path: root/src/corelib/text/qbytearrayview.qdoc

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/*!
    \class QByteArrayView
    \inmodule QtCore
    \brief The QByteArrayView class provides a view on an array of bytes with a read-only
           subset of the QByteArray API.
    \since 6.0

    \ingroup tools
    \ingroup shared
    \ingroup string-processing

    \reentrant

    A QByteArrayView references a contiguous portion of raw bytes it does
    not own. It acts as an interface type to all kinds of byte-array-like data,
    without the need to construct a QByteArray first.

    The byte array data may be represented as an array (or an array-compatible
    data-structure such as QByteArray, std::basic_string, etc.) of \c char,
    \c{signed char}, \c{unsigned char} or \c std::byte.

    QByteArrayView is designed as an interface type; its main use-case is
    as a function parameter type. When QByteArrayViews are used as automatic
    variables or data members, care must be taken to ensure that the referenced
    data (for example, owned by a QByteArray) outlives the QByteArrayView on all
    code paths, lest the byte array view ends up referencing deleted data.

    When used as an interface type, QByteArrayView allows a single function to accept
    a wide variety of byte-array-like data sources. One function accepting QByteArrayView
    thus replaces several function overloads (taking, for example, QByteArray, const char *,
    etc.) while at the same time enabling even more byte array data sources to be passed
    to the function.

    QByteArrayView should be passed by value, not by reference-to-const:
    \snippet code/src_corelib_text_qbytearrayview.cpp 0

    If you want to give your users maximum freedom in what type of data they
    can pass to your function, accompany the QByteArrayView overload with
    overloads for

    \list
        \li \e char: this overload can delegate to the QByteArrayView version:
            \snippet code/src_corelib_text_qbytearrayview.cpp 1
            even though, for technical reasons, QByteArrayView cannot provide a
            char constructor by itself.
        \li \e QByteArray: if you store an unmodified copy of the byte array and
            thus would like to take advantage of QByteArray's implicit sharing.
    \endlist

    QByteArrayView can also be used as the return value of a function. If you call a
    function returning QByteArrayView, take extra care to not keep the QByteArrayView
    around longer than the function promises to keep the referenced data alive.
    If in doubt, obtain a strong reference to the data by calling toByteArray() to convert
    the QByteArrayView into a QByteArray.

    \section1 Compatible Byte Types

    QByteArrayView can be constructed on any container of bytes, where the byte type
    is one of:

    \list
    \li \c char (both signed and unsigned)
    \li \c std::byte
    \endlist

    \sa QByteArray, QStringView
*/

/*!
    \typedef QByteArrayView::storage_type

    Alias for \c char.
*/

/*!
    \typedef QByteArrayView::value_type

    Alias for \c{const char}. Provided for compatibility with the STL.
*/

/*!
    \typedef QByteArrayView::difference_type

    Alias for \c{std::ptrdiff_t}. Provided for compatibility with the STL.
*/

/*!
    \typedef QByteArrayView::size_type

    Alias for qsizetype. Provided for compatibility with the STL.
*/

/*!
    \typedef QByteArrayView::reference

    Alias for \c{value_type &}. Provided for compatibility with the STL.

    QByteArrayView does not support mutable references, so this is the same
    as const_reference.
*/

/*!
    \typedef QByteArrayView::const_reference

    Alias for \c{value_type &}. Provided for compatibility with the STL.
*/

/*!
    \typedef QByteArrayView::pointer

    Alias for \c{value_type *}. Provided for compatibility with the STL.

    QByteArrayView does not support mutable pointers, so this is the same
    as const_pointer.
*/

/*!
    \typedef QByteArrayView::const_pointer

    Alias for \c{value_type *}. Provided for compatibility with the STL.
*/

/*!
    \typedef QByteArrayView::iterator

    This typedef provides an STL-style const iterator for QByteArrayView.

    QByteArrayView does not support mutable iterators, so this is the same
    as const_iterator.

    \sa const_iterator, reverse_iterator
*/

/*!
    \typedef QByteArrayView::const_iterator

    This typedef provides an STL-style const iterator for QByteArrayView.

    \sa iterator, const_reverse_iterator
*/

/*!
    \typedef QByteArrayView::reverse_iterator

    This typedef provides an STL-style const reverse iterator for QByteArrayView.

    QByteArrayView does not support mutable reverse iterators, so this is the
    same as const_reverse_iterator.

    \sa const_reverse_iterator, iterator
*/

/*!
    \typedef QByteArrayView::const_reverse_iterator

    This typedef provides an STL-style const reverse iterator for QByteArrayView.

    \sa reverse_iterator, const_iterator
*/

/*!
    \fn QByteArrayView::QByteArrayView()

    Constructs a null byte array view.

