git.distorted.org.uk Git - u/mdw/catacomb/blob - mpscan.c

   1 /* -*-c-*-
   2  *
   3  * $Id: mpscan.c,v 1.3 2000/07/29 17:03:31 mdw Exp $
   4  *
   5  * Sequential bit scan of multiprecision integers
   6  *
   7  * (c) 1999 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: mpscan.c,v $
  33  * Revision 1.3  2000/07/29 17:03:31  mdw
  34  * Add support for left-to-right bitscanning, for use in modular
  35  * exponentiation.
  36  *
  37  * Revision 1.2  1999/11/13 01:55:10  mdw
  38  * Fixed so that they compile.  Minor interface changes.
  39  *
  40  * Revision 1.1  1999/09/03 08:41:12  mdw
  41  * Initial import.
  42  *
  43  */
  44
  45 /*----- Header files ------------------------------------------------------*/
  46
  47 #include "mpscan.h"
  48
  49 /*----- Right-to-left scanning --------------------------------------------*/
  50
  51 /* --- @mpscan_initx@ --- *
  52  *
  53  * Arguments:   @mpscan *m@ = pointer to bitscanner structure
  54  *              @const mpw *v, *vl@ = vector of words to scan
  55  *
  56  * Returns:     ---
  57  *
  58  * Use:         Initializes a bitscanner from a low-level vector-and-length
  59  *              representation of an integer.  Initially no bit is ready; you
  60  *              must call @mpscan_step@ before anything useful will come
  61  *              out.
  62  */
  63
  64 void mpscan_initx(mpscan *m, const mpw *v, const mpw *vl)
  65 {
  66   MPSCAN_INITX(m, v, vl);
  67 }
  68
  69 /* --- @mpscan_step@ --- *
  70  *
  71  * Arguments:   @mpscan *m@ = pointer to bitscanner
  72  *
  73  * Returns:     Nonzero if there is another bit to read.
  74  *
  75  * Use:         Steps on to the next bit in the integer.  The macro version
  76  *              evaluates its argument multiple times.
  77  */
  78
  79 int mpscan_step(mpscan *m) { return (MPSCAN_STEP(m)); }
  80
  81 /* --- @mpscan_bit@ --- *
  82  *
  83  * Arguments:   @const mpscan *m@ = pointer to bitscanner
  84  *
  85  * Returns:     The value of the current bit.
  86  *
  87  * Use:         Reads the value of the current bit looked at by a
  88  *              bitscanner.
  89  */
  90
  91 int mpscan_bit(const mpscan *m) { return (MPSCAN_BIT(m)); }
  92
  93 /*----- Left-to right-scanning --------------------------------------------*/
  94
  95 /* --- @mpscan_rinitx@ --- *
  96  *
  97  * Arguments:   @mpscan *m@ = pointer to bitscanner structure
  98  *              @const mpw *v, *vl@ = vector of words to scan
  99  *
 100  * Returns:     ---
 101  *
 102  * Use:         Initializes a reverse bitscanner from a low-level
 103  *              vector-and-length representation of an integer.  Initially no
 104  *              bit is ready; you must call @mpscan_rstep@ before anything
 105  *              useful will come out.
 106  */
 107
 108 void mpscan_rinitx(mpscan *m, const mpw *v, const mpw *vl)
 109 {
 110   MPSCAN_RINITX(m, v, vl);
 111 }
 112
 113 /* --- @mpscan_rstep@ --- *
 114  *
 115  * Arguments:   @mpscan *m@ = pointer to bitscanner
 116  *
 117  * Returns:     Nonzero if there is another bit to read.
 118  *
 119  * Use:         Steps on to the next bit in the integer.  The macro version
 120  *              evaluates its argument multiple times.
 121  */
 122
 123 int mpscan_rstep(mpscan *m) { return (MPSCAN_RSTEP(m)); }
 124
 125 /* --- @mpscan_rbit@ --- *
 126  *
 127  * Arguments:   @const mpscan *m@ = pointer to bitscanner
 128  *
 129  * Returns:     The value of the current bit.
 130  *
 131  * Use:         Reads the value of the current bit looked at by a
 132  *              reverse bitscanner.
 133  */
 134
 135 int mpscan_rbit(const mpscan *m) { return (MPSCAN_RBIT(m)); }
 136
 137 /*----- That's all, folks -------------------------------------------------*/