code: func xorInGeneric(d *state, buf []byte) {
  	n := len(buf) / 8
  
  	for i := 0; i < n; i++ {
  		a := binary.LittleEndian.Uint64(buf)
  		d.a[i] ^= a
  		buf = buf[8:]
  	}
  }
docs: // xorInGeneric xors the bytes in buf into the state; it
  // makes no non-portable assumptions about memory layout
  // or alignment.