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These rights are described in the Digia Qt LGPL Exception ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 3.0 as published by the Free Software ** Foundation and appearing in the file LICENSE.GPL included in the ** packaging of this file. Please review the following information to ** ensure the GNU General Public License version 3.0 requirements will be ** met: http://www.gnu.org/copyleft/gpl.html. ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \class QVector \inmodule QtCore \brief The QVector class is a template class that provides a dynamic array. \ingroup tools \ingroup shared \reentrant QVector\ is one of Qt's generic \l{container classes}. It stores its items in adjacent memory locations and provides fast index-based access. QList\, QLinkedList\, and QVarLengthArray\ provide similar functionality. Here's an overview: \list \li For most purposes, QList is the right class to use. Operations like prepend() and insert() are usually faster than with QVector because of the way QList stores its items in memory (see \l{Algorithmic Complexity} for details), and its index-based API is more convenient than QLinkedList's iterator-based API. It also expands to less code in your executable. \li If you need a real linked list, with guarantees of \l{constant time} insertions in the middle of the list and iterators to items rather than indexes, use QLinkedList. \li If you want the items to occupy adjacent memory positions, or if your items are larger than a pointer and you want to avoid the overhead of allocating them on the heap individually at insertion time, then use QVector. \li If you want a low-level variable-size array, QVarLengthArray may be sufficient. \endlist Here's an example of a QVector that stores integers and a QVector that stores QString values: \snippet code/src_corelib_tools_qvector.cpp 0 QVector stores a vector (or array) of items. Typically, vectors are created with an initial size. For example, the following code constructs a QVector with 200 elements: \snippet code/src_corelib_tools_qvector.cpp 1 The elements are automatically initialized with a \l{default-constructed value}. If you want to initialize the vector with a different value, pass that value as the second argument to the constructor: \snippet code/src_corelib_tools_qvector.cpp 2 You can also call fill() at any time to fill the vector with a value. QVector uses 0-based indexes, just like C++ arrays. To access the item at a particular index position, you can use operator[](). On non-const vectors, operator[]() returns a reference to the item that can be used on the left side of an assignment: \snippet code/src_corelib_tools_qvector.cpp 3 For read-only access, an alternative syntax is to use at(): \snippet code/src_corelib_tools_qvector.cpp 4 at() can be faster than operator[](), because it never causes a \l{deep copy} to occur. Another way to access the data stored in a QVector is to call data(). The function returns a pointer to the first item in the vector. You can use the pointer to directly access and modify the elements stored in the vector. The pointer is also useful if you need to pass a QVector to a function that accepts a plain C++ array. If you want to find all occurrences of a particular value in a vector, use indexOf() or lastIndexOf(). The former searches forward starting from a given index position, the latter searches backward. Both return the index of the matching item if they found one; otherwise, they return -1. For example: \snippet code/src_corelib_tools_qvector.cpp 5 If you simply want to check whether a vector contains a particular value, use contains(). If you want to find out how many times a particular value occurs in the vector, use count(). QVector provides these basic functions to add, move, and remove items: insert(), replace(), remove(), prepend(), append(). With the exception of append() and replace(), these functions can be slow (\l{linear time}) for large vectors, because they require moving many items in the vector by one position in memory. If you want a container class that provides fast insertion/removal in the middle, use QList or QLinkedList instead. Unlike plain C++ arrays, QVectors can be resized at any time by calling resize(). If the new size is larger than the old size, QVector might need to reallocate the whole vector. QVector tries to reduce the number of reallocations by preallocating up to twice as much memory as the actual data needs. If you know in advance approximately how many items the QVector will contain, you can call reserve(), asking QVector to