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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.containsHeader(RtspHeaders.Names.CONTENT_LENGTH)) {
    97              return true;
    98          }
    99          return empty;
    100     }
    101 }