git.distorted.org.uk Git - u/mdw/catacomb/blob - primorial.c

   1 /* -*-c-*-
   2  *
   3  * $Id: primorial.c,v 1.1 1999/12/22 15:51:02 mdw Exp $
   4  *
   5  * Computes the product of the small primes
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: primorial.c,v $
  33  * Revision 1.1  1999/12/22 15:51:02  mdw
  34  * Calculate product of small primes for DSA prime search.
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 #include "mp.h"
  41 #include "primetab.h"
  42
  43 /*----- Global variables --------------------------------------------------*/
  44
  45 mp *primorial = 0;
  46
  47 /*----- Main code ---------------------------------------------------------*/
  48
  49 /* --- @primorial_setup@ --- *
  50  *
  51  * Arguments:   ---
  52  *
  53  * Returns:     ---
  54  *
  55  * Use:         Computes the product of the small primes in the table
  56  *              @primetab@.
  57  */
  58
  59 void primorial_setup(void)
  60 {
  61   mp *p;
  62   mp q;
  63   mpw qw;
  64   int i;
  65
  66   if (primorial)
  67     return;
  68   mp_build(&q, &qw, &qw + 1);
  69   p = MP_ONE;
  70   for (i = 0; i < NPRIME; i++) {
  71     qw = primetab[i];
  72     p = mp_mul(p, p, &q);
  73   }
  74   mp_minimize(p);
  75   primorial = p;
  76 }
  77
  78 /*----- That's all, folks -------------------------------------------------*/