preallocate a certain amount of memory. You can also call capacity() to find out how much memory QVector actually allocated. Note that using non-const operators and functions can cause QVector to do a deep copy of the data. This is due to \l{implicit sharing}. QVector'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 *. A few functions have additional requirements; for example, indexOf() and lastIndexOf() expect the value type to support \c operator==(). These requirements are documented on a per-function basis. Like the other container classes, QVector provides \l{Java-style iterators} (QVectorIterator and QMutableVectorIterator) and \l{STL-style iterators} (QVector::const_iterator and QVector::iterator). In practice, these are rarely used, because you can use indexes into the QVector. In addition to QVector, Qt also provides QVarLengthArray, a very low-level class with little functionality that is optimized for speed. QVector does \e not support inserting, prepending, appending or replacing with references to its own values. Doing so will cause your application to abort with an error message. \sa QVectorIterator, QMutableVectorIterator, QList, QLinkedList */ /*! \fn QVector QVector::mid(int pos, int length = -1) const Returns a vector whose elements are copied from this vector, starting at position \a pos. If \a length is -1 (the default), all elements after \a pos are copied; otherwise \a length elements (or all remaining elements if there are less than \a length elements) are copied. */ /*! \fn QVector::QVector() Constructs an empty vector. \sa resize() */ /*! \fn QVector::QVector(int size) Constructs a vector with an initial size of \a size elements. The elements are initialized with a \l{default-constructed value}. \sa resize() */ /*! \fn QVector::QVector(int size, const T &value) Constructs a vector with an initial size of \a size elements. Each element is initialized with \a value. \sa resize(), fill() */ /*! \fn QVector::QVector(const QVector &other) Constructs a copy of \a other. This operation takes \l{constant time}, because QVector is \l{implicitly shared}. This makes returning a QVector from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes \l{linear time}. \sa operator=() */ /*! \fn QVector::QVector(std::initializer_list args) \since 4.8 Construct a vector from the std::initilizer_list given by \a args. This constructor is only enabled if the compiler supports C++11 initializer lists. */ /*! \fn QVector::~QVector() Destroys the vector. */ /*! \fn QVector &QVector::operator=(const QVector &other) Assigns \a other to this vector and returns a reference to this vector. */ /*! \fn void QVector::swap(QVector &other) \since 4.8 Swaps vector \a other with this vector. This operation is very fast and never fails. */ /*! \fn bool QVector::operator==(const QVector &other) const Returns true if \a other is equal to this vector; otherwise returns false. Two vectors 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 bool QVector::operator!=(const QVector &other) const Returns true if \a other is not equal to this vector; otherwise returns false. Two vectors 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 int QVector::size() const Returns the number of items in the vector. \sa isEmpty(), resize() */ /*! \fn bool QVector::isEmpty() const Returns true if the vector has size 0; otherwise returns false. \sa size(), resize() */ /*! \fn void QVector::resize(int size) Sets the size of the vector to \a size. If \a size is greater than the current size, elements are added to the end; the new elements are initialized with a \l{default-constructed value}. If \a size is less than the current size, elements are removed from the end. \sa size() */ /*! \fn int QVector::capacity() const Returns the maximum number of items that can be stored in the vector without forcing a reallocation. The sole purpose of this function is to provide a means of fine tuning QVector'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 vector, call size(). \sa reserve(), squeeze() */ /*! \fn void QVector::reserve(int size) Attempts to allocate memory for at least \a size elements. If you know in advance how large the vector will be, 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 QVector will be a bit slower. The sole purpose of this function is to provide a means of fine tuning QVector's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the vector, call resize(). \sa squeeze(), capacity() */ /*! \fn void QVector::squeeze() Releases any memory not required to store the items. The sole purpose of this function is to provide a means of fine tuning