Revision control
++ // Copyright (C) 2023 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
++ // Qt-Security score:significant reason:default
++
++ #ifndef QSPAN_H
++ #define QSPAN_H
++
++ #include <QtCore/qcompilerdetection.h>
++ #include <QtCore/qtypes.h>
++ #include <QtCore/qcontainerfwd.h>
++
++ #include <array>
++ #include <cstddef>
++ #include <cassert>
++ #include <initializer_list>
++ #include <QtCore/q20iterator.h>
++ #include <QtCore/q20memory.h>
++ #ifdef __cpp_lib_span
++ #include <span>
++ #endif
++ #include <QtCore/q20type_traits.h>
++
++ QT_BEGIN_NAMESPACE
++
++ // like std::dynamic_extent
++ namespace q20 {
++ inline constexpr auto dynamic_extent = std::size_t(-1);
++ } // namespace q20
++
++ QT_BEGIN_INCLUDE_NAMESPACE
++ #ifdef __cpp_lib_span
++ #ifdef __cpp_lib_concepts
++ namespace std::ranges {
++ // Officially, these are defined in <ranges>, but that is a heavy-hitter header.
++ // OTOH, <span> must specialize these variable templates, too, so we assume that
++ // <span> includes some meaningful subset of <ranges> and just go ahead and use them:
++ template <typename T, std::size_t E>
++ constexpr inline bool enable_borrowed_range<QT_PREPEND_NAMESPACE(QSpan)<T, E>> = true;
++ template <typename T, std::size_t E>
++ constexpr inline bool enable_view<QT_PREPEND_NAMESPACE(QSpan)<T, E>> = true;
++ } // namespace std::ranges
++ #endif // __cpp_lib_concepts
++ #endif // __cpp_lib_span
++ QT_END_INCLUDE_NAMESPACE
++
++ namespace QSpanPrivate {
++
++ template <typename From, typename To>
++ std::conditional_t<std::is_const_v<From>, const To &, To &> // like [forward]/6.1 COPY_CONST
++ const_propagated(To &in) { return in; }
++
++ template <typename T, std::size_t E> class QSpanBase;
++
++ template <typename T>
++ struct is_qspan_helper : std::false_type {};
++ template <typename T, std::size_t E>
++ struct is_qspan_helper<QSpan<T, E>> : std::true_type {};
++ template <typename T, std::size_t E>
++ struct is_qspan_helper<QSpanBase<T, E>> : std::true_type {};
++ template <typename T>
++ using is_qspan = is_qspan_helper<q20::remove_cvref_t<T>>;
++
++ template <typename T>
++ struct is_std_span_helper : std::false_type {};
++ #ifdef __cpp_lib_span
++ template <typename T, std::size_t E>
++ struct is_std_span_helper<std::span<T, E>> : std::true_type {};
++ #endif // __cpp_lib_span
++ template <typename T>
++ using is_std_span = is_std_span_helper<q20::remove_cvref_t<T>>;
++
++ template <typename T>
++ struct is_std_array_helper : std::false_type {};
++ template <typename T, std::size_t N>
++ struct is_std_array_helper<std::array<T, N>> : std::true_type {};
++ template <typename T>
++ using is_std_array = is_std_array_helper<q20::remove_cvref_t<T>>;
++
++ template <typename From, typename To>
++ using is_qualification_conversion =
++ std::is_convertible<From(*)[], To(*)[]>; // https://eel.is/c++draft/span.cons#note-1
++ template <typename From, typename To>
++ constexpr inline bool is_qualification_conversion_v = is_qualification_conversion<From, To>::value;
++
++ namespace AdlTester {
++ #define MAKE_ADL_TEST(what) \
++ using std:: what; /* bring into scope */ \
++ template <typename T> using what ## _result = decltype( what (std::declval<T&&>())); \
++ /* end */
++ MAKE_ADL_TEST(begin)
++ MAKE_ADL_TEST(data)
++ MAKE_ADL_TEST(size)
++ #undef MAKE_ADL_TEST
++ }
++
++ // Replacements for std::ranges::XXX(), but only bringing in ADL XXX()s,
++ // not doing the extra work C++20 requires
++ template <typename Range>
++ AdlTester::begin_result<Range> adl_begin(Range &&r) { using std::begin; return begin(r); }
++ template <typename Range>
++ AdlTester::data_result<Range> adl_data(Range &&r) { using std::data; return data(r); }
++ template <typename Range>
++ AdlTester::size_result<Range> adl_size(Range &&r) { using std::size; return size(r); }
++
++ // Replacement for std::ranges::iterator_t (which depends on C++20 std::ranges::begin)
++ // This one uses adl_begin() instead.
