content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.activemq.broker.region.cursors;
  
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.List;
  
  import org.apache.activemq.broker.region.MessageReference;
  import org.apache.activemq.command.MessageId;
  
  public interface PendingList extends Iterable<MessageReference> {
  
      /**
       * Returns true if there are no Messages in the PendingList currently.
       * @return true if the PendingList is currently empty.
       */
      public boolean isEmpty();
  
      /**
       * Discards all Messages currently held in the PendingList.
       */
      public void clear();
  
      /**
       * Adds the given message to the head of the list.
       *
       * @param message
       *      The MessageReference that is to be added to this list.
       *
       * @return the PendingNode that contains the newly added message.
       */
      public PendingNode addMessageFirst(MessageReference message);
  
      /**
       * Adds the given message to the tail of the list.
       *
       * @param message
       *      The MessageReference that is to be added to this list.
       *
       * @return the PendingNode that contains the newly added message.
       */
      public PendingNode addMessageLast(MessageReference message);
  
      /**
       * Removes the given MessageReference from the PendingList if it is
       * contained within.
       *
       * @param message
       *      The MessageReference that is to be removed to this list.
       *
       * @return the PendingNode that contains the removed message or null if the
       *         message was not present in this list.
       */
      public PendingNode remove(MessageReference message);
  
      /**
       * Returns the number of MessageReferences that are awaiting dispatch.
       * @return current count of the pending messages.
       */
      public int size();
  
      public long messageSize();
  
      /**
       * Returns an iterator over the pending Messages.  The subclass controls how
       * the returned iterator actually traverses the list of pending messages allowing
       * for the order to vary based on factors like Message priority or some other
       * mechanism.
       *
       * @return an Iterator that returns MessageReferences contained in this list.
       */
      @Override
      public Iterator<MessageReference> iterator();
  
      /**
       * Query the PendingList to determine if the given message is contained within.
       *
       * @param message
       *      The Message that is the target of this query.
       *
       * @return true if the MessageReference is contained in this list.
       */
      public boolean contains(MessageReference message);
  
      /**
       * Returns a new Collection that contains all the MessageReferences currently
       * held in this PendingList.  The elements of the list are ordered using the
       * same rules as the subclass uses for iteration.
       *
       * @return a new Collection containing this lists MessageReferences.
       */
      public Collection<MessageReference> values();
  
      /**
       * Adds all the elements of the given PendingList to this PendingList.
       *
       * @param pendingList
       *      The PendingList that is to be added to this collection.
       */
      public void addAll(PendingList pendingList);
  
      public MessageReference get(MessageId messageId);
  
  }
  