內容

公共類型
公共函數
詳細描述
版本化
讀寫原生二進製數據
讀寫 Qt 集閤類
讀寫其它 Qt 類
使用讀取事務

QDataStream 類

The QDataStream 類提供把二進製數據序列化到 QIODevice . 更多...

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

注意： 此類的所有函數可重入 .

公共類型

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_5_12 }

公共函數

	QDataStream ()
	QDataStream (QIODevice * d )
	QDataStream (QByteArray * a , QIODevice::OpenMode mode )
	QDataStream (const QByteArray & a )
	~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 )

詳細描述

The QDataStream 類提供把二進製數據序列化到 QIODevice .

數據流是 100% 獨立於主計算機操作係統、CPU 或字節序的二進製編碼信息流。例如：運行 Solaris 的 Sun SPARC 可以讀取由 Windows PC 寫入的數據流。

還可以使用數據流來讀取/寫入原生未編碼二進製數據。若想要 "剖析" 輸入流，見 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 。 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.

範例 (把二進製數據寫入流)：

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

範例 (讀取二進製數據從流)：

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 序列化 Qt 數據類型 .

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 '\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.

版本化

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.

讀寫原生二進製數據

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 * 使用 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 () 和 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.

讀寫 Qt 集閤類

The Qt container classes can also be serialized to a QDataStream 。這些包括 QList , QLinkedList , QVector , QSet , QHash ，和 QMap . The stream operators are declared as non-members of the classes.

讀寫其它 Qt 類

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 類：

    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 相關非成員 section of the class's documentation page.

使用讀取事務

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.

另請參閱 QTextStream and QVariant .

成員類型文檔編製

enum QDataStream:: ByteOrder

用於讀/寫數據的字節序。

常量	值	描述
`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 或更高版本。

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

常量	值	描述
`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.

另請參閱 setFloatingPointPrecision () 和 floatingPointPrecision ().

enum QDataStream:: Status

此枚舉描述數據流的當前狀態。

常量	值	描述
`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

此枚舉為數據序列化格式版本號，提供符號同義詞。

常量	值	描述
`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`	如同 Qt_4_6。
`QDataStream::Qt_4_8`	`Qt_4_7`	如同 Qt_4_6。
`QDataStream::Qt_4_9`	`Qt_4_8`	如同 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`	如同 Qt_5_6
`QDataStream::Qt_5_8`	`Qt_5_7`	如同 Qt_5_6
`QDataStream::Qt_5_9`	`Qt_5_8`	如同 Qt_5_6
`QDataStream::Qt_5_10`	`Qt_5_9`	如同 Qt_5_6
`QDataStream::Qt_5_11`	`Qt_5_10`	如同 Qt_5_6
`QDataStream::Qt_5_12`	`18`	Version 18 (Qt 5.12)

另請參閱 setVersion () 和 version ().

成員函數文檔編製

QDataStream:: QDataStream ()

構造沒有 I/O 設備的數據流。

另請參閱 setDevice ().

QDataStream:: QDataStream ( QIODevice * d )

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

另請參閱 setDevice () 和 device ().

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

Constructs a data stream that operates on a byte array, a 。 mode describes how the device is to be used.

另外，可以使用 QDataStream (const QByteArray &) if you just want to read from a byte array.

由於 QByteArray 不是 QIODevice 子類，內部 QBuffer 被創建以包裹字節數組。

QDataStream:: QDataStream (const QByteArray & a )

Constructs a read-only data stream that operates on byte array a 。使用 QDataStream ( QByteArray *, int) if you want to write to a byte array.

由於 QByteArray 不是 QIODevice 子類，內部 QBuffer 被創建以包裹字節數組。

QDataStream:: ~QDataStream ()

銷毀數據流。

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 ()

中止讀取事務。

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.

把數據流的狀態設為

常量	描述
`ReadCorruptData`	.

該函數在 Qt 5.7 引入。

另請參閱 startTransaction (), commitTransaction ()，和 rollbackTransaction ().

bool QDataStream:: atEnd () const

返迴 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 .

另請參閱 QIODevice::atEnd ().

QDataStream::ByteOrder QDataStream:: byteOrder () const

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

另請參閱 setByteOrder ().

bool QDataStream:: commitTransaction ()

完成讀取事務。返迴 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 ()，或 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.

該函數在 Qt 5.7 引入。

另請參閱 startTransaction (), rollbackTransaction ()，和 abortTransaction ().

QIODevice *QDataStream:: device () const

Returns the I/O device currently set, or 0 if no device is currently set.

另請參閱 setDevice ().

QDataStream::FloatingPointPrecision QDataStream:: floatingPointPrecision () const

返迴數據流的浮點精度。

該函數在 Qt 4.6 引入。

另請參閱 FloatingPointPrecision and setFloatingPointPrecision ().

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

讀取緩衝 s from the stream and returns a reference to the stream.

