QDataStream Class

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

Header:	#include <QDataStream>
qmake:	QT += core

• List of all members, including inherited members
• Obsolete members

Note: All functions in this class are reentrant.

Public Types

enum	ByteOrder { BigEndian, LittleEndian }
enum	FloatingPointPrecision { SinglePrecision, DoublePrecision }
enum	Status { Ok, ReadPastEnd, ReadCorruptData, WriteFailed }
enum	Version { Qt_1_0, Qt_2_0, Qt_2_1, Qt_3_0, Qt_3_1, …, Qt_5_15 }

Public Functions

	QDataStream(const QByteArray &a)
	QDataStream(QByteArray *a, QIODevice::OpenMode mode)
	QDataStream(QIODevice *d)
	QDataStream()
	~QDataStream()
void	abortTransaction()
bool	atEnd() const
QDataStream::ByteOrder	byteOrder() const
bool	commitTransaction()
QIODevice *	device() const
QDataStream::FloatingPointPrecision	floatingPointPrecision() const
QDataStream &	readBytes(char *&s, uint &l)
int	readRawData(char *s, int len)
void	resetStatus()
void	rollbackTransaction()
void	setByteOrder(QDataStream::ByteOrder bo)
void	setDevice(QIODevice *d)
void	setFloatingPointPrecision(QDataStream::FloatingPointPrecision precision)
void	setStatus(QDataStream::Status status)
void	setVersion(int v)
int	skipRawData(int len)
void	startTransaction()
QDataStream::Status	status() const
int	version() const
QDataStream &	writeBytes(const char *s, uint len)
int	writeRawData(const char *s, int len)
QDataStream &	operator<<(qint8 i)
QDataStream &	operator<<(quint8 i)
QDataStream &	operator<<(qint16 i)
QDataStream &	operator<<(quint16 i)
QDataStream &	operator<<(qint32 i)
QDataStream &	operator<<(quint32 i)
QDataStream &	operator<<(qint64 i)
QDataStream &	operator<<(quint64 i)
QDataStream &	operator<<(std::nullptr_t ptr)
QDataStream &	operator<<(bool i)
QDataStream &	operator<<(qfloat16 f)
QDataStream &	operator<<(float f)
QDataStream &	operator<<(double f)
QDataStream &	operator<<(const char *s)
QDataStream &	operator>>(qint8 &i)
QDataStream &	operator>>(quint8 &i)
QDataStream &	operator>>(qint16 &i)
QDataStream &	operator>>(quint16 &i)
QDataStream &	operator>>(qint32 &i)
QDataStream &	operator>>(quint32 &i)
QDataStream &	operator>>(qint64 &i)
QDataStream &	operator>>(quint64 &i)
QDataStream &	operator>>(std::nullptr_t &ptr)
QDataStream &	operator>>(bool &i)
QDataStream &	operator>>(qfloat16 &f)
QDataStream &	operator>>(float &f)
QDataStream &	operator>>(double &f)
QDataStream &	operator>>(char *&s)

Detailed Description

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 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 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.

Versioning

QDataStream's binary format has evolved since Qt 1.0, and is likely to continue evolving to reflect changes done in Qt. When inputting or outputting complex types, it's very important to make sure that the same version of the stream (version()) is used for reading and writing. If you need both forward and backward compatibility, you can hardcode the version number in the application:

stream.setVersion(QDataStream::Qt_4_0);

If you are producing a new binary data format, such as a file format for documents created by your application, you could use a QDataStream to write the data in a portable format. Typically, you would write a brief header containing a magic string and a version number to give yourself room for future expansion. For example:

QFile file("file.xxx");
file.open(QIODevice::WriteOnly);
QDataStream out(&file);

// Write a header with a "magic number" and a version
out << (quint32)0xA0B0C0D0;
out << (qint32)123;

out.setVersion(QDataStream::Qt_4_0);

// Write the data
out << lots_of_interesting_data;

