001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.activemq.memory.buffer;
019    
020    /**
021     * Represents a collection of MessageQueue instances which are all bound by the
022     * same memory buffer to fix the amount of RAM used to some uppper bound.
023     * 
024     * 
025     */
026    public interface MessageBuffer {
027    
028        int getSize();
029    
030        /**
031         * Creates a new message queue instance
032         */
033        MessageQueue createMessageQueue();
034    
035        /**
036         * After a message queue has changed we may need to perform some evictions
037         * 
038         * @param delta
039         * @param queueSize
040         */
041        void onSizeChanged(MessageQueue queue, int delta, int queueSize);
042    
043        void clear();
044    
045    }