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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 QVarLengthArray \inmodule QtCore \brief The QVarLengthArray class provides a low-level variable-length array. \ingroup tools \reentrant The C++ language doesn't support variable-length arrays on the stack. For example, the following code won't compile: \snippet code/doc_src_qvarlengtharray.cpp 0 The alternative is to allocate the array on the heap (with \c{new}): \snippet code/doc_src_qvarlengtharray.cpp 1 However, if myfunc() is called very frequently from the application's inner loop, heap allocation can be a major source of slowdown. QVarLengthArray is an attempt to work around this gap in the C++ language. It allocates a certain number of elements on the stack, and if you resize the array to a larger size, it automatically uses the heap instead. Stack allocation has the advantage that it is much faster than heap allocation. Example: \snippet code/doc_src_qvarlengtharray.cpp 2 In the example above, QVarLengthArray will preallocate 1024 elements on the stack and use them unless \c{n + 1} is greater than 1024. If you omit the second template argument, QVarLengthArray's default of 256 is used. QVarLengthArray's value type must be an \l{assignable data type}. This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *. QVarLengthArray, like QVector, provides a resizable array data structure. The main differences between the two classes are: \list \li QVarLengthArray's API is much more low-level and it lacks some of QVector's functionality. \li QVarLengthArray doesn't initialize the memory if the value is a basic type. (QVector always does.) \li QVector uses \l{implicit sharing} as a memory optimization. QVarLengthArray doesn't provide that feature; however, it usually produces slightly better performance due to reduced overhead, especially in tight loops. \endlist In summary, QVarLengthArray is a low-level optimization class that only makes sense in very specific cases. It is used a few places inside Qt and was added to Qt's public API for the convenience of advanced users. \sa QVector, QList, QLinkedList */ /*! \fn template QVarLengthArray::QVarLengthArray(int size) Constructs an array with an initial size of \a size elements. If the value type is a primitive type (e.g., char, int, float) or a pointer type (e.g., QWidget *), the elements are not initialized. For other types, the elements are initialized with a \l{default-constructed value}. */ /*! \fn template QVarLengthArray::QVarLengthArray(std::initializer_list args) \since 5.5 Constructs an array from the std::initializer_list given by \a args. This constructor is only enabled if the compiler supports C++11 initializer lists. */ /*! \fn template QVarLengthArray::~QVarLengthArray() Destroys the array. */ /*! \fn template int QVarLengthArray::size() const Returns the number of elements in the array. \sa isEmpty(), resize() */ /*! \fn template int QVarLengthArray::count() const Same as size(). \sa isEmpty(), resize() */ /*! \fn template int QVarLengthArray::length() const \since 5.0 Same as size(). \sa isEmpty(), resize() */ /*! \fn template T& QVarLengthArray::first() Returns a reference to the first item in the array. The array must not be empty. If the array can be empty, check isEmpty() before calling this function. \sa last(), isEmpty() */ /*! \fn template const T& QVarLengthArray::first() const \overload */ /*! \fn template T& QVarLengthArray::front() \since 5.0 Same as first(). Provided for STL-compatibility. */ /*! \fn template const T& QVarLengthArray::front() const \since 5.0 \overload */ /*! \fn template T& QVarLengthArray::last() Returns a reference to the last item in the array. The array must not be empty. If the array can be empty, check isEmpty() before calling this function. \sa first(), isEmpty() */ /*! \fn template const T& QVarLengthArray::last() const \overload */ /*! \fn template T& QVarLengthArray::back() \since 5.0 Same as last(). Provided for STL-compatibility. */ /*! \fn template const T& QVarLengthArray::back() const \since 5.0 \overload */ /*! \fn template void QVarLengthArray::shrink_to_fit() \since 5.10 Same as squeeze(). Provided for STL-compatibility. */ /*! \fn template bool QVarLengthArray::isEmpty() const Returns \c true if the array has size 0; otherwise returns \c false. \sa size(), resize() */ /*! \fn template bool QVarLengthArray::empty() const \since 5.0 Returns \c true if the array has size 0; otherwise returns \c false. Same as isEmpty(). Provided for STL-compatibility. */ /*! \fn template void QVarLengthArray::clear() Removes all the elements from the array. Same as resize(0). */ /*! \fn template void QVarLengthArray::resize(int size) Sets the size of the array to \a size. If \a size is greater than the current size, elements are added to the end. If \a size is less than the current size, elements are removed from the end. If the value type is a primitive type (e.g., char, int, float) or a pointer type (e.g., QWidget *), new elements are not initialized. For other types, the elements are initialized with a \l{default-constructed value}. \sa size(), squeeze() */ /*! \fn template