\inmodule QtCore\reentrant More...

#include <qdatastream.h>

Inheritance diagram for QDataStream:

Collaboration diagram for QDataStream:

Public Types
enum	ByteOrder { BigEndian = QSysInfo::BigEndian , LittleEndian = QSysInfo::LittleEndian }
	The byte order used for reading/writing the data. More...

Public Types inherited from QIODeviceBase
enum	OpenModeFlag { NotOpen = 0x0000 , ReadOnly = 0x0001 , WriteOnly = 0x0002 , ReadWrite = ReadOnly \| WriteOnly , Append = 0x0004 , Truncate = 0x0008 , Text = 0x0010 , Unbuffered = 0x0020 , NewOnly = 0x0040 , ExistingOnly = 0x0080 }
	This enum is used with QIODevice::open() to describe the mode in which a device is opened. More...

Public Member Functions
enum Version	QT7_ONLY (:quint8)

enum Status	QT7_ONLY (:quint8)

enum FloatingPointPrecision	QT7_ONLY (:quint8)

	QDataStream ()
	Constructs a data stream that has no I/O device.

	QDataStream (QIODevice *)
	Constructs a data stream that uses the I/O device d.

	QDataStream (QByteArray *, OpenMode flags)
	Constructs a data stream that operates on a byte array, a.

	QDataStream (const QByteArray &)
	Constructs a read-only data stream that operates on byte array a.

	~QDataStream ()
	Destroys the data stream.

QIODevice *	device () const
	Returns the I/O device currently set, or \nullptr if no device is currently set.

void	setDevice (QIODevice *)
	void QDataStream::setDevice(QIODevice *d)

bool	atEnd () const
	Returns `true` if the I/O device has reached the end position (end of the stream or file) or if there is no I/O device set; otherwise returns `false`.

Status	status () const
	Returns the status of the data stream.

void	setStatus (Status status)
	Sets the status of the data stream to the status given.

void	resetStatus ()
	Resets the status of the data stream.

FloatingPointPrecision	floatingPointPrecision () const
	Returns the floating point precision of the data stream.

void	setFloatingPointPrecision (FloatingPointPrecision precision)
	Sets the floating point precision of the data stream to precision.

ByteOrder	byteOrder () const
	Returns the current byte order setting – either BigEndian or LittleEndian.

void	setByteOrder (ByteOrder)
	Sets the serialization byte order to bo.

int	version () const
	Returns the version number of the data serialization format.

void	setVersion (int)
	Sets the version number of the data serialization format to v, a value of the \l Version enum.

QDataStream &	operator>> (char &i)

QDataStream &	operator>> (qint8 &i)
	Reads a signed byte from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (quint8 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned byte from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (qint16 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a signed 16-bit integer from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (quint16 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned 16-bit integer from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (qint32 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a signed 32-bit integer from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (quint32 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned 32-bit integer from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (qint64 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a signed 64-bit integer from the stream into i, and returns a reference to the stream.

QDataStream &	operator>> (quint64 &i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned 64-bit integer from the stream, into i, and returns a reference to the stream.

QDataStream &	operator>> (std::nullptr_t &ptr)

QDataStream &	operator>> (bool &i)
	Reads a boolean value from the stream into i.

QDataStream &	operator>> (float &f)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a floating point number from the stream into f, using the standard IEEE 754 format.

QDataStream &	operator>> (double &f)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a floating point number from the stream into f, using the standard IEEE 754 format.

QDataStream &	operator>> (char *&str)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads string s from the stream and returns a reference to the stream.

QDataStream &	operator>> (char16_t &c)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QDataStream &	operator>> (char32_t &c)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QDataStream &	operator<< (char i)

QDataStream &	operator<< (qint8 i)
	Writes a signed byte, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (quint8 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned byte, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (qint16 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a signed 16-bit integer, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (quint16 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned 16-bit integer, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (qint32 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a signed 32-bit integer, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (quint32 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned integer, i, to the stream as a 32-bit unsigned integer (quint32).

QDataStream &	operator<< (qint64 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a signed 64-bit integer, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (quint64 i)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned 64-bit integer, i, to the stream and returns a reference to the stream.

QDataStream &	operator<< (std::nullptr_t)

template<typename T , std::enable_if_t< std::is_same_v< T, bool >, bool > = true>
QDataStream &	operator<< (T i)

QDataStream &	operator<< (float f)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a floating point number, f, to the stream using the standard IEEE 754 format.

