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

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Efficient reduction modulo nice primes
   6  *
   7  * (c) 2004 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 #ifndef CATACOMB_MPREDUCE_H
  31 #define CATACOMB_MPREDUCE_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 /*----- Data structures ---------------------------------------------------*/
  40
  41 typedef struct mpreduce_instr {
  42   unsigned op;                          /* Instruction opcode */
  43   size_t argx, argy;                    /* Immediate arguments */
  44 } mpreduce_instr;
  45
  46 enum {
  47   MPRI_ADD,                             /* Add @p@ offset by @x@ words */
  48   MPRI_ADDLSL,                          /* Add @p << y@ offset by @x@ */
  49   MPRI_SUB,                             /* Sub @p@ offset by @x@ words */
  50   MPRI_SUBLSL,                          /* Sub @p << y@ offset by @x@ */
  51   MPRI_MAX
  52 };
  53
  54 typedef struct mpreduce {
  55   size_t lim;                           /* Word containing top bit */
  56   unsigned s;                           /* Shift for top word */
  57   mp *p;                                /* Copy of the modulus */
  58   size_t in;                            /* Number of instruction words */
  59   mpreduce_instr *iv;                   /* Vector of instructions */
  60 } mpreduce;
  61
  62 /*----- Functions provided ------------------------------------------------*/
  63
  64 /* --- @mpreduce_create@ --- *
  65  *
  66  * Arguments:   @gfreduce *r@ = structure to fill in
  67  *              @mp *x@ = an integer
  68  *
  69  * Returns:     Zero for success, nonzero on error.
  70  *
  71  * Use:         Initializes a context structure for reduction.
  72  */
  73
  74 extern int mpreduce_create(mpreduce */*r*/, mp */*p*/);
  75
  76 /* --- @mpreduce_destroy@ --- *
  77  *
  78  * Arguments:   @mpreduce *r@ = structure to free
  79  *
  80  * Returns:     ---
  81  *
  82  * Use:         Reclaims the resources from a reduction context.
  83  */
  84
  85 extern void mpreduce_destroy(mpreduce */*r*/);
  86
  87 /* --- @mpreduce_dump@ --- *
  88  *
  89  * Arguments:   @mpreduce *r@ = structure to dump
  90  *              @FILE *fp@ = file to dump on
  91  *
  92  * Returns:     ---
  93  *
  94  * Use:         Dumps a reduction context.
  95  */
  96
  97 extern void mpreduce_dump(mpreduce */*r*/, FILE */*fp*/);
  98
  99 /* --- @mpreduce_do@ --- *
 100  *
 101  * Arguments:   @mpreduce *r@ = reduction context
 102  *              @mp *d@ = destination
 103  *              @mp *x@ = source
 104  *
 105  * Returns:     Destination, @x@ reduced modulo the reduction poly.
 106  */
 107
 108 extern mp *mpreduce_do(mpreduce */*r*/, mp */*d*/, mp */*x*/);
 109
 110 /* --- @mpreduce_exp@ --- *
 111  *
 112  * Arguments:   @mpreduce *mr@ = pointer to reduction context
 113  *              @mp *d@ = fake destination
 114  *              @mp *a@ = base
 115  *              @mp *e@ = exponent
 116  *
 117  * Returns:     Result, %$a^e \bmod m$%.
 118  */
 119
 120 extern mp *mpreduce_exp(mpreduce */*mr*/, mp */*d*/, mp */*a*/, mp */*e*/);
 121
 122 /*----- That's all, folks -------------------------------------------------*/
 123
 124 #ifdef __cplusplus
 125   }
 126 #endif
 127
 128 #endif