michael@0: /*
michael@0:  *  gcd.c
michael@0:  *
michael@0:  *  Greatest common divisor
michael@0:  *
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include <stdio.h>
michael@0: #include <stdlib.h>
michael@0: #include <string.h>
michael@0: 
michael@0: #include "mpi.h"
michael@0: 
michael@0: char     *g_prog = NULL;
michael@0: 
michael@0: void print_mp_int(mp_int *mp, FILE *ofp);
michael@0: 
michael@0: int main(int argc, char *argv[]) 
michael@0: {
michael@0:   mp_int   a, b, x, y;
michael@0:   mp_err   res;
michael@0:   int      ext = 0;
michael@0: 
michael@0:   g_prog = argv[0];
michael@0: 
michael@0:   if(argc < 3) {
michael@0:     fprintf(stderr, "Usage: %s <a> <b>\n", g_prog);
michael@0:     return 1;
michael@0:   }
michael@0: 
michael@0:   mp_init(&a); mp_read_radix(&a, argv[1], 10);
michael@0:   mp_init(&b); mp_read_radix(&b, argv[2], 10);
michael@0: 
michael@0:   /* If we were called 'xgcd', compute x, y so that g = ax + by */
michael@0:   if(strcmp(g_prog, "xgcd") == 0) {
michael@0:     ext = 1;
michael@0:     mp_init(&x); mp_init(&y);
michael@0:   }
michael@0: 
michael@0:   if(ext) {
michael@0:     if((res = mp_xgcd(&a, &b, &a, &x, &y)) != MP_OKAY) {
michael@0:       fprintf(stderr, "%s: error: %s\n", g_prog, mp_strerror(res));
michael@0:       mp_clear(&a); mp_clear(&b);
michael@0:       mp_clear(&x); mp_clear(&y);
michael@0:       return 1;
michael@0:     }
michael@0:   } else {
michael@0:     if((res = mp_gcd(&a, &b, &a)) != MP_OKAY) {
michael@0:       fprintf(stderr, "%s: error: %s\n", g_prog,
michael@0: 	      mp_strerror(res));
michael@0:       mp_clear(&a); mp_clear(&b);
michael@0:       return 1;
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   print_mp_int(&a, stdout); 
michael@0:   if(ext) {
michael@0:     fputs("x = ", stdout); print_mp_int(&x, stdout); 
michael@0:     fputs("y = ", stdout); print_mp_int(&y, stdout); 
michael@0:   }
michael@0: 
michael@0:   mp_clear(&a); mp_clear(&b);
michael@0: 
michael@0:   if(ext) {
michael@0:     mp_clear(&x);
michael@0:     mp_clear(&y);
michael@0:   }
michael@0: 
michael@0:   return 0;
michael@0: 
michael@0: }
michael@0: 
michael@0: void print_mp_int(mp_int *mp, FILE *ofp)
michael@0: {
michael@0:   char  *buf;
michael@0:   int    len;
michael@0: 
michael@0:   len = mp_radix_size(mp, 10);
michael@0:   buf = calloc(len, sizeof(char));
michael@0:   mp_todecimal(mp, buf);
michael@0:   fprintf(ofp, "%s\n", buf);
michael@0:   free(buf);
michael@0: 
michael@0: }