QDataStream &	operator<< (double f)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a floating point number, f, to the stream using the standard IEEE 754 format.

QDataStream &	operator<< (const char *str)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes the '\0'-terminated string s to the stream and returns a reference to the stream.

QDataStream &	operator<< (char16_t c)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QDataStream &	operator<< (char32_t c)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

QDataStream &	readBytes (char *&, qint64 &len)

qint64	readRawData (char *, qint64 len)
	Reads at most len bytes from the stream into s and returns the number of bytes read.

QDataStream &	writeBytes (const char *, qint64 len)
	Writes the length specifier len and the buffer s to the stream and returns a reference to the stream.

qint64	writeRawData (const char *, qint64 len)
	Writes len bytes from s to the stream.

qint64	skipRawData (qint64 len)

void	startTransaction ()

bool	commitTransaction ()

void	rollbackTransaction ()

void	abortTransaction ()

bool	isDeviceTransactionStarted () const

Friends
class	QtPrivate::StreamStateSaver

Q_CORE_EXPORT friend QDataStream &	operator<< (QDataStream &out, const QString &str)

Q_CORE_EXPORT friend QDataStream &	operator>> (QDataStream &in, QString &str)

Q_CORE_EXPORT friend QDataStream &	operator<< (QDataStream &out, const QByteArray &ba)

Q_CORE_EXPORT friend QDataStream &	operator>> (QDataStream &in, QByteArray &ba)

template<typename Container >
QDataStream &	QtPrivate::readArrayBasedContainer (QDataStream &s, Container &c)

template<typename Container >
QDataStream &	QtPrivate::readListBasedContainer (QDataStream &s, Container &c)

template<typename Container >
QDataStream &	QtPrivate::readAssociativeContainer (QDataStream &s, Container &c)

template<typename Container >
QDataStream &	QtPrivate::writeSequentialContainer (QDataStream &s, const Container &c)

template<typename Container >
QDataStream &	QtPrivate::writeAssociativeContainer (QDataStream &s, const Container &c)

template<typename Container >
QDataStream &	QtPrivate::writeAssociativeMultiContainer (QDataStream &s, const Container &c)

Related Symbols
(Note that these are not member symbols.)
	operator<< (QDataStream &ds, qfloat16 f)

	operator>> (QDataStream &ds, qfloat16 &f)

template< class T1, class T2 > QDataStream &	operator>> (QDataStream &in, std::pair< T1, T2 > &pair)

template< class T1, class T2 > QDataStream &	operator<< (QDataStream &out, const std::pair< T1, T2 > &pair)

Additional Inherited Members
Protected Member Functions inherited from QIODeviceBase
	~QIODeviceBase ()=default

Detailed Description

\inmodule QtCore

\reentrant

The QDataStream class provides serialization of binary data to a QIODevice.

A data stream is a binary stream of encoded information which is 100% independent of the host computer's operating system, CPU or byte order. For example, a data stream that is written by a PC under Windows can be read by a Sun SPARC running Solaris.

You can also use a data stream to read/write \l{raw}{raw unencoded binary data}. If you want a "parsing" input stream, see QTextStream.

The QDataStream class implements the serialization of C++'s basic data types, like char, short, int, {char *}, etc. Serialization of more complex data is accomplished by breaking up the data into primitive units.

A data stream cooperates closely with a QIODevice. A QIODevice represents an input/output medium one can read data from and write data to. The QFile class is an example of an I/O device.

Example (write binary data to a stream):

QFile file("file.dat");
file.open(QIODevice::WriteOnly);
QDataStream out(&file);   // we will serialize the data into the file
out << QString("the answer is");   // serialize a string
out << (qint32)42;        // serialize an integer

Example (read binary data from a stream):

QFile file("file.dat");
file.open(QIODevice::ReadOnly);
QDataStream in(&file);    // read the data serialized from the file
QString str;
qint32 a;
in >> str >> a;           // extract "the answer is" and 42

Each item written to the stream is written in a predefined binary format that varies depending on the item's type. Supported Qt types include QBrush, QColor, QDateTime, QFont, QPixmap, QString, QVariant and many others. For the complete list of all Qt types supporting data streaming see \l{Serializing Qt Data Types}.

For integers it is best to always cast to a Qt integer type for writing, and to read back into the same Qt integer type. This ensures that you get integers of the size you want and insulates you from compiler and platform differences.

