qglist.cpp

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/****************************************************************************
** 
**
** Implementation of QGList and QGListIterator classes
**
** Created : 920624
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of the tools module of the Qt GUI Toolkit.
**
** This file may be distributed under the terms of the Q Public License
** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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**********************************************************************/

#include "qglist.h"
#include "qgvector.h"
#include "qdatastream.h"


// NOT REVISED
/*!
  \class QLNode qglist.h
  \brief The QLNode class is an internal class for the QList template collection.

  QLNode is a doubly linked list node; it has three pointers:
  <ol>
  <li> Pointer to the previous node.
  <li> Pointer to the next node.
  <li> Pointer to the actual data.
  </ol>

  Sometimes it might be practical to have direct access to the list nodes
  in a QList, but it is seldom required.

  \warning Be very careful if you want to access the list nodes. The heap
  can easily get corrupted if you make a mistake.

  \sa QList::currentNode(), QList::removeNode(), QList::takeNode()
*/

/*!
  \fn QCollection::Item QLNode::getData()
  Returns a pointer (\c void*) to the actual data in the list node.
*/


/*!
  \class QGList qglist.h
  \brief The QGList class is an internal class for implementing Qt collection classes.

  QGList is a strictly internal class that acts as a base class for several
  \link collection.html collection classes\endlink; QList, QQueue and
  QStack.

  QGList has some virtual functions that can be reimplemented to customize
  the subclasses.
  <ul>
  <li> compareItems() compares two collection/list items.
  <li> read() reads a collection/list item from a QDataStream.
  <li> write() writes a collection/list item to a QDataStream.
  </ul>
  Normally, you do not have to reimplement any of these functions.
  If you still want to reimplement them, see the QStrList class (qstrlist.h),
  which is a good example.
*/


/*****************************************************************************
  Default implementation of virtual functions
 *****************************************************************************/

/*!
  This virtual function compares two list items.

  Returns:
  <ul>
  <li> 0 if \e item1 == \e item2
  <li> non-zero if \e item1 != \e item2
  </ul>

  This function returns \e int rather than \e bool so that
  reimplementations can return three values and use it to sort by:

  <ul>
  <li> 0 if \e item1 == \e item2
  <li> > 0 (positive integer) if \e item1 > \e item2
  <li> < 0 (negative integer) if \e item1 < \e item2
  </ul>

  The QList::inSort() function requires that compareItems() is implemented
  as described here.

  This function should not modify the list because some const functions
  call compareItems().

  The default implementation compares the pointers:
  \code

  \endcode
*/

int QGList::compareItems( QCollection::Item item1, QCollection::Item item2 )
{
    return item1 != item2;                      // compare pointers
}

#ifndef QT_NO_DATASTREAM
/*!
  Reads a collection/list item from the stream \a s and returns a reference
  to the stream.

  The default implementation sets \a item to 0.

  \sa write()
*/

QDataStream &QGList::read( QDataStream &s, QCollection::Item &item )
{
    item = 0;
    return s;
}

/*!
  Writes a collection/list item to the stream \a s and returns a reference
  to the stream.

  The default implementation does nothing.

  \sa read()
*/

QDataStream &QGList::write( QDataStream &s, QCollection::Item ) const
{
    return s;
}
#endif // QT_NO_DATASTREAM

/*****************************************************************************
  QGList member functions
 *****************************************************************************/

/*!
  \internal
  Constructs an empty list.
*/

QGList::QGList()
{
    firstNode = lastNode = curNode = 0;         // initialize list
    numNodes  = 0;
    curIndex  = -1;
    iterators = 0;                              // initialize iterator list
}

/*!
  \internal
  Constructs a copy of \e list.
*/

QGList::QGList( const QGList & list )
    : QCollection( list )
{
    firstNode = lastNode = curNode = 0;         // initialize list
    numNodes  = 0;
    curIndex  = -1;
    iterators = 0;                              // initialize iterator list
    QLNode *n = list.firstNode;
    while ( n ) {                               // copy all items from list
        append( n->data );
        n = n->next;
    }
}

