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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  }