Enumerations can be serialized through QDataStream without the need of manually defining streaming operators. Enum classes are serialized using the declared size.

The initial I/O device is usually set in the constructor, but can be changed with setDevice(). If you've reached the end of the data (or if there is no I/O device set) atEnd() will return true.

Definition at line 46 of file qdatastream.h.

Member Enumeration Documentation

◆ ByteOrder

enum QDataStream::ByteOrder

The byte order used for reading/writing the data.

\value BigEndian Most significant byte first (the default) \value LittleEndian Least significant byte first

Enumerator
BigEndian
LittleEndian

Definition at line 98 of file qdatastream.h.

Constructor & Destructor Documentation

◆ QDataStream() [1/4]

QDataStream::QDataStream ( )

Constructs a data stream that has no I/O device.

See also: setDevice()

Definition at line 285 of file qdatastream.cpp.

◆ QDataStream() [2/4]

QDataStream::QDataStream ( QIODevice * d )

explicit

Constructs a data stream that uses the I/O device d.

See also: setDevice(), device()

Definition at line 295 of file qdatastream.cpp.

◆ QDataStream() [3/4]

QDataStream::QDataStream	(	QByteArray *	a,
		OpenMode	mode )

Constructs a data stream that operates on a byte array, a.

The mode describes how the device is to be used.

Alternatively, you can use QDataStream(const QByteArray &) if you just want to read from a byte array.

Since QByteArray is not a QIODevice subclass, internally a QBuffer is created to wrap the byte array.

Definition at line 313 of file qdatastream.cpp.

◆ QDataStream() [4/4]

QDataStream::QDataStream ( const QByteArray & a )

Constructs a read-only data stream that operates on byte array a.

Use QDataStream(QByteArray*, int) if you want to write to a byte array.

Since QByteArray is not a QIODevice subclass, internally a QBuffer is created to wrap the byte array.

Definition at line 332 of file qdatastream.cpp.

◆ ~QDataStream()

QDataStream::~QDataStream ( )

Destroys the data stream.

The destructor will not affect the current I/O device, unless it is an internal I/O device (e.g. a QBuffer) processing a QByteArray passed in the constructor, in which case the internal I/O device is destroyed.

Definition at line 353 of file qdatastream.cpp.

Member Function Documentation

◆ abortTransaction()

void QDataStream::abortTransaction ( )

Since: 5.7

Aborts a read transaction.

This function is commonly used to discard the transaction after higher-level protocol errors or loss of stream synchronization.

If called on an inner transaction, aborting is delegated to the outermost transaction, and subsequently started inner transactions are forced to fail.

For the outermost transaction, discards the restoration point and any internally duplicated data of the stream. Will not affect the current read position of the stream.

Sets the status of the data stream to \value ReadCorruptData.

See also: startTransaction(), commitTransaction(), rollbackTransaction()

Definition at line 724 of file qdatastream.cpp.

◆ atEnd()

bool QDataStream::atEnd ( ) const

Returns true if the I/O device has reached the end position (end of the stream or file) or if there is no I/O device set; otherwise returns false.

See also: QIODevice::atEnd()

Definition at line 397 of file qdatastream.cpp.

◆ byteOrder()

QDataStream::ByteOrder QDataStream::byteOrder ( ) const

inline

Returns the current byte order setting – either BigEndian or LittleEndian.

See also: setByteOrder()

Definition at line 446 of file qdatastream.h.

◆ commitTransaction()

bool QDataStream::commitTransaction ( )

Since: 5.7

Completes a read transaction. Returns true if no read errors have occurred during the transaction; otherwise returns false.

If called on an inner transaction, committing will be postponed until the outermost commitTransaction(), rollbackTransaction(), or abortTransaction() call occurs.

Otherwise, if the stream status indicates reading past the end of the data, this function restores the stream data to the point of the startTransaction() call. When this situation occurs, you need to wait for more data to arrive, after which you start a new transaction. If the data stream has read corrupt data or any of the inner transactions was aborted, this function aborts the transaction.

See also: startTransaction(), rollbackTransaction(), abortTransaction()

Definition at line 650 of file qdatastream.cpp.

◆ device()

QIODevice * QDataStream::device ( ) const

inline

Returns the I/O device currently set, or \nullptr if no device is currently set.

See also: setDevice()

Definition at line 431 of file qdatastream.h.

