path: root/qtools/qarray.doc

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** QArray class documentation
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/*****************************************************************************
  QArray documentation
 *****************************************************************************/

/*!
  \class QArray qarray.h
  \brief The QArray class is a template class that provides arrays of simple types.

  \ingroup tools

  QArray is implemented as a template class. Define a template
  instance QArray\<X\> to create an array that contains X items.

  QArray stores the array elements directly in the array. It can only
  deal with simple types, i.e. C++ types, structs and classes that have
  no constructors, destructors or virtual functions.  QArray uses
  bitwise operations to copy and compare array elements.

  The QVector collection class is also a kind of array.  Like most
  \link collection.html collection classes\endlink, it has pointers to the
  contained items.

  QArray uses explicit \link shclass.html sharing\endlink with a reference
  count.  If more than one array share common data, and one array is
  modified, all arrays will be modified.

  The benefit of sharing is that a program does not need to duplicate
  data when it is not required, which results in less memory usage and
  less copying of data.

  Example:
  \code
    #include <qarray.h>
    #include <stdio.h>

    QArray<int> fib( int num )			// returns fibonacci array
    {
	ASSERT( num > 2 );
	QArray<int> f( num );			// array of ints

        f[0] = f[1] = 1;			// initialize first two numbers
	for ( int i=2; i<num; i++ )
	    f[i] = f[i-1] + f[i-2];	

	return f;
    }

    void main()
    {
	QArray<int> a = fib( 6 );		// get 6 first fibonaccis
	int i;

	for ( i=0; i<a.size(); i++ )		// print them
	    prinf( "%d: %d\n", i, a[i] );

	printf( "1 is found %d time(s)\n", a.contains(1) );
	printf( "5 is found at index %d\n", a.find(5) );
    }
  \endcode

  Program output:
  \code
	0: 1
	1: 1
	2: 2
	3: 3
	4: 5
	5: 8
	1 is found 2 times
	5 is found at index 4
  \endcode

  Note about using QArray for manipulating structs or classes:
  Compilers will often pad the size of structs of odd sizes up to the
  nearest word boundary. This will then be the size QArray will use
  for its bitwise element comparisons. Since the remaining bytes will
  typically be uninitialized, this can cause find() etc. to fail to
  find the element. Example:

  \code
    struct MyStruct
    {
      short i;                    // 2 bytes
      char c;                     // 1 byte
    };                            // sizeof(MyStruct) may be padded to 4 bytes

    QArray<MyStruct> a(1);
    a[0].i = 5;
    a[0].c = 't';

    MyStruct x;
    x.i = '5';
    x.c = 't';
    int i = a.find( x );          // May return -1 if the pad bytes differ
  \endcode

  To workaround this, make sure that you use a struct where sizeof()
  returns the same as the sum of the sizes of the members, either by
  changing the types of the struct members or by adding dummy members.

  \sa \link shclass.html Shared Classes\endlink
*/


/*!
  \fn QArray::QArray()
  Constructs a null array.
  \sa isNull()
*/

/*!
  \fn QArray::QArray( int size )
  Constructs an array with room for \e size elements.
  Makes a null array if \e size == 0.

  Note that the elements are not initialized.

  \sa resize(), isNull()
*/

/*!
  \fn QArray::QArray( const QArray<type> &a )
  Constructs a shallow copy of \e a.
  \sa assign()
*/

/*!
  \fn QArray::QArray( int, int )
  Constructs an array <em>without allocating</em> array space.
  The arguments should be (0, 0). Use at own risk.
*/

/*!
  \fn QArray::~QArray()
  Dereferences the array data and deletes it if this was the last
  reference.
*/

/*!
  \fn QArray<type> &QArray::operator=( const QArray<type> &a )
  Assigns a shallow copy of \e a to this array and returns a reference
  to this array.

  Equivalent to assign( a ).
*/

/*!
  \fn type *QArray::data() const
  Returns a pointer to the actual array data.

