queue.h

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#pragma once

/*+
________________________________________________________________________

 (C) dGB Beheer B.V.; (LICENSE) http://opendtect.org/OpendTect_license.txt
 Author:        A.H.Lammertink
 Date:          March 2004
________________*_______________________________________________________

-*/

#include "threadlock.h"


template <class T>
mClass(Basic) QueueEntry
{
public:
                        QueueEntry( T item )
                            : value( item ), next( 0 ) {}

    T                   value;
    QueueEntry<T>*      next;
};


template <class T>
mClass(Basic) ObjQueue
{
public:
                        ObjQueue() : head(0), tail(0), lock_(true)      {}

    void                add( T* item ) 
                        {
                            Threads::Locker lckr( lock_ );
                            if ( !tail )
                                head = tail = new QueueEntry<T*>( item );
                            else
                            {
                                tail->next = new QueueEntry<T*>( item );
                                tail = tail->next;
                            }
                        }

    T*                  next() 
                        {
                            if ( !head ) return 0;
                            Threads::Locker lckr( lock_ );

                            T* value = head->value;

                            QueueEntry<T*>* old = head;
                            head = head->next;
                            delete old;

                            if ( !head ) tail = 0;
                            return value;
                        }
protected:

    Threads::Lock       lock_;

    QueueEntry<T*>*     head;
    QueueEntry<T*>*     tail;

};


template <class T>
mClass(Basic) TypeQueue
{
public:
                        TypeQueue() : head(0), tail(0), lock_(true)     {}

    void                add( T item ) 
                        {
                            Threads::Locker lckr( lock_ );
                            if ( !tail )
                                head = tail = new QueueEntry<T>( item );
                            else
                            {
                                tail->next = new QueueEntry<T>( item );
                                tail = tail->next;
                            }
                        }

    bool                empty()         { return !head; }

    T                   next() 
                        {
                            if ( empty() ) return 0;
                            Threads::Locker lckr( lock_ );

                            T value = head->value;

                            QueueEntry<T>* old = head;
                            head = head->next;
                            delete old;

                            if ( !head ) tail = 0;

                            return value;
                        }
protected:

    Threads::Lock       lock_;

    QueueEntry<T>*      head;
    QueueEntry<T>*      tail;

};