◆ floatingPointPrecision()

FloatingPointPrecision QDataStream::floatingPointPrecision ( ) const

Returns the floating point precision of the data stream.

Since: 4.6

See also: FloatingPointPrecision, setFloatingPointPrecision()

◆ isDeviceTransactionStarted()

bool QDataStream::isDeviceTransactionStarted ( ) const

Definition at line 739 of file qdatastream.cpp.

◆ operator<<() [1/16]

QDataStream & QDataStream::operator<< ( char i )

inline

Definition at line 502 of file qdatastream.h.

◆ operator<<() [2/16]

QDataStream & QDataStream::operator<< ( char16_t c )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Since: 6.0

Writes a character, c, to the stream. Returns a reference to the stream

Definition at line 1366 of file qdatastream.cpp.

◆ operator<<() [3/16]

QDataStream & QDataStream::operator<< ( char32_t c )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Since: 6.0

Writes a character, c, to the stream. Returns a reference to the stream

Definition at line 1378 of file qdatastream.cpp.

◆ operator<<() [4/16]

QDataStream & QDataStream::operator<< ( const char * s )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes the '\0'-terminated string s to the stream and returns a reference to the stream.

The string is serialized using {writeBytes()}.

See also: writeBytes(), writeRawData()

Definition at line 1351 of file qdatastream.cpp.

◆ operator<<() [5/16]

QDataStream & QDataStream::operator<< ( double f )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a floating point number, f, to the stream using the standard IEEE 754 format.

Returns a reference to the stream.

See also: setFloatingPointPrecision()

Definition at line 1314 of file qdatastream.cpp.

◆ operator<<() [6/16]

QDataStream & QDataStream::operator<< ( float f )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a floating point number, f, to the stream using the standard IEEE 754 format.

Returns a reference to the stream.

See also: setFloatingPointPrecision()

Definition at line 1276 of file qdatastream.cpp.

◆ operator<<() [7/16]

QDataStream & QDataStream::operator<< ( qint16 i )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a signed 16-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 1190 of file qdatastream.cpp.

◆ operator<<() [8/16]

QDataStream & QDataStream::operator<< ( qint32 i )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a signed 32-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 1208 of file qdatastream.cpp.

◆ operator<<() [9/16]

QDataStream & QDataStream::operator<< ( qint64 i )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes a signed 64-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 1234 of file qdatastream.cpp.

◆ operator<<() [10/16]

QDataStream & QDataStream::operator<< ( qint8 i )

Writes a signed byte, i, to the stream and returns a reference to the stream.

Definition at line 1166 of file qdatastream.cpp.

◆ operator<<() [11/16]

QDataStream & QDataStream::operator<< ( quint16 i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned 16-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 508 of file qdatastream.h.

◆ operator<<() [12/16]

QDataStream & QDataStream::operator<< ( quint32 i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned integer, i, to the stream as a 32-bit unsigned integer (quint32).

Returns a reference to the stream.

Definition at line 511 of file qdatastream.h.

◆ operator<<() [13/16]

QDataStream & QDataStream::operator<< ( quint64 i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned 64-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 514 of file qdatastream.h.

◆ operator<<() [14/16]

QDataStream & QDataStream::operator<< ( quint8 i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Writes an unsigned byte, i, to the stream and returns a reference to the stream.

Definition at line 505 of file qdatastream.h.

◆ operator<<() [15/16]

QDataStream & QDataStream::operator<< ( std::nullptr_t ptr )

inline

Since: 5.9 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Simulates writing a {std::nullptr_t}, ptr, to the stream and returns a reference to the stream. This function does not actually write anything to the stream, as {std::nullptr_t} values are stored as 0 bytes.

Definition at line 172 of file qdatastream.h.

◆ operator<<() [16/16]

template<typename T , std::enable_if_t< std::is_same_v< T, bool >, bool > = true>

QDataStream & QDataStream::operator<< ( T i )

inline

Definition at line 180 of file qdatastream.h.

◆ operator>>() [1/16]

QDataStream & QDataStream::operator>> ( bool & i )

Reads a boolean value from the stream into i.

Returns a reference to the stream.

Definition at line 897 of file qdatastream.cpp.

◆ operator>>() [2/16]

QDataStream & QDataStream::operator>> ( char & i )

inline

Definition at line 487 of file qdatastream.h.

◆ operator>>() [3/16]

QDataStream & QDataStream::operator>> ( char *& s )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads string s from the stream and returns a reference to the stream.

