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** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
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****************************************************************************/
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\brief The Q3MemArray class is a template class that provides arrays of simple types.
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Q3MemArray is implemented as a template class. Define a template
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instance Q3MemArray\<X\> to create an array that contains X items.
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Q3MemArray stores the array elements directly in the array. It can
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only deal with simple types (i.e. C++ types, structs, and classes
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that have no constructors, destructors, or virtual functions).
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Q3MemArray uses bitwise operations to copy and compare array
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The Q3PtrVector collection class is also a kind of array. Like most
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old Qt collection classes, it uses pointers to the contained items.
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Q3MemArray uses explicit sharing with a
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reference count. If more than one array shares common data and one
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of the arrays is modified, all the arrays are modified.
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The benefit of sharing is that a program does not need to duplicate
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data when it is not required, which results in lower memory use
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and less copying of data.
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\snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 0
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\snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 1
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Note concerning the use of Q3MemArray for manipulating structs or
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classes: Compilers will often pad the size of structs of odd sizes
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up to the nearest word boundary. This will then be the size
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Q3MemArray will use for its bitwise element comparisons. Because
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the remaining bytes will typically be uninitialized, this can
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cause find() etc. to fail to find the element. Example:
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\snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 2
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To work around this, make sure that you use a struct where
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sizeof() returns the same as the sum of the sizes of the members
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either by changing the types of the struct members or by adding
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Q3MemArray data can be traversed by iterators (see begin() and
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end()). The number of items is returned by count(). The array can
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be resized with resize() and filled using fill().
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You can make a shallow copy of the array with assign() (or
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operator=()) and a deep copy with duplicate().
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Search for values in the array with find() and contains(). For
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sorted arrays (see sort()) you can search using bsearch().
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You can set the data directly using setRawData() and
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resetRawData(), although this requires care.
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/*! \fn Q3MemArray::operator QVector<type>() const
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Automatically converts the Q3MemArray<type> into a QVector<type>.
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/*! \typedef Q3MemArray::Iterator
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A Q3MemArray iterator.
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/*! \typedef Q3MemArray::ConstIterator
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A const Q3MemArray iterator.
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/*! \typedef Q3MemArray::ValueType
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\fn Q3MemArray::Q3MemArray()
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Constructs a null array.
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\fn Q3MemArray::Q3MemArray( int size )
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Constructs an array with room for \a size elements. Makes a null
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array if \a size == 0.
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The elements are left uninitialized.
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\sa resize(), isNull()
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\fn Q3MemArray::Q3MemArray( const Q3MemArray<type> &a )
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Constructs a shallow copy of \a a.
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\fn Q3MemArray::Q3MemArray(const QVector<type> &vector)
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Constructs a copy of \a vector.
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\fn Q3MemArray::Q3MemArray(int arg1, int arg2)
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Constructs an array \e{without allocating} array space. The
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arguments \a arg1 and \a arg2 should be zero. Use at your own
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\fn Q3MemArray::~Q3MemArray()
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Dereferences the array data and deletes it if this was the last
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\fn Q3MemArray<type> &Q3MemArray::operator=( const Q3MemArray<type> &a )
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Assigns a shallow copy of \a a to this array and returns a
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reference to this array.
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Equivalent to assign( a ).
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\fn type *Q3MemArray::data() const
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Returns a pointer to the actual array data.
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The array is a null array if data() == 0 (null pointer).
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\fn uint Q3MemArray::nrefs() const
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Returns the reference count for the shared array data. This
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reference count is always greater than zero.
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\fn uint Q3MemArray::size() const
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Returns the size of the array (maximum number of elements).
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The array is a null array if size() == 0.
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\sa isNull(), resize()
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\fn uint Q3MemArray::count() const
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Returns the same as size().
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\fn bool Q3MemArray::isEmpty() const
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Returns TRUE if the array is empty; otherwise returns FALSE.
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isEmpty() is equivalent to isNull() for Q3MemArray (unlike
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\fn bool Q3MemArray::isNull() const
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Returns TRUE if the array is null; otherwise returns FALSE.
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A null array has size() == 0 and data() == 0.
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\fn bool Q3MemArray::resize( uint size, Optimization optim )
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Resizes (expands or shrinks) the array to \a size elements. The
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array becomes a null array if \a size == 0.
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Returns TRUE if successful, or FALSE if the memory cannot be
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New elements are not initialized.
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\a optim is either Q3GArray::MemOptim (the default) or
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Q3GArray::SpeedOptim. When optimizing for speed rather than memory
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consumption, the array uses a smart grow and shrink algorithm that
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might allocate more memory than is actually needed for \a size
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elements. This speeds up subsequent resize operations, for example
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when appending many elements to an array, since the space has
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already been allocated.
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\fn bool Q3MemArray::resize( uint size )
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Resizes (expands or shrinks) the array to \a size elements. The
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array becomes a null array if \a size == 0.
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Returns TRUE if successful, i.e. if the memory can be allocated;
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otherwise returns FALSE.
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New elements are not initialized.
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\fn bool Q3MemArray::truncate( uint pos )
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Truncates the array at position \a pos.
