path: root/src/corelib/tools/qarraydata.h

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#ifndef QARRAYDATA_H
#define QARRAYDATA_H

#include <QtCore/qpair.h>
#include <QtCore/qatomic.h>
#include <string.h>

QT_BEGIN_NAMESPACE

template <class T> struct QTypedArrayData;

struct Q_CORE_EXPORT QArrayData
{
    enum ArrayOption {
        RawDataType          = 0x0001,  //!< this class is really a QArrayData
        AllocatedDataType    = 0x0002,  //!< this class is really a QArrayAllocatedData
        DataTypeBits         = 0x000f,

        CapacityReserved     = 0x0010,  //!< the capacity was reserved by the user, try to keep it
        GrowsForward         = 0x0020,  //!< allocate with eyes towards growing through append()
        GrowsBackwards       = 0x0040,  //!< allocate with eyes towards growing through prepend()
        MutableData          = 0x0080,  //!< the data can be changed; doesn't say anything about the header
        ImmutableHeader      = 0x0100,  //!< the header is static, it can't be changed

        /// this option is used by the Q_ARRAY_LITERAL and similar macros
        StaticDataFlags = RawDataType | ImmutableHeader,
        /// this option is used by the allocate() function
        DefaultAllocationFlags = MutableData,
        /// this option is used by the prepareRawData() function
        DefaultRawFlags = 0
    };
    Q_DECLARE_FLAGS(ArrayOptions, ArrayOption)

    QBasicAtomicInt ref_;
    uint flags;
    uint alloc;

    inline size_t allocatedCapacity()
    {
        return alloc;
    }

    inline size_t constAllocatedCapacity() const
    {
        return alloc;
    }

    /// Returns true if sharing took place
    bool ref()
    {
        if (!isStatic())
            ref_.ref();
        return true;
    }

    /// Returns false if deallocation is necessary
    bool deref()
    {
        if (isStatic())
            return true;
        return ref_.deref();
    }

    // This refers to array data mutability, not "header data" represented by
    // data members in QArrayData. Shared data (array and header) must still
    // follow COW principles.
    bool isMutable() const
    {
        return flags & MutableData;
    }

    bool isStatic() const
    {
        return flags & ImmutableHeader;
    }

    bool isShared() const
    {
        return ref_.loadRelaxed() != 1;
    }

    // Returns true if a detach is necessary before modifying the data
    // This method is intentionally not const: if you want to know whether
    // detaching is necessary, you should be in a non-const function already
    bool needsDetach()
    {
        // requires two conditionals
        return !isMutable() || isShared();
    }

    size_t detachCapacity(size_t newSize) const
    {
        if (flags & CapacityReserved && newSize < constAllocatedCapacity())
            return constAllocatedCapacity();
        return newSize;
    }

    ArrayOptions detachFlags() const
    {
        ArrayOptions result = DefaultAllocationFlags;
        if (flags & CapacityReserved)
            result |= CapacityReserved;
        return result;
    }

    ArrayOptions cloneFlags() const
    {
        ArrayOptions result = DefaultAllocationFlags;
        if (flags & CapacityReserved)
            result |= CapacityReserved;
        return result;
    }

    Q_REQUIRED_RESULT
#if defined(Q_CC_GNU)
    __attribute__((__malloc__))
#endif
    static void *allocate(QArrayData **pdata, size_t objectSize, size_t alignment,
            size_t capacity, ArrayOptions options = DefaultAllocationFlags) noexcept;
    Q_REQUIRED_RESULT static QArrayData *reallocateUnaligned(QArrayData *data, size_t objectSize,
            size_t newCapacity, ArrayOptions newOptions = DefaultAllocationFlags) noexcept;
    Q_REQUIRED_RESULT static QPair<QArrayData *, void *> reallocateUnaligned(QArrayData *data, void *dataPointer,
            size_t objectSize, size_t newCapacity, ArrayOptions newOptions = DefaultAllocationFlags) Q_DECL_NOTHROW;
    Q_REQUIRED_RESULT static QArrayData *prepareRawData(ArrayOptions options = ArrayOptions(RawDataType))
        Q_DECL_NOTHROW;
    static void deallocate(QArrayData *data, size_t objectSize,
            size_t alignment) noexcept;

    static const QArrayData shared_null[2];
    static QArrayData *sharedNull() noexcept { return const_cast<QArrayData*>(shared_null); }
    static void *sharedNullData()
    {
        QArrayData *const null = const_cast<QArrayData *>(&shared_null[1]);
        return null;
    }
};