int QVarLengthArray::capacity() const Returns the maximum number of elements that can be stored in the array without forcing a reallocation. The sole purpose of this function is to provide a means of fine tuning QVarLengthArray's memory usage. In general, you will rarely ever need to call this function. If you want to know how many items are in the array, call size(). \sa reserve(), squeeze() */ /*! \fn template void QVarLengthArray::reserve(int size) Attempts to allocate memory for at least \a size elements. If you know in advance how large the array can get, you can call this function and if you call resize() often, you are likely to get better performance. If \a size is an underestimate, the worst that will happen is that the QVarLengthArray will be a bit slower. The sole purpose of this function is to provide a means of fine tuning QVarLengthArray's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the array, call resize(). \sa capacity(), squeeze() */ /*! \fn template void QVarLengthArray::squeeze() \since 5.1 Releases any memory not required to store the items. If the container can fit its storage on the stack allocation, it will free the heap allocation and copy the elements back to the stack. The sole purpose of this function is to provide a means of fine tuning QVarLengthArray's memory usage. In general, you will rarely ever need to call this function. \sa reserve(), capacity(), resize() */ /*! \fn template T &QVarLengthArray::operator[](int i) Returns a reference to the item at index position \a i. \a i must be a valid index position in the array (i.e., 0 <= \a i < size()). \sa data(), at() */ /*! \fn template const T &QVarLengthArray::operator[](int i) const \overload */ /*! \fn template void QVarLengthArray::append(const T &t) Appends item \a t to the array, extending the array if necessary. \sa removeLast() */ /*! \fn template void QVarLengthArray::push_back(const T &t) \since 5.0 Appends item \a t to the array, extending the array if necessary. Provided for STL-compatibility. */ /*! \fn template void QVarLengthArray::append(T &&t) \overload append \since 5.9 \note Unlike the lvalue overload of append(), passing a reference to an object that is already an element of \c *this leads to undefined behavior: \code vla.append(std::move(vla[0])); // BUG: passing an object that is already in the container \endcode */ /*! \fn template void QVarLengthArray::push_back(T &&t) \overload push_back \since 5.9 \note Unlike the lvalue overload of push_back(), passing a reference to an object that is already an element of \c *this leads to undefined behavior: \code vla.push_back(std::move(vla[0])); // BUG: passing an object that is already in the container \endcode */ /*! \fn template inline void QVarLengthArray::removeLast() \since 4.5 Decreases the size of the array by one. The allocated size is not changed. \sa append() */ /*! \fn template void QVarLengthArray::pop_back() \since 5.0 Same as removeLast(). Provided for STL-compatibility. */ /*! \fn template void QVarLengthArray::append(const T *buf, int size) Appends \a size amount of items referenced by \a buf to this array. */ /*! \fn template T *QVarLengthArray::data() Returns a pointer to the data stored in the array. The pointer can be used to access and modify the items in the array. Example: \snippet code/doc_src_qvarlengtharray.cpp 3 The pointer remains valid as long as the array isn't reallocated. This function is mostly useful to pass an array to a function that accepts a plain C++ array. \sa constData(), operator[]() */ /*! \fn template const T *QVarLengthArray::data() const \overload */ /*! \fn template const T *QVarLengthArray::constData() const Returns a const pointer to the data stored in the array. The pointer can be used to access the items in the array. The pointer remains valid as long as the array isn't reallocated. This function is mostly useful to pass an array to a function that accepts a plain C++ array. \sa data(), operator[]() */ /*! \fn template QVarLengthArray &QVarLengthArray::operator=(const QVarLengthArray &other) Assigns \a other to this array and returns a reference to this array. */ /*! \fn template QVarLengthArray &QVarLengthArray::operator=(std::initializer_list list) \since 5.5 Assigns the values of \a list to this array, and returns a reference to this array. This constructor is only enabled if the compiler supports C++11 initializer lists. */ /*! \fn template QVarLengthArray::QVarLengthArray(const QVarLengthArray &other) Constructs a copy of \a other. */ /*! \fn template const T &QVarLengthArray::at(int i) const Returns a reference to the item at index position \a i. \a i must be a valid index position in the array (i.e., 0 <= \a i < size()). \sa value(), operator[]() */ /*! \fn template T QVarLengthArray::value(int i) const Returns the value at index position \a i. If the index \a i is out of bounds, the function returns a \l{default-constructed value}. If you are certain that \a i is within bounds, you can use at() instead, which is slightly faster. \sa at(), operator[]() */ /*! \fn template T QVarLengthArray::value(int i, const T &defaultValue) const \overload If the index \a i is out of bounds, the function returns \a defaultValue. */ /*! \typedef QVarLengthArray::size_type \since 4.7 Typedef for int. