Merge branch 'master' of git+ssh://metalzone.distorted.org.uk/~mdw/public-git/catacomb/

[u/mdw/catacomb] / mpbarrett.c

diff --git a/mpbarrett.c b/mpbarrett.c
index 934097d..b5e604e 100644 (file)
--- a/mpbarrett.c
+++ b/mpbarrett.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpbarrett.c,v 1.9 2004/04/01 12:50:09 mdw Exp $
+ * $Id$
  *
  * Barrett modular reduction
  *
@@ -27,46 +27,6 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: mpbarrett.c,v $
- * Revision 1.9  2004/04/01 12:50:09  mdw
- * Add cyclic group abstraction, with test code.  Separate off exponentation
- * functions for better static linking.  Fix a buttload of bugs on the way.
- * Generally ensure that negative exponents do inversion correctly.  Add
- * table of standard prime-field subgroups.  (Binary field subgroups are
- * currently unimplemented but easy to add if anyone ever finds a good one.)
- *
- * 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.
- *
- * Revision 1.5  2000/07/29 17:04:33  mdw
- * Change to use left-to-right bitwise exponentiation.  This will improve
- * performance when the base is small.
- *
- * 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.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "mp.h"
@@ -80,18 +40,19 @@
  *             @mp *m@ = modulus to work to
  *
  *
- * Returns:    ---
+ * Returns:    Zero on success, nonzero on error.
  *
  * Use:                Initializes a Barrett reduction context ready for use.
  */
 
-void mpbarrett_create(mpbarrett *mb, mp *m)
+int mpbarrett_create(mpbarrett *mb, mp *m)
 {
   mp *b;
 
   /* --- Validate the arguments --- */
 
-  assert(((void)"Barrett modulus must be positive", (m->f & MP_NEG) == 0));
+  if (!MP_POSP(m))
+    return (-1);
 
   /* --- Compute %$\mu$% --- */
 
@@ -103,6 +64,7 @@ void mpbarrett_create(mpbarrett *mb, mp *m)
   b->vl[-1] = 1;
   mp_div(&b, 0, b, m);
   mb->mu = b;
+  return (0);
 }
 
 /* --- @mpbarrett_destroy@ --- *