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Returns TRUE if successful, i.e. if the memory can be allocated;
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otherwise returns FALSE.
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Equivalent to resize(\a pos).
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\fn bool Q3MemArray::fill( const type &v, int size )
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Fills the array with the value \a v. If \a size is specified as
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different from -1, then the array will be resized before being
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Returns TRUE if successful, i.e. if \a size is -1, or \a size is
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!= -1 and the memory can be allocated; otherwise returns FALSE.
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\fn void Q3MemArray::detach()
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Detaches this array from shared array data; i.e. it makes a
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private, deep copy of the data.
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Copying will be performed only if the \link nrefs() reference
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count\endlink is greater than one.
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\fn Q3MemArray<type> Q3MemArray::copy() const
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Returns a deep copy of this array.
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\sa detach(), duplicate()
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\fn Q3MemArray<type> &Q3MemArray::assign( const Q3MemArray<type> &a )
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Shallow copy. Dereferences the current array and references the
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data contained in \a a instead. Returns a reference to this array.
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\fn Q3MemArray<type> &Q3MemArray::assign( const type *data, uint size )
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Shallow copy. Dereferences the current array and references the
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array data \a data, which contains \a size elements. Returns a
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reference to this array.
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Do not delete \a data later; Q3MemArray will call free() on it
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\fn Q3MemArray<type> &Q3MemArray::duplicate( const Q3MemArray<type> &a )
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Deep copy. Dereferences the current array and obtains a copy of
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the data contained in \a a instead. Returns a reference to this
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\fn Q3MemArray<type> &Q3MemArray::duplicate( const type *data, uint size )
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Deep copy. Dereferences the current array and obtains a copy of
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the array data \a data instead. Returns a reference to this array.
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The size of the array is given by \a size.
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\fn Q3MemArray<type> &Q3MemArray::setRawData( const type *data, uint size )
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Sets raw data and returns a reference to the array.
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Dereferences the current array and sets the new array data to \a
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data and the new array size to \a size. Do not attempt to resize
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or re-assign the array data when raw data has been set. Call
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resetRawData(\a data, \a size) to reset the array.
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Setting raw data is useful because it sets Q3MemArray data without
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allocating memory or copying data.
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Example I (intended use):
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\snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 3
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Example II (you don't want to do this):
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\snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 4
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\warning If you do not call resetRawData(), Q3MemArray will attempt
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to deallocate or reallocate the raw data, which might not be too
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\fn void Q3MemArray::resetRawData( const type *data, uint size )
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Removes internal references to the raw data that was set using
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setRawData(). This means that Q3MemArray no longer has access to
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the \a data, so you are free to manipulate \a data as you wish.
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You can now use the Q3MemArray without affecting the original \a
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data, for example by calling setRawData() with a pointer to some
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The arguments must be the \a data and length, \a size, that were
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passed to setRawData(). This is for consistency checking.
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\fn int Q3MemArray::find( const type &v, uint index ) const
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Finds the first occurrence of \a v, starting at position \a index.
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Returns the position of \a v, or -1 if \a v could not be found.
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\fn int Q3MemArray::contains( const type &v ) const
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Returns the number of times \a v occurs in the array.
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\fn void Q3MemArray::sort()
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Sorts the array elements in ascending order, using bitwise
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comparison (memcmp()).
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\fn int Q3MemArray::bsearch( const type &v ) const
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In a sorted array (as sorted by sort()), finds the first
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occurrence of \a v by using a binary search. For a sorted
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array this is generally much faster than find(), which does
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Returns the position of \a v, or -1 if \a v could not be found.
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\fn type &Q3MemArray::operator[]( int index ) const
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Returns a reference to the element at position \a index in the
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This can be used to both read and set an element. Equivalent to
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\fn type &Q3MemArray::at( uint index ) const
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Returns a reference to the element at position \a index in the array.
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This can be used to both read and set an element.
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\fn Q3MemArray::operator const type *() const
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Cast operator. Returns a pointer to the array.
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\fn bool Q3MemArray::operator==( const Q3MemArray<type> &a ) const
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Returns TRUE if this array is equal to \a a; otherwise returns
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The two arrays are compared bitwise.
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\fn bool Q3MemArray::operator!=( const Q3MemArray<type> &a ) const
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Returns TRUE if this array is different from \a a; otherwise
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The two arrays are compared bitwise.
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\fn Iterator Q3MemArray::begin()
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Returns an iterator pointing at the beginning of this array. This
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iterator can be used in the same way as the iterators of
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Q3ValueList and QMap, for example.
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\fn Iterator Q3MemArray::end()
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Returns an iterator pointing behind the last element of this
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array. This iterator can be used in the same way as the iterators
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of Q3ValueList and QMap, for example.
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\fn ConstIterator Q3MemArray::begin() const
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Returns a const iterator pointing at the beginning of this array.
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This iterator can be used in the same way as the iterators of
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Q3ValueList and QMap, for example.
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\fn ConstIterator Q3MemArray::end() const
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Returns a const iterator pointing behind the last element of this
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array. This iterator can be used in the same way as the iterators
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of Q3ValueList and QMap, for example.