From 02b1cf937aed3e951e96a955e56a1cc071c332d8 Mon Sep 17 00:00:00 2001
From: mdw <mdw>
Date: Sat, 17 Jun 2000 10:43:57 +0000
Subject: [PATCH] Move GCD filter to separate file.  Handle failures from
 pgen_jump.

---
 bbs-gen.c | 99 ++++++++++++++++-----------------------------------------------
 1 file changed, 24 insertions(+), 75 deletions(-)

diff --git a/bbs-gen.c b/bbs-gen.c
index 43b6990..1c2d035 100644
--- a/bbs-gen.c
+++ b/bbs-gen.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: bbs-gen.c,v 1.3 2000/02/12 18:21:02 mdw Exp $
+ * $Id: bbs-gen.c,v 1.4 2000/06/17 10:43:57 mdw Exp $
  *
  * Generate Blum integers
  *
@@ -30,6 +30,9 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: bbs-gen.c,v $
+ * Revision 1.4  2000/06/17 10:43:57  mdw
+ * Move GCD filter to separate file.  Handle failures from pgen_jump.
+ *
  * Revision 1.3  2000/02/12 18:21:02  mdw
  * Overhaul of key management (again).
  *
@@ -53,74 +56,6 @@
 #include "pgen.h"
 #include "strongprime.h"
 
-/*----- Data structures ---------------------------------------------------*/
-
-typedef struct gcdctx {
-  mp *q, *jq;
-  pfilt p, jp;
-  mp *r;
-} gcdctx;
-
-/*----- Custom stepper ----------------------------------------------------*/
-
-static int gcdstep(int rq, pgen_event *ev, void *p)
-{
-  gcdctx *g = p;
-  int rc = PGEN_ABORT;
-  mp *z = MP_NEW;
-
-  switch (rq) {
-
-    /* --- Set everything up --- */
-
-    case PGEN_BEGIN: {
-      mp *p = ev->m;
-      if ((p->v[0] & 3) != 3)
-	p = mp_add(p, p, g->jp.m);
-      rc = pfilt_create(&g->p, p);
-      g->q = mp_lsr(MP_NEW, p, 1);
-      g->jq = MP_COPY(g->jp.m);
-      pfilt_muladd(&g->jp, &g->jp, 2, 0);
-      g->jq = mp_lsr(MP_NEW, p, 1);
-      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(&z, 0, 0, g->r, g->q);
-      if (MP_CMP(z, !=, MP_ONE))
-	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);
-  }
-
-  mp_drop(z);
-  ev->m = MP_COPY(g->p.m);
-  return (rc);
-}
-
 /*----- Main code ---------------------------------------------------------*/
 
 /* --- @bbs_gen@ --- *
@@ -146,32 +81,46 @@ int bbs_gen(bbs_param *bp, unsigned nbits, grand *r, unsigned n,
 {
   rabin rb;
   pgen_safejumpctx j;
-  gcdctx g;
+  pgen_gcdstepctx g;
   unsigned nb = nbits/2;
   mp *x = MP_NEW;
 
   /* --- Generate @p@ --- */
 
+again:
   if ((x = strongprime_setup("p", x, &j.jq, nb, r, n, event, ectx)) == 0)
     goto fail_x;
   bp->p = pgen("p", MP_NEW, x, event, ectx, n, pgen_safejump, &j,
 	       rabin_iters(nb), pgen_test, &rb);
   pfilt_destroy(&j.jq);
-  if (!bp->p)
-    goto fail_p;
+  if (!bp->p) {
+    if (n)
+      goto fail_p;
+    goto again;
+  }
 
   /* --- Generate @q@ --- */
 
   nb = nbits - nb;
   if ((x = strongprime_setup("q", x, &g.jp, nb, r, n, event, ectx)) == 0)
     goto fail_q;
+  if ((x->v[0] & 3) != 3)
+    x = mp_add(x, x, g.jp.m);
+  pfilt_muladd(&g.jp, &g.jp, 2, 0);
   g.r = mp_lsr(MP_NEW, bp->p, 1);
-  bp->q = pgen("q", MP_NEW, x, event, ectx, n, gcdstep, &g,
+  g.g = MP_NEW;
+  g.max = MP_ONE;
+  bp->q = pgen("q", MP_NEW, x, event, ectx, n, pgen_gcdstep, &g,
 	       rabin_iters(nb), pgen_test, &rb);
   pfilt_destroy(&g.jp);
   mp_drop(g.r);
-  if (!bp->q)
-    goto fail_q;
+  mp_drop(g.g);
+  if (!bp->q) {
+    if (n)
+      goto fail_q;
+    mp_drop(bp->p);
+    goto again;
+  }
 
   /* --- Compute @n@ --- */
 
-- 
2.11.0