Java tutorial
/* * 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 com.ns.netty.gcd.server; 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; import java.util.List; /** * 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 void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) { System.out.println("Decoder received event"); // Wait until the length prefix is available. if (in.readableBytes() < 5) { return; } 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; } // Convert the received data into a new BigInteger. byte[] decoded = new byte[dataLength]; in.readBytes(decoded); out.add(new BigInteger(decoded)); } }