緩衝 s 的分配是使用 new [] 。銷毀它采用 delete [] 運算符。

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 a null pointer.

The serialization format is a quint32 length specifier first, then l bytes of data.

另請參閱 readRawData () 和 writeBytes ().

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

讀取最多 len bytes from the stream into s and returns the number of bytes read. If an error occurs, this function returns -1.

緩衝 s 必須預分配。數據 not 解碼。

另請參閱 readBytes (), QIODevice::read ()，和 writeRawData ().

void QDataStream:: resetStatus ()

重置數據流的狀態。

另請參閱 Status , status ()，和 setStatus ().

void QDataStream:: rollbackTransaction ()

恢復讀取事務。

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

常量	描述
`ReadPastEnd`	.

該函數在 Qt 5.7 引入。

另請參閱 startTransaction (), commitTransaction ()，和 abortTransaction ().

void QDataStream:: setByteOrder ( QDataStream::ByteOrder bo )

把序列化字節序設為 bo .

The bo 參數可以是 QDataStream::BigEndian or QDataStream::LittleEndian .

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

另請參閱 byteOrder ().

void QDataStream:: setDevice ( QIODevice * d )

void QDataStream::setDevice( QIODevice *d)

把 I/O 設備設為 d , which can be 0 to unset to current I/O device.

另請參閱 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.

默認為 DoublePrecision .

Note that this property does not affect the serialization or deserialization of qfloat16 實例。

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

該函數在 Qt 4.6 引入。

另請參閱 floatingPointPrecision ().

void QDataStream:: setStatus ( QDataStream::Status status )

把數據流的狀態設為 status 給定。

忽略後續 setStatus() 調用，直到 resetStatus () 被調用。

另請參閱 Status , status ()，和 resetStatus ().

void QDataStream:: setVersion ( int v )

Sets the version number of the data serialization format to v , a value of the Version 枚舉。

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 版本化 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);

另請參閱 version () 和 Version .

int QDataStream:: skipRawData ( int len )

跳過 len 字節從設備。返迴實際跳過字節數，或 -1 當齣錯時。

這相當於調用 readRawData () on a buffer of length len and ignoring the buffer.

該函數在 Qt 4.1 引入。

另請參閱 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 ()，或 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).

注意： 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.

該函數在 Qt 5.7 引入。

另請參閱 commitTransaction (), rollbackTransaction ()，和 abortTransaction ().

QDataStream::Status QDataStream:: status () const

返迴數據流的狀態。

另請參閱 Status , setStatus ()，和 resetStatus ().

int QDataStream:: version () const

Returns the version number of the data serialization format.

另請參閱 setVersion () 和 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 字節來自 s . Note that the data is not encoded.

另請參閱 writeRawData () 和 readBytes ().

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

寫入 len 字節來自 s to the stream. Returns the number of bytes actually written, or -1 on error. The data is not encoded.

另請參閱 writeBytes (), QIODevice::write ()，和 readRawData ().

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

寫入有符號字節 i ，到流並返迴流引用。

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

這是重載函數。

寫入無符號字節 i ，到流並返迴流引用。

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

這是重載函數。

Writes a signed 16-bit integer, i ，到流並返迴流引用。

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

這是重載函數。

Writes an unsigned 16-bit integer, i ，到流並返迴流引用。

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

這是重載函數。

Writes a signed 32-bit integer, i ，到流並返迴流引用。

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

這是重載函數。

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 )

這是重載函數。

Writes a signed 64-bit integer, i ，到流並返迴流引用。

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

這是重載函數。

Writes an unsigned 64-bit integer, i ，到流並返迴流引用。

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

這是重載函數。

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.

該函數在 Qt 5.9 引入。

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

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

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

這是重載函數。

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

該函數在 Qt 5.9 引入。

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

這是重載函數。

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

另請參閱 setFloatingPointPrecision ().

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

這是重載函數。

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

另請參閱 setFloatingPointPrecision ().

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

這是重載函數。

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

The string is serialized using writeBytes() .

另請參閱 writeBytes () 和 writeRawData ().

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

Reads a signed byte from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads an unsigned byte from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads a signed 16-bit integer from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads an unsigned 16-bit integer from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads a signed 32-bit integer from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads an unsigned 32-bit integer from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads a signed 64-bit integer from the stream into i ，並返迴流引用。

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

這是重載函數。

Reads an unsigned 64-bit integer from the stream, into i ，並返迴流引用。

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

這是重載函數。

模擬讀取 std::nullptr_t 從流進 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.

該函數在 Qt 5.9 引入。

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 )

這是重載函數。

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

該函數在 Qt 5.9 引入。

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

這是重載函數。

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

另請參閱 setFloatingPointPrecision ().

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

這是重載函數。

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

另請參閱 setFloatingPointPrecision ().

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

這是重載函數。

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

字符串的反序列化是使用 readBytes() .

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

另請參閱 readBytes () 和 readRawData ().