QUtf8StringView 类提供 UTF-8 字符串统一视图，采用只读子集的 QString API. 更多...
| 头： | #include <QUtf8StringView> |
| CMake: |
find_package(Qt6 COMPONENTS Core REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Core) |
| qmake: | QT += core |
| Since: | Qt 6.0 |
注意： 此类的所有函数 可重入 .
| const_iterator | |
| const_pointer | |
| const_reference | |
| const_reverse_iterator | |
| difference_type | |
| iterator | |
| pointer | |
| reference | |
| reverse_iterator | |
| size_type | |
| storage_type | |
| value_type |
| QUtf8StringView (const Container & str ) | |
| QUtf8StringView (const Char * str ) | |
| QUtf8StringView (const Char (&)[N] string = N) | |
| QUtf8StringView (const Char * first , const Char * last ) | |
| QUtf8StringView (const Char * str , qsizetype len ) | |
| QUtf8StringView (std::nullptr_t) | |
| QUtf8StringView () | |
| QUtf8StringView::storage_type | at (qsizetype n ) const |
| QUtf8StringView::storage_type | back () const |
| QUtf8StringView::const_iterator | begin () const |
| QUtf8StringView::const_iterator | cbegin () const |
| QUtf8StringView::const_iterator | cend () const |
| void | chop (qsizetype n ) |
| QUtf8StringView | chopped (qsizetype n ) const |
| QUtf8StringView::const_reverse_iterator | crbegin () const |
| QUtf8StringView::const_reverse_iterator | crend () const |
| QUtf8StringView::const_pointer | data () const |
| bool | empty () const |
| QUtf8StringView::const_iterator | end () const |
| QUtf8StringView | first (qsizetype n ) const |
| QUtf8StringView::storage_type | front () const |
| bool | isEmpty () const |
| bool | isNull () const |
| QUtf8StringView | last (qsizetype n ) const |
| qsizetype | length () const |
| QUtf8StringView::const_reverse_iterator | rbegin () const |
| QUtf8StringView::const_reverse_iterator | rend () const |
| qsizetype | size () const |
| QUtf8StringView | sliced (qsizetype pos ) const |
| QUtf8StringView | sliced (qsizetype pos , qsizetype n ) const |
| QString | toString () const |
| void | truncate (qsizetype n ) |
| const char8_t * | utf8 () const |
| QUtf8StringView::storage_type | operator[] (qsizetype n ) const |
| QUtf8StringView | fromArray (const Char (&)[Size] string = Size) |
A QUtf8StringView references a contiguous portion of a UTF-8 string it does not own. It acts as an interface type to all kinds of UTF-8 string, without the need to construct a QString or QByteArray 首先。
The UTF-8 string may be represented as an array (or an array-compatible data-structure such as std::basic_string, etc.) of
char8_t
,
char
,
signed char
or
unsigned char
.
QUtf8StringView is designed as an interface type; its main use-case is as a function parameter type. When QUtf8StringViews are used as automatic variables or data members, care must be taken to ensure that the referenced string data (for example, owned by a std::u8string) outlives the QUtf8StringView on all code paths, lest the string view ends up referencing deleted data.
When used as an interface type, QUtf8StringView allows a single function to accept a wide variety of UTF-8 string data sources. One function accepting QUtf8StringView thus replaces several function overloads (taking e.g.
QByteArray
), while at the same time enabling even more string data sources to be passed to the function, such as
u8"Hello World"
，
char8_t
(C++20) or
char
(C++17) string literal. The
char8_t
incompatibility between C++17 and C++20 goes away when using QUtf8StringView.
Like all views, QUtf8StringViews should be passed by value, not by reference-to-const:
void myfun1(QUtf8StringView sv); // preferred
void myfun2(const QUtf8StringView &sv); // compiles and works, but slower
If you want to give your users maximum freedom in what strings they can pass to your function, consider using QAnyStringView 代替。
QUtf8StringView can also be used as the return value of a function. If you call a function returning QUtf8StringView, take extra care to not keep the QUtf8StringView around longer than the function promises to keep the referenced string data alive. If in doubt, obtain a strong reference to the data by calling toString () to convert the QUtf8StringView into a QString .
QUtf8StringView is a Literal Type .
QUtf8StringView accepts strings over a variety of character types:
char
(有符号和无符号两者)
char8_t
(仅 C++20)
All sizes and positions in QUtf8StringView functions are in UTF-8 code points (that is, UTF-8 multibyte sequences count as two, three or four, depending on their length). QUtf8StringView does not an attempt to detect or prevent slicing right through UTF-8 multibyte sequences. This is similar to the situation with QStringView and surrogate pairs.