The string is deserialized using {readBytes()} where the serialization format is a quint32 length specifier first, followed by that many bytes of data. The resulting string is always '\0'-terminated.

Space for the string is allocated using {new []} – the caller must destroy it with {delete []}.

See also: readBytes(), readRawData()

Definition at line 995 of file qdatastream.cpp.

◆ operator>>() [4/16]

QDataStream & QDataStream::operator>> ( char16_t & c )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Since: 6.0

Reads a 16bit wide char from the stream into c and returns a reference to the stream.

Definition at line 1008 of file qdatastream.cpp.

◆ operator>>() [5/16]

QDataStream & QDataStream::operator>> ( char32_t & c )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Since: 6.0

Reads a 32bit wide character from the stream into c and returns a reference to the stream.

Definition at line 1023 of file qdatastream.cpp.

◆ operator>>() [6/16]

QDataStream & QDataStream::operator>> ( double & f )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a floating point number from the stream into f, using the standard IEEE 754 format.

Returns a reference to the stream.

See also: setFloatingPointPrecision()

Definition at line 952 of file qdatastream.cpp.

◆ operator>>() [7/16]

QDataStream & QDataStream::operator>> ( float & f )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a floating point number from the stream into f, using the standard IEEE 754 format.

Returns a reference to the stream.

See also: setFloatingPointPrecision()

Definition at line 915 of file qdatastream.cpp.

◆ operator>>() [8/16]

QDataStream & QDataStream::operator>> ( qint16 & i )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a signed 16-bit integer from the stream into i, and returns a reference to the stream.

Definition at line 814 of file qdatastream.cpp.

◆ operator>>() [9/16]

QDataStream & QDataStream::operator>> ( qint32 & i )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a signed 32-bit integer from the stream into i, and returns a reference to the stream.

Definition at line 844 of file qdatastream.cpp.

◆ operator>>() [10/16]

QDataStream & QDataStream::operator>> ( qint64 & i )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads a signed 64-bit integer from the stream into i, and returns a reference to the stream.

Definition at line 873 of file qdatastream.cpp.

◆ operator>>() [11/16]

QDataStream & QDataStream::operator>> ( qint8 & i )

Reads a signed byte from the stream into i, and returns a reference to the stream.

Definition at line 788 of file qdatastream.cpp.

◆ operator>>() [12/16]

QDataStream & QDataStream::operator>> ( quint16 & i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned 16-bit integer from the stream into i, and returns a reference to the stream.

Definition at line 493 of file qdatastream.h.

◆ operator>>() [13/16]

QDataStream & QDataStream::operator>> ( quint32 & i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned 32-bit integer from the stream into i, and returns a reference to the stream.

Definition at line 496 of file qdatastream.h.

◆ operator>>() [14/16]

QDataStream & QDataStream::operator>> ( quint64 & i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned 64-bit integer from the stream, into i, and returns a reference to the stream.

Definition at line 499 of file qdatastream.h.

◆ operator>>() [15/16]

QDataStream & QDataStream::operator>> ( quint8 & i )

inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Reads an unsigned byte from the stream into i, and returns a reference to the stream.

Definition at line 490 of file qdatastream.h.

◆ operator>>() [16/16]

QDataStream & QDataStream::operator>> ( std::nullptr_t & ptr )

inline

Since: 5.9 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Simulates reading a {std::nullptr_t} from the stream into ptr and returns a reference to the stream. This function does not actually read anything from the stream, as {std::nullptr_t} values are stored as 0 bytes.

Definition at line 151 of file qdatastream.h.

◆ QT7_ONLY() [1/3]

enum Version QDataStream::QT7_ONLY ( :quint8 )

inline

Definition at line 49 of file qdatastream.h.

◆ QT7_ONLY() [2/3]

enum Status QDataStream::QT7_ONLY ( :quint8 )

inline

Definition at line 103 of file qdatastream.h.

◆ QT7_ONLY() [3/3]

enum FloatingPointPrecision QDataStream::QT7_ONLY ( :quint8 )

inline

Definition at line 111 of file qdatastream.h.

◆ readBytes()

QDataStream & QDataStream::readBytes	(	char *&	s,
		qint64 &	l )

Since: 6.7 Reads the buffer s from the stream and returns a reference to the stream.

The buffer s is allocated using {new []}. Destroy it with the {delete []} operator.