Q_DECLARE_OPERATORS_FOR_FLAGS(QArrayData::ArrayOptions)

template <class T, size_t N>
struct QStaticArrayData
{
    // static arrays are of type RawDataType
    QArrayData header;
    T data[N];
};

// Support for returning QArrayDataPointer<T> from functions
template <class T>
struct QArrayDataPointerRef
{
    QTypedArrayData<T> *ptr;
    T *data;
    uint size;
};

template <class T>
struct QTypedArrayData
    : QArrayData
{
#ifdef QT_STRICT_ITERATORS
    class iterator {
    public:
        T *i;
        typedef std::random_access_iterator_tag  iterator_category;
        typedef int difference_type;
        typedef T value_type;
        typedef T *pointer;
        typedef T &reference;

        inline iterator() : i(nullptr) {}
        inline iterator(T *n) : i(n) {}
        inline iterator(const iterator &o): i(o.i){} // #### Qt 6: remove, the implicit version is fine
        inline T &operator*() const { return *i; }
        inline T *operator->() const { return i; }
        inline T &operator[](int j) const { return *(i + j); }
        inline bool operator==(const iterator &o) const { return i == o.i; }
        inline bool operator!=(const iterator &o) const { return i != o.i; }
        inline bool operator<(const iterator& other) const { return i < other.i; }
        inline bool operator<=(const iterator& other) const { return i <= other.i; }
        inline bool operator>(const iterator& other) const { return i > other.i; }
        inline bool operator>=(const iterator& other) const { return i >= other.i; }
        inline iterator &operator++() { ++i; return *this; }
        inline iterator operator++(int) { T *n = i; ++i; return n; }
        inline iterator &operator--() { i--; return *this; }
        inline iterator operator--(int) { T *n = i; i--; return n; }
        inline iterator &operator+=(int j) { i+=j; return *this; }
        inline iterator &operator-=(int j) { i-=j; return *this; }
        inline iterator operator+(int j) const { return iterator(i+j); }
        inline iterator operator-(int j) const { return iterator(i-j); }
        friend inline iterator operator+(int j, iterator k) { return k + j; }
        inline int operator-(iterator j) const { return i - j.i; }
        inline operator T*() const { return i; }
    };
    friend class iterator;

    class const_iterator {
    public:
        const T *i;
        typedef std::random_access_iterator_tag  iterator_category;
        typedef int difference_type;
        typedef T value_type;
        typedef const T *pointer;
        typedef const T &reference;

        inline const_iterator() : i(nullptr) {}
        inline const_iterator(const T *n) : i(n) {}
        inline const_iterator(const const_iterator &o): i(o.i) {} // #### Qt 6: remove, the default version is fine
        inline explicit const_iterator(const iterator &o): i(o.i) {}
        inline const T &operator*() const { return *i; }
        inline const T *operator->() const { return i; }
        inline const T &operator[](int j) const { return *(i + j); }
        inline bool operator==(const const_iterator &o) const { return i == o.i; }
        inline bool operator!=(const const_iterator &o) const { return i != o.i; }
        inline bool operator<(const const_iterator& other) const { return i < other.i; }
        inline bool operator<=(const const_iterator& other) const { return i <= other.i; }
        inline bool operator>(const const_iterator& other) const { return i > other.i; }
        inline bool operator>=(const const_iterator& other) const { return i >= other.i; }
        inline const_iterator &operator++() { ++i; return *this; }
        inline const_iterator operator++(int) { const T *n = i; ++i; return n; }
        inline const_iterator &operator--() { i--; return *this; }
        inline const_iterator operator--(int) { const T *n = i; i--; return n; }
        inline const_iterator &operator+=(int j) { i+=j; return *this; }
        inline const_iterator &operator-=(int j) { i-=j; return *this; }
        inline const_iterator operator+(int j) const { return const_iterator(i+j); }
        inline const_iterator operator-(int j) const { return const_iterator(i-j); }
        friend inline const_iterator operator+(int j, const_iterator k) { return k + j; }
        inline int operator-(const_iterator j) const { return i - j.i; }
        inline operator const T*() const { return i; }
    };
    friend class const_iterator;
#else
    typedef T* iterator;
    typedef const T* const_iterator;
#endif

    class AlignmentDummy { QArrayData header; T data; };

