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1   /*
2    * Copyright 2015 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.protobuf;
17  
18  import com.google.protobuf.ExtensionRegistry;
19  import com.google.protobuf.ExtensionRegistryLite;
20  import com.google.protobuf.Message;
21  import com.google.protobuf.MessageLite;
22  import io.netty.buffer.ByteBuf;
23  import io.netty.buffer.ByteBufUtil;
24  import io.netty.channel.ChannelHandler.Sharable;
25  import io.netty.channel.ChannelHandlerContext;
26  import io.netty.channel.ChannelPipeline;
27  import io.netty.handler.codec.ByteToMessageDecoder;
28  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
29  import io.netty.handler.codec.LengthFieldPrepender;
30  import io.netty.handler.codec.MessageToMessageDecoder;
31  import io.netty.util.internal.ObjectUtil;
32  
33  import java.util.List;
34  
35  /**
36   * Decodes a received {@link ByteBuf} into a
37   * <a href="https://github.com/google/protobuf">Google Protocol Buffers</a>
38   * {@link Message} and {@link MessageLite}. Please note that this decoder must
39   * be used with a proper {@link ByteToMessageDecoder} such as {@link ProtobufVarint32FrameDecoder}
40   * or {@link LengthFieldBasedFrameDecoder} if you are using a stream-based
41   * transport such as TCP/IP. A typical setup for TCP/IP would be:
42   * <pre>
43   * {@link ChannelPipeline} pipeline = ...;
44   *
45   * // Decoders
46   * pipeline.addLast("frameDecoder",
47   *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
48   * pipeline.addLast("protobufDecoder",
49   *                  new {@link ProtobufDecoder}(MyMessage.getDefaultInstance()));
50   *
51   * // Encoder
52   * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
53   * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}());
54   * </pre>
55   * and then you can use a {@code MyMessage} instead of a {@link ByteBuf}
56   * as a message:
57   * <pre>
58   * void channelRead({@link ChannelHandlerContext} ctx, Object msg) {
59   *     MyMessage req = (MyMessage) msg;
60   *     MyMessage res = MyMessage.newBuilder().setText(
61   *                               "Did you say '" + req.getText() + "'?").build();
62   *     ch.write(res);
63   * }
64   * </pre>
65   */
66  @Sharable
67  public class ProtobufDecoder extends MessageToMessageDecoder<ByteBuf> {
68  
69      private static final boolean HAS_PARSER;
70  
71      static {
72          boolean hasParser = false;
73          try {
74              // MessageLite.getParserForType() is not available until protobuf 2.5.0.
75              MessageLite.class.getDeclaredMethod("getParserForType");
76              hasParser = true;
77          } catch (Throwable t) {
78              // Ignore
79          }
80  
81          HAS_PARSER = hasParser;
82      }
83  
84      private final MessageLite prototype;
85      private final ExtensionRegistryLite extensionRegistry;
86  
87      /**
88       * Creates a new instance.
89       */
90      public ProtobufDecoder(MessageLite prototype) {
91          this(prototype, null);
92      }
93  
94      public ProtobufDecoder(MessageLite prototype, ExtensionRegistry extensionRegistry) {
95          this(prototype, (ExtensionRegistryLite) extensionRegistry);
96      }
97  
98      public ProtobufDecoder(MessageLite prototype, ExtensionRegistryLite extensionRegistry) {
99          this.prototype = ObjectUtil.checkNotNull(prototype, "prototype").getDefaultInstanceForType();
100         this.extensionRegistry = extensionRegistry;
101     }
102 
103     @Override
104     protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out)
105             throws Exception {
106         final byte[] array;
107         final int offset;
108         final int length = msg.readableBytes();
109         if (msg.hasArray()) {
110             array = msg.array();
111             offset = msg.arrayOffset() + msg.readerIndex();
112         } else {
113             array = ByteBufUtil.getBytes(msg, msg.readerIndex(), length, false);
114             offset = 0;
115         }
116 
117         if (extensionRegistry == null) {
118             if (HAS_PARSER) {
119                 out.add(prototype.getParserForType().parseFrom(array, offset, length));
120             } else {
121                 out.add(prototype.newBuilderForType().mergeFrom(array, offset, length).build());
122             }
123         } else {
124             if (HAS_PARSER) {
125                 out.add(prototype.getParserForType().parseFrom(
126                         array, offset, length, extensionRegistry));
127             } else {
128                 out.add(prototype.newBuilderForType().mergeFrom(
129                         array, offset, length, extensionRegistry).build());
130             }
131         }
132     }
133 }