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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  }