mirror of
https://github.com/rn10950/RetroZilla.git
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89 lines
2.0 KiB
C
89 lines
2.0 KiB
C
/*
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* isprime.c
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*
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* Probabilistic primality tester command-line tool
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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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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#include "mpi.h"
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#include "mpprime.h"
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#define RM_TESTS 15 /* how many iterations of Rabin-Miller? */
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#define MINIMUM 1024 /* don't bother us with a < this */
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int g_tests = RM_TESTS;
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char *g_prog = NULL;
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int main(int argc, char *argv[])
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{
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mp_int a;
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mp_digit np = prime_tab_size; /* from mpprime.h */
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int res = 0;
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g_prog = argv[0];
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if(argc < 2) {
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fprintf(stderr, "Usage: %s <a>, where <a> is a decimal integer\n"
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"Use '0x' prefix for a hexadecimal value\n", g_prog);
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return 1;
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}
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/* Read number of tests from environment, if present */
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{
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char *tmp;
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if((tmp = getenv("RM_TESTS")) != NULL) {
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if((g_tests = atoi(tmp)) <= 0)
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g_tests = RM_TESTS;
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}
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}
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mp_init(&a);
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if(argv[1][0] == '0' && argv[1][1] == 'x')
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mp_read_radix(&a, argv[1] + 2, 16);
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else
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mp_read_radix(&a, argv[1], 10);
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if(mp_cmp_d(&a, MINIMUM) <= 0) {
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fprintf(stderr, "%s: please use a value greater than %d\n",
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g_prog, MINIMUM);
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mp_clear(&a);
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return 1;
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}
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/* Test for divisibility by small primes */
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if(mpp_divis_primes(&a, &np) != MP_NO) {
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printf("Not prime (divisible by small prime %d)\n", np);
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res = 2;
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goto CLEANUP;
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}
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/* Test with Fermat's test, using 2 as a witness */
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if(mpp_fermat(&a, 2) != MP_YES) {
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printf("Not prime (failed Fermat test)\n");
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res = 2;
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goto CLEANUP;
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}
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/* Test with Rabin-Miller probabilistic test */
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if(mpp_pprime(&a, g_tests) == MP_NO) {
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printf("Not prime (failed pseudoprime test)\n");
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res = 2;
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goto CLEANUP;
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}
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printf("Probably prime, 1 in 4^%d chance of false positive\n", g_tests);
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CLEANUP:
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mp_clear(&a);
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return res;
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}
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