/**************************************************************************** ** ** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and The Qt Company. For licensing terms ** and conditions see https://www.qt.io/terms-conditions. For further ** information use the contact form at https://www.qt.io/contact-us. ** ** GNU Free Documentation License Usage ** Alternatively, this file may be used under the terms of the GNU Free ** Documentation License version 1.3 as published by the Free Software ** Foundation and appearing in the file included in the packaging of ** this file. Please review the following information to ensure ** the GNU Free Documentation License version 1.3 requirements ** will be met: https://www.gnu.org/licenses/fdl-1.3.html. ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \class QAnyStringView \inmodule QtCore \since 6.0 \brief The QAnyStringView class provides a unified view on Latin-1, UTF-8, or UTF-16 strings with a read-only subset of the QString API. \reentrant \ingroup tools \ingroup string-processing A QAnyStringView references a contiguous portion of a string it does not own. It acts as an interface type to all kinds of strings, without the need to construct a QString first. Unlike QStringView and QUtf8StringView, QAnyStringView can hold strings of any of the following encodings: UTF-8, UTF-16, and Latin-1. The latter is supported to keep old source working efficiently. It is expected that by Qt 7, the Latin-1 support will be removed. The string may be represented as an array (or an array-compatible data-structure such as QString, std::basic_string, etc.) of \c char, \c char8_t, QChar, \c ushort, \c char16_t or (on platforms, such as Windows, where it is a 16-bit type) \c wchar_t. QAnyStringView is designed as an interface type; its main use-case is as a function parameter type. When QAnyStringViews are used as automatic variables or data members, care must be taken to ensure that the referenced string data (for example, owned by a QString) outlives the QAnyStringView on all code paths, lest the string view ends up referencing deleted data. When used as an interface type, QAnyStringView allows a single function to accept a wide variety of string data sources. One function accepting QAnyStringView thus replaces five function overloads (taking QString, \c{(const QChar*, int)}, QUtf8StringView, QLatin1String (but see above), and QChar), while at the same time enabling even more string data sources to be passed to the function, such as \c{u8"Hello World"}, a \c char8_t string literal. Like elsewhere in Qt, QAnyStringView assumes \c char data is encoded in UTF-8, unless it is presented as a QLatin1String. QAnyStringViews should be passed by value, not by reference-to-const: \snippet code/src_corelib_text_qanystringview.cpp 0 QAnyStringView can also be used as the return value of a function, but this is not recommended. QUtf8StringView or QStringView are better suited as function return values. If you call a function returning QAnyStringView, take extra care to not keep the QAnyStringView 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 QAnyStringView into a QString. QAnyStringView is a \e{Literal Type}. \section Compatible Character Types QAnyStringView accepts strings over a variety of character types: \list \li \c char (both signed and unsigned) \li \c char8_t (C++20 only) \li \c char16_t \li \c wchar_t (where it's a 16-bit type, e.g. Windows) \li \c ushort \li \c QChar \endlist The 8-bit character types are interpreted as UTF-8 data (except when presented as a QLatin1String) while the 16-bit character types are interpreted as UTF-16 data in host byte order (the same as QString). \section Sizes and Sub-Strings All sizes and positions in QAnyStringView functions are in the encoding's code points (that is, UTF-16 surrogate pairs count as two for the purposes of these functions, the same as in QString, and UTF-8 multibyte sequences count as two, three or four, depending on their length). \sa QUtf8StringView, QStringView */ /*! \typedef QStringView::difference_type Alias for \c{std::ptrdiff_t}. Provided for compatibility with the STL. */ /*! \typedef QStringView::size_type Alias for qsizetype. Provided for compatibility with the STL. */ /*! \fn QAnyStringView::QAnyStringView() Constructs a null string view. \sa isNull() */ /*! \fn QAnyStringView::QAnyStringView(std::nullptr_t) Constructs a null string view. \sa isNull() */ /*! \fn template QAnyStringView::QAnyStringView(const Char *str, qsizetype len) Constructs a string view on \a str with length \a len. The range \c{[str,len)} must remain valid for the lifetime of this string view object. Passing \nullptr as \a str is safe if \a len is 0, too, and results in a null string view. The behavior is undefined if \a len is negative or, when positive, if \a str is \nullptr. This constructor only participates in overload resolution if \c Char is a compatible character type. \sa isNull(), {Compatible Character Types} */ /*! \fn template QAnyStringView::QAnyStringView(const Char *first, const Char *last) Constructs a string view on \a first with length (\a last - \a first). The range \c{[first,last)} must remain valid for the lifetime of this string view object. Passing \c \nullptr as \a first is safe if \a last is \nullptr, too, and results in a null string view. The behavior is undefined if \a last precedes \a first, or \a first is \nullptr and \a last is not. This constructor only participates in overload resolution if \c Char is a compatible character type. \sa isNull(), {Compatible Character Types} */ /*! \fn template QAnyStringView::QAnyStringView(const Char *str) Constructs a string view on \a str. The length is determined by scanning for the first \c{Char(0)}. \a str must remain valid for the lifetime of this string view object. Passing \nullptr as \a str is safe and results in a null string view. This constructor only participates in overload resolution if \a str is not an array and if \c Char is a compatible character type. \sa isNull(), {Compatible Character Types} */ /*! \fn template