++ template <typename Range>
++ using iterator_t = decltype(QSpanPrivate::adl_begin(std::declval<Range&>()));
++ template <typename Range>
++ using range_reference_t = q20::iter_reference_t<QSpanPrivate::iterator_t<Range>>;
++
++ template <typename T>
++ class QSpanCommon {
++ protected:
++ template <typename Iterator>
++ using is_compatible_iterator = std::conjunction<
++ // ### C++20: extend to contiguous_iteratorss
++ std::is_base_of<
++ std::random_access_iterator_tag,
++ typename std::iterator_traits<Iterator>::iterator_category
++ >,
++ is_qualification_conversion<
++ std::remove_reference_t<q20::iter_reference_t<Iterator>>,
++ T
++ >
++ >;
++ template <typename Iterator, typename End>
++ using is_compatible_iterator_and_sentinel = std::conjunction<
++ // ### C++20: extend to contiguous_iterators and real sentinels
++ is_compatible_iterator<Iterator>,
++ std::negation<std::is_convertible<End, std::size_t>>
++ >;
++ template <typename Range, typename = void> // wrap use of SFINAE-unfriendly iterator_t:
++ struct is_compatible_range_helper : std::false_type {};
++ template <typename Range>
++ struct is_compatible_range_helper<Range, std::void_t<QSpanPrivate::iterator_t<Range>>>
++ : is_compatible_iterator<QSpanPrivate::iterator_t<Range>> {};
++ template <typename Range>
++ using is_compatible_range = std::conjunction<
++ // ### C++20: extend to contiguous_iterators
++ std::negation<is_qspan<Range>>,
++ std::negation<is_std_span<Range>>,
++ std::negation<is_std_array<Range>>,
++ std::negation<std::is_array<q20::remove_cvref_t<Range>>>,
++ is_compatible_range_helper<Range>
++ >;
++
++ // constraints
++ template <typename Iterator>
++ using if_compatible_iterator = std::enable_if_t<
++ is_compatible_iterator<Iterator>::value
++ , bool>;
++ template <typename Iterator, typename End>
++ using if_compatible_iterator_and_sentinel = std::enable_if_t<
++ is_compatible_iterator_and_sentinel<Iterator, End>::value
++ , bool>;
++ template <typename Range>
++ using if_compatible_range = std::enable_if_t<is_compatible_range<Range>::value, bool>;
++ }; // class QSpanCommon
++
++ template <typename T, std::size_t E>
++ class QSpanBase : protected QSpanCommon<T>
++ {
++ static_assert(E < size_t{(std::numeric_limits<qsizetype>::max)()},
++ "QSpan only supports extents that fit into the signed size type (qsizetype).");
++
++ template <typename S, std::size_t N>
++ using if_compatible_array = std::enable_if_t<
++ N == E && is_qualification_conversion_v<S, T>
++ , bool>;
++
++ template <typename S>
++ using if_qualification_conversion = std::enable_if_t<
++ is_qualification_conversion_v<S, T>
++ , bool>;
++ protected:
++ using Base = QSpanCommon<T>;
++
++ // data members:
++ T *m_data;
++ static constexpr qsizetype m_size = qsizetype(E);
++
++ // types and constants:
++ // (in QSpan only)
++
++ // constructors (need to be public d/t the way ctor inheriting works):
++ public:
++ template <std::size_t E2 = E, std::enable_if_t<E2 == 0, bool> = true>
++ Q_IMPLICIT constexpr QSpanBase() noexcept : m_data{nullptr} {}
++
++ template <typename It, typename Base::template if_compatible_iterator<It> = true>
++ explicit constexpr QSpanBase(It first, qsizetype count)