In C++20,
u8""
string literals changed their type from
const char[]
to
const char8_t[]
. If Qt 6 could have depended on C++20, QUtf8StringView would store
char8_t
natively, and the following functions and aliases would use (pointers to)
char8_t
:
This is what QUtf8StringView is expected to look like in Qt 7, but for Qt 6, this was not possible. Instead of locking users into a C++17-era interface for the next decade, Qt provides two QUtf8StringView classes, in different (inline) namespaces. The first, in namespace
q_no_char8_t
, has a
value_type
of
const char
and is universally available. The second, in namespace
q_has_char8_t
, has a
value_type
of
const char8_t
and is only available when compiling in C++20 mode.
q_no_char8_t
is an inline namespace regardless of C++ edition, to avoid accidental binary incompatibilities. To use the
char8_t
version, you need to name it explicitly with
q_has_char8_t::QUtf8StringView
.
Internally, both are instantiations of the same template class, QBasicUtf8StringView. Please do not use the template class's name in your source code.
另请参阅 QAnyStringView , QUtf8StringView ，和 QString .
此 typedef 提供 STL 样式 const 迭代器为 QUtf8StringView .
另请参阅 iterator and const_reverse_iterator .
别名化的
value_type *
. Provided for compatibility with the STL.
别名化的
value_type &
. Provided for compatibility with the STL.
This typedef provides an STL-style const reverse iterator for QUtf8StringView .
另请参阅 reverse_iterator and const_iterator .
别名化的
std::ptrdiff_t
. Provided for compatibility with the STL.
此 typedef 提供 STL 样式 const 迭代器为 QUtf8StringView .
QUtf8StringView does not support mutable iterators, so this is the same as const_iterator .
另请参阅 const_iterator and reverse_iterator .
别名化的
value_type *
. Provided for compatibility with the STL.
QUtf8StringView does not support mutable pointers, so this is the same as const_pointer .
别名化的
value_type &
. Provided for compatibility with the STL.
QUtf8StringView does not support mutable references, so this is the same as const_reference .
This typedef provides an STL-style const reverse iterator for QUtf8StringView .
QUtf8StringView does not support mutable reverse iterators, so this is the same as const_reverse_iterator .
另请参阅 const_reverse_iterator and iterator .
Alias for qsizetype. Provided for compatibility with the STL.
[alias]
QUtf8StringView::
storage_type
别名化的
char
.
别名化的
const char
. Provided for compatibility with the STL.
Constructs a string view on
str
. The length is taken from
str.size()
.
str.data()
must remain valid for the lifetime of this string view object.
This constructor only participates in overload resolution if
Container
is an instantiation of
std::basic_string
with a compatible character type. The compatible character types are:
char8_t
,
char
,
signed char
and
unsigned char
.
The string view will be empty if and only if
str.empty()
. It is unspecified whether this constructor can result in a null string view (
str.data()
would have to return
nullptr
for this).
Constructs a string view on
str
. The length is determined by scanning for the first
Char(0)
.
str must remain valid for the lifetime of this string view object.
传递
nullptr
as
str
is safe and results in a null string view.
This constructor only participates in overload resolution if
str
is not an array and if
Char
is a compatible character type. The compatible character types are:
char8_t
,
char
,
signed char
and
unsigned char
.
Constructs a string view on the character string literal
string
. The view covers the array until the first
Char(0)
is encountered, or
N
, whichever comes first. If you need the full array, use
fromArray
() 代替。
string must remain valid for the lifetime of this string view object.
This constructor only participates in overload resolution if
string
is an actual array and if
Char
is a compatible character type. The compatible character types are:
char8_t
,
char
,
signed char
and
unsigned char
.
另请参阅 fromArray ().
Constructs a string view on first with length ( last - first ).
The range
[first,last)
must remain valid for the lifetime of this string view object.
传递
\nullptr
as
first
is safe if
last
is
nullptr
, too, and results in a null string view.
The behavior is undefined if
last
precedes
first
，或
first
is
nullptr
and
last
is not.
This constructor only participates in overload resolution if
Char
is a compatible character type. The compatible character types are:
char8_t
,
char
,
signed char
and
unsigned char
.
Constructs a string view on str with length len .
The range
[str,len)
must remain valid for the lifetime of this string view object.
传递
nullptr
as
str
is safe if
len
is 0, too, and results in a null string view.
The behavior is undefined if
len
is negative or, when positive, if
str
is
nullptr
.
This constructor only participates in overload resolution if
Char
is a compatible character type. The compatible character types are:
char8_t
,
char
,
signed char
and
unsigned char
.
Constructs a null string view.
另请参阅 isNull ().
Constructs a null string view.
另请参阅 isNull ().
Returns the code point at position n in this string view.
The behavior is undefined if n is negative or not less than size ().
另请参阅 operator[] (), front ()，和 back ().
Returns the last code point in the string. Same as last ().
This function is provided for STL compatibility.
警告： Calling this function on an empty string view constitutes undefined behavior.
另请参阅 front ().
返回常量 STL 样式迭代器 pointing to the first code point in the string.
