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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 compressor.
30   */
31  class PerMessageDeflateEncoder extends DeflateEncoder {
32  
33      private boolean compressing;
34  
35      /**
36       * Constructor
37       *
38       * @param compressionLevel compression level of the compressor.
39       * @param windowSize maximum size of the window compressor buffer.
40       * @param noContext true to disable context takeover.
41       */
42      PerMessageDeflateEncoder(int compressionLevel, int windowSize, boolean noContext) {
43          super(compressionLevel, windowSize, noContext, WebSocketExtensionFilter.NEVER_SKIP);
44      }
45  
46      /**
47       * Constructor
48       *
49       * @param compressionLevel compression level of the compressor.
50       * @param windowSize maximum size of the window compressor buffer.
51       * @param noContext true to disable context takeover.
52       * @param extensionEncoderFilter extension filter for per message deflate encoder.
53       */
54      PerMessageDeflateEncoder(int compressionLevel, int windowSize, boolean noContext,
55                               WebSocketExtensionFilter extensionEncoderFilter) {
56          super(compressionLevel, windowSize, noContext, extensionEncoderFilter);
57      }
58  
59      @Override
60      public boolean acceptOutboundMessage(Object msg) throws Exception {
61          if (!super.acceptOutboundMessage(msg)) {
62              return false;
63          }
64  
65          WebSocketFrame wsFrame = (WebSocketFrame) msg;
66          if (extensionEncoderFilter().mustSkip(wsFrame)) {
67              if (compressing) {
68                  throw new IllegalStateException("Cannot skip per message deflate encoder, compression in progress");
69              }
70              return false;
71          }
72  
73          return ((wsFrame instanceof TextWebSocketFrame || wsFrame instanceof BinaryWebSocketFrame) &&
74                  (wsFrame.rsv() & WebSocketExtension.RSV1) == 0) ||
75                 (wsFrame instanceof ContinuationWebSocketFrame && compressing);
76      }
77  
78      @Override
79      protected int rsv(WebSocketFrame msg) {
80          return msg instanceof TextWebSocketFrame || msg instanceof BinaryWebSocketFrame?
81                  msg.rsv() | WebSocketExtension.RSV1 : msg.rsv();
82      }
83  
84      @Override
85      protected boolean removeFrameTail(WebSocketFrame msg) {
86          return msg.isFinalFragment();
87      }
88  
89      @Override
90      protected void encode(ChannelHandlerContext ctx, WebSocketFrame msg,
91                            List<Object> out) throws Exception {
92          super.encode(ctx, msg, out);
93  
94          if (msg.isFinalFragment()) {
95              compressing = false;
96          } else if (msg instanceof TextWebSocketFrame || msg instanceof BinaryWebSocketFrame) {
97              compressing = true;
98          }
99      }
100 
101 }