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    1   /*
    2    * Copyright 2010 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.handler.codec.rtsp;
    17
    18  import org.jboss.netty.buffer.ChannelBuffer;
    19  import org.jboss.netty.channel.Channel;
    20  import org.jboss.netty.channel.ChannelHandlerContext;
    21  import org.jboss.netty.handler.codec.embedder.DecoderEmbedder;
    22  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
    23  import org.jboss.netty.handler.codec.http.HttpChunkAggregator;
    24  import org.jboss.netty.handler.codec.http.HttpMessage;
    25  import org.jboss.netty.handler.codec.http.HttpMessageDecoder;
    26
    27  /**
    28   * Decodes {@link ChannelBuffer}s into RTSP messages represented in
    29   * {@link HttpMessage}s.
    30   * <p>
    31   * <h3>Parameters that prevents excessive memory consumption</h3>
    32   * <table border="1">
    33   * <tr>
    34   * <th>Name</th><th>Meaning</th>
    35   * </tr>
    36   * <tr>
    37   * <td>{@code maxInitialLineLength}</td>
    38   * <td>The maximum length of the initial line
    39   *     (e.g. {@code "SETUP / RTSP/1.0"} or {@code "RTSP/1.0 200 OK"})
    40   *     If the length of the initial line exceeds this value, a
    41   *     {@link TooLongFrameException} will be raised.</td>
    42   * </tr>
    43   * <tr>
    44   * <td>{@code maxHeaderSize}</td>
    45   * <td>The maximum length of all headers.  If the sum of the length of each
    46   *     header exceeds this value, a {@link TooLongFrameException} will be raised.</td>
    47   * </tr>
    48   * <tr>
    49   * <td>{@code maxContentLength}</td>
    50   * <td>The maximum length of the content.  If the content length exceeds this
    51   *     value, a {@link TooLongFrameException} will be raised.</td>
    52   * </tr>
    53   * </table>
    54   *
    55   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    56   * @author <a href="http://amitbhayani.blogspot.com/">Amit Bhayani</a>
    57   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    58   * @version $Rev: 2282 $, $Date: 2010-05-19 16:51:38 +0900 (Wed, 19 May 2010) $
    59   *
    60   * @apiviz.landmark
    61   */
    62  public abstract class RtspMessageDecoder extends HttpMessageDecoder {
    63
    64      private final DecoderEmbedder<HttpMessage> aggregator;
    65
    66      /**
    67       * Creates a new instance with the default
    68       * {@code maxInitialLineLength (4096}}, {@code maxHeaderSize (8192)}, and
    69       * {@code maxContentLength (8192)}.
    70       */
    71      protected RtspMessageDecoder() {
    72          this(4096, 8192, 8192);
    73      }
    74
    75      /**
    76       * Creates a new instance with the specified parameters.
    77       */
    78      protected RtspMessageDecoder(int maxInitialLineLength, int maxHeaderSize, int maxContentLength) {
    79          super(maxInitialLineLength, maxHeaderSize, maxContentLength * 2);
    80          aggregator = new DecoderEmbedder<HttpMessage>(new HttpChunkAggregator(maxContentLength));
    81      }
    82
    83      @Override
    84      protected Object decode(ChannelHandlerContext ctx, Channel channel,
    85              ChannelBuffer buffer, State state) throws Exception {
    86          Object o = super.decode(ctx, channel, buffer, state);
    87          if (o != null && aggregator.offer(o)) {
    88              return aggregator.poll();
    89          } else {
    90              return null;
    91          }
    92      }
    93
    94      @Override
    95      protected boolean isContentAlwaysEmpty(HttpMessage msg) {
    96          // Unlike HTTP, RTSP always assumes zero-length body if Content-Length
    97          // header is absent.
    98          boolean empty = super.isContentAlwaysEmpty(msg);
    99          if (empty) {
    100             return true;
    101         }
    102         if (!msg.containsHeader(RtspHeaders.Names.CONTENT_LENGTH)) {
    103             return true;
    104         }
    105         return empty;
    106     }
    107 }