security/nss/lib/freebl/mpi/utils/fact.c

   1 /*
   2  * fact.c
   3  *
   4  * Compute factorial of input integer
   5  *
   6  * ***** BEGIN LICENSE BLOCK *****
   7  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   8  *
   9  * The contents of this file are subject to the Mozilla Public License Version
  10  * 1.1 (the "License"); you may not use this file except in compliance with
  11  * the License. You may obtain a copy of the License at
  12  * http://www.mozilla.org/MPL/
  13  *
  14  * Software distributed under the License is distributed on an "AS IS" basis,
  15  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  16  * for the specific language governing rights and limitations under the
  17  * License.
  18  *
  19  * The Original Code is the MPI Arbitrary Precision Integer Arithmetic library.
  20  *
  21  * The Initial Developer of the Original Code is
  22  * Michael J. Fromberger.
  23  * Portions created by the Initial Developer are Copyright (C) 1998
  24  * the Initial Developer. All Rights Reserved.
  25  *
  26  * Contributor(s):
  27  *
  28  * Alternatively, the contents of this file may be used under the terms of
  29  * either the GNU General Public License Version 2 or later (the "GPL"), or
  30  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  31  * in which case the provisions of the GPL or the LGPL are applicable instead
  32  * of those above. If you wish to allow use of your version of this file only
  33  * under the terms of either the GPL or the LGPL, and not to allow others to
  34  * use your version of this file under the terms of the MPL, indicate your
  35  * decision by deleting the provisions above and replace them with the notice
  36  * and other provisions required by the GPL or the LGPL. If you do not delete
  37  * the provisions above, a recipient may use your version of this file under
  38  * the terms of any one of the MPL, the GPL or the LGPL.
  39  *
  40  * ***** END LICENSE BLOCK ***** */
  41 /* $Id: fact.c,v 1.3 2004/04/27 23:04:37 gerv%gerv.net Exp $ */
  42
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46
  47 #include "mpi.h"
  48
  49 mp_err mp_fact(mp_int *a, mp_int *b);
  50
  51 int main(int argc, char *argv[])
  52 {
  53   mp_int  a;
  54   mp_err  res;
  55
  56   if(argc < 2) {
  57     fprintf(stderr, "Usage: %s <number>\n", argv[0]);
  58     return 1;
  59   }
  60
  61   mp_init(&a);
  62   mp_read_radix(&a, argv[1], 10);
  63
  64   if((res = mp_fact(&a, &a)) != MP_OKAY) {
  65     fprintf(stderr, "%s: error: %s\n", argv[0],
  66             mp_strerror(res));
  67     mp_clear(&a);
  68     return 1;
  69   }
  70
  71   {
  72     char  *buf;
  73     int    len;
  74
  75     len = mp_radix_size(&a, 10);
  76     buf = malloc(len);
  77     mp_todecimal(&a, buf);
  78
  79     puts(buf);
  80
  81     free(buf);
  82   }
  83
  84   mp_clear(&a);
  85   return 0;
  86 }
  87
  88 mp_err mp_fact(mp_int *a, mp_int *b)
  89 {
  90   mp_int    ix, s;
  91   mp_err    res = MP_OKAY;
  92
  93   if(mp_cmp_z(a) < 0)
  94     return MP_UNDEF;
  95
  96   mp_init(&s);
  97   mp_add_d(&s, 1, &s);   /* s = 1  */
  98   mp_init(&ix);
  99   mp_add_d(&ix, 1, &ix); /* ix = 1 */
 100
 101   for(/*  */; mp_cmp(&ix, a) <= 0; mp_add_d(&ix, 1, &ix)) {
 102     if((res = mp_mul(&s, &ix, &s)) != MP_OKAY)
 103       break;
 104   }
 105
 106   mp_clear(&ix);
 107
 108   /* Copy out results if we got them */
 109   if(res == MP_OKAY)
 110     mp_copy(&s, b);
 111
 112   mp_clear(&s);
 113
 114   return res;
 115 }