Duff's device

可変長のメモリのコピーをC言語のswitch-caseを使って書く技法

send(to, from, count)
register short *to, *from;
register count;
{
	register n = (count + 7) / 8;
	switch(count % 8) {
	case 0:	do {	*to = *from++;
	case 7:		*to = *from++;
	case 6:		*to = *from++;
	case 5:		*to = *from++;
	case 4:		*to = *from++;
	case 3:		*to = *from++;
	case 2:		*to = *from++;
	case 1:		*to = *from++;
		} while(--n > 0);
	}
}

「Duff’s_device」（2024-08-19 09:55 JTC）『ウィキペディア日本語版』より。