QAnyStringView::QAnyStringView(const Char (&string)[N]) Constructs a string view on the character string literal \a string. The view covers the array until the first \c{Char(0)} is encountered, or \c N, whichever comes first. If you need the full array, use fromArray() instead. \a string must remain valid for the lifetime of this string view object. This constructor only participates in overload resolution if \a string is an actual array and \c Char is a compatible character type. \sa {Compatible Character Types} */ /*! \fn QAnyStringView::QAnyStringView(const QString &str) Constructs a string view on \a str. \c{str.data()} must remain valid for the lifetime of this string view object. The string view will be null if and only if \c{str.isNull()}. */ /*! \fn QAnyStringView::QAnyStringView(const QByteArray &str) Constructs a string view on \a str. The data in \a str is interpreted as UTF-8. \c{str.data()} must remain valid for the lifetime of this string view object. The string view will be null if and only if \c{str.isNull()}. */ /*! \fn template QAnyStringView::QAnyStringView(const StdBasicString &str) Constructs a string view on \a str. The length is taken from \c{str.size()}. \c{str.data()} must remain valid for the lifetime of this string view object. This constructor only participates in overload resolution if \c StdBasicString is an instantiation of \c std::basic_string with a compatible character type. The string view will be empty if and only if \c{str.empty()}. It is unspecified whether this constructor can result in a null string view (\c{str.data()} would have to return \nullptr for this). \sa isNull(), isEmpty(), {Compatible Character Types} */ /*! \fn template static QAnyStringView fromArray(const Char (&string)[Size]) noexcept Constructs a string view on the full character string literal \a string, including any trailing \c{Char(0)}. If you don't want the null-terminator included in the view then you can use the constructor overload taking a pointer and a size: \snippet code/src_corelib_text_qanystringview.cpp 2 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. \a string must remain valid for the lifetime of this string view object. This function will work with any array literal if \c Char is a compatible character type. */ /*! \fn QString QAnyStringView::toString() const 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. */ /*! \fn const void *QStringView::data() const Returns a const pointer to the first character in the string. \note The character array represented by the return value is \e not null-terminated. \sa size_bytes() */ /*! \fn bool QAnyStringView::empty() const Returns whether this string view is empty - that is, whether \c{size() == 0}. This function is provided for STL compatibility. \sa isEmpty(), isNull(), size() */ /*! \fn bool QAnyStringView::isEmpty() const Returns whether this string view is empty - that is, whether \c{size() == 0}. This function is provided for compatibility with other Qt containers. \sa empty(), isNull(), size() */ /*! \fn bool QAnyStringView::isNull() const Returns whether this string view is null - that is, whether \c{data() == nullptr}. This functions is provided for compatibility with other Qt containers. \sa empty(), isEmpty(), size() */ /*! \fn qsizetype QAnyStringView::size() const Returns the size of this string view, in the encoding's code points. \sa empty(), isEmpty(), isNull(), size_bytes(), {Sizes and Sub-Strings} */ /*! \fn QAnyStringView::size_bytes() const Returns the size of this string view, but in bytes, not code-points. You can use this function together with data() for hashing or serialization. This function is provided for STL compatibility. \sa size(), data() */ /*! \fn int QStringView::length() const \obsolete Use size() instead, and port callers to qsizetype. Same as size(), except that it returns the result as an \c int. This function is provided for compatibility with other Qt containers. \warning QAnyStringView can represent strings with more than 2\sup{31} characters. Calling this function on a string view for which size() returns a value greater than \c{INT_MAX} constitutes undefined behavior. \sa size() */ /*! \fn QChar QAnyStringView::front() const Returns the first character in the string. This function is provided for STL compatibility. \warning Calling this function on an empty string view constitutes undefined behavior. \sa back(), {Sizes and Sub-Strings} */ /*! \fn QChar QAnyStringView::back() const Returns the last character in the string. This function is provided for STL compatibility. \warning Calling this function on an empty string view constitutes undefined behavior. \sa front(), {Sizes and Sub-Strings} */ /*! \fn QAnyStringView::compare(QAnyStringView lhs, QAnyStringView rhs, Qt::CaseSensitivity cs) Returns an integer that compares to zero as \a lhs compares to \a rhs. If \a cs is Qt::CaseSensitive (the default), the comparison is case sensitive; otherwise the comparison is case-insensitive. \sa operator==(), operator<(), operator>() */ /*! \fn template qToAnyStringViewIgnoringNull(const QStringLike &s); \since 6.0 \internal Convert \a s to a QAnyStringView ignoring \c{s.isNull()}. Returns a string-view that references \a{s}'s data, but is never null. This is a faster way to convert a QString or QByteArray to a QAnyStringView, if null QStrings or QByteArrays can legitimately be treated as empty ones. \sa QString::isNull(), QAnyStringView */ /*! \fn QAnyStringView::toWCharArray(wchar_t *array) const Transcribes this string into the given \a array. The caller is responsible for ensuring \a array is large enough to hold the \c wchar_t encoding of this string (allocating the array with space for size() elements is always sufficient). The array is encoded in UTF-16 on platforms where \c wchar_t is 2 bytes wide (e.g. Windows); otherwise (Unix systems), \c wchar_t is assumed to be 4 bytes wide and the data is written in UCS-4. \note This function writes no null terminator to the end of \a array. Returns the number of \c wchar_t entries written to \a array. \sa QString::toWCharArray() */