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

   1 /* -*-c-*-
   2  *
   3  * $Id: prim.c,v 1.2 2000/07/29 09:57:42 mdw Exp $
   4  *
   5  * Finding primitive elements
   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: prim.c,v $
  33  * Revision 1.2  2000/07/29 09:57:42  mdw
  34  * Improve primitive-element testing a lot.  Now much more sensible and
  35  * orthogonal: you can find a generator for any given subgroup order by
  36  * putting in the appropriate parameters.
  37  *
  38  * Revision 1.1  1999/12/22 15:58:59  mdw
  39  * Search for primitive elements using prime-search equipment.
  40  *
  41  */
  42
  43 /*----- Header files ------------------------------------------------------*/
  44
  45 #include "mp.h"
  46 #include "mpint.h"
  47 #include "mpmont.h"
  48 #include "mprand.h"
  49 #include "pgen.h"
  50 #include "prim.h"
  51
  52 /*----- Main code ---------------------------------------------------------*/
  53
  54 /* --- @prim_test@ --- */
  55
  56 int prim_test(int rq, pgen_event *ev, void *p)
  57 {
  58   prim_ctx *c = p;
  59   int rc = rq;
  60
  61   switch (rq) {
  62     case PGEN_BEGIN:
  63       return (PGEN_TRY);
  64     case PGEN_TRY: {
  65       mp *x;
  66       rc = PGEN_FAIL;
  67
  68       if (!c->exp)
  69         x = mp_copy(ev->m);
  70       else {
  71         x = mpmont_exp(&c->mm, MP_NEW, ev->m, c->exp);
  72         if (MP_CMP(x, ==, MP_ONE))
  73           goto done;
  74       }
  75       if (c->n == 0)
  76         goto ok;
  77       else {
  78         size_t n = c->n;
  79         mp **f = c->f;
  80         mp *y = MP_NEW;
  81         while (n) {
  82           y = mpmont_exp(&c->mm, y, x, *f);
  83           if (MP_CMP(y, ==, MP_ONE)) {
  84             mp_drop(y);
  85             goto done;
  86           }
  87           n--; f++;
  88         }
  89         mp_drop(y);
  90       }
  91     ok:
  92       rc = PGEN_DONE;
  93       mp_drop(ev->m);
  94       ev->m = x;
  95       break;
  96     done:
  97       mp_drop(x);
  98     } break;
  99   }
 100
 101   return (rc);
 102 }
 103
 104 /* --- Trivial stepping functions -----------------------------------------*/
 105
 106 /* --- @prim_step@ --- */
 107
 108 int prim_step(int rq, pgen_event *ev, void *p)
 109 {
 110   unsigned *i = p;
 111   switch (rq) {
 112     case PGEN_BEGIN:
 113     case PGEN_TRY:
 114       if (*i >= NPRIME)
 115         return PGEN_FAIL;
 116       ev->m = mp_fromint(ev->m, primetab[(*i)++]);
 117       return (PGEN_TRY);
 118   }
 119   return (0);
 120 }
 121
 122 /*----- That's all, folks -------------------------------------------------*/