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 * 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.example.factorial;
17
18 import io.netty.buffer.ByteBuf;
19 import io.netty.channel.ChannelHandlerContext;
20 import io.netty.handler.codec.MessageToByteEncoder;
21
22 import java.math.BigInteger;
23
24 /**
25 * Encodes a {@link Number} into the binary representation prepended with
26 * a magic number ('F' or 0x46) and a 32-bit length prefix. For example, 42
27 * will be encoded to { 'F', 0, 0, 0, 1, 42 }.
28 */
29 public class NumberEncoder extends MessageToByteEncoder<Number> {
30
31 @Override
32 protected void encode(ChannelHandlerContext ctx, Number msg, ByteBuf out) {
33 // Convert to a BigInteger first for easier implementation.
34 BigInteger v;
35 if (msg instanceof BigInteger) {
36 v = (BigInteger) msg;
37 } else {
38 v = new BigInteger(String.valueOf(msg));
39 }
40
41 // Convert the number into a byte array.
42 byte[] data = v.toByteArray();
43 int dataLength = data.length;
44
45 // Write a message.
46 out.writeByte((byte) 'F'); // magic number
47 out.writeInt(dataLength); // data length
48 out.writeBytes(data); // data
49 }
50 }