source: trunk/src/tools/qglist.cpp

/****************************************************************************
** $Id: qglist.cpp 2 2005-11-16 15:49:26Z dmik $
**
** 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.
**
** See http://www.trolltech.com/pricing.html or email sales@trolltech.com for
**   information about Qt Commercial License Agreements.
** See http://www.trolltech.com/qpl/ for QPL licensing information.
** See http://www.trolltech.com/gpl/ for GPL licensing information.
**
** Contact info@trolltech.com if any conditions of this licensing are
** not clear to you.
**
**********************************************************************/

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

/*!
  \class QLNode qglist.h
  \reentrant
  \ingroup collection
  \brief The QLNode class is an internal class for the QPtrList template collection.

  \internal

  QLNode is a doubly-linked list node. It has three pointers:
  \list 1
  \i Pointer to the previous node.
  \i Pointer to the next node.
  \i Pointer to the actual data.
  \endlist

  It might sometimes be practical to have direct access to the list nodes
  in a QPtrList, but it is seldom required.

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

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

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


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

  \internal

  QGList is a strictly internal class that acts as a base class for
  several collection classes; QPtrList, QPtrQueue and QPtrStack.

  QGList has some virtual functions that can be reimplemented to
  customize the subclasses, namely compareItems(), read() and
  write. Normally, you do not have to reimplement any of these
  functions.  If you still want to reimplement them, see the QStrList
  class (qstrlist.h) for an example.
*/


/* Internal helper class for QGList. Contains some optimization for
   the typically case where only one iterators is activre on the list.
 */
class QGListIteratorList
{
public:
    QGListIteratorList()
        : list(0), iterator(0) {
    }
    ~QGListIteratorList() {
        notifyClear( TRUE );
        delete list;
    }

    void add( QGListIterator* i ) {
        if ( !iterator ) {
            iterator = i;
        } else if ( list ) {
            list->push_front( i );
        } else {
            list = new QValueList<QGListIterator*>;
            list->push_front( i );
        }
    }

    void remove( QGListIterator* i ) {
        if ( iterator == i ) {
            iterator = 0;
        } else if ( list ) {
            list->remove( i );
            if ( list->isEmpty() ) {
                delete list;
                list = 0;
            }
        }
    }

    void notifyClear( bool zeroList ) {
        if ( iterator ) {
            if ( zeroList )
                iterator->list = 0;
            iterator->curNode = 0;
        }
        if ( list ) {
            for ( QValueList<QGListIterator*>::Iterator i = list->begin(); i != list->end(); ++i ) {
                if ( zeroList )
                    (*i)->list = 0;
                (*i)->curNode = 0;
            }
        }
    }

    void notifyRemove( QLNode* n, QLNode* curNode ) {
        if ( iterator ) {
            if ( iterator->curNode == n )
                iterator->curNode = curNode;
        }
        if ( list ) {
            for ( QValueList<QGListIterator*>::Iterator i = list->begin(); i != list->end(); ++i ) {
                if ( (*i)->curNode == n )
                    (*i)->curNode = curNode;
            }
        }
    }

private:
    QValueList<QGListIterator*>* list;
    QGListIterator* iterator;
};



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

/*!
  Documented as QPtrList::compareItems().

  Compares \a item1 with \a item2.
*/
int QGList::compareItems( QPtrCollection::Item item1, QPtrCollection::Item item2 )
{
    return item1 != item2;                      // compare pointers
}

#ifndef QT_NO_DATASTREAM
/*!
    \overload
  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, QPtrCollection::Item &item )
{
    item = 0;
    return s;
}

/*!
    \overload
  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, QPtrCollection::Item ) const
{
    return s;
}
#endif // QT_NO_DATASTREAM

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

/*!
  Constructs an empty list.
*/

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

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

QGList::QGList( const QGList & list )
    : QPtrCollection( 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;
    }
}

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

QGList::~QGList()
{
    clear();
    delete iterators;
    // Workaround for GCC 2.7.* bug. Compiler constructs 'static' QGList
    // instances twice on the same address and therefore tries to destruct
    // twice on the same address! This is insane but let's try not to crash
    // here.
    iterators = 0;
}


/*!
  Assigns \a list to this list.
*/

QGList& QGList::operator=( const QGList &list )
{
    if ( &list == this )
        return *this;

    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. Returns TRUE if the lists
  contain the same data, otherwise 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

  Returns the number of items in the list.
*/


/*!
  Returns the node at position \a 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 )
        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;
}


/*!
  Inserts item \a d at its sorted position in the list.
*/

void QGList::inSort( QPtrCollection::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 );
}


/*!
  Inserts item \a d at the start of the list.
*/

void QGList::prepend( QPtrCollection::Item d )
{
    register QLNode *n = new QLNode( newItem(d) );
    Q_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;
}


/*!
  Inserts item \a d at the end of the list.
*/

void QGList::append( QPtrCollection::Item d )
{
    register QLNode *n = new QLNode( newItem(d) );
    Q_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++;
}