    \sa isNull()
*/

/*!
    \fn QByteArrayView::QByteArrayView(std::nullptr_t)

    Constructs a null byte array view.

    \sa isNull()
*/

/*!
    \fn template <typename Byte> QByteArrayView::QByteArrayView(const Byte *data, qsizetype len)

    Constructs a byte array view on \a data with length \a len.

    The range \c{[data,len)} must remain valid for the lifetime of this QByteArrayView.

    Passing \nullptr as \a data is safe if \a len is 0, too, and results in a null
    byte array view.

    The behavior is undefined if \a len is negative or, when positive, if \a data is \nullptr.

    This constructor only participates in overload resolution if \c Byte is a compatible
    byte type.

    \sa {Compatible Byte Types}
*/

/*!
    \fn template <typename Byte> QByteArrayView::QByteArrayView(const Byte *first, const Byte *last)

    Constructs a byte array view on \a first with length (\a last - \a first).

    The range \c{[first,last)} must remain valid for the lifetime of
    this QByteArrayView.

    Passing \c \nullptr as \a first is safe if \a last is \nullptr, too,
    and results in a null byte array 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 Byte is
    a compatible byte type.

    \sa {Compatible Byte Types}
*/

/*!
    \fn template <typename Byte> QByteArrayView::QByteArrayView(const Byte *data)

    Constructs a byte array view on \a data. The length is determined
    by scanning for the first \c{Byte(0)}.

    \a data must remain valid for the lifetime of this byte array view object.

    Passing \nullptr as \a data is safe and results in a null byte array view.

    This constructor only participates in overload resolution if \a data is not
    an array and if \c Byte is a compatible byte type.

    \sa {Compatible Byte Types}
*/

/*!
    \fn template <size_t Size> QByteArrayView::QByteArrayView(const char (&data)[Size])

    Constructs a byte array view on the char array \a data.
    The view covers the array until the first \c{'\0'} is encountered,
    or \c Size, whichever comes first.
    If you need the full array, use fromArray() instead.

    \a data must remain valid for the lifetime of this byte array view
    object.

    \note This constructor is only available for char array literals.
    The reasoning behind that is for compatibility with C-libraries
    which predefine "large-enough" arrays, but only use some of the
    preallocated space. To support this in an intuitive way in an
    implicit constructor overload, we need to stop at the first
    \c{char(0)}. This is logical for a char array, but not
    for a \c{std::byte} array.

    \sa fromArray
*/

/*!
    \fn QByteArrayView::QByteArrayView(const QByteArray &byteArray)

    Constructs a byte array view on \a byteArray.

    \c{byteArray.data()} must remain valid for the lifetime of this byte array view object.

    The byte array view will be null if and only if \c{byteArray.isNull()}.
*/

/*!
    \fn template <typename Container> QByteArrayView::QByteArrayView(const Container &c)

    Constructs a byte array view on the array-like container \a c. The length and data
    are set via \c{std::size(c)} and \c{std::data(c)} respectively.

    The container's data must remain valid for the lifetime of this byte array view object.

    This constructor participates in overload resolution if \a c is any contiguous
    container container with elements of a compatible byte type.

    \sa {Compatible Byte Types}
*/

/*!
    \fn template <typename Byte, size_t Size> QByteArrayView QByteArrayView::fromArray(const Byte (&data)[Size])

    Constructs a byte array view on the array literal \a data. The view covers the full
    array. That includes the trailing null-terminator of \c{char} array literals.
    If you don't want the null-terminator included in the view, you can chop() it off
    when you are certain it is at the end. Alternatively you can use the constructor
    overload taking a char array literal which will create a view up to, but not including,
    the first null-terminator in the data.

    This function will work with any array literal of a compatible byte type.

    \sa {Compatible Byte Types}, QByteArrayView
*/

/*!
    \fn QByteArray QByteArrayView::toByteArray() const

    Returns a deep copy of this byte array view's data as a QByteArray.

    The return value will be a null QByteArray if and only if this byte array
    view is null.

    \warning QByteArrayView can store data with more than 2\sup{31} bytes while
    QByteArray cannot. Calling this function on a byte array view for which size()
    returns a value greater than \c{INT_MAX / 2} constitutes undefined behavior.
*/

/*!
    \fn const char *QByteArrayView::data() const

    Returns a const \c char pointer to the first byte in the byte array.

    \note The character array represented by the return value is \e not guaranteed
    to be null-terminated. The returned pointer is only safe to use for accessing
    bytes at indices that are less than this byte array view's size().

