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

   1 /* -*-c-*-
   2  *
   3  * Efficient reduction modulo nice primes
   4  *
   5  * (c) 2004 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef CATACOMB_MPREDUCE_H
  29 #define CATACOMB_MPREDUCE_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <stdio.h>
  38
  39 #ifndef CATACOMB_MP_H
  40 #  include "mp.h"
  41 #endif
  42
  43 /*----- Data structures ---------------------------------------------------*/
  44
  45 typedef struct mpreduce_instr {
  46   unsigned op;                          /* Instruction opcode */
  47   size_t argx, argy;                    /* Immediate arguments */
  48 } mpreduce_instr;
  49
  50 enum {
  51   MPRI_ADD,                             /* Add @p@ offset by @x@ words */
  52   MPRI_ADDLSL,                          /* Add @p << y@ offset by @x@ */
  53   MPRI_SUB,                             /* Sub @p@ offset by @x@ words */
  54   MPRI_SUBLSL,                          /* Sub @p << y@ offset by @x@ */
  55   MPRI_MAX
  56 };
  57
  58 typedef struct mpreduce {
  59   size_t lim;                           /* Word containing top bit */
  60   unsigned s;                           /* Shift for top word */
  61   mp *p;                                /* Copy of the modulus */
  62   size_t in;                            /* Number of instruction words */
  63   mpreduce_instr *iv;                   /* Vector of instructions */
  64 } mpreduce;
  65
  66 /*----- Functions provided ------------------------------------------------*/
  67
  68 /* --- @mpreduce_create@ --- *
  69  *
  70  * Arguments:   @gfreduce *r@ = structure to fill in
  71  *              @mp *x@ = an integer
  72  *
  73  * Returns:     Zero for success, nonzero on error.
  74  *
  75  * Use:         Initializes a context structure for reduction.
  76  */
  77
  78 extern int mpreduce_create(mpreduce */*r*/, mp */*p*/);
  79
  80 /* --- @mpreduce_destroy@ --- *
  81  *
  82  * Arguments:   @mpreduce *r@ = structure to free
  83  *
  84  * Returns:     ---
  85  *
  86  * Use:         Reclaims the resources from a reduction context.
  87  */
  88
  89 extern void mpreduce_destroy(mpreduce */*r*/);
  90
  91 /* --- @mpreduce_dump@ --- *
  92  *
  93  * Arguments:   @mpreduce *r@ = structure to dump
  94  *              @FILE *fp@ = file to dump on
  95  *
  96  * Returns:     ---
  97  *
  98  * Use:         Dumps a reduction context.
  99  */
 100
 101 extern void mpreduce_dump(mpreduce */*r*/, FILE */*fp*/);
 102
 103 /* --- @mpreduce_do@ --- *
 104  *
 105  * Arguments:   @mpreduce *r@ = reduction context
 106  *              @mp *d@ = destination
 107  *              @mp *x@ = source
 108  *
 109  * Returns:     Destination, @x@ reduced modulo the reduction poly.
 110  */
 111
 112 extern mp *mpreduce_do(mpreduce */*r*/, mp */*d*/, mp */*x*/);
 113
 114 /* --- @mpreduce_exp@ --- *
 115  *
 116  * Arguments:   @mpreduce *mr@ = pointer to reduction context
 117  *              @mp *d@ = fake destination
 118  *              @mp *a@ = base
 119  *              @mp *e@ = exponent
 120  *
 121  * Returns:     Result, %$a^e \bmod m$%.
 122  */
 123
 124 extern mp *mpreduce_exp(mpreduce */*mr*/, mp */*d*/, mp */*a*/, mp */*e*/);
 125
 126 /*----- That's all, folks -------------------------------------------------*/
 127
 128 #ifdef __cplusplus
 129   }
 130 #endif
 131
 132 #endif