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/**
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* Duff's Device
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* fast copy algorithm
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* performs 8 times faster on long strings.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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char *duffcopy (char *to, char *from, int len)
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{
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int n, pos = 0;
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n = (len + 7) / 8;
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switch (len % 8) {
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case 0:
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do {
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to[pos] = from[pos];
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pos++;
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case 7:
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to[pos] = from[pos];
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pos++;
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case 6:
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to[pos] = from[pos];
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pos++;
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case 5:
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to[pos] = from[pos];
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pos++;
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case 4:
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to[pos] = from[pos];
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pos++;
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case 3:
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to[pos] = from[pos];
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pos++;
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case 2:
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to[pos] = from[pos];
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pos++;
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case 1:
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to[pos] = from[pos];
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pos++;
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} while (--n > 0);
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}
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return to;
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}
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int main (int argc, char **argv)
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{
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char *to, *from;
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int len;
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if (argc != 2) {
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printf ("Usage: %s <string>\n", argv[0]);
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return EXIT_FAILURE;
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}
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from = argv[1];
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len = strlen (from) + 1;
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if ((to = malloc (len)) == NULL) {
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perror ("MALLOC");
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return EXIT_FAILURE;
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}
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printf ("DUFF: %s\n", duffcopy (to, from, len));
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if (to != NULL) {
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free (to);
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}
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return EXIT_SUCCESS;
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}
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