/*!
  Inserts item \a d at position \a index in the list.
*/

bool QGList::insertAt( uint index, QPtrCollection::Item d )
{
    if ( index == 0 ) {
        prepend( d );
        return TRUE;
    } else if ( index == numNodes ) {
        append( d );
        return TRUE;
    }
    QLNode *nextNode = locate( index );
    if ( !nextNode )
        return FALSE;
    QLNode *prevNode = nextNode->prev;
    register QLNode *n = new QLNode( newItem(d) );
    Q_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;
}


/*!
  Relinks node \a 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;
}


/*!
  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->notifyRemove( n, curNode );
    numNodes--;
    return n;
}


/*!
  Removes the node \a n from the list.
*/

bool QGList::removeNode( QLNode *n )
{
#if defined(QT_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;
}

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

  If \a d is 0, removes the current item.
*/

bool QGList::remove( QPtrCollection::Item d )
{
    if ( d && find(d) == -1 )
        return FALSE;
    QLNode *n = unlink();
    if ( !n )
        return FALSE;
    deleteItem( n->data );
    delete n;
    return TRUE;
}

/*!
  Removes the item \a d from the list.
*/

bool QGList::removeRef( QPtrCollection::Item d )
{
    if ( findRef(d) == -1 )
        return FALSE;
    QLNode *n = unlink();
    if ( !n )
        return FALSE;
    deleteItem( n->data );
    delete n;
    return TRUE;
}

/*!
  \fn bool QGList::removeFirst()

  Removes the first item in the list.
*/

/*!
  \fn bool QGList::removeLast()

  Removes the last item in the list.
*/

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

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


/*!
  Replaces the item at index \a index with \a d.
*/
bool QGList::replaceAt( uint index, QPtrCollection::Item d )
{
    QLNode *n = locate( index );
    if ( !n )
        return FALSE;
    if ( n->data != d ) {
        deleteItem( n->data );
        n->data = newItem( d );
    }
    return TRUE;
}



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

QPtrCollection::Item QGList::takeNode( QLNode *n )
{
#if defined(QT_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;
}

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

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

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

QPtrCollection::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;
}

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

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

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

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


/*!
  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->notifyClear( FALSE );

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


/*!
  Finds item \a d in the list. If \a fromStart is TRUE the search
  begins at the first node; otherwise it begins at the current node.
*/

int QGList::findRef( QPtrCollection::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
}

/*!
  Finds item \a d in the list using compareItems(). If \a fromStart is
  TRUE the search begins at the first node; otherwise it begins at the
  current node.
*/

int QGList::find( QPtrCollection::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
}


/*!
  Counts the number item \a d occurs in the list.
*/

uint QGList::containsRef( QPtrCollection::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;
}

/*!
  Counts the number of times item \a d occurs in the list. Uses
  compareItems().
*/

uint QGList::contains( QPtrCollection::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;
}


/*!
  \overload QPtrCollection::Item QGList::at( uint index )

  Sets the item at position \a index to the current item.
*/

/*!
  \fn int QGList::at() const

  Returns the current index.
*/

/*!
  \fn QLNode *QGList::currentNode() const

  Returns the current node.
*/

/*!
  \fn QPtrCollection::Item QGList::get() const

  Returns the current item.
*/

/*!
  \fn QPtrCollection::Item QGList::cfirst() const

  Returns the first item in the list.
*/

/*!
  \fn QPtrCollection::Item QGList::clast() const

  Returns the last item in the list.
*/


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

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

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

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

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

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

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

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


/*!
  Converts the list to a vector, \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( QPtrCollection::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 ) {
                QPtrCollection::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
                QPtrCollection::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
                QPtrCollection::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
    QPtrCollection::Item* realheap = new QPtrCollection::Item[ n ];
    // Wow, what a fake. But I want the heap to be indexed as 1...n
    QPtrCollection::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 ) {
            QPtrCollection::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 );
}

/*!
  Reads a list from the stream \a 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 );
        Q_CHECK_PTR( d );
        if ( !d )                               // no memory
            break;
        QLNode *n = new QLNode( d );
        Q_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;
}

/*!
  Writes the list to the stream \a 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



/*! \internal
 */
QLNode* QGList::erase( QLNode* it )
{
    QLNode* n = it;
    it = it->next;
    removeNode( n );
    return it;
}


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

/*!
  \class QGListIterator qglist.h
  \reentrant
  \ingroup collection
  \brief The QGListIterator class is an internal class for implementing QPtrListIterator.

  \internal

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

/*!
  \internal
  Constructs an iterator that operates on the list \a 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 QGListIteratorList;               // create iterator list
        Q_CHECK_PTR( list->iterators );
    }
    list->iterators->add( this );               // attach iterator to list
}

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

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

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

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

/*!
  \internal
  Destroys the iterator.
*/

QGListIterator::~QGListIterator()
{
    if ( list )                                 // detach iterator from list
        list->iterators->remove(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.
*/

QPtrCollection::Item QGListIterator::toFirst()
{
    if ( !list ) {
#if defined(QT_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.
*/

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


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


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

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

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

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

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

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

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

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

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

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