QDataStream Class Reference

\inmodule QtCore\reentrant More...

#include <qdatastream.h>

Inheritance diagram for QDataStream:

Collaboration diagram for QDataStream:

Public Types
enum	Version {   Qt_1_0 = 1 , Qt_2_0 = 2 , Qt_2_1 = 3 , Qt_3_0 = 4 ,   Qt_3_1 = 5 , Qt_3_3 = 6 , Qt_4_0 = 7 , Qt_4_1 = Qt_4_0 ,   Qt_4_2 = 8 , Qt_4_3 = 9 , Qt_4_4 = 10 , Qt_4_5 = 11 ,   Qt_4_6 = 12 , Qt_4_7 = Qt_4_6 , Qt_4_8 = Qt_4_7 , Qt_4_9 = Qt_4_8 ,   Qt_5_0 = 13 , Qt_5_1 = 14 , Qt_5_2 = 15 , Qt_5_3 = Qt_5_2 ,   Qt_5_4 = 16 , Qt_5_5 = Qt_5_4 , Qt_5_6 = 17 , Qt_5_7 = Qt_5_6 ,   Qt_5_8 = Qt_5_7 , Qt_5_9 = Qt_5_8 , Qt_5_10 = Qt_5_9 , Qt_5_11 = Qt_5_10 ,   Qt_5_12 = 18 , Qt_5_13 = 19 , Qt_5_14 = Qt_5_13 , Qt_5_15 = Qt_5_14 ,   Qt_6_0 = 20 , Qt_6_1 = Qt_6_0 , Qt_6_2 = Qt_6_0 , Qt_6_3 = Qt_6_0 ,   Qt_6_4 = Qt_6_0 , Qt_6_5 = Qt_6_0 , Qt_6_6 = 21 , Qt_6_7 = Qt_6_6 ,   Qt_DefaultCompiledVersion = Qt_6_7 }
	This enum provides symbolic synonyms for the data serialization format version numbers. More...
enum	ByteOrder { BigEndian = QSysInfo::BigEndian , LittleEndian = QSysInfo::LittleEndian }
	The byte order used for reading/writing the data. More...
enum	Status { Ok , ReadPastEnd , ReadCorruptData , WriteFailed }
	This enum describes the current status of the data stream. More...
enum	FloatingPointPrecision { SinglePrecision , DoublePrecision }
	The precision of floating point numbers 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
	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 the '\0'-terminated 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)
QDataStream &	operator<< (bool i)
	Writes a boolean value, i, to the stream.
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 *&, uint &len)
	Reads the buffer s from the stream and returns a reference to the stream.
int	readRawData (char *, int len)
	Reads at most len bytes from the stream into s and returns the number of bytes read.
QDataStream &	writeBytes (const char *, uint len)
	Writes the length specifier len and the buffer s to the stream and returns a reference to the stream.
int	writeRawData (const char *, int len)
	Writes len bytes from s to the stream.
int	skipRawData (int len)
void	startTransaction ()
bool	commitTransaction ()
void	rollbackTransaction ()
void	abortTransaction ()
bool	isDeviceTransactionStarted () const

Friends
class	QtPrivate::StreamStateSaver

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.

To take one example, a {char *} string is written as a 32-bit integer equal to the length of the string including the '\0' byte, followed by all the characters of the string including the '\0' byte. When reading a {char *} string, 4 bytes are read to create the 32-bit length value, then that many characters for the {char *} string including the '\0' terminator are read.

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 29 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 79 of file qdatastream.h.

FloatingPointPrecision

enum QDataStream::FloatingPointPrecision

The precision of floating point numbers used for reading/writing the data.

This will only have an effect if the version of the data stream is Qt_4_6 or higher.

Warning

The floating point precision must be set to the same value on the object that writes and the object that reads the data stream.

\value SinglePrecision All floating point numbers in the data stream have 32-bit precision. \value DoublePrecision All floating point numbers in the data stream have 64-bit precision.

