1 /* 2 * Copyright 2009 Red Hat, Inc. 3 * 4 * Red Hat licenses this file to you under the Apache License, version 2.0 5 * (the "License"); you may not use this file except in compliance with the 6 * License. You may obtain a copy of the License at: 7 * 8 * http://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 org.jboss.netty.example.factorial; 17 18 import java.math.BigInteger; 19 20 import org.jboss.netty.buffer.ChannelBuffer; 21 import org.jboss.netty.buffer.ChannelBuffers; 22 import org.jboss.netty.channel.Channel; 23 import org.jboss.netty.channel.ChannelHandlerContext; 24 import org.jboss.netty.handler.codec.oneone.OneToOneEncoder; 25 26 /** 27 * Encodes a {@link Number} into the binary representation prepended with 28 * a magic number ('F' or 0x46) and a 32-bit length prefix. For example, 42 29 * will be encoded to { 'F', 0, 0, 0, 1, 42 }. 30 * 31 * @author <a href="http://www.jboss.org/netty/">The Netty Project</a> 32 * @author <a href="http://gleamynode.net/">Trustin Lee</a> 33 * 34 * @version $Rev: 2125 $, $Date: 2010-02-02 12:13:15 +0900 (Tue, 02 Feb 2010) $ 35 * 36 */ 37 public class NumberEncoder extends OneToOneEncoder { 38 39 @Override 40 protected Object encode( 41 ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception { 42 if (!(msg instanceof Number)) { 43 // Ignore what this encoder can't encode. 44 return msg; 45 } 46 47 // Convert to a BigInteger first for easier implementation. 48 BigInteger v; 49 if (msg instanceof BigInteger) { 50 v = (BigInteger) msg; 51 } else { 52 v = new BigInteger(String.valueOf(msg)); 53 } 54 55 // Convert the number into a byte array. 56 byte[] data = v.toByteArray(); 57 int dataLength = data.length; 58 59 // Construct a message. 60 ChannelBuffer buf = ChannelBuffers.dynamicBuffer(); 61 buf.writeByte((byte) 'F'); // magic number 62 buf.writeInt(dataLength); // data length 63 buf.writeBytes(data); // data 64 65 // Return the constructed message. 66 return buf; 67 } 68 }