netty的ByteBuf

netty的ByteBuf
*

 
 *      +-------------------+------------------+------------------+ 
 *      | discardable bytes |  readable bytes  |  writable bytes  | 
 *      |                   |     (CONTENT)    |                  | 
 *      +-------------------+------------------+------------------+ 
 *      |                   |                  |                  | 
 *      0      <=      readerIndex   <=   writerIndex    <=    capacity 
 * 

通过netty的ByteBuf的readerIndex增强对byte的认识；
如果一个ByteBuf的格式是command + status + identifier = 1 + 1 + 4
那么
in.readByte()
in.readByte()
in.readInt() 这个就是4个Byte的长度即4*8=32位长度，所以，int是占32位；