    \sa begin(), end()
*/

/*!
    \fn const char *QByteArrayView::constData() const

    Returns a const \c char pointer to the first byte in the byte array.

    \note The character array represented by the return value is \e not guaranteed
    to be null-terminated. The returned pointer is only safe to use for accessing
    bytes at indices that are less than this byte array view's size().

    \sa data(), begin(), end()
*/

/*!
    \fn QByteArrayView::const_iterator QByteArrayView::begin() const

    Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the
    first byte in the byte array.

    This function is provided for STL compatibility.

    \sa end(), cbegin(), rbegin(), data()
*/

/*!
    \fn QByteArrayView::const_iterator QByteArrayView::cbegin() const

    Same as begin().

    This function is provided for STL compatibility.

    \sa cend(), begin(), crbegin(), data()
*/

/*!
    \fn QByteArrayView::const_iterator QByteArrayView::end() const

    Returns a const \l{STL-style iterators}{STL-style iterator} pointing
    just after the last byte in the byte array.

    This function is provided for STL compatibility.

    \sa begin(), cend(), rend()
*/

/*! \fn QByteArrayView::const_iterator QByteArrayView::cend() const

    Same as end().

    This function is provided for STL compatibility.

    \sa cbegin(), end(), crend()
*/

/*!
    \fn QByteArrayView::const_reverse_iterator QByteArrayView::rbegin() const

    Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing
    to the first byte in the byte array, in reverse order.

    This function is provided for STL compatibility.

    \sa rend(), crbegin(), begin()
*/

/*!
    \fn QByteArrayView::const_reverse_iterator QByteArrayView::crbegin() const

    Same as rbegin().

    This function is provided for STL compatibility.

    \sa crend(), rbegin(), cbegin()
*/

/*!
    \fn QByteArrayView::const_reverse_iterator QByteArrayView::rend() const

    Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past
    the last byte in the byte array, in reverse order.

    This function is provided for STL compatibility.

    \sa rbegin(), crend(), end()
*/

/*!
    \fn QByteArrayView::const_reverse_iterator QByteArrayView::crend() const

    Same as rend().

    This function is provided for STL compatibility.

    \sa crbegin(), rend(), cend()
*/

/*!
    \fn bool QByteArrayView::empty() const

    Returns \c true if this byte array view is empty - that is, \c{size() == 0}.

    This function is provided for STL compatibility.

    \sa isEmpty(), isNull(), size()
*/

/*!
    \fn bool QByteArrayView::isEmpty() const

    Returns \c true if this byte array view is empty - that is, \c{size() == 0}.

    \sa empty(), isNull(), size()
*/

/*!
    \fn bool QByteArrayView::isNull() const

    Returns \c true if this byte array view is null - that is, \c{data() == nullptr}.

    \sa empty(), isEmpty(), size()
*/

/*!
    \fn qsizetype QByteArrayView::size() const

    Returns the number of bytes in this byte array view.

    \sa empty(), isEmpty(), isNull()
*/

/*!
    \fn int QByteArrayView::length() const

    Same as size().

    \sa empty(), isEmpty(), isNull(), size()
*/

/*!
    \fn char QByteArrayView::operator[](qsizetype n) const

    Returns the character at position \a n in this byte array view.

    The behavior is undefined if \a n is negative or not less than size().

    \sa at(), front(), back()
*/

/*!
    \fn char QByteArrayView::at(qsizetype n) const

    Returns the character at position \a n in this byte array view.

    The behavior is undefined if \a n is negative or not less than size().

    \sa operator[](), front(), back()
*/

/*!
    \fn char QByteArrayView::front() const

    Returns the first byte in the byte array.

    This function is provided for STL compatibility.

    \warning Calling this function on an empty byte array view constitutes
    undefined behavior.

    \sa back()
*/

/*!
    \fn char QByteArrayView::back() const

    Returns the last byte in the byte array.

    This function is provided for STL compatibility.

    \warning Calling this function on an empty byte array view constitutes
    undefined behavior.

    \sa front()
*/

/*!
    \fn QByteArrayView QByteArrayView::first(qsizetype n) const

    Returns a byte array view that points to the first \a n bytes
    of this byte array view. Equivalent to \c{sliced(0, n)}.

    \note The behavior is undefined when \a n < 0 or \a n > size().

    \sa last(), startsWith(), chopped(), chop(), truncate()
*/

/*!
    \fn QByteArrayView QByteArrayView::last(qsizetype n) const

    Returns a byte array view that points to the last \a n bytes
    of this byte array view.

    \note The behavior is undefined when \a n < 0 or \a n > size().

    \sa first(), endsWith(), chopped(), chop(), truncate()
*/

/*!
    \fn QByteArrayView QByteArrayView::sliced(qsizetype pos, qsizetype n) const

    Returns a byte array view that points to \a n bytes of this byte array
    view, starting at position \a pos.