/*!
  \internal
  Removes all items from the list and destroys the list.
*/

QGList::~QGList()
{
    clear();
    if ( !iterators )                           // no iterators for this list
        return;
    QGListIterator *i = (QGListIterator*)iterators->first();
    while ( i ) {                               // notify all iterators that
        i->list = 0;                            // this list is deleted
        i->curNode = 0;
        i = (QGListIterator*)iterators->next();
    }
    delete iterators;
}


/*!
  \internal
  Assigns \e list to this list.
*/

QGList& QGList::operator=( const QGList &list )
{
    clear();
    if ( list.count() > 0 ) {
        QLNode *n = list.firstNode;
        while ( n ) {                           // copy all items from list
            append( n->data );
            n = n->next;
        }
        curNode  = firstNode;
        curIndex = 0;
    }
    return *this;
}

/*!
  Compares this list with \a list. Retruns TRUE if the lists
  contain the same data, else FALSE.
*/

bool QGList::operator==( const QGList &list ) const
{
    if ( count() != list.count() )
        return FALSE;
    
    if ( count() == 0 )
        return TRUE;
    
    QLNode *n1 = firstNode;
    QLNode *n2 = list.firstNode;
    while ( n1 && n2 ) {
        // should be mutable
        if ( ( (QGList*)this )->compareItems( n1->data, n2->data ) != 0 )
            return FALSE;
        n1 = n1->next;
        n2 = n2->next;
    }
    
    return TRUE;
}

/*!
  \fn uint QGList::count() const
  \internal
  Returns the number of items in the list.
*/


/*!
  \internal
  Returns the node at position \e index.  Sets this node to current.
*/

QLNode *QGList::locate( uint index )
{
    if ( index == (uint)curIndex )              // current node ?
        return curNode;
    if ( !curNode && firstNode ) {              // set current node
        curNode  = firstNode;
        curIndex = 0;
    }
    register QLNode *node;
    int  distance = index - curIndex;           // node distance to cur node
    bool forward;                               // direction to traverse

    if ( index >= numNodes ) {
#if defined(CHECK_RANGE)
        qWarning( "QGList::locate: Index %d out of range", index );
#endif
        return 0;
    }

    if ( distance < 0 )
        distance = -distance;
    if ( (uint)distance < index && (uint)distance < numNodes - index ) {
        node =  curNode;                        // start from current node
        forward = index > (uint)curIndex;
    } else if ( index < numNodes - index ) {    // start from first node
        node = firstNode;
        distance = index;
        forward = TRUE;
    } else {                                    // start from last node
        node = lastNode;
        distance = numNodes - index - 1;
        if ( distance < 0 )
            distance = 0;
        forward = FALSE;
    }
    if ( forward ) {                            // now run through nodes
        while ( distance-- )
            node = node->next;
    } else {
        while ( distance-- )
            node = node->prev;
    }
    curIndex = index;                           // must update index
    return curNode = node;
}


/*!
  \internal
  Inserts an item at its sorted position in the list.
*/

void QGList::inSort( QCollection::Item d )
{
    int index = 0;
    register QLNode *n = firstNode;
    while ( n && compareItems(n->data,d) < 0 ){ // find position in list
        n = n->next;
        index++;
    }
    insertAt( index, d );
}


/*!
  \internal
  Inserts an item at the start of the list.
*/

void QGList::prepend( QCollection::Item d )
{
    register QLNode *n = new QLNode( newItem(d) );
    CHECK_PTR( n );
    n->prev = 0;
    if ( (n->next = firstNode) )                // list is not empty
        firstNode->prev = n;
    else                                        // initialize list
        lastNode = n;
    firstNode = curNode = n;                    // curNode affected
    numNodes++;
    curIndex = 0;
}


