public void read(byte[] buff,int off,int len){
  System.arraycopy(data,pos,buff,off,len);
  pos+=len;
}

public void read ( byte [ ] buff , int off , int len ) { System . arraycopy ( data , pos , buff , off , len ) ; pos += len ; }
copy a number of bytes to the given buffer from the current position . the current position is incremented accordingly .
