X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/d03ab969116fe715d569304c1c474749b2f64529..59919ae4b1721ca271c3d3e5955c09d322573821:/mpscan.c

diff --git a/mpscan.c b/mpscan.c
index a49eddf..0a5b4f0 100644
--- a/mpscan.c
+++ b/mpscan.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpscan.c,v 1.1 1999/09/03 08:41:12 mdw Exp $
+ * $Id: mpscan.c,v 1.3 2000/07/29 17:03:31 mdw Exp $
  *
  * Sequential bit scan of multiprecision integers
  *
@@ -30,6 +30,13 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpscan.c,v $
+ * Revision 1.3  2000/07/29 17:03:31  mdw
+ * Add support for left-to-right bitscanning, for use in modular
+ * exponentiation.
+ *
+ * Revision 1.2  1999/11/13 01:55:10  mdw
+ * Fixed so that they compile.  Minor interface changes.
+ *
  * Revision 1.1  1999/09/03 08:41:12  mdw
  * Initial import.
  *
@@ -37,17 +44,14 @@
 
 /*----- Header files ------------------------------------------------------*/
 
-/*----- Data structures ---------------------------------------------------*/
-
-/*----- Static variables --------------------------------------------------*/
+#include "mpscan.h"
 
-/*----- Main code ---------------------------------------------------------*/
+/*----- Right-to-left scanning --------------------------------------------*/
 
 /* --- @mpscan_initx@ --- *
  *
  * Arguments:	@mpscan *m@ = pointer to bitscanner structure
- *		@const mpw *v@ = vector of words to scan
- *		@size_t len@ = length of vector in words
+ *		@const mpw *v, *vl@ = vector of words to scan
  *
  * Returns:	---
  *
@@ -57,9 +61,9 @@
  *		out.
  */
 
-void mpscan_initx(mpscan *m, const mpw *v, size_t len)
+void mpscan_initx(mpscan *m, const mpw *v, const mpw *vl)
 {
-  MPSCAN_INITX(m, v, len);
+  MPSCAN_INITX(m, v, vl);
 }
 
 /* --- @mpscan_step@ --- *
@@ -86,4 +90,48 @@ int mpscan_step(mpscan *m) { return (MPSCAN_STEP(m)); }
 
 int mpscan_bit(const mpscan *m) { return (MPSCAN_BIT(m)); }
 
+/*----- Left-to right-scanning --------------------------------------------*/
+
+/* --- @mpscan_rinitx@ --- *
+ *
+ * Arguments:	@mpscan *m@ = pointer to bitscanner structure
+ *		@const mpw *v, *vl@ = vector of words to scan
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes a reverse bitscanner from a low-level
+ *		vector-and-length representation of an integer.  Initially no
+ *		bit is ready; you must call @mpscan_rstep@ before anything
+ *		useful will come out.
+ */
+
+void mpscan_rinitx(mpscan *m, const mpw *v, const mpw *vl)
+{
+  MPSCAN_RINITX(m, v, vl);
+}
+
+/* --- @mpscan_rstep@ --- *
+ *
+ * Arguments:	@mpscan *m@ = pointer to bitscanner
+ *
+ * Returns:	Nonzero if there is another bit to read.
+ *
+ * Use:		Steps on to the next bit in the integer.  The macro version
+ *		evaluates its argument multiple times.
+ */
+
+int mpscan_rstep(mpscan *m) { return (MPSCAN_RSTEP(m)); }
+
+/* --- @mpscan_rbit@ --- *
+ *
+ * Arguments:	@const mpscan *m@ = pointer to bitscanner
+ *
+ * Returns:	The value of the current bit.
+ *
+ * Use:		Reads the value of the current bit looked at by a
+ *		reverse bitscanner.
+ */
+
+int mpscan_rbit(const mpscan *m) { return (MPSCAN_RBIT(m)); }
+
 /*----- That's all, folks -------------------------------------------------*/