/*!
  \internal
  Inserts an item at the end of the list.
*/

void QGList::append( QCollection::Item d )
{
    register QLNode *n = new QLNode( newItem(d) );
    CHECK_PTR( n );
    n->next = 0;
    if ( (n->prev = lastNode) )                 // list is not empty
        lastNode->next = n;
    else                                        // initialize list
        firstNode = n;
    lastNode = curNode = n;                     // curNode affected
    curIndex = numNodes;
    numNodes++;
}


/*!
  \internal
  Inserts an item at position \e index in the list.
*/

bool QGList::insertAt( uint index, QCollection::Item d )
{
    if ( index == 0 ) {                         // insert at head of list
        prepend( d );
        return TRUE;
    } else if ( index == numNodes ) {           // append at tail of list
        append( d );
        return TRUE;
    }
    QLNode *nextNode = locate( index );
    if ( !nextNode )                            // illegal position
        return FALSE;
    QLNode *prevNode = nextNode->prev;
    register QLNode *n = new QLNode( newItem(d) );
    CHECK_PTR( n );
    nextNode->prev = n;
    prevNode->next = n;
    n->prev = prevNode;                         // link new node into list
    n->next = nextNode;
    curNode = n;                                // curIndex set by locate()
    numNodes++;
    return TRUE;
}


/*!
  \internal
  Relinks node \e n and makes it the first node in the list.
*/

void QGList::relinkNode( QLNode *n )
{
    if ( n == firstNode )                       // already first
        return;
    curNode = n;
    unlink();
    n->prev = 0;
    if ( (n->next = firstNode) )                // list is not empty
        firstNode->prev = n;
    else                                        // initialize list
        lastNode = n;
    firstNode = curNode = n;                    // curNode affected
    numNodes++;
    curIndex = 0;
}


/*!
  \internal
  Unlinks the current list node and returns a pointer to this node.
*/

QLNode *QGList::unlink()
{
    if ( curNode == 0 )                         // null current node
        return 0;
    register QLNode *n = curNode;               // unlink this node
    if ( n == firstNode ) {                     // removing first node ?
        if ( (firstNode = n->next) ) {
            firstNode->prev = 0;
        } else {
            lastNode = curNode = 0;             // list becomes empty
            curIndex = -1;
        }
    } else {
        if ( n == lastNode ) {                  // removing last node ?
            lastNode = n->prev;
            lastNode->next = 0;
        } else {                                // neither last nor first node
            n->prev->next = n->next;
            n->next->prev = n->prev;
        }
    }
    if ( n->next ) {                            // change current node
        curNode = n->next;
    } else if ( n->prev ) {
        curNode = n->prev;
        curIndex--;
    }
    if ( iterators && iterators->count() ) {    // update iterators
        QGListIterator *i = (QGListIterator*)iterators->first();
        while ( i ) {                           // fix all iterators that
            if ( i->curNode == n )              // refers to pending node
                i->curNode = curNode;
            i = (QGListIterator*)iterators->next();
        }
    }
    numNodes--;
    return n;
}


/*!
  \internal
  Removes the node \e n from the list.
*/

bool QGList::removeNode( QLNode *n )
{
#if defined(CHECK_NULL)
    if ( n == 0 || (n->prev && n->prev->next != n) ||
         (n->next && n->next->prev != n) ) {
        qWarning( "QGList::removeNode: Corrupted node" );
        return FALSE;
    }
#endif
    curNode = n;
    unlink();                                   // unlink node
    deleteItem( n->data );                      // deallocate this node
    delete n;
    curNode  = firstNode;
    curIndex = curNode ? 0 : -1;
    return TRUE;
}

/*!
  \internal
  Removes the item \e d from the list.  Uses compareItems() to find the item.
*/

bool QGList::remove( QCollection::Item d )
{
    if ( d ) {                                  // find the item
        if ( find(d) == -1 )
            return FALSE;
    }
    QLNode *n = unlink();                       // unlink node
    if ( !n )
        return FALSE;
    deleteItem( n->data );                      // deallocate this node
    delete n;
    return TRUE;
}