++ : m_data{q20::to_address(first)}
++ {
++ Q_PRE(count == m_size);
++ }
++
++ template <typename It, typename End, typename Base::template if_compatible_iterator_and_sentinel<It, End> = true>
++ explicit constexpr QSpanBase(It first, End last)
++ : QSpanBase(first, last - first) {}
++
++ template <size_t N, std::enable_if_t<N == E, bool> = true>
++ Q_IMPLICIT constexpr QSpanBase(q20::type_identity_t<T> (&arr)[N]) noexcept
++ : QSpanBase(arr, N) {}
++
++ template <typename S, size_t N, if_compatible_array<S, N> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::array<S, N> &arr) noexcept
++ : QSpanBase(arr.data(), N) {}
++
++ template <typename S, size_t N, if_compatible_array<S, N> = true>
++ Q_IMPLICIT constexpr QSpanBase(const std::array<S, N> &arr) noexcept
++ : QSpanBase(arr.data(), N) {}
++
++ template <typename Range, typename Base::template if_compatible_range<Range> = true>
++ Q_IMPLICIT constexpr QSpanBase(Range &&r)
++ : QSpanBase(QSpanPrivate::adl_data(QSpanPrivate::const_propagated<T>(r)), // no forward<>() here (std doesn't have it, either)
++ qsizetype(QSpanPrivate::adl_size(r))) // ditto, no forward<>()
++ {}
++
++ template <typename S, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(QSpan<S, E> other) noexcept
++ : QSpanBase(other.data(), other.size())
++ {}
++
++ template <typename S, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(QSpan<S> other)
++ : QSpanBase(other.data(), other.size())
++ {}
++
++ template <typename U = T, std::enable_if_t<std::is_const_v<U>, bool> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::initializer_list<std::remove_cv_t<T>> il)
++ : QSpanBase(il.begin(), il.size())
++ {}
++
++ #ifdef __cpp_lib_span
++ template <typename S, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::span<S, E> other) noexcept
++ : QSpanBase(other.data(), other.size())
++ {}
++
++ template <typename S, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::span<S> other)
++ : QSpanBase(other.data(), other.size())
++ {}
++ #endif // __cpp_lib_span
++ }; // class QSpanBase (fixed extent)
++
++ template <typename T>
++ class QSpanBase<T, q20::dynamic_extent> : protected QSpanCommon<T>
++ {
++ template <typename S>
++ using if_qualification_conversion = std::enable_if_t<
++ is_qualification_conversion_v<S, T>
++ , bool>;
++ protected:
++ using Base = QSpanCommon<T>;
++
++ // data members:
++ T *m_data;
++ qsizetype m_size;
++
++ // constructors (need to be public d/t the way ctor inheriting works):
++ public:
++ Q_IMPLICIT constexpr QSpanBase() noexcept : m_data{nullptr}, m_size{0} {}
++
++ template <typename It, typename Base::template if_compatible_iterator<It> = true>
++ Q_IMPLICIT constexpr QSpanBase(It first, qsizetype count)
++ : m_data{q20::to_address(first)}, m_size{count}
++ {
++ Q_PRE(count >= 0);
++ }
++
++ template <typename It, typename End, typename Base::template if_compatible_iterator_and_sentinel<It, End> = true>
++ Q_IMPLICIT constexpr QSpanBase(It first, End last)
++ : QSpanBase(first, last - first) {}
++
++ template <size_t N>
++ Q_IMPLICIT constexpr QSpanBase(q20::type_identity_t<T> (&arr)[N]) noexcept
++ : QSpanBase(arr, N) {}
++