See also

setFloatingPointPrecision(), floatingPointPrecision()

Enumerator
SinglePrecision
DoublePrecision

Definition at line 91 of file qdatastream.h.

Status

enum QDataStream::Status

This enum describes the current status of the data stream.

\value Ok The data stream is operating normally. \value ReadPastEnd The data stream has read past the end of the data in the underlying device. \value ReadCorruptData The data stream has read corrupt data. \value WriteFailed The data stream cannot write to the underlying device.

Enumerator
Ok
ReadPastEnd
ReadCorruptData
WriteFailed

Definition at line 84 of file qdatastream.h.

Version

enum QDataStream::Version

This enum provides symbolic synonyms for the data serialization format version numbers.

\value Qt_1_0 Version 1 (Qt 1.x) \value Qt_2_0 Version 2 (Qt 2.0) \value Qt_2_1 Version 3 (Qt 2.1, 2.2, 2.3) \value Qt_3_0 Version 4 (Qt 3.0) \value Qt_3_1 Version 5 (Qt 3.1, 3.2) \value Qt_3_3 Version 6 (Qt 3.3) \value Qt_4_0 Version 7 (Qt 4.0, Qt 4.1) \value Qt_4_1 Version 7 (Qt 4.0, Qt 4.1) \value Qt_4_2 Version 8 (Qt 4.2) \value Qt_4_3 Version 9 (Qt 4.3) \value Qt_4_4 Version 10 (Qt 4.4) \value Qt_4_5 Version 11 (Qt 4.5) \value Qt_4_6 Version 12 (Qt 4.6, Qt 4.7, Qt 4.8) \value Qt_4_7 Same as Qt_4_6. \value Qt_4_8 Same as Qt_4_6. \value Qt_4_9 Same as Qt_4_6. \value Qt_5_0 Version 13 (Qt 5.0) \value Qt_5_1 Version 14 (Qt 5.1) \value Qt_5_2 Version 15 (Qt 5.2) \value Qt_5_3 Same as Qt_5_2 \value Qt_5_4 Version 16 (Qt 5.4) \value Qt_5_5 Same as Qt_5_4 \value Qt_5_6 Version 17 (Qt 5.6) \value Qt_5_7 Same as Qt_5_6 \value Qt_5_8 Same as Qt_5_6 \value Qt_5_9 Same as Qt_5_6 \value Qt_5_10 Same as Qt_5_6 \value Qt_5_11 Same as Qt_5_6 \value Qt_5_12 Version 18 (Qt 5.12) \value Qt_5_13 Version 19 (Qt 5.13) \value Qt_5_14 Same as Qt_5_13 \value Qt_5_15 Same as Qt_5_13 \value Qt_6_0 Version 20 (Qt 6.0) \value Qt_6_1 Same as Qt_6_0 \value Qt_6_2 Same as Qt_6_0 \value Qt_6_3 Same as Qt_6_0 \value Qt_6_4 Same as Qt_6_0 \value Qt_6_5 Same as Qt_6_0 \value Qt_6_6 Same as Qt_6_0 \value Qt_6_7 Same as Qt_6_6 \omitvalue Qt_DefaultCompiledVersion

See also

setVersion(), version()

Enumerator
Qt_1_0
Qt_2_0
Qt_2_1
Qt_3_0
Qt_3_1
Qt_3_3
Qt_4_0
Qt_4_1
Qt_4_2
Qt_4_3
Qt_4_4
Qt_4_5
Qt_4_6
Qt_4_7
Qt_4_8
Qt_4_9
Qt_5_0
Qt_5_1
Qt_5_2
Qt_5_3
Qt_5_4
Qt_5_5
Qt_5_6
Qt_5_7
Qt_5_8
Qt_5_9
Qt_5_10
Qt_5_11
Qt_5_12
Qt_5_13
Qt_5_14
Qt_5_15
Qt_6_0
Qt_6_1
Qt_6_2
Qt_6_3
Qt_6_4
Qt_6_5
Qt_6_6
Qt_6_7
Qt_DefaultCompiledVersion

Definition at line 32 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 243 of file qdatastream.cpp.

