__ctz_ - __result.__ctz_);
      __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 = std::__trailing_mask<__storage_type>(__bits_per_word - __dn);
        *__result.__seg_ &= ~__m;
        *__result.__seg_ |= __b >> (__first.__ctz_ + __ddn);
        __result.__ctz_ = static_cast<unsigned>(__dn);
      }
      ++__first.__seg_;
      // __first.__ctz_ = 0;
    }
    // __first.__ctz_ == 0;
    // do middle words
    unsigned __clz_r   = __bits_per_word - __result.__ctz_;
    __storage_type __m = std::__leading_mask<__storage_type>(__result.__ctz_);
    for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_) {
      __storage_type __b = *__first.__seg_;
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b << __result.__ctz_;
      ++__result.__seg_;
      *__result.__seg_ &= __m;
      *__result.__seg_ |= __b >> __clz_r;
    }
    // do last word
    if (__n > 0) {
      __m                 = std::__trailing_mask<__storage_type>(__bits_per_word - __n);
      __storage_type __b  = *__first.__seg_ & __m;
      __storage_type __dn = std::min(__n, static_cast<difference_type>(__clz_r));
      __m                 = std::__middle_mask<__storage_type>(__clz_r - __dn, __result.__ctz_);
      *__result.__seg_ &= ~__m;
      *__result.__seg_ |= __b << __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 = std::__trailing_mask<__storage_type>(__bits_per_word - __n);
        *__result.__seg_ &= ~__m;
        *__result.__seg_ |= __b >> __dn;
        __result.__ctz_ = static_cast<unsigned>(__n);
      }
    }
  }
  return __result;
}

struct __copy_impl {
  template <class _InIter, class _Sent, class _OutIter>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
  operator()(_InIter __first, _Sent __last, _OutIter __result) const {
    while (__first != __last) {
      *__result = *__first;
      ++__first;
      ++__result;
    }

    return std::make_pair(std::move(__first), std::move(__result));
  }

  template <class _InIter, class _OutIter>
  struct _CopySegment {
    using _Traits _LIBCPP_NODEBUG = __segmented_iterator_traits<_InIter>;

    _OutIter& __result_;

    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit _CopySegment(_OutIter& __result)
        : __result_(__result) {}

    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
    operator()(typename _Traits::__local_iterator __lfirst, typename _Traits::__local_iterator __llast) {
      __result_ = std::__copy(__lfirst, __llast, std::move(__result_)).second;
    }
  };

  template <class _InIter, class _OutIter, __enable_if_t<__is_segmented_iterator<_InIter>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
  operator()(_InIter __first, _InIter __last, _OutIter __result) const {
    std::__for_each_segment(__first, __last, _CopySegment<_InIter, _OutIter>(__result));
    return std::make_pair(__last, std::move(__result));
  }

  template <class _InIter,
            class _OutIter,
            __enable_if_t<__has_random_access_iterator_category<_InIter>::value &&
                              !__is_segmented_iterator<_InIter>::value && __is_segmented_iterator<_OutIter>::value,
                          int> = 0>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
  operator()(_InIter __first, _InIter __last, _OutIter __result) const {
    using _Traits = __segmented_iterator_traits<_OutIter>;
    using _DiffT  = typename common_type<__iter_diff_t<_InIter>, __iter_diff_t<_OutIter> >::type;

    if (__first == __last)
      return std::make_pair(std::move(__first), std::move(__result));

    auto __local_first      = _Traits::__local(__result);
    auto __segment_iterator = _Traits::__segment(__result);
    while (true) {
      auto __local_last = _Traits::__end(__segment_iterator);
      auto __size       = std::min<_DiffT>(__local_last - __local_first, __last - __first);
      auto __iters      = std::__copy(__first, __first + __size, __local_first);
      __first           = std::move(__iters.first);

      if (__first == __last)
        return std::make_pair(std::move(__first), _Traits::__compose(__segment_iterator, std::move(__iters.second)));

      __local_first = _Traits::__begin(++__segment_iterator);
    }
  }

  template <class _Cp, bool _IsConst>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<__bit_iterator<_Cp, _IsConst>, __bit_iterator<_Cp, false> >
  operator()(__bit_iterator<_Cp, _IsConst> __first,
             __bit_iterator<_Cp, _IsConst> __last,
             __bit_iterator<_Cp, false> __result) const {
    if (__first.__ctz_ == __result.__ctz_)
      return std::make_pair(__last, std::__copy_aligned(__first, __last, __result));
    return std::make_pair(__last, std::__copy_unaligned(__first, __last, __result));
  }

  // At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
  template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0>
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
  operator()(_In* __first, _In* __last, _Out* __result) const {
    return std::__copy_trivial_impl(__first, __last, __result);
  }
};

template <class _InIter, class _Sent, class _OutIter>
pair<_InIter, _OutIter> inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
__copy(_InIter __first, _Sent __last, _OutIter __result) {
  return std::__copy_move_unwrap_iters<__copy_impl>(std::move(__first), std::move(__last), std::move(__result));
}

template <class _InputIterator, class _OutputIterator>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result) {
  return std::__copy(__first, __last, __result).second;
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___ALGORITHM_COPY_H