++ template <typename S, size_t N, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::array<S, N> &arr) noexcept
++ : QSpanBase(arr.data(), N) {}
++
++ template <typename S, size_t N, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(const std::array<S, N> &arr) noexcept
++ : QSpanBase(arr.data(), N) {}
++
++ template <typename Range, typename Base::template if_compatible_range<Range> = true>
++ Q_IMPLICIT constexpr QSpanBase(Range &&r)
++ : QSpanBase(QSpanPrivate::adl_data(QSpanPrivate::const_propagated<T>(r)), // no forward<>() here (std doesn't have it, either)
++ qsizetype(QSpanPrivate::adl_size(r))) // ditto, no forward<>()
++ {}
++
++ template <typename S, size_t N, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(QSpan<S, N> other) noexcept
++ : QSpanBase(other.data(), other.size())
++ {}
++
++ template <typename U = T, std::enable_if_t<std::is_const_v<U>, bool> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::initializer_list<std::remove_cv_t<T>> il) noexcept
++ : QSpanBase(il.begin(), il.size())
++ {}
++
++ #ifdef __cpp_lib_span
++ template <typename S, size_t N, if_qualification_conversion<S> = true>
++ Q_IMPLICIT constexpr QSpanBase(std::span<S, N> other) noexcept
++ : QSpanBase(other.data(), other.size())
++ {}
++ #endif // __cpp_lib_span
++ }; // class QSpanBase (dynamic extent)
++
++ } // namespace QSpanPrivate
++
++ template <typename T, std::size_t E>
++ class QSpan
++ #ifndef Q_QDOC
++ : private QSpanPrivate::QSpanBase<T, E>
++ #endif
++ {
++ using Base = QSpanPrivate::QSpanBase<T, E>;
++ Q_ALWAYS_INLINE constexpr void verify([[maybe_unused]] qsizetype pos = 0,
++ [[maybe_unused]] qsizetype n = 1) const
++ {
++ Q_ASSERT(pos >= 0);
++ Q_ASSERT(pos <= size());
++ Q_ASSERT(n >= 0);
++ Q_ASSERT(n <= size() - pos);
++ }
++
++ template <std::size_t N>
++ static constexpr bool subspan_always_succeeds_v = N <= E && E != q20::dynamic_extent;
++ public:
++ // constants and types
++ using value_type = std::remove_cv_t<T>;
++ #ifdef QT_COMPILER_HAS_LWG3346
++ using iterator_concept = std::contiguous_iterator_tag;
++ using element_type = T;
++ #endif
++ using size_type = qsizetype; // difference to std::span
++ using difference_type = qptrdiff; // difference to std::span
++ using pointer = T*;
++ using const_pointer = const T*;
++ using reference = T&;
++ using const_reference = const T&;
++ using iterator = pointer; // implementation-defined choice
++ using const_iterator = const_pointer; // implementation-defined choice
++ using reverse_iterator = std::reverse_iterator<iterator>;
++ using const_reverse_iterator = std::reverse_iterator<const_iterator>;
++ static constexpr std::size_t extent = E;
++
++ // [span.cons], constructors, copy, and assignment
++ using Base::Base;
++ #ifdef Q_QDOC
++ template <typename It> using if_compatible_iterator = bool;
++ template <typename S> using if_qualification_conversion = bool;
++ template <typename Range> using if_compatible_range = bool;
++ template <typename It, if_compatible_iterator<It> = true> constexpr QSpan(It first, qsizetype count);
++ template <typename It, if_compatible_iterator<It> = true> constexpr QSpan(It first, It last);
++ template <size_t N> constexpr QSpan(q20::type_identity_t<T> (&arr)[N]) noexcept;
