The QDataStream class provides serialization of binary data to a QIODevice. More...
#include <qdatastream.h>
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_DefaultCompiledVersion = Qt_6_3 } |
| enum | ByteOrder { BigEndian = QSysInfo::BigEndian , LittleEndian = QSysInfo::LittleEndian } |
| enum | Status { Ok , ReadPastEnd , ReadCorruptData , WriteFailed } |
| enum | FloatingPointPrecision { SinglePrecision , DoublePrecision } |
 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 } |
Friends | |
| class | QtPrivate::StreamStateSaver |
Related Functions | |
(Note that these are not member functions.) | |
| 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
The QDataStream class provides serialization of binary data to a QIODevice.
\inmodule QtCore \reentrant
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):
Example (read binary data from a stream):
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 65 of file qdatastream.h.
Member Enumeration Documentation
◆ 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 111 of file qdatastream.h.
◆ 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.
| Enumerator | |
|---|---|
| SinglePrecision | |
| DoublePrecision | |
Definition at line 123 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 116 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 \omitvalue Qt_DefaultCompiledVersion
- See also
- setVersion(), version()
Definition at line 68 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 278 of file qdatastream.cpp.
◆ QDataStream() [2/4]
|
explicit |
Constructs a data stream that uses the I/O device d.
- See also
- setDevice(), device()
Definition at line 294 of file qdatastream.cpp.
◆ QDataStream() [3/4]
| QDataStream::QDataStream | ( | QByteArray * | a, |
| OpenMode | mode | ||
| ) |
Constructs a data stream that operates on a byte array, a. The mode describes how the device is to be used.
Alternatively, you can use QDataStream(const QByteArray &) if you just want to read from a byte array.
Since QByteArray is not a QIODevice subclass, internally a QBuffer is created to wrap the byte array.
Definition at line 317 of file qdatastream.cpp.
◆ QDataStream() [4/4]
| QDataStream::QDataStream | ( | const QByteArray & | a | ) |
Constructs a read-only data stream that operates on byte array a. Use QDataStream(QByteArray*, int) if you want to write to a byte array.
Since QByteArray is not a QIODevice subclass, internally a QBuffer is created to wrap the byte array.
Definition at line 340 of file qdatastream.cpp.
◆ ~QDataStream()
| QDataStream::~QDataStream | ( | ) |
Destroys the data stream.
The destructor will not affect the current I/O device, unless it is an internal I/O device (e.g. a QBuffer) processing a QByteArray passed in the constructor, in which case the internal I/O device is destroyed.
Definition at line 365 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.
Definition at line 737 of file qdatastream.cpp.
◆ atEnd()
| bool QDataStream::atEnd | ( | ) | const |
Returns true if the I/O device has reached the end position (end of the stream or file) or if there is no I/O device set; otherwise returns false.
- See also
- QIODevice::atEnd()
Definition at line 409 of file qdatastream.cpp.
◆ byteOrder()
|
inline |
Returns the current byte order setting – either BigEndian or LittleEndian.
- See also
- setByteOrder()
Definition at line 379 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.
Definition at line 663 of file qdatastream.cpp.
◆ device()
|
inline |
Returns the I/O device currently set, or \nullptr if no device is currently set.
- See also
- setDevice()
Definition at line 376 of file qdatastream.h.
◆ floatingPointPrecision()
| QDataStream::FloatingPointPrecision QDataStream::floatingPointPrecision | ( | ) | const |
Returns the floating point precision of the data stream.
- Since
- 4.6
Definition at line 421 of file qdatastream.cpp.
◆ isDeviceTransactionStarted()
| bool QDataStream::isDeviceTransactionStarted | ( | ) | const |
◆ 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 1247 of file qdatastream.cpp.
◆ operator<<() [2/16]
|
inline |
Definition at line 403 of file qdatastream.h.
◆ 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 1358 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 1370 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 1339 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.
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 1302 of file qdatastream.cpp.
◆ operator<<() [7/16]
| QDataStream & QDataStream::operator<< | ( | float | f | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
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 1264 of file qdatastream.cpp.
◆ operator<<() [8/16]
| QDataStream & QDataStream::operator<< | ( | qint16 | i | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Writes a signed 16-bit integer, i, to the stream and returns a reference to the stream.
Definition at line 1173 of file qdatastream.cpp.
◆ operator<<() [9/16]
| QDataStream & QDataStream::operator<< | ( | qint32 | i | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Writes a signed 32-bit integer, i, to the stream and returns a reference to the stream.
Definition at line 1191 of file qdatastream.cpp.
◆ operator<<() [10/16]
| QDataStream & QDataStream::operator<< | ( | qint64 | i | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Writes a signed 64-bit integer, i, to the stream and returns a reference to the stream.
Definition at line 1217 of file qdatastream.cpp.
◆ 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 1149 of file qdatastream.cpp.
◆ operator<<() [12/16]
|
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 409 of file qdatastream.h.
◆ operator<<() [13/16]
|
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 412 of file qdatastream.h.
◆ operator<<() [14/16]
|
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 415 of file qdatastream.h.
◆ operator<<() [15/16]
|
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 406 of file qdatastream.h.
◆ operator<<() [16/16]
|
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 182 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 910 of file qdatastream.cpp.
◆ operator>>() [2/16]
|
inline |
Definition at line 388 of file qdatastream.h.
◆ operator>>() [3/16]
| QDataStream & QDataStream::operator>> | ( | char *& | s | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Reads 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 1007 of file qdatastream.cpp.
◆ operator>>() [4/16]
| QDataStream & QDataStream::operator>> | ( | char16_t & | c | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
- Since
- 6.0
Reads a 16bit wide char from the stream into c and returns a reference to the stream.
