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公共类型
公共函数
静态公共成员
详细描述

QStringConverter 类

QStringConverter 类提供用于编码和解码文本的基类。更多...

头：	#include <QStringConverter>
CMake:	find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core
继承者：	QStringDecoder and QStringEncoder

所有成员列表，包括继承成员

注意： 此类的所有函数可重入 .

公共类型

enum	编码 { Utf8, Utf16, Utf16BE, Utf16LE, Utf32, …, System }
enum class	Flag { Default, ConvertInvalidToNull, WriteBom, ConvertInitialBom, Stateless }
flags	Flags

公共函数

bool	hasError () const
bool	isValid () const
const char *	name () const
void	resetState ()

静态公共成员

std::optional<Encoding>	encodingForData (QByteArrayView data , char16_t expectedFirstCharacter = 0)
std::optional<Encoding>	encodingForHtml (QByteArrayView data )
std::optional<Encoding>	encodingForName (const char * name )
const char *	nameForEncoding (QStringConverter::Encoding e )

详细描述

Qt uses UTF-16 to store, draw and manipulate strings. In many situations you may wish to deal with data that uses a different encoding. Most text data transferred over files and network connections is encoded in UTF-8.

The QStringConverter class is a base class for the QStringEncoder and QStringDecoder classes that help with converting between different text encodings. QStringDecoder can decode a string from an encoded representation into UTF-16, the format Qt uses internally. QStringEncoder does the opposite operation, encoding UTF-16 encoded data (usually in the form of a QString ) to the requested encoding.

支持的编码：

UTF-8
UTF-16
UTF-16BE
UTF-16LE
UTF-32
UTF-32BE
UTF-32LE
ISO-8859-1 (Latin-1)
The system encoding

QStringConverter s can be used as follows to convert some encoded string to and from UTF-16.

Suppose you have some string encoded in UTF-8, and want to convert it to a QString . The simple way to do it is to use a QStringDecoder 像这样：

QByteArray encodedString = "...";
auto toUtf16 = QStringDecoder(QStringDecoder::Utf8);
QString string = toUtf16(encodedString);

After this, string holds the text in decoded form. Converting a string from Unicode to the local encoding is just as easy using the QStringEncoder 类：

QString string = "...";
auto fromUtf16 = QStringEncoder(QStringEncoder::Utf8);
QByteArray encodedString = fromUtf16(string);

To read or write text files in various encodings, use QTextStream 及其 setEncoding() 函数。

Some care must be taken when trying to convert the data in chunks, for example, when receiving it over a network. In such cases it is possible that a multi-byte character will be split over two chunks. At best this might result in the loss of a character and at worst cause the entire conversion to fail.

Both QStringEncoder and QStringDecoder make this easy, by tracking this in an internal state. So simply calling the encoder or decoder again with the next chunk of data will automatically continue encoding or decoding the data correctly:

auto toUtf16 = QStringDecoder(QStringDecoder::Utf8);
QString string;
while (new_data_available()) {
    QByteArray chunk = get_new_data();
    string += toUtf16(chunk);
}

QStringDecoder object maintains state between chunks and therefore works correctly even if a multi-byte character is split between chunks.

QStringConverter objects can't be copied because of their internal state, but can be moved.

另请参阅 QTextStream , QStringDecoder ，和 QStringEncoder .

成员类型文档编制

enum QStringConverter:: 编码

常量	值	描述
`QStringConverter::Utf8`	`0`	Create a converter to or from UTF-8
`QStringConverter::Utf16`	`1`	Create a converter to or from UTF-16. When decoding, the byte order will get automatically detected by a leading byte order mark. If none exists or when encoding, the system byte order will be assumed.
`QStringConverter::Utf16BE`	`3`	Create a converter to or from big-endian UTF-16.
`QStringConverter::Utf16LE`	`2`	Create a converter to or from little-endian UTF-16.
`QStringConverter::Utf32`	`4`	Create a converter to or from UTF-32. When decoding, the byte order will get automatically detected by a leading byte order mark. If none exists or when encoding, the system byte order will be assumed.
`QStringConverter::Utf32BE`	`6`	Create a converter to or from big-endian UTF-32.
`QStringConverter::Utf32LE`	`5`	Create a converter to or from little-endian UTF-32.
`QStringConverter::Latin1`	`7`	Create a converter to or from ISO-8859-1 (Latin1).
`QStringConverter::System`	`8`	Create a converter to or from the underlying encoding of the operating systems locale. This is always assumed to be UTF-8 for Unix based systems. On Windows, this converts to and from the locale code page.

enum class QStringConverter:: Flag
flags QStringConverter:: Flags

常量	值	描述
`QStringConverter::Flag::Default`	`0`	Default conversion rules apply.
`QStringConverter::Flag::ConvertInvalidToNull`	`0x2`	If this flag is set, each invalid input character is output as a null character. If it is not set, invalid input characters are represented as QChar::ReplacementCharacter if the output encoding can represent that character, otherwise as a question mark.
`QStringConverter::Flag::WriteBom`	`0x4`	When converting from a QString to an output encoding, write a QChar::ByteOrderMark as the first character if the output encoding supports this. This is the case for UTF-8, UTF-16 and UTF-32 encodings.
`QStringConverter::Flag::ConvertInitialBom`	`0x8`	When converting from an input encoding to a QString QStringDecoder usually skips an leading QChar::ByteOrderMark . When this flag is set, the byte order mark will not be skipped, but converted to utf-16 and inserted at the start of the created QString .
`QStringConverter::Flag::Stateless`	`0x1`	Ignore possible converter states between different function calls to encode or decode strings. This will also cause the QStringConverter to raise an error if an incomplete sequence of data is encountered.

Flags 类型是 typedef 对于 QFlags <Flag>。它存储 Flag 值的 OR 组合。

成员函数文档编制

`[static]` std::optional < 编码 > QStringConverter:: encodingForData ( QByteArrayView data , char16_t expectedFirstCharacter = 0)

Returns the encoding for the content of data if it can be determined. expectedFirstCharacter can be passed as an additional hint to help determine the encoding.

The returned optional is empty, if the encoding is unclear.

`[static]` std::optional < 编码 > QStringConverter:: encodingForHtml ( QByteArrayView data )

Tries to determine the encoding of the HTML in data by looking at leading byte order marks or a charset specifier in the HTML meta tag. If the optional is empty, the encoding specified is not supported by QStringConverter . If no encoding is detected, the method returns Utf8.

`[static]` std::optional < 编码 > QStringConverter:: encodingForName (const char * name )

Returns an optional encoding for name . The optional is empty if the name could not get converted to a valid encoding.

bool QStringConverter:: hasError () const

Returns true if a conversion could not correctly convert a character. This could for example get triggered by an invalid UTF-8 sequence or when a character can't get converted due to limitations in the target encoding.

bool QStringConverter:: isValid () const

Returns true if this is a valid string converter that can be used for encoding or decoding text.

Default constructed string converters or converters constructed with an unsupported name are not valid.

const char *QStringConverter:: name () const

Returns the canonical name of the encoding this QStringConverter can encode or decode. Returns a nullptr if the converter is not valid.

另请参阅 isValid ().

`[static]` const char *QStringConverter:: nameForEncoding ( QStringConverter::Encoding e )

Returns the canonical name for encoding e .

void QStringConverter:: resetState ()

Resets the internal state of the converter, clearing potential errors or partial conversions.

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