  The array is a null array if data() == 0 (null pointer).

  \sa isNull()
*/

/*!
  \fn uint QArray::nrefs() const
  Returns the reference count for the shared array data. This reference count
  is always greater than zero.
*/

/*!
  \fn uint QArray::size() const
  Returns the size of the array (max number of elements).

  The array is a null array if size() == 0.

  \sa isNull(), resize()
*/

/*!
  \fn uint QArray::count() const
  Returns the same as size().

  \sa size()
*/

/*!
  \fn bool QArray::isEmpty() const
  Returns TRUE if the array is empty, i.e. size() == 0, otherwise FALSE.

  isEmpty() is equivalent with isNull() for QArray.  Note that this is not
  the case for QCString::isEmpty().
*/

/*!
  \fn bool QArray::isNull() const
  Returns TRUE if the array is null, otherwise FALSE.

  A null array has size() == 0 and data() == 0.
*/

/*!
  \fn bool QArray::resize( uint size )
  Resizes (expands or shrinks) the array to \e size elements. The array
  becomes a null array if \e size == 0.

  Returns TRUE if successful, or FALSE if the memory cannot be allocated.

  New elements will not be initialized.

  \sa size()
*/

/*!
  \fn bool QArray::truncate( uint pos )
  Truncates the array at position \e pos.

  Returns TRUE if successful, or FALSE if the memory cannot be allocated.

  Equivalent to resize(\e pos).

  \sa resize()
*/

/*!
  \fn bool QArray::fill( const type &v, int size )
  Fills the array with the value \e v. If \e size is specified as different
  from -1, then the array will be resized before filled.

  Returns TRUE if successful, or FALSE if the memory cannot be allocated
  (only when \e size != -1).

  \sa resize()
*/

/*!
  \fn void QArray::detach()
  Detaches this array from shared array data, i.e. makes a private, deep
  copy of the data.

  Copying will only be performed if the
  \link nrefs() reference count\endlink is greater than one.

  \sa copy()
*/

/*!
  \fn QArray<type> QArray::copy() const
  Returns a deep copy of this array.
  \sa detach(), duplicate()
*/

/*!
  \fn QArray<type> &QArray::assign( const QArray<type> &a )
  Shallow copy. Dereferences the current array and references the data
  contained in \e a instead. Returns a reference to this array.
  \sa operator=()
*/

/*!
  \fn QArray<type> &QArray::assign( const type *data, uint size )
  Shallow copy. Dereferences the current array and references the
  array data \e data, which contains \e size elements.
  Returns a reference to this array.

  Do not delete \e data later, QArray takes care of that.
*/

/*!
  \fn QArray<type> &QArray::duplicate( const QArray<type> &a )
  Deep copy. Dereferences the current array and obtains a copy of the data
  contained in \e a instead. Returns a reference to this array.
  \sa copy()
*/

/*!
  \fn QArray<type> &QArray::duplicate( const type *data, uint size )
  Deep copy. Dereferences the current array and obtains a copy of the
  array data \e data instead.  Returns a reference to this array.
  \sa copy()
*/

/*!
  \fn QArray<type> &QArray::setRawData( const type *data, uint size )

  Sets raw data and returns a reference to the array.

  Dereferences the current array and sets the new array data to \e data and
  the new array size to \e size.  Do not attempt to resize or re-assign the
  array data when raw data has been set.
  Call resetRawData(d,len) to reset the array.

  Setting raw data is useful because it sets QArray data without allocating
  memory or copying data.

