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

#include <qdatastream.h>

Tipos públicos
enum	ByteOrder { BigEndian, LittleEndian, BigEndian, LittleEndian }
enum	ByteOrder { BigEndian, LittleEndian, BigEndian, LittleEndian }
Métodos públicos
	QDataStream ()
	QDataStream (QIODevice *)
	QDataStream (QByteArray, int mode)
virtual	~QDataStream ()
QIODevice *	device () const
void	setDevice (QIODevice *)
void	unsetDevice ()
bool	atEnd () const
bool	eof () const
int	byteOrder () const
void	setByteOrder (int)
bool	isPrintableData () const
void	setPrintableData (bool)
int	version () const
void	setVersion (int)
QDataStream &	operator>> (Q_INT8 &i)
QDataStream &	operator>> (Q_UINT8 &i)
QDataStream &	operator>> (Q_INT16 &i)
QDataStream &	operator>> (Q_UINT16 &i)
QDataStream &	operator>> (Q_INT32 &i)
QDataStream &	operator>> (Q_UINT32 &i)
QDataStream &	operator>> (Q_INT64 &i)
QDataStream &	operator>> (Q_UINT64 &i)
QDataStream &	operator>> (Q_LONG &i)
QDataStream &	operator>> (Q_ULONG &i)
QDataStream &	operator>> (float &f)
QDataStream &	operator>> (double &f)
QDataStream &	operator>> (char *&str)
QDataStream &	operator<< (Q_INT8 i)
QDataStream &	operator<< (Q_UINT8 i)
QDataStream &	operator<< (Q_INT16 i)
QDataStream &	operator<< (Q_UINT16 i)
QDataStream &	operator<< (Q_INT32 i)
QDataStream &	operator<< (Q_UINT32 i)
QDataStream &	operator<< (Q_INT64 i)
QDataStream &	operator<< (Q_UINT64 i)
QDataStream &	operator<< (Q_LONG i)
QDataStream &	operator<< (Q_ULONG i)
QDataStream &	operator<< (float f)
QDataStream &	operator<< (double f)
QDataStream &	operator<< (const char *str)
QDataStream &	readBytes (char *&, uint &len)
QDataStream &	readRawBytes (char *, uint len)
QDataStream &	writeBytes (const char *, uint len)
QDataStream &	writeRawBytes (const char *, uint len)
	QDataStream ()
	QDataStream (QIODevice *)
	QDataStream (QByteArray, int mode)
virtual	~QDataStream ()
QIODevice *	device () const
void	setDevice (QIODevice *)
void	unsetDevice ()
bool	atEnd () const
bool	eof () const
int	byteOrder () const
void	setByteOrder (int)
bool	isPrintableData () const
void	setPrintableData (bool)
int	version () const
void	setVersion (int)
QDataStream &	operator>> (Q_INT8 &i)
QDataStream &	operator>> (Q_UINT8 &i)
QDataStream &	operator>> (Q_INT16 &i)
QDataStream &	operator>> (Q_UINT16 &i)
QDataStream &	operator>> (Q_INT32 &i)
QDataStream &	operator>> (Q_UINT32 &i)
QDataStream &	operator>> (Q_INT64 &i)
QDataStream &	operator>> (Q_UINT64 &i)
QDataStream &	operator>> (Q_LONG &i)
QDataStream &	operator>> (Q_ULONG &i)
QDataStream &	operator>> (float &f)
QDataStream &	operator>> (double &f)
QDataStream &	operator>> (char *&str)
QDataStream &	operator<< (Q_INT8 i)
QDataStream &	operator<< (Q_UINT8 i)
QDataStream &	operator<< (Q_INT16 i)
QDataStream &	operator<< (Q_UINT16 i)
QDataStream &	operator<< (Q_INT32 i)
QDataStream &	operator<< (Q_UINT32 i)
QDataStream &	operator<< (Q_INT64 i)
QDataStream &	operator<< (Q_UINT64 i)
QDataStream &	operator<< (Q_LONG i)
QDataStream &	operator<< (Q_ULONG i)
QDataStream &	operator<< (float f)
QDataStream &	operator<< (double f)
QDataStream &	operator<< (const char *str)
QDataStream &	readBytes (char *&, uint &len)
QDataStream &	readRawBytes (char *, uint len)
QDataStream &	writeBytes (const char *, uint len)
QDataStream &	writeRawBytes (const char *, uint len)

Descripción detallada

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 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 IO device.