/*!
  \internal
  Removes the item \e d from the list.
*/

bool QGList::removeRef( QCollection::Item d )
{
    if ( d ) {                                  // find the item
        if ( findRef(d) == -1 )
            return FALSE;
    }
    QLNode *n = unlink();                       // unlink node
    if ( !n )
        return FALSE;
    deleteItem( n->data );                      // deallocate this node
    delete n;
    return TRUE;
}

/*!
  \fn bool QGList::removeFirst()
  \internal
  Removes the first item in the list.
*/

/*!
  \fn bool QGList::removeLast()
  \internal
  Removes the last item in the list.
*/

/*!
  \internal
  Removes the item at position \e index from the list.
*/

bool QGList::removeAt( uint index )
{
    if ( !locate(index) )
        return FALSE;
    QLNode *n = unlink();                       // unlink node
    if ( !n )
        return FALSE;
    deleteItem( n->data );                      // deallocate this node
    delete n;
    return TRUE;
}


/*!
  \internal
  Takes the node \e n out of the list.
*/

QCollection::Item QGList::takeNode( QLNode *n )
{
#if defined(CHECK_NULL)
    if ( n == 0 || (n->prev && n->prev->next != n) ||
         (n->next && n->next->prev != n) ) {
        qWarning( "QGList::takeNode: Corrupted node" );
        return 0;
    }
#endif
    curNode = n;
    unlink();                                   // unlink node
    Item d = n->data;
    delete n;                                   // delete the node, not data
    curNode  = firstNode;
    curIndex = curNode ? 0 : -1;
    return d;
}

/*!
  \internal
  Takes the current item out of the list.
*/

QCollection::Item QGList::take()
{
    QLNode *n = unlink();                       // unlink node
    Item d = n ? n->data : 0;
    delete n;                                   // delete node, keep contents
    return d;
}

/*!
  \internal
  Takes the item at position \e index out of the list.
*/

QCollection::Item QGList::takeAt( uint index )
{
    if ( !locate(index) )
        return 0;
    QLNode *n = unlink();                       // unlink node
    Item d = n ? n->data : 0;
    delete n;                                   // delete node, keep contents
    return d;
}

/*!
  \internal
  Takes the first item out of the list.
*/

QCollection::Item QGList::takeFirst()
{
    first();
    QLNode *n = unlink();                       // unlink node
    Item d = n ? n->data : 0;
    delete n;
    return d;
}

/*!
  \internal
  Takes the last item out of the list.
*/

QCollection::Item QGList::takeLast()
{
    last();
    QLNode *n = unlink();                       // unlink node
    Item d = n ? n->data : 0;
    delete n;
    return d;
}


/*!
  \internal
  Removes all items from the list.
*/

void QGList::clear()
{
    register QLNode *n = firstNode;

    firstNode = lastNode = curNode = 0;         // initialize list
    numNodes = 0;
    curIndex = -1;

    if ( iterators && iterators->count() ) {
        QGListIterator *i = (QGListIterator*)iterators->first();
        while ( i ) {                           // notify all iterators that
            i->curNode = 0;                     // this list is empty
            i = (QGListIterator*)iterators->next();
        }
    }

    QLNode *prevNode;
    while ( n ) {                               // for all nodes ...
        deleteItem( n->data );                  // deallocate data
        prevNode = n;
        n = n->next;
        delete prevNode;                        // deallocate node
    }
}


/*!
  \internal
  Finds an item in the list.
*/

int QGList::findRef( QCollection::Item d, bool fromStart )
{
    register QLNode *n;
    int      index;
    if ( fromStart ) {                          // start from first node
        n = firstNode;
        index = 0;
    } else {                                    // start from current node
        n = curNode;
        index = curIndex;
    }
    while ( n && n->data != d ) {               // find exact match
        n = n->next;
        index++;
    }
    curNode = n;
    curIndex = n ? index : -1;
    return curIndex;                            // return position of item
}

