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# Format of the QDataStream Operators

The QDataStream allows you to serialize some of the Qt data types. The table below lists the data types that QDataStream can serialize and how they are represented.

It is best to always cast integers to a Qt integer type when writing, and to read back into the same Qt integer type when reading.

Q_INT8

- signed byte

Q_INT16

- signed 16 bit integer

Q_INT32

- signed 32 bit integer

Q_UINT8

- unsigned byte

Q_UINT16

- unsigned 16 bit integer

Q_UINT32

- unsigned 32 bit integer

float

- 32-bit floating point number using the standard IEEE-754 format

double

- 64-bit floating point number using the standard IEEE-754 format

char *

- The size of the string including the terminating 0 (Q_UINT32)
- The string bytes including the terminating 0

The null string is represented as `(Q_UINT32) 0`.

QBitArray

- The array size (Q_UINT32)
- The array bits, i.e. (size + 7)/8 bytes

QBrush

- The brush style (Q_UINT8)
- The brush color (QColor)
- If style is CustomPattern, the brush pixmap (QPixmap)

QByteArray

- The array size (Q_UINT32)
- The array bytes, i.e. size bytes

QCString

- The size of the string including the terminating 0 (Q_UINT32)
- The string bytes including the terminating 0

The null string is represented as `(Q_UINT32) 0`.

QColor

- RGB value serialized as a Q_UINT32

QColorGroup

- foreground (QBrush)
- button (QBrush)
- light (QBrush)
- midLight (QBrush)
- dark (QBrush)
- mid (QBrush)
- text (QBrush)
- brightText (QBrush)
- ButtonText (QBrush)
- base (QBrush)
- background (QBrush)
- shadow (QBrush)
- highlight (QBrush)
- highlightedText (QBrush)

QCursor

- Shape id (Q_INT16)
- If shape is BitmapCursor: The bitmap (QPixmap), mask (QPixmap) and hot spot (QPoint)

QDate

- Julian day (Q_UINT32)

QDateTime

- Date (QDate)
- Time (QTime)

QFont

- The family (QCString)
- The point size (Q_INT16)
- The style hint (Q_UINT8)
- The char set (Q_UINT8)
- The weight (Q_UINT8)
- The font bits (Q_UINT8)

QImage

- If the image is null a "null image" marker is saved; otherwise the image is saved in PNG or BMP format (depending on the stream version). If you want control of the format, stream the image into a QBuffer (using QImageIO) and stream that.

QMap

- The number of items (Q_UINT32)
- For all items, the key and value

QPalette

- active (QColorGroup)
- disabled (QColorGroup)
- inactive (QColorGroup)

QPen

- The pen styles (Q_UINT8)
- The pen width (Q_UINT8)
- The pen color (QColor)

QPicture

- The size of the picture data (Q_UINT32)
- The raw bytes of picture data (char)

QPixmap

- Save it as a PNG image.

QPoint

- The x coordinate (Q_INT32)
- The y coordinate (Q_INT32)

QPointArray

- The array size (Q_UINT32)
- The array points (QPoint)

QRect

- left (Q_INT32)
- top (Q_INT32)
- right (Q_INT32)
- bottom (Q_INT32)

QRegion

- The size of the data, i.e. 8 + 16 * (number of rectangles) (Q_UINT32)
- QRGN_RECTS (Q_INT32)
- The number of rectangles (Q_UINT32)
- The rectangles in sequential order (QRect)

QSize

- width (Q_INT32)
- height (Q_INT32)

QString

- If the string is null: 0xffffffff (Q_UINT32)
  otherwise: The string length (Q_UINT32) followed by the data in UTF-16

QTime

- Milliseconds since midnight (Q_UINT32)

QValueList

- The number of list elements (Q_UINT32)
- All the elements in sequential order

QVariant

- The type of the data (Q_UINT32)
- The data of the specified type

QWMatrix

- m11 (double)
- m12 (double)
- m21 (double)
- m22 (double)
- dx (double)
- dy (double)