QVector's memory usage. In general, you will rarely ever need to call this function. \sa reserve(), capacity() */ /*! \fn void QVector::detach() \internal */ /*! \fn bool QVector::isDetached() const \internal */ /*! \fn void QVector::setSharable(bool sharable) \internal */ /*! \fn bool QVector::isSharedWith(const QVector &other) const \internal */ /*! \fn T *QVector::data() Returns a pointer to the data stored in the vector. The pointer can be used to access and modify the items in the vector. Example: \snippet code/src_corelib_tools_qvector.cpp 6 The pointer remains valid as long as the vector isn't reallocated. This function is mostly useful to pass a vector to a function that accepts a plain C++ array. \sa constData(), operator[]() */ /*! \fn const T *QVector::data() const \overload */ /*! \fn const T *QVector::constData() const Returns a const pointer to the data stored in the vector. The pointer can be used to access the items in the vector. The pointer remains valid as long as the vector isn't reallocated. This function is mostly useful to pass a vector to a function that accepts a plain C++ array. \sa data(), operator[]() */ /*! \fn void QVector::clear() Removes all the elements from the vector and releases the memory used by the vector. */ /*! \fn const T &QVector::at(int i) const Returns the item at index position \a i in the vector. \a i must be a valid index position in the vector (i.e., 0 <= \a i < size()). \sa value(), operator[]() */ /*! \fn T &QVector::operator[](int i) Returns the item at index position \a i as a modifiable reference. \a i must be a valid index position in the vector (i.e., 0 <= \a i < size()). Note that using non-const operators can cause QVector to do a deep copy. \sa at(), value() */ /*! \fn const T &QVector::operator[](int i) const \overload Same as at(\a i). */ /*! \fn void QVector::append(const T &value) Inserts \a value at the end of the vector. Example: \snippet code/src_corelib_tools_qvector.cpp 7 This is the same as calling resize(size() + 1) and assigning \a value to the new last element in the vector. This operation is relatively fast, because QVector typically allocates more memory than necessary, so it can grow without reallocating the entire vector each time. \sa operator<<(), prepend(), insert() */ /*! \fn void QVector::prepend(const T &value) Inserts \a value at the beginning of the vector. Example: \snippet code/src_corelib_tools_qvector.cpp 8 This is the same as vector.insert(0, \a value). For large vectors, 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 void QVector::insert(int i, const T &value) Inserts \a value at index position \a i in the vector. If \a i is 0, the value is prepended to the vector. If \a i is size(), the value is appended to the vector. Example: \snippet code/src_corelib_tools_qvector.cpp 9 For large vectors, 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 append(), prepend(), remove() */ /*! \fn void QVector::insert(int i, int count, const T &value) \overload Inserts \a count copies of \a value at index position \a i in the vector. Example: \snippet code/src_corelib_tools_qvector.cpp 10 */ /*! \fn QVector::iterator QVector::insert(iterator before, const T &value) \overload Inserts \a value in front of the item pointed to by the iterator \a before. Returns an iterator pointing at the inserted item. */ /*! \fn QVector::iterator QVector::insert(iterator before, int count, const T &value) 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 void QVector::replace(int i, const T &value) Replaces the item at index position \a i with \a value. \a i must be a valid index position in the vector (i.e., 0 <= \a i < size()). \sa operator[](), remove() */ /*! \fn void QVector::remove(int i) \overload Removes the element at index position \a i. \sa insert(), replace(), fill() */ /*! \fn void QVector::remove(int i, int count) \overload Removes \a count elements from the middle of the vector, starting at index position \a i. \sa insert(), replace(), fill() */ /*! \fn void QVector::removeFirst() \since 5.1 Removes the first item in the vector. Calling this function is equivalent to calling remove(0). The vector must not be empty. If the vector can be empty, call isEmpty() before calling this function. \sa remove(), takeFirst(), isEmpty() */ /*! \fn void QVector::removeLast() \since 5.1 Removes the last item in the vector. Calling this function is equivalent to calling remove(size() - 1). The vector must not be empty. If the vector can be empty, call isEmpty() before calling this function. \sa remove(), takeLast(), removeFirst(), isEmpty() */ /*! \fn T