View Javadoc
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.buffer.ByteBuf;
19  import io.netty.buffer.CompositeByteBuf;
20  import io.netty.buffer.Unpooled;
21  import io.netty.channel.ChannelHandlerContext;
22  import io.netty.channel.embedded.EmbeddedChannel;
23  import io.netty.handler.codec.CodecException;
24  import io.netty.handler.codec.compression.ZlibCodecFactory;
25  import io.netty.handler.codec.compression.ZlibWrapper;
26  import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame;
27  import io.netty.handler.codec.http.websocketx.ContinuationWebSocketFrame;
28  import io.netty.handler.codec.http.websocketx.TextWebSocketFrame;
29  import io.netty.handler.codec.http.websocketx.WebSocketFrame;
30  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionDecoder;
31  import io.netty.handler.codec.http.websocketx.extensions.WebSocketExtensionFilter;
32  
33  import java.util.List;
34  
35  import static io.netty.util.internal.ObjectUtil.*;
36  
37  /**
38   * Deflate implementation of a payload decompressor for
39   * <tt>io.netty.handler.codec.http.websocketx.WebSocketFrame</tt>.
40   */
41  abstract class DeflateDecoder extends WebSocketExtensionDecoder {
42  
43      static final ByteBuf FRAME_TAIL = Unpooled.unreleasableBuffer(
44              Unpooled.wrappedBuffer(new byte[] {0x00, 0x00, (byte) 0xff, (byte) 0xff}))
45              .asReadOnly();
46  
47      static final ByteBuf EMPTY_DEFLATE_BLOCK = Unpooled.unreleasableBuffer(
48              Unpooled.wrappedBuffer(new byte[] { 0x00 }))
49              .asReadOnly();
50  
51      private final boolean noContext;
52      private final WebSocketExtensionFilter extensionDecoderFilter;
53  
54      private EmbeddedChannel decoder;
55  
56      /**
57       * Constructor
58       *
59       * @param noContext true to disable context takeover.
60       * @param extensionDecoderFilter extension decoder filter.
61       */
62      DeflateDecoder(boolean noContext, WebSocketExtensionFilter extensionDecoderFilter) {
63          this.noContext = noContext;
64          this.extensionDecoderFilter = checkNotNull(extensionDecoderFilter, "extensionDecoderFilter");
65      }
66  
67      /**
68       * Returns the extension decoder filter.
69       */
70      protected WebSocketExtensionFilter extensionDecoderFilter() {
71          return extensionDecoderFilter;
72      }
73  
74      protected abstract boolean appendFrameTail(WebSocketFrame msg);
75  
76      protected abstract int newRsv(WebSocketFrame msg);
77  
78      @Override
79      protected void decode(ChannelHandlerContext ctx, WebSocketFrame msg, List<Object> out) throws Exception {
80          final ByteBuf decompressedContent = decompressContent(ctx, msg);
81  
82          final WebSocketFrame outMsg;
83          if (msg instanceof TextWebSocketFrame) {
84              outMsg = new TextWebSocketFrame(msg.isFinalFragment(), newRsv(msg), decompressedContent);
85          } else if (msg instanceof BinaryWebSocketFrame) {
86              outMsg = new BinaryWebSocketFrame(msg.isFinalFragment(), newRsv(msg), decompressedContent);
87          } else if (msg instanceof ContinuationWebSocketFrame) {
88              outMsg = new ContinuationWebSocketFrame(msg.isFinalFragment(), newRsv(msg), decompressedContent);
89          } else {
90              throw new CodecException("unexpected frame type: " + msg.getClass().getName());
91          }
92  
93          out.add(outMsg);
94      }
95  
96      @Override
97      public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
98          cleanup();
99          super.handlerRemoved(ctx);
100     }
101 
102     @Override
103     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
104         cleanup();
105         super.channelInactive(ctx);
106     }
107 
108     private ByteBuf decompressContent(ChannelHandlerContext ctx, WebSocketFrame msg) {
109         if (decoder == null) {
110             if (!(msg instanceof TextWebSocketFrame) && !(msg instanceof BinaryWebSocketFrame)) {
111                 throw new CodecException("unexpected initial frame type: " + msg.getClass().getName());
112             }
113             decoder = new EmbeddedChannel(ZlibCodecFactory.newZlibDecoder(ZlibWrapper.NONE));
114         }
115 
116         boolean readable = msg.content().isReadable();
117         boolean emptyDeflateBlock = EMPTY_DEFLATE_BLOCK.equals(msg.content());
118 
119         decoder.writeInbound(msg.content().retain());
120         if (appendFrameTail(msg)) {
121             decoder.writeInbound(FRAME_TAIL.duplicate());
122         }
123 
124         CompositeByteBuf compositeDecompressedContent = ctx.alloc().compositeBuffer();
125         for (;;) {
126             ByteBuf partUncompressedContent = decoder.readInbound();
127             if (partUncompressedContent == null) {
128                 break;
129             }
130             if (!partUncompressedContent.isReadable()) {
131                 partUncompressedContent.release();
132                 continue;
133             }
134             compositeDecompressedContent.addComponent(true, partUncompressedContent);
135         }
136         // Correctly handle empty frames
137         // See https://github.com/netty/netty/issues/4348
138         if (!emptyDeflateBlock && readable && compositeDecompressedContent.numComponents() <= 0) {
139             // Sometimes after fragmentation the last frame
140             // May contain left-over data that doesn't affect decompression
141             if (!(msg instanceof ContinuationWebSocketFrame)) {
142                 compositeDecompressedContent.release();
143                 throw new CodecException("cannot read uncompressed buffer");
144             }
145         }
146 
147         if (msg.isFinalFragment() && noContext) {
148             cleanup();
149         }
150 
151         return compositeDecompressedContent;
152     }
153 
154     private void cleanup() {
155         if (decoder != null) {
156             // Clean-up the previous encoder if not cleaned up correctly.
157             decoder.finishAndReleaseAll();
158             decoder = null;
159         }
160     }
161 }