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 // Copyright (C) 2018 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
 // Copyright (C) 2018 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
 // Copyright (C) 2020 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #if 0
 #pragma qt_sync_skip_header_check
 #pragma qt_sync_stop_processing
 #endif
 
 #ifndef QCONTAINERTOOLS_IMPL_H
 #define QCONTAINERTOOLS_IMPL_H
 
 #include <QtCore/qglobal.h>
 #include <QtCore/qtypeinfo.h>
 
 #include <QtCore/qxptype_traits.h>
 
 #include <cstring>
 #include <iterator>
 #include <memory>
 #include <algorithm>
 
 QT_BEGIN_NAMESPACE
 
 namespace QtPrivate
 {
 
 /*!
   \internal
 
   Returns whether \a p is within a range [b, e). In simplest form equivalent to:
   b <= p < e.
 */
 template<typename T, typename Cmp = std::less<>>
 static constexpr bool q_points_into_range(const T *p, const T *b, const T *e,
                                           Cmp less = {}) noexcept
 {
     return !less(p, b) && less(p, e);
 }
 
 /*!
   \internal
 
   Returns whether \a p is within container \a c. In its simplest form equivalent to:
   c.data() <= p < c.data() + c.size()
 */
 template <typename C, typename T>
 static constexpr bool q_points_into_range(const T &p, const C &c) noexcept
 {
     static_assert(std::is_same_v<decltype(std::data(c)), T>);
 
     // std::distance because QArrayDataPointer has a "qsizetype size"
     // member but no size() function
     return q_points_into_range(p, std::data(c),
                                std::data(c) + std::distance(std::begin(c), std::end(c)));
 }
 
 QT_WARNING_PUSH
 QT_WARNING_DISABLE_GCC("-Wmaybe-uninitialized")
 
 template <typename T, typename N>
 void q_uninitialized_move_if_noexcept_n(T* first, N n, T* out)
 {
     if constexpr (std::is_nothrow_move_constructible_v<T> || !std::is_copy_constructible_v<T>)
         std::uninitialized_move_n(first, n, out);
     else
         std::uninitialized_copy_n(first, n, out);
 }
 
 template <typename T, typename N>
 void q_uninitialized_relocate_n(T* first, N n, T* out)
 {
     if constexpr (QTypeInfo<T>::isRelocatable) {
         static_assert(std::is_copy_constructible_v<T> || std::is_move_constructible_v<T>,
                       "Refusing to relocate this non-copy/non-move-constructible type.");
         if (n != N(0)) { // even if N == 0, out == nullptr or first == nullptr are UB for memcpy()
             std::memcpy(static_cast<void *>(out),
                         static_cast<const void *>(first),
                         n * sizeof(T));
         }
     } else {
         q_uninitialized_move_if_noexcept_n(first, n, out);
         if constexpr (QTypeInfo<T>::isComplex)
             std::destroy_n(first, n);
     }
 }
 
 QT_WARNING_POP
 
 /*!
     \internal
 
     A wrapper around std::rotate(), with an optimization for
     Q_RELOCATABLE_TYPEs. We omit the return value, as it would be more work to
     compute in the Q_RELOCATABLE_TYPE case and, unlike std::rotate on
     ForwardIterators, callers can compute the result in constant time
     themselves.
 */
 template <typename T>
 void q_rotate(T *first, T *mid, T *last)
 {
     if constexpr (QTypeInfo<T>::isRelocatable) {
         const auto cast = [](T *p) { return reinterpret_cast<uchar*>(p); };
         std::rotate(cast(first), cast(mid), cast(last));
     } else {
         std::rotate(first, mid, last);
     }
 }
 
 /*!
     \internal
     Copies all elements, except the ones for which \a pred returns \c true, from
     range [first, last), to the uninitialized memory buffer starting at \a out.
 
     It's undefined behavior if \a out points into [first, last).
 
     Returns a pointer one past the last copied element.
 