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::value_type \since 4.7 Typedef for T. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::difference_type \since 4.7 Typedef for ptrdiff_t. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::pointer \since 4.7 Typedef for T *. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::const_pointer \since 4.7 Typedef for const T *. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::reference \since 4.7 Typedef for T &. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::const_reference \since 4.7 Typedef for const T &. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::const_iterator \since 4.7 Typedef for const T *. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::iterator \since 4.7 Typedef for T *. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::const_reverse_iterator \since 5.6 Typedef for \c{std::reverse_iterator}. Provided for STL compatibility. */ /*! \typedef QVarLengthArray::reverse_iterator \since 5.6 Typedef for \c{std::reverse_iterator}. Provided for STL compatibility. */ /*! \fn template void QVarLengthArray::prepend(const T &value) \fn template void QVarLengthArray::prepend(T &&value) \since 4.8 Inserts \a value at the beginning of the array. This is the same as vector.insert(0, \a value). For large arrays, this operation can be slow (\l{linear time}), because it requires moving all the items in the vector by one position further in memory. If you want a container class that provides a fast prepend() function, use QList or QLinkedList instead. \sa append(), insert() */ /*! \fn template void QVarLengthArray::replace(int i, const T &value) \since 4.8 Replaces the item at index position \a i with \a value. \a i must be a valid index position in the array (i.e., 0 <= \a i < size()). \sa operator[](), remove() */ /*! \fn template void QVarLengthArray::remove(int i) \overload \since 4.8 Removes the element at index position \a i. \sa insert(), replace() */ /*! \fn template void QVarLengthArray::remove(int i, int count) \overload \since 4.8 Removes \a count elements from the middle of the array, starting at index position \a i. \sa insert(), replace() */ /*! \fn template QVarLengthArray::iterator QVarLengthArray::begin() \since 4.8 Returns an \l{STL-style iterators}{STL-style iterator} pointing to the first item in the array. \sa constBegin(), end() */ /*! \fn template QVarLengthArray::const_iterator QVarLengthArray::begin() const \since 4.8 \overload */ /*! \fn template QVarLengthArray::const_iterator QVarLengthArray::cbegin() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the array. \sa begin(), cend() */ /*! \fn template QVarLengthArray::const_iterator QVarLengthArray::constBegin() const \since 4.8 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the array. \sa begin(), constEnd() */ /*! \fn template QVarLengthArray::iterator QVarLengthArray::end() \since 4.8 Returns an \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the array. \sa begin(), constEnd() */ /*! \fn template QVarLengthArray::const_iterator QVarLengthArray::end() const \since 4.8 \overload */ /*! \fn template QVarLengthArray::const_iterator QVarLengthArray::cend() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the array. \sa cbegin(), end() */ /*! \fn template QVarLengthArray::const_iterator QVarLengthArray::constEnd() const \since 4.8 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the array. \sa constBegin(), end() */ /*! \fn template QVarLengthArray::reverse_iterator QVarLengthArray::rbegin() \since 5.6 Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to the first item in the variable length array, in reverse order. \sa begin(), crbegin(), rend() */ /*! \fn template QVarLengthArray::const_reverse_iterator QVarLengthArray::rbegin() const \since 5.6 \overload */ /*! \fn template QVarLengthArray::const_reverse_iterator QVarLengthArray::crbegin() const \since 5.6 Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first item in the variable length array, in reverse order. \sa begin(), rbegin(), rend() */ /*! \fn template QVarLengthArray::reverse_iterator QVarLengthArray::rend() \since 5.6 Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past the last item in the variable length array, in reverse order. \sa end(), crend(), rbegin() */ /*! \fn template QVarLengthArray::const_reverse_iterator QVarLengthArray::rend() const \since 5.6 \overload */ /*! \fn template QVarLengthArray::const_reverse_iterator QVarLengthArray::crend() const \since 5.6 Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to one past the last item in the variable length array, in reverse order. \sa end(), rend(), rbegin() */ /*! \fn template QVarLengthArray::iterator QVarLengthArray::erase(const_iterator pos) \since 4.8 Removes the item pointed to by the iterator \a pos from the vector, and returns an iterator to the next item in the vector (which may be end()). \sa insert(), remove() */ /*! \fn template QVarLengthArray::iterator QVarLengthArray::erase(const_iterator begin, const_iterator end) \overload \since 4.8 Removes