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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.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   * @apiviz.landmark
55   */
56  public abstract class RtspMessageDecoder extends HttpMessageDecoder {
57  
58      private final DecoderEmbedder<HttpMessage> aggregator;
59  
60      /**
61       * Creates a new instance with the default
62       * {@code maxInitialLineLength (4096}}, {@code maxHeaderSize (8192)}, and
63       * {@code maxContentLength (8192)}.
64       */
65      protected RtspMessageDecoder() {
66          this(4096, 8192, 8192);
67      }
68  
69      /**
70       * Creates a new instance with the specified parameters.
71       */
72      protected RtspMessageDecoder(int maxInitialLineLength, int maxHeaderSize, int maxContentLength) {
73          super(maxInitialLineLength, maxHeaderSize, maxContentLength * 2);
74          aggregator = new DecoderEmbedder<HttpMessage>(new HttpChunkAggregator(maxContentLength));
75      }
76  
77      @Override
78      protected Object decode(ChannelHandlerContext ctx, Channel channel,
79              ChannelBuffer buffer, State state) throws Exception {
80          Object o = super.decode(ctx, channel, buffer, state);
81          if (o != null && aggregator.offer(o)) {
82              return aggregator.poll();
83          } else {
84              return null;
85          }
86      }
87  
88      @Override
89      protected boolean isContentAlwaysEmpty(HttpMessage msg) {
90          // Unlike HTTP, RTSP always assumes zero-length body if Content-Length
91          // header is absent.
92          boolean empty = super.isContentAlwaysEmpty(msg);
93          if (empty) {
94              return true;
95          }
96          if (!msg.headers().contains(RtspHeaders.Names.CONTENT_LENGTH)) {
97              return true;
98          }
99          return empty;
100     }
101 }