     If an exception is thrown, all the already copied elements in the destination
     buffer are destroyed.
 */
 template <typename T, typename Predicate>
 T *q_uninitialized_remove_copy_if(T *first, T *last, T *out, Predicate &pred)
 {
     static_assert(std::is_nothrow_destructible_v<T>,
                   "This algorithm requires that T has a non-throwing destructor");
     Q_ASSERT(!q_points_into_range(out, first, last));
 
     T *dest_begin = out;
     QT_TRY {
         while (first != last) {
             if (!pred(*first)) {
                 new (std::addressof(*out)) T(*first);
                 ++out;
             }
             ++first;
         }
     } QT_CATCH (...) {
         std::destroy(std::reverse_iterator(out), std::reverse_iterator(dest_begin));
         QT_RETHROW;
     }
     return out;
 }
 
 template<typename iterator, typename N>
 void q_relocate_overlap_n_left_move(iterator first, N n, iterator d_first)
 {
     // requires: [first, n) is a valid range
     // requires: d_first + n is reachable from d_first
     // requires: iterator is at least a random access iterator
     // requires: value_type(iterator) has a non-throwing destructor
 
     Q_ASSERT(n);
     Q_ASSERT(d_first < first); // only allow moves to the "left"
     using T = typename std::iterator_traits<iterator>::value_type;
 
     // Watches passed iterator. Unless commit() is called, all the elements that
     // the watched iterator passes through are deleted at the end of object
     // lifetime. freeze() could be used to stop watching the passed iterator and
     // remain at current place.
     //
     // requires: the iterator is expected to always point to an invalid object
     //           (to uninitialized memory)
     struct Destructor
     {
         iterator *iter;
         iterator end;
         iterator intermediate;
 
         Destructor(iterator &it) noexcept : iter(std::addressof(it)), end(it) { }
         void commit() noexcept { iter = std::addressof(end); }
         void freeze() noexcept
         {
             intermediate = *iter;
             iter = std::addressof(intermediate);
         }
         ~Destructor() noexcept
         {
             for (const int step = *iter < end ? 1 : -1; *iter != end;) {
                 std::advance(*iter, step);
                 (*iter)->~T();
             }
         }
     } destroyer(d_first);
 
     const iterator d_last = d_first + n;
     // Note: use pair and explicitly copy iterators from it to prevent
     // accidental reference semantics instead of copy. equivalent to:
     //
     // auto [overlapBegin, overlapEnd] = std::minmax(d_last, first);
     auto pair = std::minmax(d_last, first);
 
     // overlap area between [d_first, d_first + n) and [first, first + n) or an
     // uninitialized memory area between the two ranges
     iterator overlapBegin = pair.first;
     iterator overlapEnd = pair.second;
 
     // move construct elements in uninitialized region
     while (d_first != overlapBegin) {
         // account for std::reverse_iterator, cannot use new(d_first) directly
         new (std::addressof(*d_first)) T(std::move_if_noexcept(*first));
         ++d_first;
         ++first;
     }
 
     // cannot commit but have to stop - there might be an overlap region
     // which we don't want to delete (because it's part of existing data)
     destroyer.freeze();
 
     // move assign elements in overlap region
     while (d_first != d_last) {
         *d_first = std::move_if_noexcept(*first);
         ++d_first;
         ++first;
     }
 
     Q_ASSERT(d_first == destroyer.end + n);
     destroyer.commit(); // can commit here as ~T() below does not throw
 
     while (first != overlapEnd)
         (--first)->~T();
 }
 
 /*!
   \internal
 
   Relocates a range [first, n) to [d_first, n) taking care of potential memory
   overlaps. This is a generic equivalent of memmove.
 
