X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/21a7c4b1cffbf33a19e4cf421e29420187ed7a89..d34decd2b2b88240cf4ca68a2a5feb7bf36de6e7:/mpbarrett.c

diff --git a/mpbarrett.c b/mpbarrett.c
index e438d02..aaa1bb7 100644
--- a/mpbarrett.c
+++ b/mpbarrett.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpbarrett.c,v 1.1 1999/12/10 23:21:59 mdw Exp $
+ * $Id: mpbarrett.c,v 1.4 2000/06/17 11:45:09 mdw Exp $
  *
  * Barrett modular reduction
  *
@@ -30,6 +30,18 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpbarrett.c,v $
+ * Revision 1.4  2000/06/17 11:45:09  mdw
+ * Major memory management overhaul.  Added arena support.  Use the secure
+ * arena for secret integers.  Replace and improve the MP management macros
+ * (e.g., replace MP_MODIFY by MP_DEST).
+ *
+ * Revision 1.3  1999/12/12 15:08:52  mdw
+ * Don't bother shifting %$q$% in @mpbarrett_reduce@, just skip the least
+ * significant digits.
+ *
+ * Revision 1.2  1999/12/11 01:50:56  mdw
+ * Improve initialization slightly.
+ *
  * Revision 1.1  1999/12/10 23:21:59  mdw
  * Barrett reduction support: works with even moduli.
  *
@@ -66,7 +78,9 @@ void mpbarrett_create(mpbarrett *mb, mp *m)
   mp_shrink(m);
   mb->k = MP_LEN(m);
   mb->m = MP_COPY(m);
-  b = mp_lsl(MP_NEW, MP_ONE, 2 * MPW_BITS * mb->k);
+  b = mp_new(2 * mb->k + 1, 0);
+  MPX_ZERO(b->v, b->vl - 1);
+  b->vl[-1] = 1;
   mp_div(&b, 0, b, m);
   mb->mu = b;
 }
@@ -109,7 +123,8 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *m)
 
   if (MP_LEN(m) < k) {
     m = MP_COPY(m);
-    MP_DROP(d);
+    if (d)
+      MP_DROP(d);
     return (m);
   }
 
@@ -119,7 +134,12 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *m)
     mp qq;
     mp_build(&qq, m->v + (k - 1), m->vl);
     q = mp_mul(MP_NEW, &qq, mb->mu);
-    q = mp_lsr(q, q, MPW_BITS * (k + 1));
+    if (MP_LEN(q) <= k) {
+      m = MP_COPY(m);
+      if (d)
+	MP_DROP(d);
+      return (m);
+    }
   }
 
   /* --- Second stage --- */
@@ -133,10 +153,9 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *m)
       mvl = m->vl;
     else
       mvl = m->v + k + 1;
-    r = mp_create(k + 1);
-    mpx_umul(r->v, r->vl, q->v, q->vl, mb->m->v, mb->m->vl);
-    r->f = (q->f | mb->m->f) & MP_BURN;
-    MP_MODIFY(d, k + 1);
+    r = mp_new(k + 1, (q->f | mb->m->f) & MP_BURN);
+    mpx_umul(r->v, r->vl, q->v + k + 1, q->vl, mb->m->v, mb->m->vl);
+    MP_DEST(d, k + 1, r->f);
     mpx_usub(d->v, d->vl, m->v, mvl, r->v, r->vl);
     d->f = (m->f | r->f) & MP_BURN;
     MP_DROP(r);
@@ -172,6 +191,8 @@ mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e)
 
   a = MP_COPY(a);
   mp_scan(&sc, e);
+  if (e->f & MP_BURN)
+    spare = MP_NEWSEC;
   if (MP_STEP(&sc)) {
     size_t sq = 0;
     for (;;) {