++ template <typename S, size_t N, if_qualification_conversion<S> = true> constexpr QSpan(std::array<S, N> &arr) noexcept;
++ template <typename S, size_t N, if_qualification_conversion<S> = true> constexpr QSpan(const std::array<S, N> &arr) noexcept;
++ template <typename Range, if_compatible_range<Range> = true> constexpr QSpan(Range &&r);
++ template <typename S, size_t N, if_qualification_conversion<S> = true> constexpr QSpan(QSpan<S, N> other) noexcept;
++ template <typename S, size_t N, if_qualification_conversion<S> = true> constexpr QSpan(std::span<S, N> other) noexcept;
++ constexpr QSpan(std::initializer_list<value_type> il);
++ #endif // Q_QDOC
++
++ // [span.obs]
++ [[nodiscard]] constexpr size_type size() const noexcept { return this->m_size; }
++ [[nodiscard]] constexpr size_type size_bytes() const noexcept { return size() * sizeof(T); }
++ [[nodiscard]] constexpr bool empty() const noexcept { return size() == 0; }
++
++ // [span.elem]
++ [[nodiscard]] constexpr reference operator[](size_type idx) const
++ { verify(idx); return data()[idx]; }
++ [[nodiscard]] constexpr reference front() const { verify(); return *data(); }
++ [[nodiscard]] constexpr reference back() const { verify(); return data()[size() - 1]; }
++ [[nodiscard]] constexpr pointer data() const noexcept { return this->m_data; }
++
++ // [span.iterators]
++ [[nodiscard]] constexpr iterator begin() const noexcept { return data(); }
++ [[nodiscard]] constexpr iterator end() const noexcept { return data() + size(); }
++ [[nodiscard]] constexpr const_iterator cbegin() const noexcept { return begin(); }
++ [[nodiscard]] constexpr const_iterator cend() const noexcept { return end(); }
++ [[nodiscard]] constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator{end()}; }
++ [[nodiscard]] constexpr reverse_iterator rend() const noexcept { return reverse_iterator{begin()}; }
++ [[nodiscard]] constexpr const_reverse_iterator crbegin() const noexcept { return rbegin(); }
++ [[nodiscard]] constexpr const_reverse_iterator crend() const noexcept { return rend(); }
++
++ // [span.sub]
++ template <std::size_t Count>
++ [[nodiscard]] constexpr QSpan<T, Count> first() const
++ noexcept(subspan_always_succeeds_v<Count>)
++ {
++ static_assert(Count <= E,
++ "Count cannot be larger than the span's extent.");
++ verify(0, Count);
++ return QSpan<T, Count>{data(), Count};
++ }
++
++ template <std::size_t Count>
++ [[nodiscard]] constexpr QSpan<T, Count> last() const
++ noexcept(subspan_always_succeeds_v<Count>)
++ {
++ static_assert(Count <= E,
++ "Count cannot be larger than the span's extent.");
++ verify(0, Count);
++ return QSpan<T, Count>{data() + (size() - Count), Count};
++ }
++
++ template <std::size_t Offset>
++ [[nodiscard]] constexpr auto subspan() const
++ noexcept(subspan_always_succeeds_v<Offset>)
++ {
++ static_assert(Offset <= E,
++ "Offset cannot be larger than the span's extent.");
++ verify(Offset, 0);
++ if constexpr (E == q20::dynamic_extent)
++ return QSpan<T>{data() + Offset, qsizetype(size() - Offset)};
++ else
++ return QSpan<T, E - Offset>{data() + Offset, qsizetype(E - Offset)};
++ }
++
++ template <std::size_t Offset, std::size_t Count>