/*!
  \internal
  Finds an item in the list.  Uses compareItems().
*/

int QGList::find( QCollection::Item d, bool fromStart )
{
    register QLNode *n;
    int      index;
    if ( fromStart ) {                          // start from first node
        n = firstNode;
        index = 0;
    } else {                                    // start from current node
        n = curNode;
        index = curIndex;
    }
    while ( n && compareItems(n->data,d) ){     // find equal match
        n = n->next;
        index++;
    }
    curNode = n;
    curIndex = n ? index : -1;
    return curIndex;                            // return position of item
}


/*!
  \internal
  Counts the number an item occurs in the list.
*/

uint QGList::containsRef( QCollection::Item d ) const
{
    register QLNode *n = firstNode;
    uint     count = 0;
    while ( n ) {                               // for all nodes...
        if ( n->data == d )                     // count # exact matches
            count++;
        n = n->next;
    }
    return count;
}

/*!
  \internal
  Counts the number an item occurs in the list.  Uses compareItems().
*/

uint QGList::contains( QCollection::Item d ) const
{
    register QLNode *n = firstNode;
    uint     count = 0;
    QGList  *that = (QGList*)this;              // mutable for compareItems()
    while ( n ) {                               // for all nodes...
        if ( !that->compareItems(n->data,d) )   // count # equal matches
            count++;
        n = n->next;
    }
    return count;
}


/*!
  \fn QCollection::Item QGList::at( uint index )
  \internal
  Sets the item at position \e index to the current item.
*/

/*!
  \fn int QGList::at() const
  \internal
  Returns the current index.
*/

/*!
  \fn QLNode *QGList::currentNode() const
  \internal
  Returns the current node.
*/

/*!
  \fn QCollection::Item QGList::get() const
  \internal
  Returns the current item.
*/

/*!
  \fn QCollection::Item QGList::cfirst() const
  \internal
  Returns the first item in the list.
*/

/*!
  \fn QCollection::Item QGList::clast() const
  \internal
  Returns the last item in the list.
*/


/*!
  \internal
  Returns the first list item.  Sets this to current.
*/

QCollection::Item QGList::first()
{
    if ( firstNode ) {
        curIndex = 0;
        return (curNode=firstNode)->data;
    }
    return 0;
}

/*!
  \internal
  Returns the last list item.  Sets this to current.
*/

QCollection::Item QGList::last()
{
    if ( lastNode ) {
        curIndex = numNodes-1;
        return (curNode=lastNode)->data;
    }
    return 0;
}

/*!
  \internal
  Returns the next list item (after current).  Sets this to current.
*/

QCollection::Item QGList::next()
{
    if ( curNode ) {
        if ( curNode->next ) {
            curIndex++;
            curNode = curNode->next;
            return curNode->data;
        }
        curIndex = -1;
        curNode = 0;
    }
    return 0;
}

/*!
  \internal
  Returns the previous list item (before current).  Sets this to current.
*/

QCollection::Item QGList::prev()
{
    if ( curNode ) {
        if ( curNode->prev ) {
            curIndex--;
            curNode = curNode->prev;
            return curNode->data;
        }
        curIndex = -1;
        curNode = 0;
    }
    return 0;
}


/*!
  \internal
  Converts the list to a vector.
*/

void QGList::toVector( QGVector *vector ) const
{
    vector->clear();
    if ( !vector->resize( count() ) )
        return;
    register QLNode *n = firstNode;
    uint i = 0;
    while ( n ) {
        vector->insert( i, n->data );
        n = n->next;
        i++;
    }
}

