+++ /dev/null
-/* -*-c-*-
- *
- * $Id: pgen-gcd.c,v 1.3 2004/04/08 01:36:15 mdw Exp $
- *
- * Prime search stepper ensuring a low GCD for %$(p - 1)/2$%
- *
- * (c) 2000 Straylight/Edgeware
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of Catacomb.
- *
- * Catacomb is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * Catacomb is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with Catacomb; if not, write to the Free
- * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- * MA 02111-1307, USA.
- */
-
-/*----- Header files ------------------------------------------------------*/
-
-#include "mp.h"
-#include "pgen.h"
-
-/*----- Main code ---------------------------------------------------------*/
-
-int pgen_gcdstep(int rq, pgen_event *ev, void *p)
-{
- pgen_gcdstepctx *g = p;
- int rc = PGEN_ABORT;
-
- switch (rq) {
-
- /* --- Set everything up --- *
- *
- * Call things off if @p@ and @jp@ have common factors, or if @q@, @r@
- * and @jq@ have common factors greater than @max@.
- */
-
- case PGEN_BEGIN: {
- mp *p = ev->m;
- mp_gcd(&g->g, 0, 0, p, g->jp.m);
- if (MP_CMP(g->g, >, MP_ONE))
- return (PGEN_ABORT);
- g->q = mp_lsr(MP_NEW, p, 1);
- g->jq = mp_lsr(MP_NEW, g->jp.m, 1);
- mp_gcd(&g->g, 0, 0, g->q, g->jq);
- mp_gcd(&g->g, 0, 0, g->g, g->r);
- if (MP_CMP(g->g, >, g->max)) {
- mp_drop(g->q);
- mp_drop(g->jq);
- return (PGEN_ABORT);
- }
- rc = pfilt_create(&g->p, p);
- mp_drop(p);
- } break;
-
- /* --- Grind through another iteration --- */
-
- case PGEN_TRY:
- mp_drop(ev->m);
- rc = pfilt_jump(&g->p, &g->jp);
- g->q = mp_add(g->q, g->q, g->jq);
- break;
-
- /* --- Finished --- */
-
- case PGEN_DONE:
- pfilt_destroy(&g->p);
- mp_drop(g->q);
- mp_drop(g->jq);
- return (PGEN_DONE);
- }
-
- /* --- Step on until everything is OK --- */
-
- for (;;) {
- if (rc != PGEN_FAIL) {
- mp_gcd(&g->g, 0, 0, g->r, g->q);
- if (MP_CMP(g->g, >, g->max))
- rc = PGEN_FAIL;
- }
- if (rc != PGEN_FAIL)
- break;
- rc = pfilt_jump(&g->p, &g->jp);
- g->q = mp_add(g->q, g->q, g->jq);
- }
-
- ev->m = MP_COPY(g->p.m);
- return (rc);
-}
-
-/*----- That's all, folks -------------------------------------------------*/