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QDataStream 类

The QDataStream 类提供把二进制数据序列化到 QIODevice . 更多...

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

注意： 此类的所有函数 可重入 .

公共类型

enum ByteOrder { BigEndian, LittleEndian }
enum FloatingPointPrecision { SinglePrecision, DoublePrecision }
enum Status { Ok, ReadPastEnd, ReadCorruptData, WriteFailed }
enum 版本 { Qt_1_0, Qt_2_0, Qt_2_1, Qt_3_0, ..., Qt_5_12 }

公共函数

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 )

详细描述

The QDataStream 类提供把二进制数据序列化到 QIODevice .

数据流是 100% 独立于主计算机操作系统、CPU 或字节序的二进制编码信息流。例如：运行 Solaris 的 Sun SPARC 可以读取由 Windows PC 写入的数据流。

还可以使用数据流来读取/写入 原生未编码二进制数据 。若想要 "剖析" 输入流，见 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.

范例 (把二进制数据写入流)： 

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

范例 (读取二进制数据从流)： 

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 数据类型 .

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.

读写原生二进制数据

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.

读写 Qt 集合类

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

读写其它 Qt 类

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 类： 

    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 相关非成员 section of the class's documentation page.

使用读取事务

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.

另请参阅 QTextStream and QVariant .

成员类型文档编制

enum QDataStream:: ByteOrder

用于读/写数据的字节序。

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 or higher.

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.

另请参阅 setFloatingPointPrecision () 和 floatingPointPrecision ().

enum QDataStream:: Status

此枚举描述数据流的当前状态。

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:: 版本

此枚举为数据序列化格式版本号，提供符号同义词。

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 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)

另请参阅 setVersion () 和 version ().

成员函数文档编制

QDataStream:: QDataStream ()

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

另请参阅 setDevice ().

QDataStream:: QDataStream ( QIODevice * d )

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

另请参阅 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.

Alternatively, you can use QDataStream (const QByteArray &) if you just want to read from a byte array.

由于 QByteArray is not a QIODevice subclass, internally a QBuffer is created to wrap the byte array.

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.

由于 QByteArray is not a QIODevice subclass, internally a QBuffer is created to wrap the byte array.

QDataStream:: ~QDataStream ()

销毁数据流。

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 ()

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

常量 描述
ReadCorruptData .

该函数在 Qt 5.7 引入。

另请参阅 startTransaction (), commitTransaction ()，和 rollbackTransaction ().

bool QDataStream:: atEnd () const

返回 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 .

另请参阅 QIODevice::atEnd ().

QDataStream::ByteOrder QDataStream:: byteOrder () const

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

另请参阅 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 ()，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.

该函数在 Qt 5.7 引入。

另请参阅 startTransaction (), rollbackTransaction ()，和 abortTransaction ().

QIODevice *QDataStream:: device () const

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

另请参阅 setDevice ().

QDataStream::FloatingPointPrecision QDataStream:: floatingPointPrecision () const

Returns the floating point precision of the data stream.

该函数在 Qt 4.6 引入。

另请参阅 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 [] 运算符。

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.

另请参阅 readRawData () 和 writeBytes ().

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

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

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

另请参阅 readBytes (), QIODevice::read ()，和 writeRawData ().

void QDataStream:: resetStatus ()

Resets the status of the data stream.

另请参阅 Status , status ()，和 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

常量 描述
ReadPastEnd .

该函数在 Qt 5.7 引入。

另请参阅 startTransaction (), commitTransaction ()，和 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.

另请参阅 byteOrder ().

void QDataStream:: setDevice ( QIODevice * d )

void QDataStream::setDevice( QIODevice *d)

Sets the I/O device to d , which can be 0 to unset to current I/O device.

另请参阅 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.

默认为 DoublePrecision .

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

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

该函数在 Qt 4.6 引入。

另请参阅 floatingPointPrecision ().

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

Sets the status of the data stream to the status 给定。

忽略后续 setStatus() 调用，直到 resetStatus () 被调用。

另请参阅 Status , status ()，和 resetStatus ().

void QDataStream:: setVersion ( int v )

Sets the version number of the data serialization format to v , a value of the 版本 枚举。

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 版本 enum provides symbolic constants for the different versions of Qt. For example: 

QDataStream out(file);
out.setVersion(QDataStream::Qt_4_0);

另请参阅 version () 和 版本 .

int QDataStream:: skipRawData ( int len )

Skips len 字节从设备。返回实际跳过字节数，或 -1 当出错时。

这相当于调用 readRawData () on a buffer of length len and ignoring the buffer.

该函数在 Qt 4.1 引入。

另请参阅 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.

该函数在 Qt 5.7 引入。

另请参阅 commitTransaction (), rollbackTransaction ()，和 abortTransaction ().

QDataStream::Status QDataStream:: status () const

Returns the status of the data stream.

另请参阅 Status , setStatus ()，和 resetStatus ().

int QDataStream:: version () const

Returns the version number of the data serialization format.

另请参阅 setVersion () 和 版本 .

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 字节来自 s . Note that the data is not encoded.

另请参阅 writeRawData () 和 readBytes ().

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

写入 len 字节来自 s to the stream. Returns the number of bytes actually written, or -1 on error. The data is not encoded.

另请参阅 writeBytes (), QIODevice::write ()，和 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 )

这是重载函数。

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

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

这是重载函数。

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

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

这是重载函数。

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

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

这是重载函数。

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

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

这是重载函数。

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 )

这是重载函数。

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

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

这是重载函数。

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

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

这是重载函数。

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.

该函数在 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 )

这是重载函数。

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

该函数在 Qt 5.9 引入。

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

这是重载函数。

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

另请参阅 setFloatingPointPrecision ().

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

这是重载函数。

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

另请参阅 setFloatingPointPrecision ().

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

这是重载函数。

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

The string is serialized using writeBytes() .

另请参阅 writeBytes () 和 writeRawData ().

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

Reads a signed byte from the stream into i ，并返回流引用。

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

这是重载函数。

Reads an unsigned byte from the stream into i ，并返回流引用。

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

这是重载函数。

Reads a signed 16-bit integer from the stream into i ，并返回流引用。

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

这是重载函数。

Reads an unsigned 16-bit integer from the stream into i ，并返回流引用。

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

这是重载函数。

Reads a signed 32-bit integer from the stream into i ，并返回流引用。

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

这是重载函数。

Reads an unsigned 32-bit integer from the stream into i ，并返回流引用。

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

这是重载函数。

Reads a signed 64-bit integer from the stream into i ，并返回流引用。

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

这是重载函数。

Reads an unsigned 64-bit integer from the stream, into i ，并返回流引用。

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

这是重载函数。

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.

该函数在 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 )

这是重载函数。

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

该函数在 Qt 5.9 引入。

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

这是重载函数。

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

另请参阅 setFloatingPointPrecision ().

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

这是重载函数。

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

另请参阅 setFloatingPointPrecision ().

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

这是重载函数。

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 [] .

另请参阅 readBytes () 和 readRawData ().