The l parameter is set to the length of the buffer. If the string read is empty, l is set to 0 and s is set to \nullptr.

The serialization format is a length specifier first, then l bytes of data. The length specifier is one quint32 if the version is less than 6.7 or if the number of elements is less than 0xfffffffe (2^32 -2), otherwise there is an extend value 0xfffffffe followed by one quint64 with the actual value. In addition for containers that support isNull(), it is encoded as a single quint32 with all bits set and no data.

See also: readRawData(), writeBytes()

Definition at line 1074 of file qdatastream.cpp.

◆ readRawData()

qint64 QDataStream::readRawData	(	char *	s,
		qint64	len )

Reads at most len bytes from the stream into s and returns the number of bytes read.

If an error occurs, this function returns -1.

The buffer s must be preallocated. The data is not decoded.

See also: readBytes(), QIODevice::read(), writeRawData()

Definition at line 1122 of file qdatastream.cpp.

◆ resetStatus()

void QDataStream::resetStatus ( )

Resets the status of the data stream.

See also: Status, status(), setStatus()

Definition at line 450 of file qdatastream.cpp.

◆ rollbackTransaction()

void QDataStream::rollbackTransaction ( )

Since: 5.7

Reverts a read transaction.

This function is commonly used to rollback the transaction when an incomplete read was detected prior to committing the transaction.

If called on an inner transaction, reverting is delegated to the outermost transaction, and subsequently started inner transactions are forced to fail.

For the outermost transaction, restores the stream data to the point of the startTransaction() call. If the data stream has read corrupt data or any of the inner transactions was aborted, this function aborts the transaction.

If the preceding stream operations were successful, sets the status of the data stream to \value ReadPastEnd.

See also: startTransaction(), commitTransaction(), abortTransaction()

Definition at line 688 of file qdatastream.cpp.

◆ setByteOrder()

void QDataStream::setByteOrder ( ByteOrder bo )

Sets the serialization byte order to bo.

The bo parameter can be QDataStream::BigEndian or QDataStream::LittleEndian.

The default setting is big-endian. We recommend leaving this setting unless you have special requirements.

See also: byteOrder()

Definition at line 490 of file qdatastream.cpp.

◆ setDevice()

void QDataStream::setDevice ( QIODevice * d )

void QDataStream::setDevice(QIODevice *d)

Sets the I/O device to d, which can be \nullptr to unset to current I/O device.

See also: device()

Definition at line 378 of file qdatastream.cpp.

◆ setFloatingPointPrecision()

void QDataStream::setFloatingPointPrecision ( FloatingPointPrecision precision )

Sets the floating point precision of the data stream to precision.

If the floating point precision is DoublePrecision and the version of the data stream is Qt_4_6 or higher, all floating point numbers will be written and read with 64-bit precision. If the floating point precision is SinglePrecision and the version is Qt_4_6 or higher, all floating point numbers will be written and read with 32-bit precision.

For versions prior to Qt_4_6, the precision of floating point numbers in the data stream depends on the stream operator called.

The default is DoublePrecision.

Note that this property does not affect the serialization or deserialization of qfloat16 instances.

Warning: This property must be set to the same value on the object that writes and the object that reads the data stream.

Since: 4.6

Definition at line 432 of file qdatastream.cpp.

◆ setStatus()

void QDataStream::setStatus ( Status status )

Sets the status of the data stream to the status given.

Subsequent calls to setStatus() are ignored until resetStatus() is called.

See also: Status, status(), resetStatus()

Definition at line 463 of file qdatastream.cpp.

◆ setVersion()

void QDataStream::setVersion ( int v )

inline

Sets the version number of the data serialization format to v, a value of the \l Version enum.

You don't have to set a version if you are using the current version of Qt, but for your own custom binary formats we recommend that you do; see \l{Versioning} in the Detailed Description.

To accommodate new functionality, the datastream serialization format of some Qt classes has changed in some versions of Qt. If you want to read data that was created by an earlier version of Qt, or write data that can be read by a program that was compiled with an earlier version of Qt, use this function to modify the serialization format used by QDataStream.

The \l Version enum provides symbolic constants for the different versions of Qt. For example:

QDataStream out(file);

out.setVersion(QDataStream::Qt_4_0);

See also: version(), Version

Definition at line 456 of file qdatastream.h.