QVector::takeFirst() Removes the first item in the vector and returns it. This function assumes the vector is not empty. To avoid failure, call isEmpty() before calling this function. \sa takeLast(), removeFirst() */ /*! \fn T QVector::takeLast() Removes the last item in the list and returns it. This function assumes the vector is not empty. To avoid failure, call isEmpty() before calling this function. If you don't use the return value, removeLast() is more efficient. \sa takeFirst(), removeLast() */ /*! \fn QVector &QVector::fill(const T &value, int size = -1) Assigns \a value to all items in the vector. If \a size is different from -1 (the default), the vector is resized to size \a size beforehand. Example: \snippet code/src_corelib_tools_qvector.cpp 11 \sa resize() */ /*! \fn int QVector::indexOf(const T &value, int from = 0) const Returns the index position of the first occurrence of \a value in the vector, searching forward from index position \a from. Returns -1 if no item matched. Example: \snippet code/src_corelib_tools_qvector.cpp 12 This function requires the value type to have an implementation of \c operator==(). \sa lastIndexOf(), contains() */ /*! \fn int QVector::lastIndexOf(const T &value, int from = -1) const Returns the index position of the last occurrence of the value \a value in the vector, 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. Example: \snippet code/src_corelib_tools_qvector.cpp 13 This function requires the value type to have an implementation of \c operator==(). \sa indexOf() */ /*! \fn bool QVector::contains(const T &value) const Returns true if the vector contains an occurrence of \a value; otherwise returns false. This function requires the value type to have an implementation of \c operator==(). \sa indexOf(), count() */ /*! \fn bool QVector::startsWith(const T &value) const \since 4.5 Returns true if this vector is not empty and its first item is equal to \a value; otherwise returns false. \sa isEmpty(), first() */ /*! \fn bool QVector::endsWith(const T &value) const \since 4.5 Returns true if this vector is not empty and its last item is equal to \a value; otherwise returns false. \sa isEmpty(), last() */ /*! \fn int QVector::count(const T &value) const Returns the number of occurrences of \a value in the vector. This function requires the value type to have an implementation of \c operator==(). \sa contains(), indexOf() */ /*! \fn int QVector::count() const \overload Same as size(). */ /*! \fn QVector::iterator QVector::begin() Returns an \l{STL-style iterators}{STL-style iterator} pointing to the first item in the vector. \sa constBegin(), end() */ /*! \fn QVector::const_iterator QVector::begin() const \overload */ /*! \fn QVector::const_iterator QVector::cbegin() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the vector. \sa begin(), cend() */ /*! \fn QVector::const_iterator QVector::constBegin() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the vector. \sa begin(), constEnd() */ /*! \fn QVector::iterator QVector::end() Returns an \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the vector. \sa begin(), constEnd() */ /*! \fn QVector::const_iterator QVector::end() const \overload */ /*! \fn QVector::const_iterator QVector::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 vector. \sa cbegin(), end() */ /*! \fn QVector::const_iterator QVector::constEnd() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the vector. \sa constBegin(), end() */ /*! \fn QVector::iterator QVector::erase(iterator pos) 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 QVector::iterator QVector::erase(iterator begin, iterator end) \overload 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 T& QVector::first() Returns a reference to the first item in the vector. This function assumes that the vector isn't empty. \sa last(), isEmpty() */ /*! \fn const T& QVector::first() const \overload */ /*! \fn T& QVector::last() Returns a reference to the last item in the vector. This function assumes that the vector isn't empty. \sa first(), isEmpty() */ /*! \fn const T& QVector::last() const \overload */ /*! \fn T QVector::value(int i) const Returns the value at index position \a i in the vector. 