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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the 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  public interface ReceiveBufferSizePredictor {
34  
35      /**
36       * Predicts the capacity of the {@link ChannelBuffer} for the next
37       * read operation depending on the actual number of read bytes in the
38       * previous read operation.
39       *
40       * @return the expected number of readable bytes this time
41       */
42      int nextReceiveBufferSize();
43  
44      /**
45       * Updates this predictor by specifying the actual number of read bytes
46       * in the previous read operation.
47       *
48       * @param previousReceiveBufferSize
49       *        the actual number of read bytes in the previous read operation
50       */
51      void previousReceiveBufferSize(int previousReceiveBufferSize);
52  }