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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  }