    \note The behavior is undefined when \a pos < 0, \a n < 0,
    or \a pos + \a n > size().

    \sa first(), last(), chopped(), chop(), truncate()
*/

/*!
    \fn QByteArrayView QByteArrayView::sliced(qsizetype pos) const

    Returns a byte array view starting at position \a pos in this object,
    and extending to its end.

    \note The behavior is undefined when \a pos < 0 or \a pos > size().

    \sa first(), last(), chopped(), chop(), truncate()
*/

/*!
    \fn QByteArrayView QByteArrayView::chopped(qsizetype length) const

    Returns a copy of this byte array view that omits its last \a length bytes.
    In other words, returns a byte array view of length size() - \a length starting
    at the beginning of this object.

    Same as \c{first(size() - length)}.

    \note The behavior is undefined when \a length < 0 or \a length > size().

    \sa first(), last(), sliced(), chop(), truncate()
*/

/*!
    \fn void QByteArrayView::truncate(qsizetype length)

    Truncates this byte array view to length \a length.

    Same as \c{*this = first(length)}.

    \note The behavior is undefined when \a length < 0 or \a length > size().

    \sa first(), last(), sliced(), chopped(), chop()
*/

/*!
    \fn void QByteArrayView::chop(qsizetype length)

    Truncates this byte array view by \a length characters.

    Same as \c{*this = first(size() - length)}.

    \note The behavior is undefined when \a length < 0 or \a length > size().

    \sa sliced(), first(), last(), chopped(), truncate()
*/

/*!
    \fn bool QByteArrayView::startsWith(QByteArrayView bv) const
    \fn bool QByteArrayView::startsWith(char ch) const

    Returns \c true if this byte array view starts with byte array view \a bv
    or character \a ch, respectively; otherwise returns \c false.

    \sa endsWith()
*/

/*!
    \fn bool QByteArrayView::endsWith(QByteArrayView bv) const
    \fn bool QByteArrayView::endsWith(char ch) const

    Returns \c true if this byte array view ends with byte array view \a bv
    or character \a ch, respectively; otherwise returns \c false.

    \sa startsWith()
*/

/*!
    \fn qsizetype QByteArrayView::indexOf(QByteArrayView bv, qsizetype from = 0) const
    \fn qsizetype QByteArrayView::indexOf(char ch, qsizetype from = 0) const

    Returns the index position of either the start of the first occurrence of
    the sequence of bytes viewed by \a bv or the first occurrence of byte \a ch,
    respectively, in this byte array view, searching forward from index position
    \a from.Returns -1 if no match is found.

    If \a from is -1, the search starts at the last character; if it is
    -2, at the next to last character and so on.

    \sa lastIndexOf(), contains()
*/

/*!
    \fn bool QByteArrayView::contains(QByteArrayView bv) const
    \fn bool QByteArrayView::contains(char ch) const

    Returns \c true if this byte array view contains an occurrence of the sequence
    of bytes viewed by \a bv or character \a ch, respectively; otherwise returns
    \c false.

    \sa indexOf(), lastIndexOf()
*/

/*!
    \fn qsizetype QByteArrayView::lastIndexOf(QByteArrayView bv, qsizetype from = -1) const
    \fn qsizetype QByteArrayView::lastIndexOf(char ch, qsizetype from = -1) const

    Returns the index position of either the start of the last occurrence of
    the sequence of bytes viewed by \a bv or the last occurrence of byte \a ch,
    respectively, in this byte array view, searching forward from index position
    \a from. If \a from is -1 (the default), the search starts from the end of the
    byte array view. Returns -1 if no match is found.

    \sa indexOf(), contains()
*/

/*!
    \fn qsizetype QByteArrayView::count(QByteArrayView bv) const

    Returns the number of (potentially overlapping) occurrences of the
    sequence of bytes viewed by \a bv in this byte array view.

    \sa contains(), indexOf()
*/

/*!
    \fn bool QByteArrayView::count(char ch) const
    \overload

    Returns the number of occurrences of byte \a ch in this byte array view.

    \sa contains(), indexOf()
*/

/*!
    \fn QByteArrayView qToByteArrayViewIgnoringNull(const QByteArray &b);
    \internal

    Convert \a b to a QByteArrayView ignoring \c{b.isNull()}.

    Returns a byte array view that references \a{b}'s data, but is never null.

    This is a faster way to convert a QByteArray to a QByteArrayView,
    if null QByteArray can legitimately be treated as empty ones.

    \sa QByteArray::isNull(), QByteArrayView
*/