QByteArrayView Class▲
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Header: QByteArrayView
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Since: Qt 6.0
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CMake:
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core)
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qmake: QT += core
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Group: QByteArrayView is part of tools, Implicitly Shared Classes, string-processing
Detailed Description▲
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 char, signed char, unsigned char or 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:
void myfun1(QByteArrayView bv); // preferred
void myfun2(const QByteArrayView &bv); // compiles and works, but slowerIf 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
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char: this overload can delegate to the QByteArrayView version:
Sélectionnezvoidfun(QByteArrayView bv);voidfun(charch){fun(QByteArrayView(&ch,1));}even though, for technical reasons, QByteArrayView cannot provide a char constructor by itself.
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QByteArray: if you store an unmodified copy of the byte array and thus would like to take advantage of QByteArray's implicit sharing.
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.
Compatible Byte Types▲
QByteArrayView can be constructed on any container of bytes, where the byte type is one of:
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char (both signed and unsigned)
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std::byte
See Also▲
See also QByteArray, QStringView
Member Type Documentation▲
QByteArrayView::const_iterator▲
This typedef provides an STL-style const iterator for QByteArrayView.
See Also▲
See also iterator, const_reverse_iterator
QByteArrayView::const_pointer▲
Alias for value_type *. Provided for compatibility with the STL.
QByteArrayView::const_reference▲
Alias for value_type &. Provided for compatibility with the STL.
QByteArrayView::const_reverse_iterator▲
This typedef provides an STL-style const reverse iterator for QByteArrayView.
See Also▲
See also reverse_iterator, const_iterator
QByteArrayView::difference_type▲
Alias for std::ptrdiff_t. Provided for compatibility with the STL.
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.
See Also▲
See also const_iterator, reverse_iterator
QByteArrayView::pointer▲
Alias for value_type *. Provided for compatibility with the STL.
QByteArrayView does not support mutable pointers, so this is the same as const_pointer.
QByteArrayView::reference▲
Alias for value_type &. Provided for compatibility with the STL.
QByteArrayView does not support mutable references, so this is the same as const_reference.
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.
See Also▲
See also const_reverse_iterator, iterator
QByteArrayView::size_type▲
Alias for qsizetype. Provided for compatibility with the STL.
QByteArrayView::storage_type▲
Alias for char.
QByteArrayView::value_type▲
Alias for const char. Provided for compatibility with the STL.
Member Function Documentation▲
bool QByteArrayView::startsWith(QByteArrayView bv) const▲
bool QByteArrayView::startsWith(char ch) const
Returns true if this byte array view starts with byte array view bv or character ch, respectively; otherwise returns false.
See Also▲
See also endsWith()
bool QByteArrayView::endsWith(QByteArrayView bv) const▲
bool QByteArrayView::endsWith(char ch) const
Returns true if this byte array view ends with byte array view bv or character ch, respectively; otherwise returns false.
See Also▲
See also startsWith()
qsizetype QByteArrayView::indexOf(QByteArrayView bv, qsizetype from = 0) const▲
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 bv or the first occurrence of byte ch, respectively, in this byte array view, searching forward from index position from.Returns -1 if no match is found.
If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.
See Also▲
See also lastIndexOf(), contains()
bool QByteArrayView::contains(QByteArrayView bv) const▲
bool QByteArrayView::contains(char ch) const
Returns true if this byte array view contains an occurrence of the sequence of bytes viewed by bv or character ch, respectively; otherwise returns false.
See Also▲
See also indexOf(), lastIndexOf()
qsizetype QByteArrayView::lastIndexOf(QByteArrayView bv, qsizetype from = -1) const▲
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 bv or the last occurrence of byte ch, respectively, in this byte array view, searching forward from index position from. If from is -1 (the default), the search starts from the end of the byte array view. Returns -1 if no match is found.
See Also▲
[constexpr] QByteArrayView::QByteArrayView()▲
[constexpr] QByteArrayView::QByteArrayView(std::nullptr_t)▲
[constexpr] QByteArrayView::QByteArrayView(const Byte *data, qsizetype len)▲
Constructs a byte array view on data with length len.