References QSysInfo::BigEndian, BigEndian, QSysInfo::ByteOrder, Ok, and Qt_DefaultCompiledVersion.

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 259 of file qdatastream.cpp.

References QSysInfo::BigEndian, BigEndian, QSysInfo::ByteOrder, d, Ok, and Qt_DefaultCompiledVersion.

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 282 of file qdatastream.cpp.

References QSysInfo::BigEndian, BigEndian, QSysInfo::ByteOrder, Ok, and Qt_DefaultCompiledVersion.

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 305 of file qdatastream.cpp.

References QSysInfo::BigEndian, BigEndian, QObject::blockSignals(), QSysInfo::ByteOrder, Ok, Qt_DefaultCompiledVersion, and QIODeviceBase::ReadOnly.

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~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 330 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 706 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, CHECK_STREAM_TRANSACTION_PRECOND, QIODevice::commitTransaction(), Q_VOID, ReadCorruptData, and QDataStreamPrivate::transactionDepth.

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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 374 of file qdatastream.cpp.

References QIODevice::atEnd().

Referenced by QQmlDebugMessageClient::messageReceived(), QQmlEngineDebugClient::messageReceived(), and QMainWindowLayoutState::restoreState().

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byteOrder()

QDataStream::ByteOrder QDataStream::byteOrder ( ) const

inline

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

See also

setByteOrder()

Definition at line 347 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 632 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, CHECK_STREAM_TRANSACTION_PRECOND, QIODevice::commitTransaction(), Ok, ReadPastEnd, QIODevice::rollbackTransaction(), and QDataStreamPrivate::transactionDepth.

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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 344 of file qdatastream.h.

Referenced by QQmlDebugTranslation::createChangeLanguageRequest(), QQmlDebugTranslation::createChangeStateRequest(), QQmlDebugTranslation::createDisableWatchTextElidesRequest(), QQmlDebugTranslation::createMissingTranslationsRequest(), QQmlDebugTranslation::createStateListRequest(), QQmlDebugTranslation::createTranslatableTextOccurrencesRequest(), QQmlDebugTranslation::createTranslationIssuesRequest(), QQmlDebugTranslation::createWatchTextElidesRequest(), and QTlsPrivate::X509CertificateGeneric::parse().

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floatingPointPrecision()

QDataStream::FloatingPointPrecision QDataStream::floatingPointPrecision

(

)

const

Returns the floating point precision of the data stream.

Since

4.6

See also

FloatingPointPrecision, setFloatingPointPrecision()

Definition at line 386 of file qdatastream.cpp.

References DoublePrecision, and QDataStreamPrivate::floatingPointPrecision.

Referenced by operator<<(), operator<<(), operator>>(), and operator>>().

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isDeviceTransactionStarted()

bool QDataStream::isDeviceTransactionStarted

(

)

const

Definition at line 721 of file qdatastream.cpp.

References QIODevice::isTransactionStarted().

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operator<<() [1/16]

QDataStream & QDataStream::operator<<

(

bool

i

)

Writes a boolean value, i, to the stream.

Returns a reference to the stream.

Definition at line 1216 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, i, QIODevice::putChar(), qint8, and WriteFailed.

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operator<<() [2/16]

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

inline

Definition at line 371 of file qdatastream.h.

References i, and qint8.

operator<<() [3/16]

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 1327 of file qdatastream.cpp.

operator<<() [4/16]

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 1339 of file qdatastream.cpp.

operator<<() [5/16]

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 1308 of file qdatastream.cpp.

References qstrlen(), and writeRawData().

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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.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 1271 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, floatingPointPrecision(), qbswap(), Qt_4_6, SinglePrecision, version(), QIODevice::write(), and WriteFailed.

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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.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 1233 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, DoublePrecision, floatingPointPrecision(), qbswap(), Qt_4_6, version(), QIODevice::write(), and WriteFailed.