all the items from \a begin up to (but not including) \a end. Returns an iterator to the same item that \a end referred to before the call. */ /*! \fn template void QVarLengthArray::insert(int i, const T &value) \fn template void QVarLengthArray::insert(int i, T &&value) \since 4.8 Inserts \a value at index position \a i in the array. If \a i is 0, the value is prepended to the vector. If \a i is size(), the value is appended to the vector. For large arrays, this operation can be slow (\l{linear time}), because it requires moving all the items at indexes \a i and above by one position further in memory. If you want a container class that provides a fast insert() function, use QLinkedList instead. \sa remove() */ /*! \fn template void QVarLengthArray::insert(int i, int count, const T &value) \overload \since 4.8 Inserts \a count copies of \a value at index position \a i in the vector. */ /*! \fn template QVarLengthArray::iterator QVarLengthArray::insert(const_iterator before, const T &value) \fn template QVarLengthArray::iterator QVarLengthArray::insert(const_iterator before, T &&value) \overload \since 4.8 Inserts \a value in front of the item pointed to by the iterator \a before. Returns an iterator pointing at the inserted item. */ /*! \fn template QVarLengthArray::iterator QVarLengthArray::insert(const_iterator before, int count, const T &value) \since 4.8 Inserts \a count copies of \a value in front of the item pointed to by the iterator \a before. Returns an iterator pointing at the first of the inserted items. */ /*! \fn template bool operator==(const QVarLengthArray &left, const QVarLengthArray &right) \relates QVarLengthArray \since 4.8 Returns \c true if the two arrays, specified by \a left and \a right, are equal. Two arrays are considered equal if they contain the same values in the same order. This function requires the value type to have an implementation of \c operator==(). \sa operator!=() */ /*! \fn template bool operator!=(const QVarLengthArray &left, const QVarLengthArray &right) \relates QVarLengthArray \since 4.8 Returns \c true if the two arrays, specified by \a left and \a right, are \e not equal. Two arrays are considered equal if they contain the same values in the same order. This function requires the value type to have an implementation of \c operator==(). \sa operator==() */ /*! \fn template bool operator<(const QVarLengthArray &lhs, const QVarLengthArray &rhs) \since 5.6 \relates QVarLengthArray Returns \c true if variable length array \a lhs is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexicographically less than} \a rhs; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template bool operator<=(const QVarLengthArray &lhs, const QVarLengthArray &rhs) \since 5.6 \relates QVarLengthArray Returns \c true if variable length array \a lhs is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexicographically less than or equal to} \a rhs; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template bool operator>(const QVarLengthArray &lhs, const QVarLengthArray &rhs) \since 5.6 \relates QVarLengthArray Returns \c true if variable length array \a lhs is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexicographically greater than} \a rhs; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template bool operator>=(const QVarLengthArray &lhs, const QVarLengthArray &rhs) \since 5.6 \relates QVarLengthArray Returns \c true if variable length array \a lhs is \l{http://en.cppreference.com/w/cpp/algorithm/lexicographical_compare} {lexicographically greater than or equal to} \a rhs; otherwise returns \c false. This function requires the value type to have an implementation of \c operator<(). */ /*! \fn template QVarLengthArray &QVarLengthArray::operator<<(const T &value) \since 4.8 Appends \a value to the array and returns a reference to this vector. \sa append(), operator+=() */ /*! \fn template QVarLengthArray &QVarLengthArray::operator+=(const T &value) \since 4.8 Appends \a value to the array and returns a reference to this vector. \sa append(), operator<<() */ /*! \fn template int QVarLengthArray::indexOf(const T &value, int from = 0) const \since 5.3 Returns the index position of the first occurrence of \a value in the array, searching forward from index position \a from. Returns -1 if no item matched. This function requires the value type to have an implementation of \c operator==(). \sa lastIndexOf(), contains() */ /*! \fn template int QVarLengthArray::lastIndexOf(const T &value, int from = -1) const \since 5.3 Returns the index position of the last occurrence of the value \a value in the array, searching backward from index position \a from. If \a from is -1 (the default), the search starts at the last item. Returns -1 if no item matched. This function requires the value type to have an implementation of \c operator==(). \sa indexOf(), contains() */ /*! \fn template bool QVarLengthArray::contains(const T &value) const \since 5.3 Returns \c true if the array contains an occurrence of \a value; otherwise returns \c false. This function requires the value type to have an implementation of \c operator==(). \sa indexOf(), lastIndexOf() */