/*
* Copyright 2012 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.example.factorial;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import io.netty.handler.codec.CorruptedFrameException;
import java.math.BigInteger;
/**
* Decodes the binary representation of a {@link BigInteger} prepended
* with a magic number ('F' or 0x46) and a 32-bit integer length prefix into a
* {@link BigInteger} instance. For example, { 'F', 0, 0, 0, 1, 42 } will be
* decoded into new BigInteger("42").
*/
public class BigIntegerDecoder extends ByteToMessageDecoder {
@Override
protected BigInteger decode(ChannelHandlerContext ctx, ByteBuf in) {
// Wait until the length prefix is available.
if (in.readableBytes() < 5) {
return null;
}
in.markReaderIndex();
// Check the magic number.
int magicNumber = in.readUnsignedByte();
if (magicNumber != 'F') {
in.resetReaderIndex();
throw new CorruptedFrameException(
"Invalid magic number: " + magicNumber);
}
// Wait until the whole data is available.
int dataLength = in.readInt();
if (in.readableBytes() < dataLength) {
in.resetReaderIndex();
return null;
}
// Convert the received data into a new BigInteger.
byte[] decoded = new byte[dataLength];
in.readBytes(decoded);
return new BigInteger(decoded);
}
}