◆ skipRawData()

qint64 QDataStream::skipRawData ( qint64 len )

Since: 4.1

Skips len bytes from the device. Returns the number of bytes actually skipped, or -1 on error.

This is equivalent to calling readRawData() on a buffer of length len and ignoring the buffer.

See also: QIODevice::seek()

Definition at line 1435 of file qdatastream.cpp.

◆ startTransaction()

void QDataStream::startTransaction ( )

Since: 5.7

Starts a new read transaction on the stream.

Defines a restorable point within the sequence of read operations. For sequential devices, read data will be duplicated internally to allow recovery in case of incomplete reads. For random-access devices, this function saves the current position of the stream. Call commitTransaction(), rollbackTransaction(), or abortTransaction() to finish the current transaction.

Once a transaction is started, subsequent calls to this function will make the transaction recursive. Inner transactions act as agents of the outermost transaction (i.e., report the status of read operations to the outermost transaction, which can restore the position of the stream).

Note: Restoring to the point of the nested startTransaction() call is not supported.

When an error occurs during a transaction (including an inner transaction failing), reading from the data stream is suspended (all subsequent read operations return empty/zero values) and subsequent inner transactions are forced to fail. Starting a new outermost transaction recovers from this state. This behavior makes it unnecessary to error-check every read operation separately.

See also: commitTransaction(), rollbackTransaction(), abortTransaction()

Definition at line 620 of file qdatastream.cpp.

◆ status()

Status QDataStream::status ( ) const

Returns the status of the data stream.

See also: Status, setStatus(), resetStatus()

◆ version()

int QDataStream::version ( ) const

inline

Returns the version number of the data serialization format.

See also: setVersion(), Version

Definition at line 453 of file qdatastream.h.

◆ writeBytes()

QDataStream & QDataStream::writeBytes	(	const char *	s,
		qint64	len )

Writes the length specifier len and the buffer s to the stream and returns a reference to the stream.

The len is serialized as a quint32 and an optional quint64, followed by len bytes from s. Note that the data is not encoded.

See also: writeRawData(), readBytes()

Definition at line 1394 of file qdatastream.cpp.

◆ writeRawData()

qint64 QDataStream::writeRawData	(	const char *	s,
		qint64	len )

Writes len bytes from s to the stream.

Returns the number of bytes actually written, or -1 on error. The data is not encoded.

See also: writeBytes(), QIODevice::write(), readRawData()

Definition at line 1415 of file qdatastream.cpp.

Friends And Related Symbol Documentation

◆ operator<<() [1/4]

operator<<	(	QDataStream &	ds,
		qfloat16	f )

Since: 5.9

Writes a floating point number, f, to the stream ds using the standard IEEE 754 format. Returns a reference to the stream.

Note: In Qt versions prior to 6.3, this was a member function on QDataStream.

Definition at line 400 of file qfloat16.cpp.

◆ operator<< [2/4]

Q_CORE_EXPORT friend QDataStream & operator<<	(	QDataStream &	out,
		const QByteArray &	ba )

friend

◆ operator<< [3/4]

Q_CORE_EXPORT friend QDataStream & operator<<	(	QDataStream &	out,
		const QString &	str )

friend

Definition at line 9602 of file qstring.cpp.

◆ operator<<() [4/4]

template< class T1, class T2 > QDataStream & operator<<	(	QDataStream &	out,
		const std::pair< T1, T2 > &	pair )

Since: 6.0

Writes the pair pair to stream out.

This function requires the T1 and T2 types to implement operator<<().

See also: {Serializing Qt Data Types}

Definition at line 620 of file qdatastream.h.

◆ operator>>() [1/4]

operator>>	(	QDataStream &	ds,
		qfloat16 &	f )

Since: 5.9

Reads a floating point number from the stream ds into f, using the standard IEEE 754 format. Returns a reference to the stream.

Note: In Qt versions prior to 6.3, this was a member function on QDataStream.

Definition at line 417 of file qfloat16.cpp.

◆ operator>> [2/4]

Q_CORE_EXPORT friend QDataStream & operator>>	(	QDataStream &	in,
		QByteArray &	ba )

friend

◆ operator>> [3/4]

Q_CORE_EXPORT friend QDataStream & operator>>	(	QDataStream &	in,
		QString &	str )

friend

Definition at line 9633 of file qstring.cpp.

◆ operator>>() [4/4]

template< class T1, class T2 > QDataStream & operator>>	(	QDataStream &	in,
		std::pair< T1, T2 > &	pair )

Since: 6.0

Reads a pair from stream in into pair.