Example (write binary data to a stream):

    QFile file( "file.dat" );
    file.open( IO_WriteOnly );
    QDataStream stream( &file ); // we will serialize the data into the file
    stream << "the answer is";   // serialize a string
    stream << (Q_INT32)42;       // serialize an integer

Example (read binary data from a stream):

    QFile file( "file.dat" );
    file.open( IO_ReadOnly );
    QDataStream stream( &file );  // read the data serialized from the file
    QString str;
    Q_INT32 a;
    stream >> 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 the Format of the QDataStream operators .

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.

To take one example, a char* string is written as a 32-bit integer equal to the length of the string including the NUL byte ('\0'), followed by all the characters of the string including the NUL 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 NUL are read.

The initial IODevice 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 IODevice set) atEnd() will return TRUE.

If you want the data to be compatible with an earlier version of Qt use setVersion().

If you want the data to be human-readable, e.g. for debugging, you can set the data stream into printable data mode with setPrintableData(). The data is then written slower, in a bloated but human readable format.

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( IO_WriteOnly );
    QDataStream stream( &file );

    // Write a header with a "magic number" and a version
    stream << (Q_UINT32)0xA0B0C0D0;
    stream << (Q_INT32)123;

    // Write the data
    stream << [lots of interesting data]

Then read it in with:

    QFile file( "file.xxx" );
    file.open( IO_ReadOnly );
    QDataStream stream( &file );

    // Read and check the header
    Q_UINT32 magic;
    stream >> magic;
    if ( magic != 0xA0B0C0D0 )
        return XXX_BAD_FILE_FORMAT;

    // Read the version
    Q_INT32 version;
    stream >> version;
    if ( version < 100 )
        return XXX_BAD_FILE_TOO_OLD;
    if ( version > 123 )
        return XXX_BAD_FILE_TOO_NEW;
    if ( version <= 110 )
        stream.setVersion(1);

    // Read the data
    stream >> [lots of interesting data];
    if ( version > 120 )
        stream >> [data new in XXX version 1.2];
    stream >> [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.

raw

Documentación de las enumeraciones miembro de la clase

enum QDataStream::ByteOrder

The byte order used for reading/writing the data.

BigEndian the default LittleEndian

Valores de enumeraciones:

BigEndian
LittleEndian
BigEndian
LittleEndian

enum QDataStream::ByteOrder

Valores de enumeraciones:

BigEndian
LittleEndian
BigEndian
LittleEndian

Documentación del constructor y destructor

QDataStream::QDataStream ( )

Constructs a data stream that has no IO device.

Ver también:: setDevice()

QDataStream::QDataStream ( QIODevice * d )

Constructs a data stream that uses the IO device d.

Atención:: If you use QSocket or QSocketDevice as the IO device d for reading data, you must make sure that enough data is available on the socket for the operation to successfully proceed; QDataStream does not have any means to handle or recover from short-reads.

Ver también:: setDevice(), device()

QDataStream::QDataStream	(	QByteArray	a,
		int	mode
	)

Constructs a data stream that operates on a byte array, a, through an internal QBuffer device. The mode is a QIODevice::mode(), usually either IO_ReadOnly or IO_WriteOnly.

Example:

    static char bindata[] = { 231, 1, 44, ... };
    QByteArray a;
    a.setRawData( bindata, sizeof(bindata) );   // a points to bindata
    QDataStream stream( a, IO_ReadOnly );       // open on a's data
    stream >> [something];                      // read raw bindata
    a.resetRawData( bindata, sizeof(bindata) ); // finished

The QByteArray::setRawData() function is not for the inexperienced.

QDataStream::~QDataStream ( ) [virtual]

Destroys the data stream.

The destructor will not affect the current IO device, unless it is an internal IO device processing a QByteArray passed in the constructor, in which case the internal IO device is destroyed.

QDataStream::QDataStream ( )

QDataStream::QDataStream ( QIODevice * )

QDataStream::QDataStream	(	QByteArray	,
		int	mode
	)

virtual QDataStream::~QDataStream ( ) [virtual]

Documentación de las funciones miembro

bool QDataStream::atEnd ( ) const [inline]

Returns TRUE if the IO device has reached the end position (end of the stream or file) or if there is no IO device set; otherwise returns FALSE, i.e. if the current position of the IO device is before the end position.

