code: func (s *asmState) copyIntoBuf(b []byte) {
  	bufLen := len(s.buf)
  	s.buf = s.buf[:len(s.buf)+len(b)]
  	copy(s.buf[bufLen:], b)
  }
docs: // copyIntoBuf copies b into buf. It will panic if there is not enough space to
  // store all of b.