The range [data,len) must remain valid for the lifetime of this QByteArrayView.
Passing nullptr as data is safe if len is 0, too, and results in a null byte array view.
The behavior is undefined if len is negative or, when positive, if data is nullptr.
This constructor only participates in overload resolution if Byte is a compatible byte type.
See Also▲
See also Compatible Byte Types
[constexpr] QByteArrayView::QByteArrayView(const Byte *first, const Byte *last)▲
Constructs a byte array view on first with length (last - first).
The range [first,last) must remain valid for the lifetime of this QByteArrayView.
Passing \nullptr as first is safe if last is nullptr, too, and results in a null byte array view.
The behavior is undefined if last precedes first, or first is nullptr and last is not.
This constructor only participates in overload resolution if Byte is a compatible byte type.
See Also▲
See also Compatible Byte Types
[constexpr] QByteArrayView::QByteArrayView(const Byte *data)▲
Constructs a byte array view on data. The length is determined by scanning for the first Byte(0).
data must remain valid for the lifetime of this byte array view object.
Passing nullptr as data is safe and results in a null byte array view.
This constructor only participates in overload resolution if data is not an array and if Byte is a compatible byte type.
See Also▲
See also Compatible Byte Types
QByteArrayView::QByteArrayView(const QByteArray &byteArray)▲
Constructs a byte array view on byteArray.
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 byteArray.isNull().
[constexpr] QByteArrayView::QByteArrayView(const Container &c)▲
Constructs a byte array view on the array-like container c. The length and data are set via std::size(c) and 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 c is any contiguous container container with elements of a compatible byte type.
See Also▲
See also Compatible Byte Types
[constexpr] QByteArrayView::QByteArrayView(const char (&)[Size] data = Size)▲
Constructs a byte array view on the char array data. The view covers the array until the first '\0' is encountered, or Size, whichever comes first. If you need the full array, use fromArray() instead.
data must remain valid for the lifetime of this byte array view object.
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 char(0). This is logical for a char array, but not for a std::byte array.
See Also▲
See also fromArray
[constexpr] char QByteArrayView::at(qsizetype n) const▲
Returns the character at position n in this byte array view.
The behavior is undefined if n is negative or not less than size().
See Also▲
See also operator[](), front(), back()
[constexpr] char QByteArrayView::back() const▲
Returns the last byte in the byte array.
This function is provided for STL compatibility.
Calling this function on an empty byte array view constitutes undefined behavior.
See Also▲
See also front()
[constexpr] QByteArrayView::const_iterator QByteArrayView::begin() const▲
Returns a const STL-style iterator pointing to the first byte in the byte array.
This function is provided for STL compatibility.
See Also▲
[constexpr] QByteArrayView::const_iterator QByteArrayView::cbegin() const▲
[constexpr] QByteArrayView::const_iterator QByteArrayView::cend() const▲
[constexpr] void QByteArrayView::chop(qsizetype length)▲
Truncates this byte array view by length characters.
Same as *this = first(size() - length).
The behavior is undefined when length < 0 or length > size().
See Also▲
[constexpr] QByteArrayView QByteArrayView::chopped(qsizetype length) const▲
Returns a copy of this byte array view that omits its last length bytes. In other words, returns a byte array view of length size() - length starting at the beginning of this object.
Same as first(size() - length).
The behavior is undefined when length < 0 or length > size().
See Also▲
[constexpr] QByteArrayView::const_pointer QByteArrayView::constData() const▲
Returns a const char pointer to the first byte in the byte array.
The character array represented by the return value is 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().
See Also▲
qsizetype QByteArrayView::count(QByteArrayView bv) const▲
Returns the number of (potentially overlapping) occurrences of the sequence of bytes viewed by bv in this byte array view.
See Also▲
qsizetype QByteArrayView::count(char ch) const▲
This is an overloaded function.
Returns the number of occurrences of byte ch in this byte array view.