Then read it in with:

QFile file("file.xxx");
file.open(QIODevice::ReadOnly);
QDataStream in(&file);

// Read and check the header
quint32 magic;
in >> magic;
if (magic != 0xA0B0C0D0)
    return XXX_BAD_FILE_FORMAT;

// Read the version
qint32 version;
in >> version;
if (version < 100)
    return XXX_BAD_FILE_TOO_OLD;
if (version > 123)
    return XXX_BAD_FILE_TOO_NEW;

if (version <= 110)
    in.setVersion(QDataStream::Qt_3_2);
else
    in.setVersion(QDataStream::Qt_4_0);

// Read the data
in >> lots_of_interesting_data;
if (version >= 120)
    in >> data_new_in_XXX_version_1_2;
in >> other_interesting_data;

You can select which byte order to use when serializing data. The default setting is big endian (MSB first). Changing it to little endian breaks the portability (unless the reader also changes to little endian). We recommend keeping this setting unless you have special requirements.

Reading and Writing Raw Binary Data

You may wish to read/write your own raw binary data to/from the data stream directly. Data may be read from the stream into a preallocated char * using readRawData(). Similarly data can be written to the stream using writeRawData(). Note that any encoding/decoding of the data must be done by you.

A similar pair of functions is readBytes() and writeBytes(). These differ from their raw counterparts as follows: readBytes() reads a quint32 which is taken to be the length of the data to be read, then that number of bytes is read into the preallocated char *; writeBytes() writes a quint32 containing the length of the data, followed by the data. Note that any encoding/decoding of the data (apart from the length quint32) must be done by you.

Reading and Writing Qt Collection Classes

The Qt container classes can also be serialized to a QDataStream. These include QList, QLinkedList, QVector, QSet, QHash, and QMap. The stream operators are declared as non-members of the classes.

Reading and Writing Other Qt Classes

In addition to the overloaded stream operators documented here, any Qt classes that you might want to serialize to a QDataStream will have appropriate stream operators declared as non-member of the class:

    QDataStream &operator<<(QDataStream &, const QXxx &);
    QDataStream &operator>>(QDataStream &, QXxx &);

For example, here are the stream operators declared as non-members of the QImage class:

    QDataStream & operator<< (QDataStream& stream, const QImage& image);
    QDataStream & operator>> (QDataStream& stream, QImage& image);

To see if your favorite Qt class has similar stream operators defined, check the Related Non-Members section of the class's documentation page.

Using Read Transactions

When a data stream operates on an asynchronous device, the chunks of data can arrive at arbitrary points in time. The QDataStream class implements a transaction mechanism that provides the ability to read the data atomically with a series of stream operators. As an example, you can handle incomplete reads from a socket by using a transaction in a slot connected to the readyRead() signal:

in.startTransaction();
QString str;
qint32 a;
in >> str >> a; // try to read packet atomically

if (!in.commitTransaction())
    return;     // wait for more data

If no full packet is received, this code restores the stream to the initial position, after which you need to wait for more data to arrive.

See also QTextStream and QVariant.

Member Type Documentation

enum QDataStream::ByteOrder

The byte order used for reading/writing the data.

Constant	Value	Description
QDataStream::BigEndian	QSysInfo::BigEndian	Most significant byte first (the default)
QDataStream::LittleEndian	QSysInfo::LittleEndian	Least significant byte first

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.

Constant	Value	Description
QDataStream::SinglePrecision	0	All floating point numbers in the data stream have 32-bit precision.
QDataStream::DoublePrecision	1	All floating point numbers in the data stream have 64-bit precision.

See also setFloatingPointPrecision() and floatingPointPrecision().

enum QDataStream::Status

This enum describes the current status of the data stream.