++ [[nodiscard]] constexpr auto subspan() const
++ noexcept(subspan_always_succeeds_v<Offset + Count>)
++ { return subspan<Offset>().template first<Count>(); }
++
++ [[nodiscard]] constexpr QSpan<T> first(size_type n) const { verify(0, n); return {data(), n}; }
++ [[nodiscard]] constexpr QSpan<T> last(size_type n) const { verify(0, n); return {data() + (size() - n), n}; }
++ [[nodiscard]] constexpr QSpan<T> subspan(size_type pos) const { verify(pos, 0); return {data() + pos, size() - pos}; }
++ [[nodiscard]] constexpr QSpan<T> subspan(size_type pos, size_type n) const { return subspan(pos).first(n); }
++
++ // Qt-compatibility API:
++ [[nodiscard]] constexpr bool isEmpty() const noexcept { return empty(); }
++ // nullary first()/last() clash with first<>() and last<>(), so they're not provided for QSpan
++ [[nodiscard]] constexpr QSpan<T> sliced(size_type pos) const { return subspan(pos); }
++ [[nodiscard]] constexpr QSpan<T> sliced(size_type pos, size_type n) const { return subspan(pos, n); }
++ [[nodiscard]] constexpr QSpan<T> chopped(size_type n) const { verify(0, n); return first(size() - n); }
++
++ #ifdef __cpp_concepts
++ # define QT_ONLY_IF_DYNAMIC_SPAN(DECL) \
++ DECL requires(E == q20::dynamic_extent)
++ #else
++ # define QT_ONLY_IF_DYNAMIC_SPAN(DECL) \
++ template <size_t M = E, typename = std::enable_if_t<M == q20::dynamic_extent>> DECL
++ #endif
++ QT_ONLY_IF_DYNAMIC_SPAN(
++ constexpr void slice(size_type pos)
++ )
++ { *this = sliced(pos); }
++ QT_ONLY_IF_DYNAMIC_SPAN(
++ constexpr void slice(size_type pos, size_type n)
++ )
++ { *this = sliced(pos, n); }
++ QT_ONLY_IF_DYNAMIC_SPAN(
++ constexpr void chop(size_type n)
++ )
++ { *this = chopped(n); }
++ #undef QT_ONLY_IF_DYNAMIC_SPAN
++
++ private:
++ // [span.objectrep]
++ [[nodiscard]] friend
++ QSpan<const std::byte, E == q20::dynamic_extent ? q20::dynamic_extent : E * sizeof(T)>
++ as_bytes(QSpan s) noexcept
++ {
++ using R = QSpan<const std::byte, E == q20::dynamic_extent ? q20::dynamic_extent : E * sizeof(T)>;
++ return R{reinterpret_cast<const std::byte *>(s.data()), s.size_bytes()};
++ }
++
++ template <typename U>
++ using if_mutable = std::enable_if_t<!std::is_const_v<U>, bool>;
++
++ #ifndef Q_QDOC
++ template <typename T2 = T, if_mutable<T2> = true>
++ #endif
++ [[nodiscard]] friend
++ QSpan<std::byte, E == q20::dynamic_extent ? q20::dynamic_extent : E * sizeof(T)>
++ as_writable_bytes(QSpan s) noexcept
++ {
++ using R = QSpan<std::byte, E == q20::dynamic_extent ? q20::dynamic_extent : E * sizeof(T)>;
++ return R{reinterpret_cast<std::byte *>(s.data()), s.size_bytes()};
++ }
++ }; // class QSpan
++
++ // [span.deduct]
++ template <class It, class EndOrSize>
++ QSpan(It, EndOrSize) -> QSpan<std::remove_reference_t<q20::iter_reference_t<It>>>;
++ template <class T, std::size_t N>
++ QSpan(T (&)[N]) -> QSpan<T, N>;
++ template <class T, std::size_t N>
++ QSpan(std::array<T, N> &) -> QSpan<T, N>;
++ template <class T, std::size_t N>
++ QSpan(const std::array<T, N> &) -> QSpan<const T, N>;
++ template <class R>
++ QSpan(R&&) -> QSpan<std::remove_reference_t<QSpanPrivate::range_reference_t<R>>>;
++
++ QT_END_NAMESPACE
++
++ #endif // QSPAN_H