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 T QVector::value(int i, const T &defaultValue) const \overload If the index \a i is out of bounds, the function returns \a defaultValue. */ /*! \fn void QVector::push_back(const T &value) This function is provided for STL compatibility. It is equivalent to append(\a value). */ /*! \fn void QVector::push_front(const T &value) This function is provided for STL compatibility. It is equivalent to prepend(\a value). */ /*! \fn void QVector::pop_front() This function is provided for STL compatibility. It is equivalent to removeFirst(). */ /*! \fn void QVector::pop_back() This function is provided for STL compatibility. It is equivalent to removeLast(). */ /*! \fn T& QVector::front() This function is provided for STL compatibility. It is equivalent to first(). */ /*! \fn QVector::const_reference QVector::front() const \overload */ /*! \fn QVector::reference QVector::back() This function is provided for STL compatibility. It is equivalent to last(). */ /*! \fn QVector::const_reference QVector::back() const \overload */ /*! \fn bool QVector::empty() const This function is provided for STL compatibility. It is equivalent to isEmpty(), returning true if the vector is empty; otherwise returns false. */ /*! \fn QVector &QVector::operator+=(const QVector &other) Appends the items of the \a other vector to this vector and returns a reference to this vector. \sa operator+(), append() */ /*! \fn void QVector::operator+=(const T &value) \overload Appends \a value to the vector. \sa append(), operator<<() */ /*! \fn QVector QVector::operator+(const QVector &other) const Returns a vector that contains all the items in this vector followed by all the items in the \a other vector. \sa operator+=() */ /*! \fn QVector &QVector::operator<<(const T &value) Appends \a value to the vector and returns a reference to this vector. \sa append(), operator+=() */ /*! \fn QVector &QVector::operator<<(const QVector &other) Appends \a other to the vector and returns a reference to the vector. */ /*! \typedef QVector::iterator The QVector::iterator typedef provides an STL-style non-const iterator for QVector and QStack. QVector provides both \l{STL-style iterators} and \l{Java-style iterators}. The STL-style non-const iterator is simply a typedef for "T *" (pointer to T). \sa QVector::begin(), QVector::end(), QVector::const_iterator, QMutableVectorIterator */ /*! \typedef QVector::const_iterator The QVector::const_iterator typedef provides an STL-style const iterator for QVector and QStack. QVector provides both \l{STL-style iterators} and \l{Java-style iterators}. The STL-style const iterator is simply a typedef for "const T *" (pointer to const T). \sa QVector::constBegin(), QVector::constEnd(), QVector::iterator, QVectorIterator */ /*! \typedef QVector::Iterator Qt-style synonym for QVector::iterator. */ /*! \typedef QVector::ConstIterator Qt-style synonym for QVector::const_iterator. */ /*! \typedef QVector::const_pointer Typedef for const T *. Provided for STL compatibility. */ /*! \typedef QVector::const_reference Typedef for T &. Provided for STL compatibility. */ /*! \typedef QVector::difference_type Typedef for ptrdiff_t. Provided for STL compatibility. */ /*! \typedef QVector::pointer Typedef for T *. Provided for STL compatibility. */ /*! \typedef QVector::reference Typedef for T &. Provided for STL compatibility. */ /*! \typedef QVector::size_type Typedef for int. Provided for STL compatibility. */ /*! \typedef QVector::value_type Typedef for T. Provided for STL compatibility. */ /*! \fn QList QVector::toList() const Returns a QList object with the data contained in this QVector. Example: \snippet code/src_corelib_tools_qvector.cpp 14 \sa fromList(), QList::fromVector() */ /*! \fn QVector QVector::fromList(const QList &list) Returns a QVector object with the data contained in \a list. Example: \snippet code/src_corelib_tools_qvector.cpp 15 \sa toList(), QList::toVector() */ /*! \fn QVector QVector::fromStdVector(const std::vector &vector) Returns a QVector object with the data contained in \a vector. The order of the elements in the QVector is the same as in \a vector. Example: \snippet code/src_corelib_tools_qvector.cpp 16 \sa toStdVector(), QList::fromStdList() */ /*! \fn std::vector QVector::toStdVector() const Returns a std::vector object with the data contained in this QVector. Example: \snippet code/src_corelib_tools_qvector.cpp 17 \sa fromStdVector(), QList::toStdList() */ /*! \fn QDataStream &operator<<(QDataStream &out, const QVector &vector) \relates QVector Writes the vector \a vector to stream \a out. This function requires the value type to implement \c operator<<(). \sa{Serializing Qt Data Types}{Format of the QDataStream operators} */ /*! \fn QDataStream &operator>>(QDataStream &in, QVector &vector) \relates QVector Reads a vector from stream \a in into \a vector. This function requires the value type to implement \c operator>>(). \sa{Serializing Qt Data Types}{Format of the QDataStream operators} */