This function requires the T1 and T2 types to implement operator>>().

See also: {Serializing Qt Data Types}

Definition at line 620 of file qdatastream.h.

◆ QtPrivate::readArrayBasedContainer

template<typename Container >

QDataStream & QtPrivate::readArrayBasedContainer	(	QDataStream &	s,
		Container &	c )

friend

◆ QtPrivate::readAssociativeContainer

template<typename Container >

QDataStream & QtPrivate::readAssociativeContainer	(	QDataStream &	s,
		Container &	c )

friend

◆ QtPrivate::readListBasedContainer

template<typename Container >

QDataStream & QtPrivate::readListBasedContainer	(	QDataStream &	s,
		Container &	c )

friend

◆ QtPrivate::StreamStateSaver

friend class QtPrivate::StreamStateSaver

friend

Definition at line 243 of file qdatastream.h.

◆ QtPrivate::writeAssociativeContainer

template<typename Container >

QDataStream & QtPrivate::writeAssociativeContainer	(	QDataStream &	s,
		const Container &	c )

friend

◆ QtPrivate::writeAssociativeMultiContainer

template<typename Container >

QDataStream & QtPrivate::writeAssociativeMultiContainer	(	QDataStream &	s,
		const Container &	c )

friend

◆ QtPrivate::writeSequentialContainer

template<typename Container >

QDataStream & QtPrivate::writeSequentialContainer	(	QDataStream &	s,
		const Container &	c )

friend

The documentation for this class was generated from the following files:

qtbase/src/corelib/serialization/qdatastream.h (0c010cd9c792859551f6d0e34d413809cbf4ae74)
qtbase/src/corelib/global/qfloat16.cpp (4281495f52c22326ae961849d8ad7362c30168d2)
qtbase/src/corelib/serialization/qdatastream.cpp (4ce7235fdd6183478eebfcf2f1d6058a172b285a)

Public Types

Public Member Functions

Friends

Related Symbols

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ ByteOrder

Constructor & Destructor Documentation

◆ QDataStream() [1/4]

◆ QDataStream() [2/4]

◆ QDataStream() [3/4]

◆ QDataStream() [4/4]

◆ ~QDataStream()

Member Function Documentation

◆ abortTransaction()

◆ atEnd()

◆ byteOrder()

◆ commitTransaction()

◆ device()

◆ floatingPointPrecision()

◆ isDeviceTransactionStarted()

◆ operator<<() [1/16]

◆ operator<<() [2/16]

◆ operator<<() [3/16]

◆ operator<<() [4/16]

◆ operator<<() [5/16]

◆ operator<<() [6/16]

◆ operator<<() [7/16]

◆ operator<<() [8/16]

◆ operator<<() [9/16]

◆ operator<<() [10/16]

◆ operator<<() [11/16]

◆ operator<<() [12/16]

◆ operator<<() [13/16]

◆ operator<<() [14/16]

◆ operator<<() [15/16]

◆ operator<<() [16/16]

◆ operator>>() [1/16]

◆ operator>>() [2/16]

◆ operator>>() [3/16]

◆ operator>>() [4/16]

◆ operator>>() [5/16]

◆ operator>>() [6/16]

◆ operator>>() [7/16]

◆ operator>>() [8/16]

◆ operator>>() [9/16]

◆ operator>>() [10/16]

◆ operator>>() [11/16]

◆ operator>>() [12/16]

◆ operator>>() [13/16]

◆ operator>>() [14/16]

◆ operator>>() [15/16]

◆ operator>>() [16/16]

◆ QT7_ONLY() [1/3]

◆ QT7_ONLY() [2/3]

◆ QT7_ONLY() [3/3]

◆ readBytes()

◆ readRawData()

◆ resetStatus()

◆ rollbackTransaction()

◆ setByteOrder()

◆ setDevice()

◆ setFloatingPointPrecision()

◆ setStatus()

◆ setVersion()

◆ skipRawData()

◆ startTransaction()

◆ status()

◆ version()

◆ writeBytes()

◆ writeRawData()

Friends And Related Symbol Documentation

◆ operator<<() [1/4]

◆ operator<< [2/4]

◆ operator<< [3/4]

◆ operator<<() [4/4]

◆ operator>>() [1/4]

◆ operator>> [2/4]

◆ operator>> [3/4]