Gather up another utility.

[u/mdw/catacomb] / mp-arith.c

diff --git a/mp-arith.c b/mp-arith.c
index a070675..736be2f 100644 (file)
--- a/mp-arith.c
+++ b/mp-arith.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mp-arith.c,v 1.14 2002/10/15 19:18:31 mdw Exp $
+ * $Id: mp-arith.c,v 1.18 2004/04/08 01:36:15 mdw Exp $
  *
  * Basic arithmetic on multiprecision integers
  *
@@ -27,57 +27,6 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: mp-arith.c,v $
- * Revision 1.14  2002/10/15 19:18:31  mdw
- * New operation to negate numbers.
- *
- * Revision 1.13  2002/10/15 00:19:40  mdw
- * Bit setting and clearing functions.
- *
- * Revision 1.12  2002/10/09 00:36:03  mdw
- * Fix bounds on workspace for Karatsuba operations.
- *
- * Revision 1.11  2002/10/06 22:52:50  mdw
- * Pile of changes for supporting two's complement properly.
- *
- * Revision 1.10  2001/04/03 19:36:05  mdw
- * Add some simple bitwise operations so that Perl can use them.
- *
- * Revision 1.9  2000/10/08 15:48:35  mdw
- * Rename Karatsuba constants now that we have @gfx_kmul@ too.
- *
- * Revision 1.8  2000/10/08 12:02:21  mdw
- * Use @MP_EQ@ instead of @MP_CMP@.
- *
- * Revision 1.7  2000/06/22 19:02:53  mdw
- * New function @mp_odd@ to extract powers of two from an integer.  This is
- * common code from the Rabin-Miller test, RSA key recovery and modular
- * square-root extraction.
- *
- * Revision 1.6  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 1.5  1999/12/22 15:54:41  mdw
- * Adjust Karatsuba parameters.  Calculate destination size better.
- *
- * Revision 1.4  1999/12/13 15:35:16  mdw
- * Slightly different rules on memory allocation.
- *
- * Revision 1.3  1999/12/11 10:57:43  mdw
- * Karatsuba squaring algorithm.
- *
- * Revision 1.2  1999/12/10 23:18:39  mdw
- * Change interface for suggested destinations.
- *
- * Revision 1.1  1999/11/17 18:02:16  mdw
- * New multiprecision integer arithmetic suite.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "mp.h"
@@ -88,13 +37,18 @@
 
 /*----- Main code ---------------------------------------------------------*/
 
-/* --- @mp_lsl@, @mp_lsr@ --- *
+/* --- @mp_lsl@, @mp_lslc@, @mp_lsr@ --- *
  *
  * Arguments:  @mp *d@ = destination
  *             @mp *a@ = source
  *             @size_t n@ = number of bits to move
  *
  * Returns:    Result, @a@ shifted left or right by @n@.
+ *
+ * Use:                Bitwise shift operators.  @mp_lslc@ fills the bits introduced
+ *             on the right with ones instead of zeroes: it's used
+ *             internally by @mp_lsl2c@, though it may be useful on its
+ *             own.
  */
 
 mp *mp_lsl(mp *d, mp *a, size_t n)
@@ -106,6 +60,15 @@ mp *mp_lsl(mp *d, mp *a, size_t n)
   return (d);
 }
 
+mp *mp_lslc(mp *d, mp *a, size_t n)
+{
+  MP_DEST(d, MP_LEN(a) + (n + MPW_BITS - 1) / MPW_BITS, a->f);
+  mpx_lslc(d->v, d->vl, a->v, a->vl, n);
+  d->f = a->f & (MP_NEG | MP_BURN);
+  MP_SHRINK(d);
+  return (d);
+}
+
 mp *mp_lsr(mp *d, mp *a, size_t n)
 {
   MP_DEST(d, MP_LEN(a), a->f);
@@ -130,7 +93,7 @@ mp *mp_lsl2c(mp *d, mp *a, size_t n)
   if (!(a->f & MP_NEG))
     return (mp_lsl(d, a, n));
   d = mp_not2c(d, a);
-  d = mp_lsl(d, d, n);
+  d = mp_lslc(d, d, n);
   d = mp_not2c(d, d);
   return (d);
 }
@@ -290,10 +253,10 @@ mp *mp_neg(mp *d, mp *a)
 
   MP_SHRINK(a);
   MP_COPY(a);
-  if (d) MP_DROP(d);
-  if (a->v == a->vl) {
+  if (d)
+    MP_DROP(d);
+  if (a->v == a->vl)
     return (a);
-  }
   MP_DEST(a, MP_LEN(a), a->f);
   a->f ^= MP_NEG;
   return (a);
@@ -318,7 +281,7 @@ mp *mp_neg(mp *d, mp *a)
                                                                        \
 mp *mp_bit##string(mp *d, mp *a, mp *b)                                        \
 {                                                                      \
-  MP_DEST(d, MAX(MP_LEN(a), MP_LEN(b)), a->f | b->f);                  \
+  MP_DEST(d, MAX(MP_LEN(a), MP_LEN(b)), (a->f | b->f) & ~MP_NEG);      \
   mpx_bit##string(d->v, d->vl, a->v, a->vl, b->v, b->vl);              \
   d->f = (a->f | b->f) & MP_BURN;                                      \
   MP_SHRINK(d);                                                                \
@@ -599,7 +562,7 @@ void mp_div(mp **qq, mp **rr, mp *a, mp *b)
   if (r)
     MP_DROP(r);
   r = a;
-  MP_DEST(r, MP_LEN(a) + 2, a->f | b->f);
+  MP_DEST(r, MAX(MP_LEN(a), MP_LEN(b)) + 2, a->f | b->f);
 
   /* --- Fix up the quotient too --- */