ReplayingDecoder to read a sequence of uploaded files

FileUploadReplayingDecoder.java

/**
 * 
 */
package net.example;

import java.nio.charset.Charset;
import java.util.List;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ReplayingDecoder;

public class FileUploadReplayingDecoder extends ReplayingDecoder<FileUploadReplayingDecoder.FileUploadField> {
	public static final Charset UTF8 = Charset.forName("UTF8");
	protected int fileNumber = -1;
	protected int filesRead = 0;
	protected int nextSize = -1;
	protected int nameSize = -1;
	protected byte[] nameBytes = null;
	protected String fileName = null;
	
	public FileUploadReplayingDecoder() {
		super(FileUploadField.NUMBER);
	}
	
	public static class Upload {
		public String fileName = null;
		public ByteBuf content = null;

		Upload(String fileName, ByteBuf content) {
			super();
			this.fileName = fileName;
			this.content = content;
		}
	}
	
	public static enum FileUploadField {
		NUMBER,
		SIZE,
		NAME_SIZE,
		NAME,
		CONTENT;
	}
	
	@Override
	protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
		switch(state()) {
		case NUMBER:
			fileNumber = in.readInt();
			checkpoint(FileUploadField.SIZE);
		case SIZE:
			nextSize = in.readInt();
			checkpoint(FileUploadField.NAME_SIZE);	
		case NAME_SIZE:
			nameSize = in.readInt();
			nameBytes = new byte[nameSize];
			checkpoint(FileUploadField.NAME);
		case NAME:
			in.readBytes(nameBytes);
			fileName = new String(nameBytes, UTF8);
			checkpoint(FileUploadField.CONTENT);
		case CONTENT:
			// Need to ReferenceCountUtil.release(fileContent) after use.
			ByteBuf fileContent = in.readBytes(nextSize);			
			out.add(new Upload(fileName, fileContent));
			filesRead++;
			if(filesRead == fileNumber) {
				ctx.pipeline().remove(this);
			} else {
				checkpoint(FileUploadField.SIZE);
			}
			break;
		default:
			throw new Error("Shouldn't reach here.");
		
		}		
	}
}