See Also▲
[constexpr] QByteArrayView::const_reverse_iterator QByteArrayView::crbegin() const▲
[constexpr] QByteArrayView::const_reverse_iterator QByteArrayView::crend() const▲
[constexpr] QByteArrayView::const_pointer QByteArrayView::data() const▲
Returns a const char pointer to the first byte in the byte array.
The character array represented by the return value is 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().
See Also▲
[constexpr] bool QByteArrayView::empty() const▲
Returns true if this byte array view is empty - that is, size() == 0.
This function is provided for STL compatibility.
See Also▲
[constexpr] QByteArrayView::const_iterator QByteArrayView::end() const▲
Returns a const STL-style iterator pointing just after the last byte in the byte array.
This function is provided for STL compatibility.
See Also▲
[constexpr] QByteArrayView QByteArrayView::first(qsizetype n) const▲
Returns a byte array view that points to the first n bytes of this byte array view. Equivalent to sliced(0, n).
The behavior is undefined when n < 0 or n > size().
See Also▲
See also last(), startsWith(), chopped(), chop(), truncate()
[static constexpr] QByteArrayView QByteArrayView::fromArray(const Byte (&)[Size] data = Size)▲
Constructs a byte array view on the array literal data. The view covers the full array. That includes the trailing null-terminator of 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.
See Also▲
See also Compatible Byte Types, QByteArrayView
[constexpr] char QByteArrayView::front() const▲
Returns the first byte in the byte array.
This function is provided for STL compatibility.
Calling this function on an empty byte array view constitutes undefined behavior.
See Also▲
See also back()
[constexpr] bool QByteArrayView::isEmpty() const▲
Returns true if this byte array view is empty - that is, size() == 0.
See Also▲
[constexpr] bool QByteArrayView::isNull() const▲
Returns true if this byte array view is null - that is, data() == nullptr.
See Also▲
[constexpr] QByteArrayView QByteArrayView::last(qsizetype n) const▲
Returns a byte array view that points to the last n bytes of this byte array view.
The behavior is undefined when n < 0 or n > size().
See Also▲
[constexpr] QByteArrayView::const_reverse_iterator QByteArrayView::rbegin() const▲
Returns a const STL-style reverse iterator pointing to the first byte in the byte array, in reverse order.
This function is provided for STL compatibility.
See Also▲
[constexpr] QByteArrayView::const_reverse_iterator QByteArrayView::rend() const▲
Returns a 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.
See Also▲
[constexpr] qsizetype QByteArrayView::size() const▲
Returns the number of bytes in this byte array view.
See Also▲
[constexpr] QByteArrayView QByteArrayView::sliced(qsizetype pos) const▲
Returns a byte array view starting at position pos in this object, and extending to its end.
The behavior is undefined when pos < 0 or pos > size().
See Also▲
[constexpr] QByteArrayView QByteArrayView::sliced(qsizetype pos, qsizetype n) const▲
Returns a byte array view that points to n bytes of this byte array view, starting at position pos.
The behavior is undefined when pos < 0, n < 0, or pos + n > size().
See Also▲
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.
QByteArrayView can store data with more than 231 bytes while QByteArray cannot. Calling this function on a byte array view for which size() returns a value greater than INT_MAX / 2 constitutes undefined behavior.
[constexpr] void QByteArrayView::truncate(qsizetype length)▲
Truncates this byte array view to length length.
Same as *this = first(length).
The behavior is undefined when length < 0 or length > size().
See Also▲
[constexpr] char QByteArrayView::operator[](qsizetype n) const▲
Obsolete Members for QByteArrayView▲
The following members of class QByteArrayView are deprecated. We strongly advise against using them in new code.
Obsolete Member Function Documentation▲
[constexpr] int QByteArrayView::length() const▲
This function is deprecated. We strongly advise against using it in new code.
Use size() and port callers to qsizetype.
Same as size(), but returns the result as an int.
This function is provided for compatibility with other Qt containers.
QByteArrayView can represent data with more than 231 bytes. Calling this function on a byte array view for which size() returns a value greater than INT_MAX constitutes undefined behavior.