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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.http.websocketx;
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.frame.TooLongFrameException;
22  import org.jboss.netty.handler.codec.replay.ReplayingDecoder;
23  import org.jboss.netty.handler.codec.replay.VoidEnum;
24  
25  /**
26   * Decodes {@link ChannelBuffer}s into {@link WebSocketFrame}s.
27   * <p>
28   * For the detailed instruction on adding add Web Socket support to your HTTP server, take a look into the
29   * <tt>WebSocketServer</tt> example located in the {@code org.jboss.netty.example.http.websocket} package.
30   *
31   * @apiviz.landmark
32   * @apiviz.uses org.jboss.netty.handler.codec.http.websocket.WebSocketFrame
33   */
34  public class WebSocket00FrameDecoder extends ReplayingDecoder<VoidEnum> {
35  
36      private static final long DEFAULT_MAX_FRAME_SIZE = 16384;
37  
38      private final long maxFrameSize;
39      private boolean receivedClosingHandshake;
40  
41      public WebSocket00FrameDecoder() {
42          this(DEFAULT_MAX_FRAME_SIZE);
43      }
44  
45      /**
46       * Creates a new instance of {@code WebSocketFrameDecoder} with the specified {@code maxFrameSize}. If the client
47       * sends a frame size larger than {@code maxFrameSize}, the channel will be closed.
48       *
49       * @param maxFrameSize
50       *            the maximum frame size to decode
51       */
52      public WebSocket00FrameDecoder(long maxFrameSize) {
53          this.maxFrameSize = maxFrameSize;
54      }
55  
56      @Override
57      protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer, VoidEnum state)
58              throws Exception {
59  
60          // Discard all data received if closing handshake was received before.
61          if (receivedClosingHandshake) {
62              buffer.skipBytes(actualReadableBytes());
63              return null;
64          }
65  
66          // Decode a frame otherwise.
67          byte type = buffer.readByte();
68          if ((type & 0x80) == 0x80) {
69              // If the MSB on type is set, decode the frame length
70              return decodeBinaryFrame(type, buffer);
71          } else {
72              // Decode a 0xff terminated UTF-8 string
73              return decodeTextFrame(buffer);
74          }
75      }
76  
77      private WebSocketFrame decodeBinaryFrame(byte type, ChannelBuffer buffer) throws TooLongFrameException {
78          long frameSize = 0;
79          int lengthFieldSize = 0;
80          byte b;
81          do {
82              b = buffer.readByte();
83              frameSize <<= 7;
84              frameSize |= b & 0x7f;
85              if (frameSize > maxFrameSize) {
86                  throw new TooLongFrameException();
87              }
88              lengthFieldSize++;
89              if (lengthFieldSize > 8) {
90                  // Perhaps a malicious peer?
91                  throw new TooLongFrameException();
92              }
93          } while ((b & 0x80) == 0x80);
94  
95          if (type == (byte) 0xFF && frameSize == 0) {
96              receivedClosingHandshake = true;
97              return new CloseWebSocketFrame();
98          }
99  
100         return new BinaryWebSocketFrame(buffer.readBytes((int) frameSize));
101     }
102 
103     private WebSocketFrame decodeTextFrame(ChannelBuffer buffer) throws TooLongFrameException {
104         int ridx = buffer.readerIndex();
105         int rbytes = actualReadableBytes();
106         int delimPos = buffer.indexOf(ridx, ridx + rbytes, (byte) 0xFF);
107         if (delimPos == -1) {
108             // Frame delimiter (0xFF) not found
109             if (rbytes > maxFrameSize) {
110                 // Frame length exceeded the maximum
111                 throw new TooLongFrameException();
112             } else {
113                 // Wait until more data is received
114                 return null;
115             }
116         }
117 
118         int frameSize = delimPos - ridx;
119         if (frameSize > maxFrameSize) {
120             throw new TooLongFrameException();
121         }
122 
123         ChannelBuffer binaryData = buffer.readBytes(frameSize);
124         buffer.skipBytes(1);
125 
126         int ffDelimPos = binaryData.indexOf(binaryData.readerIndex(), binaryData.writerIndex(), (byte) 0xFF);
127         if (ffDelimPos >= 0) {
128             throw new IllegalArgumentException("a text frame should not contain 0xFF.");
129         }
130 
131         return new TextWebSocketFrame(binaryData);
132     }
133 }