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1   /*
2    * Copyright 2009 Red Hat, Inc.
3    *
4    * Red Hat licenses this file to you under the Apache License, version 2.0
5    * (the "License"); you may not use this file except in compliance with the
6    * 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.protobuf;
17  
18  import org.jboss.netty.buffer.ChannelBuffer;
19  import org.jboss.netty.buffer.ChannelBufferInputStream;
20  import org.jboss.netty.channel.Channel;
21  import org.jboss.netty.channel.ChannelHandler.Sharable;
22  import org.jboss.netty.channel.ChannelHandlerContext;
23  import org.jboss.netty.channel.ChannelPipeline;
24  import org.jboss.netty.channel.MessageEvent;
25  import org.jboss.netty.handler.codec.frame.FrameDecoder;
26  import org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
27  import org.jboss.netty.handler.codec.frame.LengthFieldPrepender;
28  import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;
29  
30  import com.google.protobuf.ExtensionRegistry;
31  import com.google.protobuf.Message;
32  import com.google.protobuf.MessageLite;
33  
34  /**
35   * Decodes a received {@link ChannelBuffer} into a
36   * <a href="http://code.google.com/p/protobuf/">Google Protocol Buffers</a>
37   * {@link Message} and {@link MessageLite}.  Please note that this decoder must
38   * be used with a proper {@link FrameDecoder} such as {@link ProtobufVarint32FrameDecoder}
39   * or {@link LengthFieldBasedFrameDecoder} if you are using a stream-based
40   * transport such as TCP/IP.  A typical setup for TCP/IP would be:
41   * <pre>
42   * {@link ChannelPipeline} pipeline = ...;
43   *
44   * // Decoders
45   * pipeline.addLast("frameDecoder",
46   *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
47   * pipeline.addLast("protobufDecoder",
48   *                  new {@link ProtobufDecoder}(MyMessage.getDefaultInstance()));
49   *
50   * // Encoder
51   * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
52   * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}());
53   * </pre>
54   * and then you can use a {@code MyMessage} instead of a {@link ChannelBuffer}
55   * as a message:
56   * <pre>
57   * void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
58   *     MyMessage req = (MyMessage) e.getMessage();
59   *     MyMessage res = MyMessage.newBuilder().setText(
60   *                               "Did you say '" + req.getText() + "'?").build();
61   *     ch.write(res);
62   * }
63   * </pre>
64   *
65   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
66   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
67   *
68   * @version $Rev:231 $, $Date:2008-06-12 16:44:50 +0900 (목, 12 6월 2008) $
69   *
70   * @apiviz.landmark
71   */
72  @Sharable
73  public class ProtobufDecoder extends OneToOneDecoder {
74  
75      private final MessageLite prototype;
76      private final ExtensionRegistry extensionRegistry;
77  
78      /**
79       * Creates a new instance.
80       */
81      public ProtobufDecoder(MessageLite prototype) {
82          this(prototype, null);
83      }
84  
85      public ProtobufDecoder(MessageLite prototype, ExtensionRegistry extensionRegistry) {
86          if (prototype == null) {
87              throw new NullPointerException("prototype");
88          }
89          this.prototype = prototype.getDefaultInstanceForType();
90          this.extensionRegistry = extensionRegistry;
91      }
92  
93      @Override
94      protected Object decode(
95              ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
96          if (!(msg instanceof ChannelBuffer)) {
97              return msg;
98          }
99  
100         ChannelBuffer buf = (ChannelBuffer) msg;
101         if (buf.hasArray()) {
102             final int offset = buf.readerIndex();
103             if(extensionRegistry == null) {
104                 return prototype.newBuilderForType().mergeFrom(
105                         buf.array(), buf.arrayOffset() + offset, buf.readableBytes()).build();
106             } else {
107                 return prototype.newBuilderForType().mergeFrom(
108                         buf.array(), buf.arrayOffset() + offset, buf.readableBytes(), extensionRegistry).build();
109             }
110         } else {
111             if (extensionRegistry == null) {
112                 return prototype.newBuilderForType().mergeFrom(
113                         new ChannelBufferInputStream((ChannelBuffer) msg)).build();
114             } else {
115                 return prototype.newBuilderForType().mergeFrom(
116                         new ChannelBufferInputStream((ChannelBuffer) msg), extensionRegistry).build();
117             }
118         }
119     }
120 }