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.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 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
32 * @author <a href="http://gleamynode.net/">Trustin Lee</a>
33 *
34 * @version $Rev: 2125 $, $Date: 2010-02-02 12:13:15 +0900 (Tue, 02 Feb 2010) $
35 *
36 */
37 public class NumberEncoder extends OneToOneEncoder {
38
39 @Override
40 protected Object encode(
41 ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
42 if (!(msg instanceof Number)) {
43 // Ignore what this encoder can't encode.
44 return msg;
45 }
46
47 // Convert to a BigInteger first for easier implementation.
48 BigInteger v;
49 if (msg instanceof BigInteger) {
50 v = (BigInteger) msg;
51 } else {
52 v = new BigInteger(String.valueOf(msg));
53 }
54
55 // Convert the number into a byte array.
56 byte[] data = v.toByteArray();
57 int dataLength = data.length;
58
59 // Construct a message.
60 ChannelBuffer buf = ChannelBuffers.dynamicBuffer();
61 buf.writeByte((byte) 'F'); // magic number
62 buf.writeInt(dataLength); // data length
63 buf.writeBytes(data); // data
64
65 // Return the constructed message.
66 return buf;
67 }
68 }