--- /dev/null
+/* -*-c-*-
+ *
+ * Sequential bit scan of multiprecision integers
+ *
+ * (c) 1999 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------*
+ *
+ * This file is part of Catacomb.
+ *
+ * Catacomb is free software; you can redistribute it and/or modify
+ * 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.
+ */
+
+#ifndef CATACOMB_MPSCAN_H
+#define CATACOMB_MPSCAN_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#ifndef CATACOMB_MPW_H
+# include "mpw.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct mpscan {
+ const mpw *v, *vl; /* Vector of words to scan */
+ mpw w; /* Current word to scan */
+ int bits; /* Number of bits left in @w@ */
+} mpscan;
+
+/*----- Right-to-left scanning --------------------------------------------*/
+
+/* --- @mpscan_initx@ --- *
+ *
+ * Arguments: @mpscan *m@ = pointer to bitscanner structure
+ * @const mpw *v, *vl@ = vector of words to scan
+ *
+ * Returns: ---
+ *
+ * Use: Initializes a bitscanner from a low-level base-and-limit
+ * representation of an integer. Initially no bit is ready; you
+ * must call @mpscan_step@ before anything useful will come
+ * out.
+ */
+
+#define MPSCAN_INITX(m_, v_, vl_) do { \
+ mpscan *_m = (m_); \
+ _m->v = (v_); \
+ _m->vl = (vl_); \
+ _m->bits = 0; \
+} while (0)
+
+extern void mpscan_initx(mpscan */*m*/, const mpw */*v*/, const mpw */*vl*/);
+
+/* --- @mpscan_step@ --- *
+ *
+ * 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_STEP(m) \
+ ((m)->bits ? ((m)->w >>= 1, (m)->bits--, 1) : \
+ (m)->v < (m)->vl ? ((m)->w = *(m)->v++, \
+ (m)->bits = MPW_BITS - 1, 1) : \
+ 0)
+
+extern int mpscan_step(mpscan */*m*/);
+
+/* --- @mpscan_bit@ --- *
+ *
+ * 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
+ * bitscanner.
+ */
+
+#define MPSCAN_BIT(m) ((m)->w & 1)
+
+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
+ }
+#endif
+
+#endif
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