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.netty5.example.factorial;
17
18 import io.netty5.buffer.api.Buffer;
19 import io.netty5.channel.ChannelHandlerContext;
20 import io.netty5.handler.codec.ByteToMessageDecoder;
21 import io.netty5.handler.codec.CorruptedFrameException;
22
23 import java.math.BigInteger;
24
25 /**
26 * Decodes the binary representation of a {@link BigInteger} prepended
27 * with a magic number ('F' or 0x46) and a 32-bit integer length prefix into a
28 * {@link BigInteger} instance. For example, { 'F', 0, 0, 0, 1, 42 } will be
29 * decoded into new BigInteger("42").
30 */
31 public class BigIntegerDecoder extends ByteToMessageDecoder {
32
33 @Override
34 protected void decode(ChannelHandlerContext ctx, Buffer in) {
35 // Wait until the length prefix is available.
36 if (in.readableBytes() < 5) {
37 return;
38 }
39
40 int readerOffset = in.readerOffset();
41
42 // Check the magic number.
43 int magicNumber = in.readUnsignedByte();
44 if (magicNumber != 'F') {
45 in.readerOffset(readerOffset);
46 throw new CorruptedFrameException("Invalid magic number: " + magicNumber);
47 }
48
49 // Wait until the whole data is available.
50 int dataLength = in.readInt();
51 if (in.readableBytes() < dataLength) {
52 in.readerOffset(readerOffset);
53 return;
54 }
55
56 // Convert the received data into a new BigInteger.
57 byte[] decoded = new byte[dataLength];
58 in.readBytes(decoded, 0, dataLength);
59
60 ctx.fireChannelRead(new BigInteger(decoded));
61 }
62 }