Ver también:: QIODevice::atEnd()

bool QDataStream::atEnd ( ) const

int QDataStream::byteOrder ( ) const

int QDataStream::byteOrder ( ) const [inline]

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

Ver también:: setByteOrder()

QIODevice * QDataStream::device ( ) const [inline]

Returns the IO device currently set.

Ver también:: setDevice(), unsetDevice()

QIODevice* QDataStream::device ( ) const

bool QDataStream::eof ( ) const [inline]

Returns TRUE if the IO device has reached the end position (end of stream or file) or if there is no IO device set.

Returns FALSE if the current position of the read/write head of the IO device is somewhere before the end position.

Ver también:: QIODevice::atEnd()

bool QDataStream::eof ( ) const

bool QDataStream::isPrintableData ( ) const [inline]

Returns TRUE if the printable data flag has been set; otherwise returns FALSE.

Ver también:: setPrintableData()

bool QDataStream::isPrintableData ( ) const

QDataStream& QDataStream::operator<< ( Q_UINT64 i )

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

QDataStream& QDataStream::operator<< ( Q_UINT32 i )

QDataStream& QDataStream::operator<< ( Q_INT32 i )

QDataStream& QDataStream::operator<< ( Q_UINT16 i )

QDataStream & QDataStream::operator<< ( Q_UINT64 i ) [inline]

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes a signed integer i, of the system's word length, to the stream and returns a reference to the stream.

QDataStream& QDataStream::operator<< ( Q_INT8 i )

QDataStream& QDataStream::operator<< ( Q_UINT8 i )

QDataStream & QDataStream::operator<< ( Q_ULONG i ) [inline]

QDataStream& QDataStream::operator<< ( Q_INT16 i )

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes a 32-bit floating point number, f, to the stream using the standard IEEE754 format. Returns a reference to the stream.

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes a 64-bit floating point number, f, to the stream using the standard IEEE754 format. Returns a reference to the stream.

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes the '\0'-terminated string s to the stream and returns a reference to the stream.

The string is serialized using writeBytes().

QDataStream& QDataStream::operator<< ( Q_INT64 i )

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

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

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

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

QDataStream & QDataStream::operator<< ( Q_INT8 i )

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

QDataStream & QDataStream::operator<< ( Q_UINT8 i ) [inline]

QDataStream & QDataStream::operator<< ( Q_INT16 i )

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes a signed 16-bit integer, i, to the stream and returns a reference to the stream.

QDataStream & QDataStream::operator<< ( Q_UINT16 i ) [inline]

QDataStream & QDataStream::operator<< ( Q_INT32 i )

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes a signed 32-bit integer, i, to the stream and returns a reference to the stream.

QDataStream & QDataStream::operator<< ( Q_UINT32 i ) [inline]

QDataStream & QDataStream::operator<< ( Q_INT64 i )

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Writes a signed 64-bit integer, i, to the stream and returns a reference to the stream.

QDataStream& QDataStream::operator>> ( Q_INT16 & i )

QDataStream & QDataStream::operator>> ( Q_UINT32 & i ) [inline]

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

QDataStream & QDataStream::operator>> ( Q_INT32 & i )

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads a signed 32-bit integer from the stream into i, and returns a reference to the stream.

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

QDataStream& QDataStream::operator>> ( Q_INT32 & i )

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

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

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

QDataStream& QDataStream::operator>> ( Q_UINT32 & i )

QDataStream& QDataStream::operator>> ( Q_UINT64 & i )

QDataStream& QDataStream::operator>> ( Q_INT64 & i )

QDataStream & QDataStream::operator>> ( Q_UINT64 & i ) [inline]

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads a signed integer of the system's word length from the stream into i, and returns a reference to the stream.

QDataStream & QDataStream::operator>> ( Q_ULONG & i ) [inline]

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads a 32-bit floating point number from the stream into f, using the standard IEEE754 format. Returns a reference to the stream.

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads a 64-bit floating point number from the stream into f, using the standard IEEE754 format. Returns a reference to the stream.