void QGList::heapSortPushDown( QCollection::Item* heap, int first, int last )
{
    int r = first;
    while( r <= last/2 ) {
        // Node r has only one child ?
        if ( last == 2*r ) {
            // Need for swapping ?
            if ( compareItems( heap[r], heap[ 2*r ] ) > 0 ) {
                QCollection::Item tmp = heap[r];
                heap[ r ] = heap[ 2*r ];
                heap[ 2*r ] = tmp;
            }
            // That's it ...
            r = last;
        } else {
            // Node has two children
            if ( compareItems( heap[r], heap[ 2*r ] ) > 0 &&
                 compareItems( heap[ 2*r ], heap[ 2*r+1 ] ) <= 0 ) {
                // Swap with left child
                QCollection::Item tmp = heap[r];
                heap[ r ] = heap[ 2*r ];
                heap[ 2*r ] = tmp;
                r *= 2;
            } else if ( compareItems( heap[r], heap[ 2*r+1 ] ) > 0 &&
                        compareItems( heap[ 2*r+1 ], heap[ 2*r ] ) < 0 ) {
                // Swap with right child
                QCollection::Item tmp = heap[r];
                heap[ r ] = heap[ 2*r+1 ];
                heap[ 2*r+1 ] = tmp;
                r = 2*r+1;
            } else {
                // We are done
                r = last;
            }
        }
    }
}


/*! Sorts the list by the result of the virtual compareItems() function.

  The Heap-Sort algorithm is used for sorting.  It sorts n items with
  O(n*log n) compares.  This is the asymptotic optimal solution of the
  sorting problem.
*/

void QGList::sort()
{
    uint n = count();
    if ( n < 2 )
        return;

    // Create the heap
    QCollection::Item* realheap = new QCollection::Item[ n ];
    // Wow, what a fake. But I want the heap to be indexed as 1...n
    QCollection::Item* heap = realheap - 1;
    int size = 0;
    QLNode* insert = firstNode;
    for( ; insert != 0; insert = insert->next ) {
        heap[++size] = insert->data;
        int i = size;
        while( i > 1 && compareItems( heap[i], heap[ i / 2 ] ) < 0 ) {
            QCollection::Item tmp = heap[ i ];
            heap[ i ] = heap[ i/2 ];
            heap[ i/2 ] = tmp;
            i /= 2;
        }
    }

    insert = firstNode;
    // Now do the sorting
    for ( int i = n; i > 0; i-- ) {
        insert->data = heap[1];
        insert = insert->next;
        if ( i > 1 ) {
            heap[1] = heap[i];
            heapSortPushDown( heap, 1, i - 1 );
        }
    }

    delete [] realheap;
}


/*****************************************************************************
  QGList stream functions
 *****************************************************************************/

#ifndef QT_NO_DATASTREAM
QDataStream &operator>>( QDataStream &s, QGList &list )
{                                               // read list
    return list.read( s );
}

QDataStream &operator<<( QDataStream &s, const QGList &list )
{                                               // write list
    return list.write( s );
}

/*!
  \internal
  Reads a list from the stream \e s.
*/

QDataStream &QGList::read( QDataStream &s )
{
    uint num;
    s >> num;                                   // read number of items
    clear();                                    // clear list
    while ( num-- ) {                           // read all items
        Item d;
        read( s, d );
        CHECK_PTR( d );
        if ( !d )                               // no memory
            break;
        QLNode *n = new QLNode( d );
        CHECK_PTR( n );
        if ( !n )                               // no memory
            break;
        n->next = 0;
        if ( (n->prev = lastNode) )             // list is not empty
            lastNode->next = n;
        else                                    // initialize list
            firstNode = n;
        lastNode = n;
        numNodes++;
    }
    curNode  = firstNode;
    curIndex = curNode ? 0 : -1;
    return s;
}

/*!
  \internal
  Writes the list to the stream \e s.
*/

QDataStream &QGList::write( QDataStream &s ) const
{
    s << count();                               // write number of items
    QLNode *n = firstNode;
    while ( n ) {                               // write all items
        write( s, n->data );
        n = n->next;
    }
    return s;
}

#endif // QT_NO_DATASTREAM

/*****************************************************************************
  QGListIterator member functions
 *****************************************************************************/

/*!
  \class QGListIterator qglist.h
  \brief The QGListIterator class is an internal class for implementing QListIterator.

