mirror of
https://github.com/rn10950/RetroZilla.git
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60 lines
1.0 KiB
C
60 lines
1.0 KiB
C
/*
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* invmod.c
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*
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* Compute modular inverses
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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 "mpi.h"
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int main(int argc, char *argv[])
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{
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mp_int a, m;
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mp_err res;
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char *buf;
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int len, out = 0;
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if(argc < 3) {
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fprintf(stderr, "Usage: %s <a> <m>\n", argv[0]);
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return 1;
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}
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mp_init(&a); mp_init(&m);
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mp_read_radix(&a, argv[1], 10);
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mp_read_radix(&m, argv[2], 10);
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if(mp_cmp(&a, &m) > 0)
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mp_mod(&a, &m, &a);
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switch((res = mp_invmod(&a, &m, &a))) {
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case MP_OKAY:
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len = mp_radix_size(&a, 10);
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buf = malloc(len);
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mp_toradix(&a, buf, 10);
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printf("%s\n", buf);
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free(buf);
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break;
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case MP_UNDEF:
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printf("No inverse\n");
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out = 1;
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break;
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default:
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printf("error: %s (%d)\n", mp_strerror(res), res);
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out = 2;
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break;
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}
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mp_clear(&a);
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mp_clear(&m);
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return out;
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}
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