1 /*
2 * Copyright 2009 Red Hat, Inc.
3 *
4 * Red Hat licenses this file to you under the Apache License, version 2.0
5 * (the "License"); you may not use this file except in compliance with the
6 * License. You may obtain a copy of the License at:
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package org.jboss.netty.channel;
17
18 import org.jboss.netty.buffer.ChannelBuffer;
19
20 /**
21 * Predicts the number of readable bytes in the receive buffer of a
22 * {@link Channel}.
23 * <p>
24 * It calculates the close-to-optimal capacity of the {@link ChannelBuffer}
25 * for the next read operation depending on the actual number of read bytes
26 * in the previous read operation. More accurate the prediction is, more
27 * effective the memory utilization will be.
28 * <p>
29 * Once a read operation is performed and the actual number of read bytes is
30 * known, an I/O thread will call {@link #previousReceiveBufferSize(int)} to
31 * update the predictor so it can predict more accurately next time.
32 *
33 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
34 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
35 *
36 * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
37 *
38 */
39 public interface ReceiveBufferSizePredictor {
40
41 /**
42 * Predicts the capacity of the {@link ChannelBuffer} for the next
43 * read operation depending on the actual number of read bytes in the
44 * previous read operation.
45 *
46 * @return the expected number of readable bytes this time
47 */
48 int nextReceiveBufferSize();
49
50 /**
51 * Updates this predictor by specifying the actual number of read bytes
52 * in the previous read operation.
53 *
54 * @param previousReceiveBufferSize
55 * the actual number of read bytes in the previous read operation
56 */
57 void previousReceiveBufferSize(int previousReceiveBufferSize);
58 }