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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.Writes a signed 16-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 1142 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, i, qbswap(), QIODevice::write(), and WriteFailed.

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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.Writes a signed 32-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 1160 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, i, qbswap(), QIODevice::write(), and WriteFailed.

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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.Writes a signed 64-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 1186 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, i, qbswap(), version(), QIODevice::write(), and WriteFailed.

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operator<<() [11/16]

QDataStream & QDataStream::operator<<

(

qint8

i

)

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

Definition at line 1118 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, i, QIODevice::putChar(), and WriteFailed.

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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.Writes an unsigned 16-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 377 of file qdatastream.h.

References i.

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.Writes an unsigned integer, i, to the stream as a 32-bit unsigned integer (quint32).

Returns a reference to the stream.

Definition at line 380 of file qdatastream.h.

References i.

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.Writes an unsigned 64-bit integer, i, to the stream and returns a reference to the stream.

Definition at line 383 of file qdatastream.h.

References i.

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

Definition at line 374 of file qdatastream.h.

References i, and qint8.

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 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 150 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 879 of file qdatastream.cpp.

References i, and qint8.

operator>>() [2/16]

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

inline

Definition at line 356 of file qdatastream.h.

References i, and qint8.

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 the '\0'-terminated string s from the stream and returns a reference to the stream.

The string is deserialized using {readBytes()}.

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

See also

readBytes(), readRawData()

Definition at line 976 of file qdatastream.cpp.

References readBytes().

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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 989 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 1004 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 934 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, d, floatingPointPrecision(), qbswap(), Qt_4_6, SinglePrecision, and version().

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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 897 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, d, DoublePrecision, floatingPointPrecision(), qbswap(), Qt_4_6, and version().

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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 796 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, i, and qbswap().

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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 826 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, i, and qbswap().

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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 855 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, i, qbswap(), and version().

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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 770 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, i, and qint8.

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 362 of file qdatastream.h.

References i.

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 365 of file qdatastream.h.

References i.

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 368 of file qdatastream.h.

References i.

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 359 of file qdatastream.h.

References i, and qint8.

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 129 of file qdatastream.h.

References ptr().

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readBytes()

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

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 quint32 length specifier first, then l bytes of data.

See also

readRawData(), writeBytes()

Definition at line 1028 of file qdatastream.cpp.

References blockSize, CHECK_STREAM_PRECOND, and qMin().

Referenced by operator>>().

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readRawData()

int QDataStream::readRawData	(	char *	s,
		int	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 1074 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND.

Referenced by operator>>(), QTlsPrivate::X509CertificateGeneric::parse(), parseTzHeader(), qExtractServerTime(), qNtlmDecodePhase2(), and QMainWindowLayoutState::restoreState().

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resetStatus()

void QDataStream::resetStatus

(

)

Resets the status of the data stream.

See also

Status, status(), setStatus()

Definition at line 434 of file qdatastream.cpp.

References Ok.

Referenced by startTransaction().

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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 670 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, CHECK_STREAM_TRANSACTION_PRECOND, QIODevice::commitTransaction(), Q_VOID, ReadPastEnd, QIODevice::rollbackTransaction(), setStatus(), and QDataStreamPrivate::transactionDepth.

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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 474 of file qdatastream.cpp.

References QSysInfo::BigEndian, BigEndian, QSysInfo::ByteOrder, and LittleEndian.

Referenced by qEncodeNtlmv2Response(), qExtractServerTime(), qNtlmDecodePhase2(), qNtlmPhase1(), qNtlmPhase3(), QSSGMesh::MeshInternal::readFileHeader(), QSSGMesh::MeshInternal::readMeshData(), QBmpHandler::write(), QSSGMesh::MeshInternal::writeFileHeader(), QSSGMesh::MeshInternal::writeMeshData(), and QSSGMesh::MeshInternal::writeMeshHeader().

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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 355 of file qdatastream.cpp.

References d.

Referenced by QPacket::QPacket(), and QPacket::QPacket().

