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

   1 /* -*-c-*-
   2  *
   3  * $Id: mpscan.h,v 1.1 1999/09/03 08:41:12 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.h,v $
  33  * Revision 1.1  1999/09/03 08:41:12  mdw
  34  * Initial import.
  35  *
  36  */
  37
  38 #ifndef MPSCAN_H
  39 #define MPSCAN_H
  40
  41 #ifdef __cplusplus
  42   extern "C" {
  43 #endif
  44
  45 /*----- Header files ------------------------------------------------------*/
  46
  47 #ifndef MPTYPES_H
  48 #  include "mptypes.h"
  49 #endif
  50
  51 /*----- Data structures ---------------------------------------------------*/
  52
  53 typedef struct mpscan {
  54   const mpw *v;                         /* Vector of words to scan */
  55   mpw w;                                /* Current word to scan */
  56   int bits;                             /* Number of bits left in @w@ */
  57   size_t len;                           /* Length of the vector in words */
  58 } mpscan;
  59
  60 /*----- Functions provided ------------------------------------------------*/
  61
  62 /* --- @mpscan_initx@ --- *
  63  *
  64  * Arguments:   @mpscan *m@ = pointer to bitscanner structure
  65  *              @const mpw *v@ = vector of words to scan
  66  *              @size_t len@ = length of vector in words
  67  *
  68  * Returns:     ---
  69  *
  70  * Use:         Initializes a bitscanner from a low-level vector-and-length
  71  *              representation of an integer.  Initially no bit is ready; you
  72  *              must call @mpscan_step@ before anything useful will come
  73  *              out.
  74  */
  75
  76 #define MPSCAN_INITX(m_, v_, len_) do {                                 \
  77   mpscan *_m = (m_);                                                    \
  78   _m->v = (v_);                                                         \
  79   _m->len = (len_);                                                     \
  80   _m->bits = 0;                                                         \
  81 } while (0)
  82
  83 extern void mpscan_initx(mpscan */*m*/, const mpw */*v*/, size_t /*len*/);
  84
  85 /* --- @mpscan_step@ --- *
  86  *
  87  * Arguments:   @mpscan *m@ = pointer to bitscanner
  88  *
  89  * Returns:     Nonzero if there is another bit to read.
  90  *
  91  * Use:         Steps on to the next bit in the integer.  The macro version
  92  *              evaluates its argument multiple times.
  93  */
  94
  95 #define MPSCAN_STEP(m)                                                  \
  96   ((m)->bits ? ((m)->w >>= 1,                                           \
  97                 (m)->bits--, 1) :                                       \
  98    (m)->len ? ((m)->len--,                                              \
  99                (m)->w = *(m)->v++,                                      \
 100                (m)->bits = MP_WBITS - 1, 1) :                           \
 101    0)
 102
 103 extern int mpscan_step(mpscan */*m*/);
 104
 105 /* --- @mpscan_bit@ --- *
 106  *
 107  * Arguments:   @const mpscan *m@ = pointer to bitscanner
 108  *
 109  * Returns:     The value of the current bit.
 110  *
 111  * Use:         Reads the value of the current bit looked at by a
 112  *              bitscanner.
 113  */
 114
 115 #define MPSCAN_BIT(m) ((m)->w & 1)
 116
 117 extern int mpscan_bit(const mpscan */*m*/);
 118
 119 /*----- That's all, folks -------------------------------------------------*/
 120
 121 #ifdef __cplusplus
 122   }
 123 #endif
 124
 125 #endif