Definition at line 1020 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 1035 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 965 of file qdatastream.cpp.
◆ operator>>() [7/16]
| QDataStream & QDataStream::operator>> | ( | float & | f | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Reads a floating point number from the stream into f, using the standard IEEE 754 format. Returns a reference to the stream.
- See also
- setFloatingPointPrecision()
Definition at line 928 of file qdatastream.cpp.
◆ operator>>() [8/16]
| QDataStream & QDataStream::operator>> | ( | qint16 & | i | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Reads a signed 16-bit integer from the stream into i, and returns a reference to the stream.
Definition at line 827 of file qdatastream.cpp.
◆ operator>>() [9/16]
| QDataStream & QDataStream::operator>> | ( | qint32 & | i | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Reads a signed 32-bit integer from the stream into i, and returns a reference to the stream.
Definition at line 857 of file qdatastream.cpp.
◆ operator>>() [10/16]
| QDataStream & QDataStream::operator>> | ( | qint64 & | i | ) |
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Reads a signed 64-bit integer from the stream into i, and returns a reference to the stream.
Definition at line 886 of file qdatastream.cpp.
◆ operator>>() [11/16]
| QDataStream & QDataStream::operator>> | ( | qint8 & | i | ) |
Reads a signed byte from the stream into i, and returns a reference to the stream.
Definition at line 801 of file qdatastream.cpp.
◆ operator>>() [12/16]
|
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 394 of file qdatastream.h.
◆ operator>>() [13/16]
|
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 397 of file qdatastream.h.
◆ operator>>() [14/16]
|
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 400 of file qdatastream.h.
◆ operator>>() [15/16]
|
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 391 of file qdatastream.h.
◆ operator>>() [16/16]
|
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 161 of file qdatastream.h.
◆ 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 1059 of file qdatastream.cpp.
◆ 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 1105 of file qdatastream.cpp.
◆ resetStatus()
| void QDataStream::resetStatus | ( | ) |
Resets the status of the data stream.
- See also
- Status, status(), setStatus()
Definition at line 469 of file qdatastream.cpp.
◆ rollbackTransaction()
| void QDataStream::rollbackTransaction | ( | ) |
- Since
- 5.7
Reverts a read transaction.
This function is commonly used to rollback the transaction when an incomplete read was detected prior to committing the transaction.
If called on an inner transaction, reverting is delegated to the outermost transaction, and subsequently started inner transactions are forced to fail.
For the outermost transaction, restores the stream data to the point of the startTransaction() call. If the data stream has read corrupt data or any of the inner transactions was aborted, this function aborts the transaction.
If the preceding stream operations were successful, sets the status of the data stream to \value ReadPastEnd.
Definition at line 701 of file qdatastream.cpp.
◆ setByteOrder()
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 509 of file qdatastream.cpp.
◆ setDevice()
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 390 of file qdatastream.cpp.
◆ 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 446 of file qdatastream.cpp.
◆ setStatus()
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 482 of file qdatastream.cpp.
◆ setVersion()
|
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:
Definition at line 385 of file qdatastream.h.
◆ 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 1423 of file qdatastream.cpp.
◆ startTransaction()
| void QDataStream::startTransaction | ( | ) |
- Since
- 5.7
Starts a new read transaction on the stream.
Defines a restorable point within the sequence of read operations. For sequential devices, read data will be duplicated internally to allow recovery in case of incomplete reads. For random-access devices, this function saves the current position of the stream. Call commitTransaction(), rollbackTransaction(), or abortTransaction() to finish the current transaction.
Once a transaction is started, subsequent calls to this function will make the transaction recursive. Inner transactions act as agents of the outermost transaction (i.e., report the status of read operations to the outermost transaction, which can restore the position of the stream).
- Note
- Restoring to the point of the nested startTransaction() call is not supported.
When an error occurs during a transaction (including an inner transaction failing), reading from the data stream is suspended (all subsequent read operations return empty/zero values) and subsequent inner transactions are forced to fail. Starting a new outermost transaction recovers from this state. This behavior makes it unnecessary to error-check every read operation separately.
Definition at line 630 of file qdatastream.cpp.
◆ status()
| QDataStream::Status QDataStream::status | ( | ) | const |
Returns the status of the data stream.
- See also
- Status, setStatus(), resetStatus()
Definition at line 459 of file qdatastream.cpp.
◆ version()
|
inline |
Returns the version number of the data serialization format.
- See also
- setVersion(), Version
Definition at line 382 of file qdatastream.h.
◆ 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 1385 of file qdatastream.cpp.
◆ 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 1403 of file qdatastream.cpp.
Friends And Related Function Documentation
◆ operator<<() [1/2]
|
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 327 of file qfloat16.cpp.
◆ operator<<() [2/2]
|
related |
- Since
- 6.0
Writes the pair pair to stream out.
This function requires the T1 and T2 types to implement operator<<().
Definition at line 517 of file qdatastream.h.
◆ operator>>() [1/2]
|
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 344 of file qfloat16.cpp.
◆ operator>>() [2/2]
|
related |
- Since
- 6.0
Reads a pair from stream in into pair.
This function requires the T1 and T2 types to implement operator>>().
Definition at line 517 of file qdatastream.h.
◆ QtPrivate::StreamStateSaver
|
friend |
Definition at line 221 of file qdatastream.h.
The documentation for this class was generated from the following files:
- src/corelib/serialization/qdatastream.h
- src/corelib/global/qfloat16.cpp
- src/corelib/serialization/qdatastream.cpp