This function is provided for STL compatibility.
另请参阅 end (), cbegin (), rbegin ()，和 data ().
如同 begin ().
This function is provided for STL compatibility.
另请参阅 cend (), begin (), crbegin ()，和 data ().
如同 end ().
This function is provided for STL compatibility.
另请参阅 cbegin (), end ()，和 crend ().
Truncates this string view by n code points.
如同
*this = first(size() - n)
.
注意： The behavior is undefined when n < 0 or n > size ().
另请参阅 sliced (), first (), last (), chopped ()，和 truncate ().
返回子字符串长度 size () - n starting at the beginning of this object.
如同
first(size() - n)
.
注意： The behavior is undefined when n < 0 or n > size ().
另请参阅 sliced (), first (), last (), chop ()，和 truncate ().
如同 rbegin ().
This function is provided for STL compatibility.
另请参阅 crend (), rbegin ()，和 cbegin ().
如同 rend ().
This function is provided for STL compatibility.
另请参阅 crbegin (), rend ()，和 cend ().
Returns a const pointer to the first code point in the string.
注意： The character array represented by the return value is not null-terminated.
另请参阅 begin (), end ()，和 utf8 ().
Returns whether this string view is empty - that is, whether
size() == 0
.
This function is provided for STL compatibility.
另请参阅 isEmpty (), isNull (), size ()，和 length ().
返回常量 STL 样式迭代器 pointing to the imaginary code point after the last code point in the list.
This function is provided for STL compatibility.
另请参阅 begin (), cend ()，和 rend ().
Returns a string view that contains the first n code points of this string.
注意： The behavior is undefined when n < 0 or n > size ().
另请参阅 last (), sliced (), chopped (), chop ()，和 truncate ().
[static]
template <typename Char, size_t Size, if_compatible_char<Char>>
QUtf8StringView
QUtf8StringView::
fromArray
(const
Char
(&)[
Size
]
string
= Size)
Constructs a string view on the full character string literal
string
, including any trailing
Char(0)
. If you don't want the null-terminator included in the view then you can
chop
() it off when you are certain it is at the end. Alternatively you can use the constructor overload taking an array literal which will create a view up to, but not including, the first null-terminator in the data.
string must remain valid for the lifetime of this string view object.
This function will work with any array literal if
Char
is a compatible character type. The compatible character types are:
char8_t
,
char
,
signed char
and
unsigned char
.
Returns the first code point in the string. Same as first ().
This function is provided for STL compatibility.
警告： Calling this function on an empty string view constitutes undefined behavior.
另请参阅 back ().
Returns whether this string view is empty - that is, whether
size() == 0
.
This function is provided for compatibility with other Qt containers.
另请参阅 empty (), isNull (), size ()，和 length ().
Returns whether this string view is null - that is, whether
data() == nullptr
.
This functions is provided for compatibility with other Qt containers.
另请参阅 empty (), isEmpty (), size ()，和 length ().
Returns a string view that contains the last n code points of this string.
注意： The behavior is undefined when n < 0 or n > size ().
另请参阅 first (), sliced (), chopped (), chop ()，和 truncate ().
如同 size ().
This function is provided for compatibility with other Qt containers.
另请参阅 empty (), isEmpty (), isNull ()，和 size ().
返回常量 STL-style reverse iterator pointing to the first code point in the string, in reverse order.
This function is provided for STL compatibility.
另请参阅 rend (), crbegin ()，和 begin ().
返回 STL-style reverse iterator pointing to one past the last code point in the string, in reverse order.
This function is provided for STL compatibility.
另请参阅 rbegin (), crend ()，和 end ().
Returns the size of this string view, in UTF-8 code points (that is, multi-byte sequences count as more than one for the purposes of this function, the same as surrogate pairs in QString and QStringView ).
另请参阅 empty (), isEmpty (), isNull ()，和 length ().
Returns a string view starting at position pos in this object, and extending to its end.
注意： The behavior is undefined when pos < 0 or pos > size ().
另请参阅 first (), last (), chopped (), chop ()，和 truncate ().
Returns a string view containing n code points of this string view, starting at position pos .
注意： The behavior is undefined when pos < 0, n < 0, or pos + n > size ().
另请参阅 first (), last (), chopped (), chop ()，和 truncate ().
Returns a deep copy of this string view's data as a QString .
The return value will be a null QString if and only if this string view is null.
Truncates this string view to n code points.
如同
*this = first(n)
.
注意： The behavior is undefined when n < 0 or n > size ().
另请参阅 sliced (), first (), last (), chopped ()，和 chop ().
Returns a const pointer to the first code point in the string.
The result is returned as a
const char8_t*
, so this function is only available when compiling in C++20 mode.
注意： The character array represented by the return value is not null-terminated.
另请参阅 begin (), end ()，和 data ().
Returns the code point at position n in this string view.
The behavior is undefined if n is negative or not less than size ().