protected AbstractStoreCursor(Destination destination) 
{
        this.regionDestination=destination;
}

 public final synchronized  void addMessageFirst(MessageReference node) throws Exception 
{
        cacheEnabled=false;
        size++;
}

 public final synchronized  void addMessageLast(MessageReference node) throws Exception 
{
        if (cacheEnabled && hasSpace()) {
            recoverMessage(node.getMessage(),true);
            lastCachedId = node.getMessageId();
        } else {
            if (cacheEnabled) {
                cacheEnabled=false;
                if (LOG.isDebugEnabled()) {
                    LOG.debug(regionDestination.getActiveMQDestination().getPhysicalName() + " disabling cache on size:" + size
                            + ", lastCachedIdSeq: " + (lastCachedId == null ? -1 : lastCachedId.getBrokerSequenceId())
                            + " current node seqId: " + node.getMessageId().getBrokerSequenceId());
                }
                // sync with store on disabling the cache
                if (lastCachedId != null) {
                    setBatch(lastCachedId);
                }
            }
        }
        size++;
}

 public final synchronized  void clear() 
{
        gc();
}

 abstract protected  void doFillBatch() throws Exception

 protected final synchronized  void fillBatch() 
{
        if (batchResetNeeded) {
            resetBatch();
            this.batchResetNeeded = false;
        }
        if( this.batchList.isEmpty() && (this.storeHasMessages ||this.size  >0)) {
            this.storeHasMessages = false;
            try {
                doFillBatch();
            } catch (Exception e) {
                LOG.error("Failed to fill batch", e);
                throw new RuntimeException(e);
            }
            if (!this.batchList.isEmpty()) {
                this.storeHasMessages=true;
            }
        }
}

 public final  void finished() 
{

}

 public final synchronized  void gc() 
{
        for (Message msg : batchList.values()) {
            rollback(msg.getMessageId());
            msg.decrementReferenceCount();
        }
        batchList.clear();
        clearIterator(false);
        batchResetNeeded = true;
        this.cacheEnabled=false;
        if (isStarted()) { 
            size = getStoreSize();
        } else {
            size = 0;
        }
}

 abstract protected int getStoreSize()

 public final synchronized boolean hasMessagesBufferedToDeliver() 
{
        return !batchList.isEmpty();
}

 public final synchronized boolean hasNext() 
{
        if (batchList.isEmpty()) {
            try {
                fillBatch();
            } catch (Exception e) {
                LOG.error("Failed to fill batch", e);
                throw new RuntimeException(e);
            }
        }
        ensureIterator();
        return this.iterator.hasNext();
}

 public final synchronized boolean isEmpty() 
{
        // negative means more messages added to store through queue.send since last reset
        return size == 0;
}

 abstract protected boolean isStoreEmpty()

 public final synchronized MessageReference next() 
{
        MessageReference result = null;
        if (!this.batchList.isEmpty()&&this.iterator.hasNext()) {
            result = this.iterator.next().getValue();
        }
        last = result;
        if (result != null) {
            result.incrementReferenceCount();
        }
        return result;
}

 public final boolean recoverMessage(Message message) throws Exception 
{
        return recoverMessage(message,false);
}

 public synchronized boolean recoverMessage(Message message,
    boolean cached) throws Exception 
{
        boolean recovered = false;
        if (recordUniqueId(message.getMessageId())) {
            if (!cached) {
                message.setRegionDestination(regionDestination);
                if( message.getMemoryUsage()==null ) {
                    message.setMemoryUsage(this.getSystemUsage().getMemoryUsage());
                }
            }
            message.incrementReferenceCount();
            batchList.put(message.getMessageId(), message);
            clearIterator(true);
            recovered = true;
        } else {
            /*
             * we should expect to get these - as the message is recorded as it before it goes into
             * the cache. If subsequently, we pull out that message from the store (before its deleted)
             * it will be a duplicate - but should be ignored
             */
            //LOG.error(regionDestination.getActiveMQDestination().getPhysicalName() + " cursor got duplicate: " + message);
            storeHasMessages = true;
        }
        return recovered;
}

 public synchronized  void release() 
{
        clearIterator(false);
}

 public final synchronized  void remove() 
{
        size--;
        if (iterator!=null) {
            iterator.remove();
        }
        if (last != null) {
            last.decrementReferenceCount();
        }
        if (size==0 && isStarted() && useCache && hasSpace() && isStoreEmpty()) {
            if (LOG.isDebugEnabled()) {
                LOG.debug(regionDestination.getActiveMQDestination().getPhysicalName() + " enabling cache on last remove");
            }
            cacheEnabled=true;
        }
}

 public final synchronized  void remove(MessageReference node) 
{
        size--;
        cacheEnabled=false;
        batchList.remove(node.getMessageId());
}

 public final  void reset() 
{
        if (batchList.isEmpty()) {
            try {
                fillBatch();
            } catch (Exception e) {
                LOG.error("Failed to fill batch", e);
                throw new RuntimeException(e);
            }
        }
        clearIterator(true);
        size();
}

 abstract protected  void resetBatch()

 protected  void setBatch(MessageId messageId) throws Exception 
{

}

 public final synchronized int size() 
{
        if (size <  0) {
            this.size = getStoreSize();
        }
        return size;
}

 public final synchronized  void start() throws Exception 
{
        if (!isStarted()) {
            super.start();
            clear();
            resetBatch();
            this.size = getStoreSize();
            this.storeHasMessages=this.size  > 0;
            if (!this.storeHasMessages&&useCache) {
                cacheEnabled=true;
            }
        }
}

 public final synchronized  void stop() throws Exception 
{
        resetBatch();
        super.stop();
        gc();
}