   If an exception is thrown during the relocation, all the relocated elements
   are destroyed and [first, n) may contain valid but unspecified values,
   including moved-from values (basic exception safety).
 */
 template<typename T, typename N>
 void q_relocate_overlap_n(T *first, N n, T *d_first)
 {
     static_assert(std::is_nothrow_destructible_v<T>,
                   "This algorithm requires that T has a non-throwing destructor");
 
     if (n == N(0) || first == d_first || first == nullptr || d_first == nullptr)
         return;
 
     if constexpr (QTypeInfo<T>::isRelocatable) {
         std::memmove(static_cast<void *>(d_first), static_cast<const void *>(first), n * sizeof(T));
     } else { // generic version has to be used
         if (d_first < first) {
             q_relocate_overlap_n_left_move(first, n, d_first);
         } else { // first < d_first
             auto rfirst = std::make_reverse_iterator(first + n);
             auto rd_first = std::make_reverse_iterator(d_first + n);
             q_relocate_overlap_n_left_move(rfirst, n, rd_first);
         }
     }
 }
 
 template <typename Iterator>
 using IfIsInputIterator = typename std::enable_if<
     std::is_convertible<typename std::iterator_traits<Iterator>::iterator_category, std::input_iterator_tag>::value,
     bool>::type;
 
 template <typename Iterator>
 using IfIsForwardIterator = typename std::enable_if<
     std::is_convertible<typename std::iterator_traits<Iterator>::iterator_category, std::forward_iterator_tag>::value,
     bool>::type;
 
 template <typename Iterator>
 using IfIsNotForwardIterator = typename std::enable_if<
     !std::is_convertible<typename std::iterator_traits<Iterator>::iterator_category, std::forward_iterator_tag>::value,
     bool>::type;
 
 template <typename Container,
           typename InputIterator,
           IfIsNotForwardIterator<InputIterator> = true>
 void reserveIfForwardIterator(Container *, InputIterator, InputIterator)
 {
 }
 
 template <typename Container,
           typename ForwardIterator,
           IfIsForwardIterator<ForwardIterator> = true>
 void reserveIfForwardIterator(Container *c, ForwardIterator f, ForwardIterator l)
 {
     c->reserve(static_cast<typename Container::size_type>(std::distance(f, l)));
 }
 
 template <typename Iterator>
 using KeyAndValueTest = decltype(
     std::declval<Iterator &>().key(),
     std::declval<Iterator &>().value()
 );
 
 template <typename Iterator>
 using FirstAndSecondTest = decltype(
     std::declval<Iterator &>()->first,
     std::declval<Iterator &>()->second
 );
 
 template <typename Iterator>
 using IfAssociativeIteratorHasKeyAndValue =
     std::enable_if_t<qxp::is_detected_v<KeyAndValueTest, Iterator>, bool>;
 
 template <typename Iterator>
 using IfAssociativeIteratorHasFirstAndSecond =
     std::enable_if_t<
         std::conjunction_v<
             std::negation<qxp::is_detected<KeyAndValueTest, Iterator>>,
             qxp::is_detected<FirstAndSecondTest, Iterator>
         >, bool>;
 
 template <typename Iterator>
 using MoveBackwardsTest = decltype(
     std::declval<Iterator &>().operator--()
 );
 
 template <typename Iterator>
 using IfIteratorCanMoveBackwards =
     std::enable_if_t<qxp::is_detected_v<MoveBackwardsTest, Iterator>, bool>;
 
 template <typename T, typename U>
 using IfIsNotSame =
     typename std::enable_if<!std::is_same<T, U>::value, bool>::type;
 
 template<typename T, typename U>
 using IfIsNotConvertible = typename std::enable_if<!std::is_convertible<T, U>::value, bool>::type;
 
 template <typename Container, typename Predicate>
 auto sequential_erase_if(Container &c, Predicate &pred)
 {
     // This is remove_if() modified to perform the find_if step on
     // const_iterators to avoid shared container detaches if nothing needs to
     // be removed. We cannot run remove_if after find_if: doing so would apply
     // the predicate to the first matching element twice!
 