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setFloatingPointPrecision()

void QDataStream::setFloatingPointPrecision

(

QDataStream::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 411 of file qdatastream.cpp.

References QDataStreamPrivate::floatingPointPrecision, and QScopedPointer< T, Cleanup >::reset().

Referenced by QSSGMesh::MeshInternal::readFileHeader(), QSSGMesh::MeshInternal::readMeshData(), QSSGMesh::MeshInternal::writeFileHeader(), QSSGMesh::MeshInternal::writeMeshData(), and QSSGMesh::MeshInternal::writeMeshHeader().

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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 447 of file qdatastream.cpp.

References Ok, and status().

Referenced by QUuid::operator>>(), rollbackTransaction(), and skipRawData().

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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 353 of file qdatastream.h.

Referenced by QPacket::QPacket(), QPacket::QPacket(), QQsbIODeviceCollection::addEntry(), QQsbIODeviceCollection::extractEntry(), QShader::fromSerialized(), QQsbInMemoryCollection::load(), QQsbCollection::readEndHeader(), QMainWindowLayoutState::restoreState(), QQsbInMemoryCollection::save(), QShader::serialized(), and QQsbCollection::writeEndHeader().

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skipRawData()

int QDataStream::skipRawData

(

int

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 1392 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, QIODevice::isTransactionStarted(), Ok, ReadPastEnd, setStatus(), and QIODevice::skip().

Referenced by qExtractServerTime().

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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 599 of file qdatastream.cpp.

References CHECK_STREAM_PRECOND, Q_VOID, QScopedPointer< T, Cleanup >::reset(), resetStatus(), QIODevice::startTransaction(), and QDataStreamPrivate::transactionDepth.

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status()

QDataStream::Status QDataStream::status

(

)

const

Returns the status of the data stream.

See also

Status, setStatus(), resetStatus()

Definition at line 424 of file qdatastream.cpp.

Referenced by QEvdevKeyboardHandler::loadKeymap(), parseTzAbbreviations(), parseTzHeader(), parseTzIndicators(), parseTzLeapSeconds(), parseTzPosixRule(), parseTzTransitions(), parseTzTypes(), and setStatus().

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version()

int QDataStream::version ( ) const

inline

Returns the version number of the data serialization format.

See also

setVersion(), Version

Definition at line 350 of file qdatastream.h.

Referenced by QPacket::QPacket(), QPacket::QPacket(), operator<<(), operator<<(), operator<<(), operator>>(), operator>>(), operator>>(), and QMainWindowLayoutState::restoreState().

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writeBytes()

QDataStream & QDataStream::writeBytes	(	const char *	s,
		uint	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, followed by len bytes from s. Note that the data is not encoded.

See also

writeRawData(), readBytes()

Definition at line 1354 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, and writeRawData().

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writeRawData()

int QDataStream::writeRawData	(	const char *	s,
		int	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 1372 of file qdatastream.cpp.

References CHECK_STREAM_WRITE_PRECOND, ret, QIODevice::write(), and WriteFailed.

Referenced by operator<<(), operator<<(), operator<<(), operator<<(), qEncodeNtlmv2Response(), qStreamNtlmBuffer(), and writeBytes().

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Friends And Related Symbol Documentation

operator<<() [1/2]

operator<< ( QDataStream &  ds, qfloat16  f  )

related

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 378 of file qfloat16.cpp.

operator<<() [2/2]

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

related

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 485 of file qdatastream.h.

operator>>() [1/2]

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

related

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 395 of file qfloat16.cpp.

operator>>() [2/2]

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

related

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 485 of file qdatastream.h.

QtPrivate::StreamStateSaver

friend class QtPrivate::StreamStateSaver

friend

Definition at line 189 of file qdatastream.h.

---

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

• qtbase/src/corelib/serialization/qdatastream.h
• qtbase/src/corelib/global/qfloat16.cpp
• qtbase/src/corelib/serialization/qdatastream.cpp