TITLE: another way to swap bytes


RESPONSE: neil@ninthwv.demon.co.uk (Neil Topham)

For a 16-bit types use;

    newvalue = ((oldvalue & 0xff) << 8) |
               ((oldvalue & 0xff00) >> 8);


RESPONSE: Peter Gustav Lindstrom <lindstro@cc.gatech.edu>, 20 Jul 95

This is only guaranteed to work if oldvalue is unsigned, otherwise it is
implementation dependent (i.e. either 0's or 1's will be shifted in from
the left). A better way of doing it would be to do the AND after the shift:

newvalue = ((oldvalue << 8) & 0xff00) |
           ((oldvalue >> 8) & 0xff);

Another alternative is to use unions (this is assuming 16 bit shorts):

unsigned short swapShort(unsigned short x)
{
  union	{	unsigned short	s;
		unsigned char	c[2];
	}	u;

  u.s = x;
  u.c[0] ^= u.c[1];
  u.c[1] ^= u.c[0];
  u.c[0] ^= u.c[1];
  return u.s;
}