X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/962405ef18fa03650b4c0607d176cdf967e7fd66..5278d9afdf1aff9fd6f64073ea42395d756ee58c:/mpscan.h

diff --git a/mpscan.h b/mpscan.h
index af7306d..0d02519 100644
--- a/mpscan.h
+++ b/mpscan.h
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: mpscan.h,v 1.2 1999/11/13 01:55:10 mdw Exp $
+ * $Id: mpscan.h,v 1.5 2004/04/08 01:36:15 mdw Exp $
  *
  * Sequential bit scan of multiprecision integers
  *
  * (c) 1999 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Catacomb.
  *
@@ -15,31 +15,20 @@
  * it under the terms of the GNU Library General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
- * 
+ *
  * Catacomb is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Library General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Library General Public
  * License along with Catacomb; if not, write to the Free
  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: mpscan.h,v $
- * 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.
- *
- */
-
-#ifndef MPSCAN_H
-#define MPSCAN_H
+#ifndef CATACOMB_MPSCAN_H
+#define CATACOMB_MPSCAN_H
 
 #ifdef __cplusplus
   extern "C" {
@@ -47,7 +36,7 @@
 
 /*----- Header files ------------------------------------------------------*/
 
-#ifndef MPW_H
+#ifndef CATACOMB_MPW_H
 #  include "mpw.h"
 #endif
 
@@ -59,7 +48,7 @@ typedef struct mpscan {
   int bits;				/* Number of bits left in @w@ */
 } mpscan;
 
-/*----- Functions provided ------------------------------------------------*/
+/*----- Right-to-left scanning --------------------------------------------*/
 
 /* --- @mpscan_initx@ --- *
  *
@@ -94,8 +83,7 @@ extern void mpscan_initx(mpscan */*m*/, const mpw */*v*/, const mpw */*vl*/);
  */
 
 #define MPSCAN_STEP(m)							\
-  ((m)->bits ? ((m)->w >>= 1,						\
-		(m)->bits--, 1) :					\
+  ((m)->bits ? ((m)->w >>= 1, (m)->bits--, 1) :				\
    (m)->v < (m)->vl ? ((m)->w = *(m)->v++,				\
 		       (m)->bits = MPW_BITS - 1, 1) :			\
    0)
@@ -116,6 +104,65 @@ extern int mpscan_step(mpscan */*m*/);
 
 extern int mpscan_bit(const mpscan */*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.
+ */
+
+#define MPSCAN_RINITX(m_, v_, vl_) do {					\
+  mpscan *_m = (m_);							\
+  _m->v = (v_);								\
+  _m->vl = (vl_);							\
+  while (_m->vl > _m->v && !_m->vl[-1])					\
+    _m->vl--;								\
+  _m->bits = 0;								\
+} while (0)
+
+extern void mpscan_rinitx(mpscan */*m*/,
+			  const mpw */*v*/, const mpw */*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.
+ */
+
+#define MPSCAN_RSTEP(m)							\
+  ((m)->bits ? ((m)->w <<= 1, (m)->bits--, 1) :				\
+   (m)->vl > (m)->v ? ((m)->w = *--(m)->vl,				\
+		       (m)->bits = MPW_BITS - 1, 1) :			\
+   0)
+
+extern int mpscan_rstep(mpscan */*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.
+ */
+
+#define MPSCAN_RBIT(m) (((m)->w >> (MPW_BITS - 1)) & 1)
+
+extern int mpscan_rbit(const mpscan */*m*/);
+
 /*----- That's all, folks -------------------------------------------------*/
 
 #ifdef __cplusplus