  Example I (intended use):
  \code
    static char bindata[] = { 231, 1, 44, ... };
    QByteArray	a;
    a.setRawData( bindata, sizeof(bindata) );	// a points to bindata
    QDataStream s( a, IO_ReadOnly );		// open on a's data
    s >> <something>;				// read raw bindata
    a.resetRawData( bindata, sizeof(bindata) ); // finished
  \endcode

  Example II (you don't want to do this):
  \code
    static char bindata[] = { 231, 1, 44, ... };
    QByteArray	a, b;
    a.setRawData( bindata, sizeof(bindata) );	// a points to bindata
    a.resize( 8 );				// will crash
    b = a;					// will crash
    a[2] = 123;					// might crash
      // forget to resetRawData - will crash
  \endcode

  \warning If you do not call resetRawData(), QArray will attempt to
  deallocate or reallocate the raw data, which might not be too good.
  Be careful.

  \sa resetRawData()
*/

/*!
  \fn void QArray::resetRawData( const type *data, uint size )
  Resets raw data that was set using setRawData().

  The arguments must be the data and length that were passed to
  setRawData().	 This is for consistency checking.

  \sa setRawData()
*/

/*!
  \fn int QArray::find( const type &v, uint index ) const
  Finds the first occurrence of \e v, starting at position \e index.

  Returns the position of \e v, or -1 if \e v could not be found.

  \sa contains()
*/

/*!
  \fn int QArray::contains( const type &v ) const
  Returns the number of times \e v occurs in the array.
  \sa find()
*/

/*!
  \fn void QArray::sort()
  Sorts the array elements in ascending order, using bitwise
  comparison (memcmp()).

  \sa bsearch()
*/

/*!
  \fn int QArray::bsearch( const type &v ) const
  In a sorted array, finds the first occurrence of \e v using binary
  search. For a sorted array, this is generally much faster than
  find(), which does a linear search.

  Returns the position of \e v, or -1 if \e v could not be found.

  \sa sort(), find()
*/

/*!
  \fn type &QArray::operator[]( int index ) const
  Returns a reference to the element at position \e index in the array.

  This can be used to both read and set an element.  Equivalent to at().

  \sa at()
*/

/*!
  \fn type &QArray::at( uint index ) const
  Returns a reference to the element at position \e index in the array.

  This can be used to both read and set an element.

  \sa operator[]()
*/

/*!
  \fn QArray::operator const type *() const
  Cast operator.  Returns a pointer to the array.
  \sa data()
*/

/*!
  \fn bool QArray::operator==( const QArray<type> &a ) const
  Returns TRUE if this array is equal to \e a, otherwise FALSE.

  The two arrays are bitwise compared.

  \sa operator!=()
*/

/*!
  \fn bool QArray::operator!=( const QArray<type> &a ) const
  Returns TRUE if this array is different from \e a, otherwise FALSE.

  The two arrays are bitwise compared.

  \sa operator==()
*/

/*!
  \fn Iterator QArray::begin()
  Returns an iterator pointing at the beginning of this array.
  This iterator can be used as the iterators of QValueList and QMap
  for example. In fact it does not only behave like a usual pointer:
  It is a pointer.
*/

/*!
  \fn Iterator QArray::end()
  Returns an iterator pointing behind the last element of this array.
  This iterator can be used as the iterators of QValueList and QMap
  for example. In fact it does not only behave like a usual pointer:
  It is a pointer.
*/

/*!
  \fn ConstIterator QArray::begin() const
  Returns a const iterator pointing at the beginning of this array.
  This iterator can be used as the iterators of QValueList and QMap
  for example. In fact it does not only behave like a usual pointer:
  It is a pointer.
*/

/*!
  \fn ConstIterator QArray::end() const
  Returns a const iterator pointing behind the last element of this array.
  This iterator can be used as the iterators of QValueList and QMap
  for example. In fact it does not only behave like a usual pointer:
  It is a pointer.
*/


/*****************************************************************************
  QByteArray documentation
 *****************************************************************************/

/*!
  \class QByteArray qcstring.h
  \brief The QByteArray class provides an array of bytes.

  \inherit QArray

  \ingroup tools

  The QByteArray class provides an explicitly shared array of
  bytes. It is useful for manipulating memory areas with custom
  data. QByteArray is implemented as QArray<char>. See the QArray
  documentation for further information.
*/