Constant	Value	Description
QDataStream::Ok	0	The data stream is operating normally.
QDataStream::ReadPastEnd	1	The data stream has read past the end of the data in the underlying device.
QDataStream::ReadCorruptData	2	The data stream has read corrupt data.
QDataStream::WriteFailed	3	The data stream cannot write to the underlying device.

enum QDataStream::Version

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

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

See also setVersion() and version().

Member Function Documentation

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.

QDataStream::QDataStream(QByteArray *a, QIODevice::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.

QDataStream::QDataStream(QIODevice *d)

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

See also setDevice() and device().

QDataStream::QDataStream()

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

See also setDevice().

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.

void QDataStream::abortTransaction()

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

Constant	Description
ReadCorruptData	.

This function was introduced in Qt 5.7.

See also startTransaction(), commitTransaction(), and rollbackTransaction().

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().

QDataStream::ByteOrder QDataStream::byteOrder() const

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

See also setByteOrder().

bool QDataStream::commitTransaction()

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.

This function was introduced in Qt 5.7.

See also startTransaction(), rollbackTransaction(), and abortTransaction().

QIODevice *QDataStream::device() const

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

See also setDevice().

QDataStream::FloatingPointPrecision QDataStream::floatingPointPrecision() const

Returns the floating point precision of the data stream.

This function was introduced in Qt 4.6.

See also FloatingPointPrecision and setFloatingPointPrecision().

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() and writeBytes().

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(), and writeRawData().

void QDataStream::resetStatus()

Resets the status of the data stream.

See also Status, status(), and setStatus().

void QDataStream::rollbackTransaction()

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

Constant	Description
ReadPastEnd	.

This function was introduced in Qt 5.7.

See also startTransaction(), commitTransaction(), and abortTransaction().

void QDataStream::setByteOrder(QDataStream::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().

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().

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.

This function was introduced in Qt 4.6.

See also floatingPointPrecision().

void QDataStream::setStatus(QDataStream::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(), and resetStatus().

void QDataStream::setVersion(int v)

Sets the version number of the data serialization format to v, a value of the 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 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 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() and Version.

int QDataStream::skipRawData(int len)

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.

This function was introduced in Qt 4.1.

See also QIODevice::seek().

void QDataStream::startTransaction()

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.

This function was introduced in Qt 5.7.

See also commitTransaction(), rollbackTransaction(), and abortTransaction().

QDataStream::Status QDataStream::status() const

Returns the status of the data stream.

See also Status, setStatus(), and resetStatus().

int QDataStream::version() const

Returns the version number of the data serialization format.

See also setVersion() and Version.

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() and readBytes().

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(), and readRawData().

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

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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.

This function was introduced in Qt 5.9.

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

Writes a boolean value, i, to the stream. Returns a reference to the stream.

QDataStream &QDataStream::operator<<(qfloat16 f)

This is an overloaded function.

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

This function was introduced in Qt 5.9.

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

This is an overloaded function.

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

See also setFloatingPointPrecision().

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

This is an overloaded function.

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

See also setFloatingPointPrecision().

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

This is an overloaded function.

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() and writeRawData().

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

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

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

This is an overloaded function.

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

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

This is an overloaded function.

Reads a signed 16-bit integer from the stream into i, and returns a reference to the stream.

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

This is an overloaded function.

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

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

This is an overloaded function.

Reads a signed 32-bit integer from the stream into i, and returns a reference to the stream.

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

This is an overloaded function.

Reads an unsigned 32-bit integer from the stream into i, and returns a reference to the stream.

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

This is an overloaded function.

Reads a signed 64-bit integer from the stream into i, and returns a reference to the stream.

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

This is an overloaded function.

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

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

This is an overloaded function.

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.

This function was introduced in Qt 5.9.

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

Reads a boolean value from the stream into i. Returns a reference to the stream.

QDataStream &QDataStream::operator>>(qfloat16 &f)

This is an overloaded function.

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

This function was introduced in Qt 5.9.

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

This is an overloaded function.

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().

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

This is an overloaded function.

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().

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

This is an overloaded function.

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() and readRawData().