Mac-4.7.4/src/corelib/tools/qvarlengtharray.qdoc - platform/external/qt - Git at Google

 /****************************************************************************
 **
 ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation (qt-info@nokia.com)
 **
 ** This file is part of the documentation of the Qt Toolkit.
 **
 ** $QT_BEGIN_LICENSE:FDL$
 ** GNU Free Documentation License
 ** 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.
 **
 ** Other Usage
 ** Alternatively, this file may be used in accordance with the terms
 ** and conditions contained in a signed written agreement between you
 ** and Nokia.
 **
 **
 **
 **
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 /*!
     \class QVarLengthArray
     \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 doc/src/snippets/code/doc_src_qvarlengtharray.cpp 0

     The alternative is to allocate the array on the heap (with
     \c{new}):

     \snippet doc/src/snippets/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 doc/src/snippets/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
     \o QVarLengthArray's API is much more low-level. It provides no
        iterators and lacks much of QVector's functionality.

     \o QVarLengthArray doesn't initialize the memory if the value is
        a basic type. (QVector always does.)

     \o 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 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 QVarLengthArray::~QVarLengthArray()

     Destroys the array.
 */

 /*! \fn int QVarLengthArray::size() const

     Returns the number of elements in the array.

     \sa isEmpty(), resize()
 */

 /*! \fn int QVarLengthArray::count() const

     Same as size().

     \sa isEmpty(), resize()
 */

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

     Returns true if the array has size 0; otherwise returns false.

     \sa size(), resize()
 */

 /*! \fn void QVarLengthArray::clear()

     Removes all the elements from the array.

     Same as resize(0).
 */

 /*! \fn 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()
 */

 /*! \fn 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()
 */

 /*! \fn 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()
 */

 /*! \fn 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 const T &QVarLengthArray::operator[](int i) const

     \overload
 */


 /*!
     \fn void QVarLengthArray::append(const T &t)

     Appends item \a t to the array, extending the array if necessary.

     \sa removeLast()
 */


 /*!
     \fn inline void QVarLengthArray::removeLast()
     \since 4.5

     Decreases the size of the array by one.  The allocated size is not changed.

     \sa append()
 */

 /*!
     \fn void QVarLengthArray::append(const T *buf, int size)

     Appends \a size amount of items referenced by \a buf to this array.
 */


 /*! \fn 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 doc/src/snippets/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 const T *QVarLengthArray::data() const

     \overload
 */

 /*! \fn 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 QVarLengthArray<T, Prealloc> &QVarLengthArray::operator=(const QVarLengthArray<T, Prealloc> &other)
     Assigns \a other to this array and returns a reference to this array.
  */

 /*! \fn QVarLengthArray::QVarLengthArray(const QVarLengthArray<T, Prealloc> &other)
     Constructs a copy of \a other.
  */

 /*! \fn 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 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 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.
 */
	/****************************************************************************
	**
	** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
	** All rights reserved.
	** Contact: Nokia Corporation (qt-info@nokia.com)
	**
	** This file is part of the documentation of the Qt Toolkit.
	**
	** $QT_BEGIN_LICENSE:FDL$
	** GNU Free Documentation License
	** 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.
	**
	** Other Usage
	** Alternatively, this file may be used in accordance with the terms
	** and conditions contained in a signed written agreement between you
	** and Nokia.
	**
	**
	**
	**
	** $QT_END_LICENSE$
	**
	****************************************************************************/

	/*!
	\class QVarLengthArray
	\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 doc/src/snippets/code/doc_src_qvarlengtharray.cpp 0

	The alternative is to allocate the array on the heap (with
	\c{new}):

	\snippet doc/src/snippets/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 doc/src/snippets/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
	\o QVarLengthArray's API is much more low-level. It provides no
	iterators and lacks much of QVector's functionality.

	\o QVarLengthArray doesn't initialize the memory if the value is
	a basic type. (QVector always does.)

	\o 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 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 QVarLengthArray::~QVarLengthArray()

	Destroys the array.
	*/

	/*! \fn int QVarLengthArray::size() const

	Returns the number of elements in the array.

	\sa isEmpty(), resize()
	*/

	/*! \fn int QVarLengthArray::count() const

	Same as size().

	\sa isEmpty(), resize()
	*/

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

	Returns true if the array has size 0; otherwise returns false.

	\sa size(), resize()
	*/

	/*! \fn void QVarLengthArray::clear()

	Removes all the elements from the array.

	Same as resize(0).
	*/

	/*! \fn 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()
	*/

	/*! \fn 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()
	*/

	/*! \fn 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()
	*/

	/*! \fn 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 const T &QVarLengthArray::operator[](int i) const

	\overload
	*/


	/*!
	\fn void QVarLengthArray::append(const T &t)

	Appends item \a t to the array, extending the array if necessary.

	\sa removeLast()
	*/


	/*!
	\fn inline void QVarLengthArray::removeLast()
	\since 4.5

	Decreases the size of the array by one. The allocated size is not changed.

	\sa append()
	*/

	/*!
	\fn void QVarLengthArray::append(const T *buf, int size)

	Appends \a size amount of items referenced by \a buf to this array.
	*/


	/! \fn 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 doc/src/snippets/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 const T QVarLengthArray::data() const

	\overload
	*/

	/! \fn 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 QVarLengthArray<T, Prealloc> &QVarLengthArray::operator=(const QVarLengthArray<T, Prealloc> &other)
	Assigns \a other to this array and returns a reference to this array.
	*/

	/*! \fn QVarLengthArray::QVarLengthArray(const QVarLengthArray<T, Prealloc> &other)
	Constructs a copy of \a other.
	*/

	/*! \fn 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 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 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.
	*/