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.ByteToMessageDecoder;
21 import io.netty.handler.codec.CorruptedFrameException;
22
23 import java.math.BigInteger;
24 import java.util.List;
25
26 /**
27 * Decodes the binary representation of a {@link BigInteger} prepended
28 * with a magic number ('F' or 0x46) and a 32-bit integer length prefix into a
29 * {@link BigInteger} instance. For example, { 'F', 0, 0, 0, 1, 42 } will be
30 * decoded into new BigInteger("42").
31 */
32 public class BigIntegerDecoder extends ByteToMessageDecoder {
33
34 @Override
35 protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {
36 // Wait until the length prefix is available.
37 if (in.readableBytes() < 5) {
38 return;
39 }
40
41 in.markReaderIndex();
42
43 // Check the magic number.
44 int magicNumber = in.readUnsignedByte();
45 if (magicNumber != 'F') {
46 in.resetReaderIndex();
47 throw new CorruptedFrameException("Invalid magic number: " + magicNumber);
48 }
49
50 // Wait until the whole data is available.
51 int dataLength = in.readInt();
52 if (in.readableBytes() < dataLength) {
53 in.resetReaderIndex();
54 return;
55 }
56
57 // Convert the received data into a new BigInteger.
58 byte[] decoded = new byte[dataLength];
59 in.readBytes(decoded);
60
61 out.add(new BigInteger(decoded));
62 }
63 }