The Tor Browser: security/nss/lib/freebl/mpi/utils/fact.c@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /*

     2  * fact.c

     3  *

     4  * Compute factorial of input integer

     5  *

     6  * This Source Code Form is subject to the terms of the Mozilla Public

     7  * License, v. 2.0. If a copy of the MPL was not distributed with this

     8  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

    10 #include <stdio.h>

    11 #include <stdlib.h>

    12 #include <string.h>

    14 #include "mpi.h"

    16 mp_err mp_fact(mp_int *a, mp_int *b);

    18 int main(int argc, char *argv[])

    19 {

    20   mp_int  a;

    21   mp_err  res;

    23   if(argc < 2) {

    24     fprintf(stderr, "Usage: %s <number>\n", argv[0]);

    25     return 1;

    26   }

    28   mp_init(&a);

    29   mp_read_radix(&a, argv[1], 10);

    31   if((res = mp_fact(&a, &a)) != MP_OKAY) {

    32     fprintf(stderr, "%s: error: %s\n", argv[0],

    33 	    mp_strerror(res));

    34     mp_clear(&a);

    35     return 1;

    36   }

    38   {

    39     char  *buf;

    40     int    len;

    42     len = mp_radix_size(&a, 10);

    43     buf = malloc(len);

    44     mp_todecimal(&a, buf);

    46     puts(buf);

    48     free(buf);

    49   }

    51   mp_clear(&a);

    52   return 0;

    53 }

    55 mp_err mp_fact(mp_int *a, mp_int *b)

    56 {

    57   mp_int    ix, s;

    58   mp_err    res = MP_OKAY;

    60   if(mp_cmp_z(a) < 0)

    61     return MP_UNDEF;

    63   mp_init(&s);

    64   mp_add_d(&s, 1, &s);   /* s = 1  */

    65   mp_init(&ix);

    66   mp_add_d(&ix, 1, &ix); /* ix = 1 */

    68   for(/*  */; mp_cmp(&ix, a) <= 0; mp_add_d(&ix, 1, &ix)) {

    69     if((res = mp_mul(&s, &ix, &s)) != MP_OKAY)

    70       break;

    71   }

    73   mp_clear(&ix);

    75   /* Copy out results if we got them */

    76   if(res == MP_OKAY)

    77     mp_copy(&s, b);

    79   mp_clear(&s);

    81   return res;

    82 }

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