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 /*----- Data structures ---------------------------------------------------*/
  38
  39 typedef struct mpreduce_instr {
  40   unsigned op;                          /* Instruction opcode */
  41   size_t argx, argy;                    /* Immediate arguments */
  42 } mpreduce_instr;
  43
  44 enum {
  45   MPRI_ADD,                             /* Add @p@ offset by @x@ words */
  46   MPRI_ADDLSL,                          /* Add @p << y@ offset by @x@ */
  47   MPRI_SUB,                             /* Sub @p@ offset by @x@ words */
  48   MPRI_SUBLSL,                          /* Sub @p << y@ offset by @x@ */
  49   MPRI_MAX
  50 };
  51
  52 typedef struct mpreduce {
  53   size_t lim;                           /* Word containing top bit */
  54   unsigned s;                           /* Shift for top word */
  55   mp *p;                                /* Copy of the modulus */
  56   size_t in;                            /* Number of instruction words */
  57   mpreduce_instr *iv;                   /* Vector of instructions */
  58 } mpreduce;
  59
  60 /*----- Functions provided ------------------------------------------------*/
  61
  62 /* --- @mpreduce_create@ --- *
  63  *
  64  * Arguments:   @gfreduce *r@ = structure to fill in
  65  *              @mp *x@ = an integer
  66  *
  67  * Returns:     Zero for success, nonzero on error.
  68  *
  69  * Use:         Initializes a context structure for reduction.
  70  */
  71
  72 extern int mpreduce_create(mpreduce */*r*/, mp */*p*/);
  73
  74 /* --- @mpreduce_destroy@ --- *
  75  *
  76  * Arguments:   @mpreduce *r@ = structure to free
  77  *
  78  * Returns:     ---
  79  *
  80  * Use:         Reclaims the resources from a reduction context.
  81  */
  82
  83 extern void mpreduce_destroy(mpreduce */*r*/);
  84
  85 /* --- @mpreduce_dump@ --- *
  86  *
  87  * Arguments:   @mpreduce *r@ = structure to dump
  88  *              @FILE *fp@ = file to dump on
  89  *
  90  * Returns:     ---
  91  *
  92  * Use:         Dumps a reduction context.
  93  */
  94
  95 extern void mpreduce_dump(mpreduce */*r*/, FILE */*fp*/);
  96
  97 /* --- @mpreduce_do@ --- *
  98  *
  99  * Arguments:   @mpreduce *r@ = reduction context
 100  *              @mp *d@ = destination
 101  *              @mp *x@ = source
 102  *
 103  * Returns:     Destination, @x@ reduced modulo the reduction poly.
 104  */
 105
 106 extern mp *mpreduce_do(mpreduce */*r*/, mp */*d*/, mp */*x*/);
 107
 108 /* --- @mpreduce_exp@ --- *
 109  *
 110  * Arguments:   @mpreduce *mr@ = pointer to reduction context
 111  *              @mp *d@ = fake destination
 112  *              @mp *a@ = base
 113  *              @mp *e@ = exponent
 114  *
 115  * Returns:     Result, %$a^e \bmod m$%.
 116  */
 117
 118 extern mp *mpreduce_exp(mpreduce */*mr*/, mp */*d*/, mp */*a*/, mp */*e*/);
 119
 120 /*----- That's all, folks -------------------------------------------------*/
 121
 122 #ifdef __cplusplus
 123   }
 124 #endif
 125
 126 #endif