1 /*
2 * Copyright 2012 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 org.jboss.netty.example.factorial;
17
18 import java.math.BigInteger;
19
20 import org.jboss.netty.buffer.ChannelBuffer;
21 import org.jboss.netty.buffer.ChannelBuffers;
22 import org.jboss.netty.channel.Channel;
23 import org.jboss.netty.channel.ChannelHandlerContext;
24 import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
25
26 /**
27 * Encodes a {@link Number} into the binary representation prepended with
28 * a magic number ('F' or 0x46) and a 32-bit length prefix. For example, 42
29 * will be encoded to { 'F', 0, 0, 0, 1, 42 }.
30 */
31 public class NumberEncoder extends OneToOneEncoder {
32
33 @Override
34 protected Object encode(
35 ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
36 if (!(msg instanceof Number)) {
37 // Ignore what this encoder can't encode.
38 return msg;
39 }
40
41 // Convert to a BigInteger first for easier implementation.
42 BigInteger v;
43 if (msg instanceof BigInteger) {
44 v = (BigInteger) msg;
45 } else {
46 v = new BigInteger(String.valueOf(msg));
47 }
48
49 // Convert the number into a byte array.
50 byte[] data = v.toByteArray();
51 int dataLength = data.length;
52
53 // Construct a message.
54 ChannelBuffer buf = ChannelBuffers.dynamicBuffer();
55 buf.writeByte((byte) 'F'); // magic number
56 buf.writeInt(dataLength); // data length
57 buf.writeBytes(data); // data
58
59 // Return the constructed message.
60 return buf;
61 }
62 }