public void add(int i,byte[] buffer,int offset,int length){
  if (_length + length > _capacity)   ensureCapacity(_length + length);
  System.arraycopy(_buffer,i,_buffer,i + length,_length - i);
  System.arraycopy(buffer,offset,_buffer,i,length);
  _length+=length;
}

public void add ( int i , byte [ ] buffer , int offset , int length ) { if ( _length + length > _capacity ) ensureCapacity ( _length + length ) ; System . arraycopy ( _buffer , i , _buffer , i + length , _length - i ) ; System . arraycopy ( buffer , offset , _buffer , i , length ) ; _length += length ; }
inserts a byte array
