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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    *   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 io.netty.handler.codec.protobuf;
17  
18  import com.google.protobuf.nano.CodedOutputByteBufferNano;
19  import com.google.protobuf.nano.MessageNano;
20  
21  import java.util.List;
22  
23  import io.netty.buffer.ByteBuf;
24  import io.netty.channel.ChannelHandler;
25  import io.netty.channel.ChannelHandlerContext;
26  import io.netty.channel.ChannelPipeline;
27  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
28  import io.netty.handler.codec.LengthFieldPrepender;
29  import io.netty.handler.codec.MessageToMessageEncoder;
30  
31  /**
32   * Encodes the requested <a href="https://github.com/google/protobuf">Google
33   * Protocol Buffers</a> {@link MessageNano} into a
34   * {@link ByteBuf}. A typical setup for TCP/IP would be:
35   * <pre>
36   * {@link ChannelPipeline} pipeline = ...;
37   *
38   * // Decoders
39   * pipeline.addLast("frameDecoder",
40   *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
41   * pipeline.addLast("protobufDecoder",
42   *                  new {@link ProtobufDecoderNano}(MyMessage.getDefaultInstance()));
43   *
44   * // Encoder
45   * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
46   * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoderNano}());
47   * </pre>
48   * and then you can use a {@code MyMessage} instead of a {@link ByteBuf}
49   * as a message:
50   * <pre>
51   * void channelRead({@link ChannelHandlerContext} ctx, Object msg) {
52   *     MyMessage req = (MyMessage) msg;
53   *     MyMessage res = MyMessage.newBuilder().setText(
54   *                               "Did you say '" + req.getText() + "'?").build();
55   *     ch.write(res);
56   * }
57   * </pre>
58   */
59  @ChannelHandler.Sharable
60  public class ProtobufEncoderNano extends MessageToMessageEncoder<MessageNano> {
61      @Override
62      protected void encode(
63              ChannelHandlerContext ctx, MessageNano msg, List<Object> out) throws Exception {
64          final int size = msg.getSerializedSize();
65          final ByteBuf buffer = ctx.alloc().heapBuffer(size, size);
66          final byte[] array = buffer.array();
67          CodedOutputByteBufferNano cobbn = CodedOutputByteBufferNano.newInstance(array,
68                  buffer.arrayOffset(), buffer.capacity());
69          msg.writeTo(cobbn);
70          buffer.writerIndex(size);
71          out.add(buffer);
72      }
73  }