  QGListIterator is a strictly internal class that does the heavy work for
  QListIterator.
*/

/*!
  \internal
  Constructs an iterator that operates on the list \e l.
*/

QGListIterator::QGListIterator( const QGList &l )
{
    list = (QGList *)&l;                        // get reference to list
    curNode = list->firstNode;                  // set to first node
    if ( !list->iterators ) {
        list->iterators = new QGList;           // create iterator list
        CHECK_PTR( list->iterators );
    }
    list->iterators->append( this );            // attach iterator to list
}

/*!
  \internal
  Constructs a copy of the iterator \e it.
*/

QGListIterator::QGListIterator( const QGListIterator &it )
{
    list = it.list;
    curNode = it.curNode;
    if ( list )
        list->iterators->append( this );        // attach iterator to list
}

/*!
  \internal
  Assigns a copy of the iterator \e it and returns a reference to this
  iterator.
*/

QGListIterator &QGListIterator::operator=( const QGListIterator &it )
{
    if ( list )                                 // detach from old list
        list->iterators->removeRef( this );
    list = it.list;
    curNode = it.curNode;
    if ( list )
        list->iterators->append( this );        // attach to new list
    return *this;
}

/*!
  \internal
  Destroys the iterator.
*/

QGListIterator::~QGListIterator()
{
    if ( list )                                 // detach iterator from list
        list->iterators->removeRef(this);
}


/*!
  \fn bool QGListIterator::atFirst() const
  \internal
  Returns TRUE if the iterator points to the first item, otherwise FALSE.
*/

/*!
  \fn bool QGListIterator::atLast() const
  \internal
  Returns TRUE if the iterator points to the last item, otherwise FALSE.
*/


/*!
  \internal
  Sets the list iterator to point to the first item in the list.
*/

QCollection::Item QGListIterator::toFirst()
{
    if ( !list ) {
#if defined(CHECK_NULL)
        qWarning( "QGListIterator::toFirst: List has been deleted" );
#endif
        return 0;
    }
    return list->firstNode ? (curNode = list->firstNode)->getData() : 0;
}

/*!
  \internal
  Sets the list iterator to point to the last item in the list.
*/

QCollection::Item QGListIterator::toLast()
{
    if ( !list ) {
#if defined(CHECK_NULL)
        qWarning( "QGListIterator::toLast: List has been deleted" );
#endif
        return 0;
    }
    return list->lastNode ? (curNode = list->lastNode)->getData() : 0;
}


/*!
  \fn QCollection::Item QGListIterator::get() const
  \internal
  Returns the iterator item.
*/


/*!
  \internal
  Moves to the next item (postfix).
*/

QCollection::Item QGListIterator::operator()()
{
    if ( !curNode )
        return 0;
    QCollection::Item d = curNode->getData();
    curNode = curNode->next;
    return  d;
}

/*!
  \internal
  Moves to the next item (prefix).
*/

QCollection::Item QGListIterator::operator++()
{
    if ( !curNode )
        return 0;
    curNode = curNode->next;
    return curNode ? curNode->getData() : 0;
}

/*!
  \internal
  Moves \e jumps positions forward.
*/

QCollection::Item QGListIterator::operator+=( uint jumps )
{
    while ( curNode && jumps-- )
        curNode = curNode->next;
    return curNode ? curNode->getData() : 0;
}

/*!
  \internal
  Moves to the previous item (prefix).
*/

QCollection::Item QGListIterator::operator--()
{
    if ( !curNode )
        return 0;
    curNode = curNode->prev;
    return curNode ? curNode->getData() : 0;
}

/*!
  \internal
  Moves \e jumps positions backward.
*/

QCollection::Item QGListIterator::operator-=( uint jumps )
{
    while ( curNode && jumps-- )
        curNode = curNode->prev;
    return curNode ? curNode->getData() : 0;
}