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/*
* makeprime.c
*
* A simple prime generator function (and test driver). Prints out the
* first prime it finds greater than or equal to the starting value.
*
* Usage: makeprime <start>
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
/* These two must be included for make_prime() to work */
#include "mpi.h"
#include "mpprime.h"
/*
make_prime(p, nr)
Find the smallest prime integer greater than or equal to p, where
primality is verified by 'nr' iterations of the Rabin-Miller
probabilistic primality test. The caller is responsible for
generating the initial value of p.
Returns MP_OKAY if a prime has been generated, otherwise the error
code indicates some other problem. The value of p is clobbered; the
caller should keep a copy if the value is needed.
*/
mp_err make_prime(mp_int *p, int nr);
/* The main() is not required -- it's just a test driver */
int
main(int argc, char *argv[])
{
mp_int start;
mp_err res;
if (argc < 2) {
fprintf(stderr, "Usage: %s <start-value>\n", argv[0]);
return 1;
}
mp_init(&start);
if (argv[1][0] == '0' && tolower(argv[1][1]) == 'x') {
mp_read_radix(&start, argv[1] + 2, 16);
} else {
mp_read_radix(&start, argv[1], 10);
}
mp_abs(&start, &start);
if ((res = make_prime(&start, 5)) != MP_OKAY) {
fprintf(stderr, "%s: error: %s\n", argv[0], mp_strerror(res));
mp_clear(&start);
return 1;
} else {
char *buf = malloc(mp_radix_size(&start, 10));
mp_todecimal(&start, buf);
printf("%s\n", buf);
free(buf);
mp_clear(&start);
return 0;
}
} /* end main() */
/*------------------------------------------------------------------------*/
mp_err
make_prime(mp_int *p, int nr)
{
mp_err res;
if (mp_iseven(p)) {
mp_add_d(p, 1, p);
}
do {
mp_digit which = prime_tab_size;
/* First test for divisibility by a few small primes */
if ((res = mpp_divis_primes(p, &which)) == MP_YES)
continue;
else if (res != MP_NO)
goto CLEANUP;
/* If that passes, try one iteration of Fermat's test */
if ((res = mpp_fermat(p, 2)) == MP_NO)
continue;
else if (res != MP_YES)
goto CLEANUP;
/* If that passes, run Rabin-Miller as often as requested */
if ((res = mpp_pprime(p, nr)) == MP_YES)
break;
else if (res != MP_NO)
goto CLEANUP;
} while ((res = mp_add_d(p, 2, p)) == MP_OKAY);
CLEANUP:
return res;
} /* end make_prime() */
/*------------------------------------------------------------------------*/
/* HERE THERE BE DRAGONS */
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