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1   /*
2    * Copyright 2014 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    *   https://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 io.netty.handler.codec.http.websocketx.extensions.compression;
17  
18  import io.netty.channel.ChannelHandlerContext;
19  import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
20  import io.netty.handler.codec.http.websocketx.ContinuationWebSocketFrame;
21  import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
22  import io.netty.handler.codec.http.websocketx.WebSocketFrame;
23  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtension;
24  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionFilter;
25  
26  import java.util.List;
27  
28  /**
29   * Per-message implementation of deflate decompressor.
30   */
31  class PerMessageDeflateDecoder extends DeflateDecoder {
32  
33      private boolean compressing;
34  
35      /**
36       * Constructor
37       *
38       * @param noContext true to disable context takeover.
39       */
40      PerMessageDeflateDecoder(boolean noContext) {
41          super(noContext, WebSocketExtensionFilter.NEVER_SKIP);
42      }
43  
44      /**
45       * Constructor
46       *
47       * @param noContext true to disable context takeover.
48       * @param extensionDecoderFilter extension decoder for per message deflate decoder.
49       */
50      PerMessageDeflateDecoder(boolean noContext, WebSocketExtensionFilter extensionDecoderFilter) {
51          super(noContext, extensionDecoderFilter);
52      }
53  
54      @Override
55      public boolean acceptInboundMessage(Object msg) throws Exception {
56          if (!super.acceptInboundMessage(msg)) {
57              return false;
58          }
59  
60          WebSocketFrame wsFrame = (WebSocketFrame) msg;
61          if (extensionDecoderFilter().mustSkip(wsFrame)) {
62              if (compressing) {
63                  throw new IllegalStateException("Cannot skip per message deflate decoder, compression in progress");
64              }
65              return false;
66          }
67  
68          return ((wsFrame instanceof TextWebSocketFrame || wsFrame instanceof BinaryWebSocketFrame) &&
69                  (wsFrame.rsv() & WebSocketExtension.RSV1) > 0) ||
70                 (wsFrame instanceof ContinuationWebSocketFrame && compressing);
71      }
72  
73      @Override
74      protected int newRsv(WebSocketFrame msg) {
75          return (msg.rsv() & WebSocketExtension.RSV1) > 0?
76                  msg.rsv() ^ WebSocketExtension.RSV1 : msg.rsv();
77      }
78  
79      @Override
80      protected boolean appendFrameTail(WebSocketFrame msg) {
81          return msg.isFinalFragment();
82      }
83  
84      @Override
85      protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg,
86                            List<Object> out) throws Exception {
87          super.decode(ctx, msg, out);
88  
89          if (msg.isFinalFragment()) {
90              compressing = false;
91          } else if (msg instanceof TextWebSocketFrame || msg instanceof BinaryWebSocketFrame) {
92              compressing = true;
93          }
94      }
95  
96  }