QDataStream& QDataStream::operator>> ( Q_INT8 & i )

QDataStream & QDataStream::operator>> ( Q_INT8 & i )

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

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

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads the '\0'-terminated string s from the stream and returns a reference to the stream.

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

QDataStream& QDataStream::operator>> ( Q_UINT8 & i )

QDataStream & QDataStream::operator>> ( Q_UINT8 & i ) [inline]

QDataStream & QDataStream::operator>> ( Q_INT64 & i )

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads a signed 64-bit integer from the stream into i, and returns a reference to the stream.

QDataStream& QDataStream::operator>> ( Q_UINT16 & i )

QDataStream & QDataStream::operator>> ( Q_INT16 & i )

Esta es una función miembro sobrecargada que se suministra por conveniencia. Difiere de la anterior función solamente en los argumentos que acepta. Reads a signed 16-bit integer from the stream into i, and returns a reference to the stream.

QDataStream & QDataStream::operator>> ( Q_UINT16 & i ) [inline]

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. If the length is zero or s cannot be allocated, s is set to 0.

The l parameter will be set to the length of the buffer.

The serialization format is a Q_UINT32 length specifier first, then l bytes of data. Note that the data is not encoded.

Ver también:: readRawBytes(), writeBytes()

QDataStream& QDataStream::readBytes	(	char *&	,
		uint &	len
	)

QDataStream& QDataStream::readRawBytes	(	char *	,
		uint	len
	)

QDataStream & QDataStream::readRawBytes	(	char *	s,
		uint	len
	)

Reads len bytes from the stream into s and returns a reference to the stream.

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

Ver también:: readBytes(), QIODevice::readBlock(), writeRawBytes()

void QDataStream::setByteOrder ( int 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.

Ver también:: byteOrder()

void QDataStream::setByteOrder ( int )

void QDataStream::setDevice ( QIODevice * d )

void QDataStream::setDevice(QIODevice *d )

Sets the IO device to d.

Ver también:: device(), unsetDevice()

void QDataStream::setDevice ( QIODevice * )

void QDataStream::setPrintableData ( bool enable ) [inline]

If enable is TRUE, data will be output in a human readable format. If enable is FALSE, data will be output in a binary format.

If enable is TRUE, the write functions will generate output that consists of printable characters (7 bit ASCII). This output will typically be a lot larger than the default binary output, and consequently slower to write.

We recommend only enabling printable data for debugging purposes.

void QDataStream::setPrintableData ( bool )

void QDataStream::setVersion ( int v ) [inline]

Sets the version number of the data serialization format to v.

You don't need to set a version if you are using the current version of Qt.

In order 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 of QDataStream.

Qt Version QDataStream Version Qt 3.3 6 Qt 3.2 5 Qt 3.1 5 Qt 3.0 4 Qt 2.1.x and Qt 2.2.x 3 Qt 2.0.x 2 Qt 1.x 1

Ver también:: version()

void QDataStream::setVersion ( int )

void QDataStream::unsetDevice ( )

Unsets the IO device. This is the same as calling setDevice( 0 ).

Ver también:: device(), setDevice()

int QDataStream::version ( ) const

int QDataStream::version ( ) const [inline]

Returns the version number of the data serialization format. In Qt 3.1, this number is 5.

Ver también:: setVersion()

QDataStream& QDataStream::writeBytes	(	const char *	,
		uint	len
	)

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 Q_UINT32, followed by len bytes from s. Note that the data is not encoded.

Ver también:: writeRawBytes(), readBytes()

QDataStream& QDataStream::writeRawBytes	(	const char *	,
		uint	len
	)

QDataStream & QDataStream::writeRawBytes	(	const char *	s,
		uint	len
	)

Writes len bytes from s to the stream and returns a reference to the stream. The data is not encoded.

Ver también:: writeBytes(), QIODevice::writeBlock(), readRawBytes()

La documentación para esta clase fue generada a partir de los siguientes ficheros:

src/qt/include/qdatastream.h
src/qt/src/tools/qdatastream.h
src/qt/src/tools/qdatastream.cpp

Tipos públicos

Métodos públicos

Descripción detallada

Documentación de las enumeraciones miembro de la clase

Documentación del constructor y destructor

Documentación de las funciones miembro