/**

 * Duff's Device

 * fast copy algorithm

 * performs 8 times faster on long strings.

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

char *duffcopy (char *to, char *from, int num)

{

    int n, pos = 0;

    n = (num + 7) / 8;

    switch (num % 8) {

    case 0:

        do {

            to[pos] = from[pos];

            pos++;

    case 7:

            to[pos] = from[pos];

            pos++;

    case 6:

            to[pos] = from[pos];

            pos++;

    case 5:

            to[pos] = from[pos];

            pos++;

    case 4:

            to[pos] = from[pos];

            pos++;

    case 3:

            to[pos] = from[pos];

            pos++;

    case 2:

            to[pos] = from[pos];

            pos++;

    case 1:

            to[pos] = from[pos];

            pos++;

        } while (--n > 0);

    }

    return to;

}

int main (int argc, char **argv)

{

    char to[80], *from;

    if (argc != 2) {

        printf ("Usage: %s <string>\n", argv[0]);

        return EXIT_FAILURE;

    }

    from = argv[1];

    printf ("DUFF: %s\n", duffcopy (to, from, strlen (from)));

    return EXIT_SUCCESS;

}