X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/81578196d5732e443c75768ba9118c581c407cc7..b817bfc642225b8c3c0b6a7e42d1fb949b61a606:/mpx.c

diff --git a/mpx.c b/mpx.c
index f40d7d9..e122760 100644
--- a/mpx.c
+++ b/mpx.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpx.c,v 1.16 2003/05/16 09:09:24 mdw Exp $
+ * $Id: mpx.c,v 1.20 2004/04/08 01:36:15 mdw Exp $
  *
  * Low-level multiprecision arithmetic
  *
@@ -27,61 +27,6 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: mpx.c,v $
- * Revision 1.16  2003/05/16 09:09:24  mdw
- * Fix @mp_lsl2c@.  Turns out to be surprisingly tricky.
- *
- * Revision 1.15  2002/10/20 01:12:31  mdw
- * Two's complement I/O fixes.
- *
- * Revision 1.14  2002/10/19 18:55:08  mdw
- * Fix overflows in shift primitives.
- *
- * Revision 1.13  2002/10/19 17:56:50  mdw
- * Fix bit operations.  Test them (a bit) better.
- *
- * Revision 1.12  2002/10/06 22:52:50  mdw
- * Pile of changes for supporting two's complement properly.
- *
- * Revision 1.11  2001/04/03 19:36:05  mdw
- * Add some simple bitwise operations so that Perl can use them.
- *
- * Revision 1.10  2000/10/08 12:06:12  mdw
- * Provide @mpx_ueq@ for rapidly testing equality of two integers.
- *
- * Revision 1.9  2000/06/26 07:52:50  mdw
- * Portability fix for the bug fix.
- *
- * Revision 1.8  2000/06/25 12:59:02  mdw
- * (mpx_udiv): Fix bug in quotient digit estimation.
- *
- * Revision 1.7  1999/12/22 15:49:07  mdw
- * New function for division by a small integer.
- *
- * Revision 1.6  1999/11/20 22:43:44  mdw
- * Integrate testing for MPX routines.
- *
- * Revision 1.5  1999/11/20 22:23:27  mdw
- * Add function versions of some low-level macros with wider use.
- *
- * Revision 1.4  1999/11/17 18:04:09  mdw
- * Add two's-complement functionality.  Improve mpx_udiv a little by
- * performing the multiplication of the divisor by q with the subtraction
- * from r.
- *
- * Revision 1.3  1999/11/13 01:57:31  mdw
- * Remove stray debugging code.
- *
- * Revision 1.2  1999/11/13 01:50:59  mdw
- * Multiprecision routines finished and tested.
- *
- * Revision 1.1  1999/09/03 08:41:12  mdw
- * Initial import.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include <assert.h>
@@ -650,7 +595,7 @@ void mpx_lsr(mpw *dv, mpw *dvl, const mpw *av, const mpw *avl, size_t n)
   /* --- Single bit shifting --- */
 
   else if (n == 1) {
-    mpw w = *av++ >> 1;
+    mpw w = av < avl ? *av++ >> 1 : 0;
     while (av < avl) {
       mpw t;
       if (dv >= dvl)
@@ -877,6 +822,30 @@ void mpx_uadd(mpw *dv, mpw *dvl, const mpw *av, const mpw *avl,
 
 void mpx_uaddn(mpw *dv, mpw *dvl, mpw n) { MPX_UADDN(dv, dvl, n); }
 
+/* --- @mpx_uaddnlsl@ --- *
+ *
+ * Arguments:	@mpw *dv, *dvl@ = destination and first argument vector
+ *		@mpw a@ = second argument
+ *		@unsigned o@ = offset in bits
+ *
+ * Returns:	---
+ *
+ * Use:		Computes %$d + 2^o a$%.  If the result overflows then
+ *		high-order bits are discarded, as usual.  We must have
+ *		@0 < o < MPW_BITS@.
+ */
+
+void mpx_uaddnlsl(mpw *dv, mpw *dvl, mpw a, unsigned o)
+{
+  mpd x = (mpd)a << o;
+
+  while (x && dv < dvl) {
+    x += *dv;
+    *dv++ = MPW(x);
+    x >>= MPW_BITS;
+  }
+}
+
 /* --- @mpx_usub@ --- *
  *
  * Arguments:	@mpw *dv, *dvl@ = destination vector base and limit
@@ -931,6 +900,33 @@ void mpx_usub(mpw *dv, mpw *dvl, const mpw *av, const mpw *avl,
 
 void mpx_usubn(mpw *dv, mpw *dvl, mpw n) { MPX_USUBN(dv, dvl, n); }
 
+/* --- @mpx_uaddnlsl@ --- *
+ *
+ * Arguments:	@mpw *dv, *dvl@ = destination and first argument vector
+ *		@mpw a@ = second argument
+ *		@unsigned o@ = offset in bits
+ *
+ * Returns:	---
+ *
+ * Use:		Computes %$d + 2^o a$%.  If the result overflows then
+ *		high-order bits are discarded, as usual.  We must have
+ *		@0 < o < MPW_BITS@.
+ */
+
+void mpx_usubnlsl(mpw *dv, mpw *dvl, mpw a, unsigned o)
+{
+  mpw b = a >> (MPW_BITS - o);
+  a <<= o;
+
+  if (dv < dvl) {
+    mpd x = (mpd)*dv - (mpd)a;
+    *dv++ = MPW(x);
+    if (x >> MPW_BITS)
+      b++;
+    MPX_USUBN(dv, dvl, b);
+  }
+}
+
 /* --- @mpx_umul@ --- *
  *
  * Arguments:	@mpw *dv, *dvl@ = destination vector base and limit
@@ -1125,7 +1121,7 @@ void mpx_udiv(mpw *qv, mpw *qvl, mpw *rv, mpw *rvl,
 
     d = dvl[-1];
     for (b = MPW_BITS / 2; b; b >>= 1) {
-      if (d < (MPW_MAX >> b)) {
+      if (d <= (MPW_MAX >> b)) {
 	d <<= b;
 	norm += b;
       }