Use the generic exponentiation functions.

[u/mdw/catacomb] / mpbarrett.c

diff --git a/mpbarrett.c b/mpbarrett.c
index 0af753e..b38aa91 100644 (file)
--- a/mpbarrett.c
+++ b/mpbarrett.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpbarrett.c,v 1.6 2000/10/08 12:03:44 mdw Exp $
+ * $Id: mpbarrett.c,v 1.8 2001/06/16 13:00:20 mdw Exp $
  *
  * Barrett modular reduction
  *
@@ -30,6 +30,12 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpbarrett.c,v $
+ * Revision 1.8  2001/06/16 13:00:20  mdw
+ * Use the generic exponentiation functions.
+ *
+ * Revision 1.7  2001/04/19 18:25:26  mdw
+ * Use sliding-window exponentiation.
+ *
  * Revision 1.6  2000/10/08 12:03:44  mdw
  * (mpbarrett_reduce): Cope with negative numbers.
  *
@@ -58,6 +64,7 @@
 
 #include "mp.h"
 #include "mpbarrett.h"
+#include "mpbarrett-exp.h"
 
 /*----- Main code ---------------------------------------------------------*/
 
@@ -198,60 +205,18 @@ mp *mpbarrett_reduce(mpbarrett *mb, mp *d, mp *m)
 
 mp *mpbarrett_exp(mpbarrett *mb, mp *d, mp *a, mp *e)
 {
-  mpscan sc;
   mp *x = MP_ONE;
   mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
-  unsigned sq = 0;
-
-  a = MP_COPY(a);
-  mp_rscan(&sc, e);
-  if (!MP_RSTEP(&sc))
-    goto exit;
-  while (!MP_RBIT(&sc))
-    MP_RSTEP(&sc);
-
-  /* --- Do the main body of the work --- */
-
-  for (;;) {
-    sq++;
-    while (sq) {
-      mp *y;
-      y = mp_sqr(spare, x);
-      y = mpbarrett_reduce(mb, y, y);
-      spare = x; x = y;
-      sq--;
-    }
-    {
-      mp *y = mp_mul(spare, x, a);
-      y = mpbarrett_reduce(mb, y, y);
-      spare = x; x = y;
-    }
-    for (;;) {
-      if (!MP_RSTEP(&sc))
-       goto done;
-      if (MP_RBIT(&sc))
-       break;
-      sq++;
-    }
-  }
 
-  /* --- Do a final round of squaring --- */
-
-done:
-  while (sq) {
-    mp *y;
-    y = mp_sqr(spare, x);
-    y = mpbarrett_reduce(mb, y, y);
-    spare = x; x = y;
-    sq--;
-  }  
-
-exit:
-  MP_DROP(a);
-  if (spare != MP_NEW)
-    MP_DROP(spare);
-  if (d != MP_NEW)
-    MP_DROP(d);
+  MP_SHRINK(e);
+  if (!MP_LEN(e))
+    ;
+  else if (MP_LEN(e) < EXP_THRESH)
+    EXP_SIMPLE(x, a, e);
+  else
+    EXP_WINDOW(x, a, e);
+  mp_drop(d);
+  mp_drop(spare);
   return (x);
 }