netty 数据包分包解码问题

Question

有谁精通netty ，数据包解码是，不确定数据包大小，怎么能收到完整的数据包？

Answer 1

我有个程序的包结构是这样的：1byte(包类型)+4byte（包体长度）+实际包体，于是写了下面的代码：
[code="java"]
public class ReceivingPacketHandler extends FrameDecoder {
public static fianl int HEADER_SIZE=5;

@Override
protected Object decode(ChannelHandlerContext ctx, Channel channel,
        ChannelBuffer buf) throws Exception {
    if (buf.readableBytes() < HEADER_SIZE) {
        // The header length field was not received yet - return null.
        return null;
    }
    buf.markReaderIndex();
    // Read protocol header
    buf.readByte();
    // Read the data length field.
    int length = buf.readInt();
    buf.resetReaderIndex();
    // Make sure if there's enough bytes in the buffer.
    int totalLength = length + HEADER_SIZE;
    if (buf.readableBytes() < totalLength) {
                //the whole packet was not received yet - return null.
        return null;
    }
    Packet recievedPacket = new Packet(size >= 0 ? size : bufSize);
    recievedPacket.clear();
    recievedPacket.readPacket(buf, totalLength);
    return recievedPacket;
}

}
[/code]