     const auto cbegin = c.cbegin();
     const auto cend = c.cend();
     const auto t_it = std::find_if(cbegin, cend, pred);
     auto result = std::distance(cbegin, t_it);
     if (result == c.size())
         return result - result; // `0` of the right type
 
     // now detach:
     const auto e = c.end();
 
     auto it = std::next(c.begin(), result);
     auto dest = it;
 
     // Loop Invariants:
     // - it != e
     // - [next(it), e[ still to be checked
     // - [c.begin(), dest[ are result
     while (++it != e) {
         if (!pred(*it)) {
             *dest = std::move(*it);
             ++dest;
         }
     }
 
     result = std::distance(dest, e);
     c.erase(dest, e);
     return result;
 }
 
 template <typename Container, typename T>
 auto sequential_erase(Container &c, const T &t)
 {
     // use the equivalence relation from http://eel.is/c++draft/list.erasure#1
     auto cmp = [&](auto &e) { return e == t; };
     return sequential_erase_if(c, cmp); // can't pass rvalues!
 }
 
 template <typename Container, typename T>
 auto sequential_erase_with_copy(Container &c, const T &t)
 {
     using CopyProxy = std::conditional_t<std::is_copy_constructible_v<T>, T, const T &>;
     return sequential_erase(c, CopyProxy(t));
 }
 
 template <typename Container, typename T>
 auto sequential_erase_one(Container &c, const T &t)
 {
     const auto cend = c.cend();
     const auto it = std::find(c.cbegin(), cend, t);
     if (it == cend)
         return false;
     c.erase(it);
     return true;
 }
 
 template <typename T, typename Predicate>
 qsizetype qset_erase_if(QSet<T> &set, Predicate &pred)
 {
     qsizetype result = 0;
     auto it = set.begin();
     const auto e = set.end();
     while (it != e) {
         if (pred(*it)) {
             ++result;
             it = set.erase(it);
         } else {
             ++it;
         }
     }
     return result;
 }
 
 
 // Prerequisite: F is invocable on ArgTypes
 template <typename R, typename F, typename ... ArgTypes>
 struct is_invoke_result_explicitly_convertible : std::is_constructible<R, std::invoke_result_t<F, ArgTypes...>>
 {};
 
 // is_invocable_r checks for implicit conversions, but we need to check
 // for explicit conversions in remove_if. So, roll our own trait.
 template <typename R, typename F, typename ... ArgTypes>
 constexpr bool is_invocable_explicit_r_v = std::conjunction_v<
     std::is_invocable<F, ArgTypes...>,
     is_invoke_result_explicitly_convertible<R, F, ArgTypes...>
 >;
 
 template <typename Container, typename Predicate>
 auto associative_erase_if(Container &c, Predicate &pred)
 {
     // we support predicates callable with either Container::iterator
     // or with std::pair<const Key &, Value &>
     using Iterator = typename Container::iterator;
     using Key = typename Container::key_type;
     using Value = typename Container::mapped_type;
     using KeyValuePair = std::pair<const Key &, Value &>;
 
     typename Container::size_type result = 0;
 
     auto it = c.begin();
     const auto e = c.end();
     while (it != e) {
         if constexpr (is_invocable_explicit_r_v<bool, Predicate &, Iterator &>) {
             if (pred(it)) {
                 it = c.erase(it);
                 ++result;
             } else {
                 ++it;
             }
         } else if constexpr (is_invocable_explicit_r_v<bool, Predicate &, KeyValuePair &&>) {
             KeyValuePair p(it.key(), it.value());
             if (pred(std::move(p))) {
                 it = c.erase(it);
                 ++result;
             } else {
                 ++it;
             }
         } else {
             static_assert(sizeof(Container) == 0, "Predicate has an incompatible signature");
         }
     }
 
     return result;
 }
 
 } // namespace QtPrivate
 
 QT_END_NAMESPACE
 
 #endif // QCONTAINERTOOLS_IMPL_H

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