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

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