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 if successful; nonzero on failure.  The current
  74  *              algorithm always succeeds when given positive @x@.  Earlier
  75  *              versions used to fail on particular kinds of integers, but
  76  *              this is guaranteed not to happen any more.
  77  *
  78  * Use:         Initializes a context structure for reduction.
  79  */
  80
  81 extern int mpreduce_create(mpreduce */*r*/, mp */*p*/);
  82
  83 /* --- @mpreduce_destroy@ --- *
  84  *
  85  * Arguments:   @mpreduce *r@ = structure to free
  86  *
  87  * Returns:     ---
  88  *
  89  * Use:         Reclaims the resources from a reduction context.
  90  */
  91
  92 extern void mpreduce_destroy(mpreduce */*r*/);
  93
  94 /* --- @mpreduce_dump@ --- *
  95  *
  96  * Arguments:   @mpreduce *r@ = structure to dump
  97  *              @FILE *fp@ = file to dump on
  98  *
  99  * Returns:     ---
 100  *
 101  * Use:         Dumps a reduction context.
 102  */
 103
 104 extern void mpreduce_dump(mpreduce */*r*/, FILE */*fp*/);
 105
 106 /* --- @mpreduce_do@ --- *
 107  *
 108  * Arguments:   @mpreduce *r@ = reduction context
 109  *              @mp *d@ = destination
 110  *              @mp *x@ = source
 111  *
 112  * Returns:     Destination, @x@ reduced modulo the reduction poly.
 113  */
 114
 115 extern mp *mpreduce_do(mpreduce */*r*/, mp */*d*/, mp */*x*/);
 116
 117 /* --- @mpreduce_exp@ --- *
 118  *
 119  * Arguments:   @mpreduce *mr@ = pointer to reduction context
 120  *              @mp *d@ = fake destination
 121  *              @mp *a@ = base
 122  *              @mp *e@ = exponent
 123  *
 124  * Returns:     Result, %$a^e \bmod m$%.
 125  */
 126
 127 extern mp *mpreduce_exp(mpreduce */*mr*/, mp */*d*/, mp */*a*/, mp */*e*/);
 128
 129 /*----- That's all, folks -------------------------------------------------*/
 130
 131 #ifdef __cplusplus
 132   }
 133 #endif
 134
 135 #endif