    Q_REQUIRED_RESULT static QPair<QTypedArrayData *, T *> allocate(size_t capacity,
            ArrayOptions options = DefaultAllocationFlags)
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        QArrayData *d;
        void *result = QArrayData::allocate(&d, sizeof(T), alignof(AlignmentDummy), capacity, options);
#if (defined(Q_CC_GNU) && Q_CC_GNU >= 407) || QT_HAS_BUILTIN(__builtin_assume_aligned)
        result = __builtin_assume_aligned(result, Q_ALIGNOF(AlignmentDummy));
#endif
        return qMakePair(static_cast<QTypedArrayData *>(d), static_cast<T *>(result));
    }

    static QPair<QTypedArrayData *, T *>
    reallocateUnaligned(QTypedArrayData *data, T *dataPointer, size_t capacity,
            ArrayOptions options = DefaultAllocationFlags)
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        QPair<QArrayData *, void *> pair =
                QArrayData::reallocateUnaligned(data, dataPointer, sizeof(T), capacity, options);
        return qMakePair(static_cast<QTypedArrayData *>(pair.first), static_cast<T *>(pair.second));
    }

    static void deallocate(QArrayData *data)
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        QArrayData::deallocate(data, sizeof(T), alignof(AlignmentDummy));
    }

    static QArrayDataPointerRef<T> fromRawData(const T *data, size_t n,
            ArrayOptions options = DefaultRawFlags)
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        QArrayDataPointerRef<T> result = {
            static_cast<QTypedArrayData *>(prepareRawData(options)), const_cast<T *>(data), uint(n)
        };
        if (result.ptr) {
            Q_ASSERT(!result.ptr->isShared()); // No shared empty, please!
        }
        return result;
    }

    static QTypedArrayData *sharedNull() noexcept
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        return static_cast<QTypedArrayData *>(QArrayData::sharedNull());
    }

    static QTypedArrayData *sharedEmpty()
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        return allocate(/* capacity */ 0);
    }

    static T *sharedNullData()
    {
        Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
        return static_cast<T *>(QArrayData::sharedNullData());
    }
};

////////////////////////////////////////////////////////////////////////////////
//  Q_ARRAY_LITERAL

// The idea here is to place a (read-only) copy of header and array data in an
// mmappable portion of the executable (typically, .rodata section). This is
// accomplished by hiding a static const instance of QStaticArrayData, which is
// POD.

// Hide array inside a lambda
#define Q_ARRAY_LITERAL(Type, ...)                                              \
    ([]() -> QArrayDataPointerRef<Type> {                                       \
            /* MSVC 2010 Doesn't support static variables in a lambda, but */   \
            /* happily accepts them in a static function of a lambda-local */   \
            /* struct :-) */                                                    \
            struct StaticWrapper {                                              \
                static QArrayDataPointerRef<Type> get()                         \
                {                                                               \
                    Q_ARRAY_LITERAL_IMPL(Type, __VA_ARGS__)                     \
                    return ref;                                                 \
                }                                                               \
            };                                                                  \
            return StaticWrapper::get();                                        \
        }())                                                                    \
    /**/

#ifdef Q_COMPILER_CONSTEXPR
#define Q_ARRAY_LITERAL_CHECK_LITERAL_TYPE(Type) Q_STATIC_ASSERT(std::is_literal_type<Type>::value)
#else
#define Q_ARRAY_LITERAL_CHECK_LITERAL_TYPE(Type) do {} while (0)
#endif

#define Q_ARRAY_LITERAL_IMPL(Type, ...)                                         \
    Q_ARRAY_LITERAL_CHECK_LITERAL_TYPE(Type);                                   \
                                                                                \
    /* Portable compile-time array size computation */                          \
    static Type const data[] = { __VA_ARGS__ };                                 \
    enum { Size = sizeof(data) / sizeof(data[0]) };                             \
                                                                                \
    static const QArrayData literal = { Q_BASIC_ATOMIC_INITIALIZER(-1), QArrayData::StaticDataFlags, 0 };          \
                                                                                \
    QArrayDataPointerRef<Type> ref =                                            \
        { static_cast<QTypedArrayData<Type> *>(                                 \
            const_cast<QArrayData *>(&literal)),                                \
          const_cast<Type *>(data),                                             \
          Size };                                                               \
    /**/

namespace QtPrivate {
struct Q_CORE_EXPORT QContainerImplHelper
{
    enum CutResult { Null, Empty, Full, Subset };
    static CutResult mid(int originalLength, int *position, int *length);
};
}

QT_END_NAMESPACE

#endif // include guard