/*
 * Copyright 2009 Red Hat, Inc.
 *
 * Red Hat 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.jboss.netty.channel;

import org.jboss.netty.buffer.ChannelBuffer;

/**
 * Predicts the number of readable bytes in the receive buffer of a
 * {@link Channel}.
 * <p>
 * It calculates the close-to-optimal capacity of the {@link ChannelBuffer}
 * for the next read operation depending on the actual number of read bytes
 * in the previous read operation.  More accurate the prediction is, more
 * effective the memory utilization will be.
 * <p>
 * Once a read operation is performed and the actual number of read bytes is
 * known, an I/O thread will call {@link #previousReceiveBufferSize(int)} to
 * update the predictor so it can predict more accurately next time.
 *
 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
 *
 * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
 *
 */
public interface ReceiveBufferSizePredictor {

    /**
     * Predicts the capacity of the {@link ChannelBuffer} for the next
     * read operation depending on the actual number of read bytes in the
     * previous read operation.
     *
     * @return the expected number of readable bytes this time
     */
    int nextReceiveBufferSize();

    /**
     * Updates this predictor by specifying the actual number of read bytes
     * in the previous read operation.
     *
     * @param previousReceiveBufferSize
     *        the actual number of read bytes in the previous read operation
     */
    void previousReceiveBufferSize(int previousReceiveBufferSize);
}