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

   1 /* -*-c-*-
   2  *
   3  * Reduction modulo sparse binary polynomials
   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_GFREDUCE_H
  29 #define CATACOMB_GFREDUCE_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <stdio.h>
  38
  39 #ifndef CATACOMB_GF_H
  40 #  include "gf.h"
  41 #endif
  42
  43 /*----- Data structures ---------------------------------------------------*/
  44
  45 typedef struct gfreduce_instr {
  46   unsigned op;                          /* Instruction opcode */
  47   size_t arg;                           /* Immediate argument */
  48 } gfreduce_instr;
  49
  50 enum {
  51   GFRI_LOAD,                            /* Load @p[arg]@ */
  52   GFRI_LSL,                             /* XOR with @w << arg@ */
  53   GFRI_LSR,                             /* XOR with @w >> arg@ */
  54   GFRI_STORE,                           /* Store @p[arg]@ */
  55   GFRI_MAX
  56 };
  57
  58 typedef struct gfreduce {
  59   size_t lim;                           /* Word of degree bit */
  60   mpw mask;                             /* Mask for degree word */
  61   mp *p;                                /* Copy of the polynomial */
  62   size_t in;                            /* Number of instruction words */
  63   gfreduce_instr *iv;                   /* Vector of instructions */
  64   gfreduce_instr *fiv;                  /* Final-pass instruction suffix */
  65 } gfreduce;
  66
  67 /*----- Functions provided ------------------------------------------------*/
  68
  69 /* --- @gfreduce_create@ --- *
  70  *
  71  * Arguments:   @gfreduce *r@ = structure to fill in
  72  *              @mp *x@ = a (hopefully sparse) polynomial
  73  *
  74  * Returns:     ---
  75  *
  76  * Use:         Initializes a context structure for reduction.
  77  */
  78
  79 extern void gfreduce_create(gfreduce */*r*/, mp */*p*/);
  80
  81 /* --- @gfreduce_destroy@ --- *
  82  *
  83  * Arguments:   @gfreduce *r@ = structure to free
  84  *
  85  * Returns:     ---
  86  *
  87  * Use:         Reclaims the resources from a reduction context.
  88  */
  89
  90 extern void gfreduce_destroy(gfreduce */*r*/);
  91
  92 /* --- @gfreduce_dump@ --- *
  93  *
  94  * Arguments:   @gfreduce *r@ = structure to dump
  95  *              @FILE *fp@ = file to dump on
  96  *
  97  * Returns:     ---
  98  *
  99  * Use:         Dumps a reduction context.
 100  */
 101
 102 extern void gfreduce_dump(gfreduce */*r*/, FILE */*fp*/);
 103
 104 /* --- @gfreduce_do@ --- *
 105  *
 106  * Arguments:   @gfreduce *r@ = reduction context
 107  *              @mp *d@ = destination
 108  *              @mp *x@ = source
 109  *
 110  * Returns:     Destination, @x@ reduced modulo the reduction poly.
 111  */
 112
 113 extern mp *gfreduce_do(gfreduce */*r*/, mp */*d*/, mp */*x*/);
 114
 115 /* --- @gfreduce_sqrt@ --- *
 116  *
 117  * Arguments:   @gfreduce *r@ = pointer to reduction context
 118  *              @mp *d@ = destination
 119  *              @mp *x@ = some polynomial
 120  *
 121  * Returns:     The square root of @x@ modulo @r->p@, or null.
 122  */
 123
 124 extern mp *gfreduce_sqrt(gfreduce */*r*/, mp */*d*/, mp */*x*/);
 125
 126 /* --- @gfreduce_trace@ --- *
 127  *
 128  * Arguments:   @gfreduce *r@ = pointer to reduction context
 129  *              @mp *x@ = some polynomial
 130  *
 131  * Returns:     The trace of @x@. (%$\Tr(x)=x + x^2 + \cdots + x^{2^{m-1}}$%
 132  *              if %$x \in \gf{2^m}$%).
 133  */
 134
 135 extern int gfreduce_trace(gfreduce */*r*/, mp */*x*/);
 136
 137 /* --- @gfreduce_halftrace@ --- *
 138  *
 139  * Arguments:   @gfreduce *r@ = pointer to reduction context
 140  *              @mp *d@ = destination
 141  *              @mp *x@ = some polynomial
 142  *
 143  * Returns:     The half-trace of @x@.
 144  *              (%$\HfTr(x)= x + x^{2^2} + \cdots + x^{2^{m-1}}$%
 145  *              if %$x \in \gf{2^m}$% with %$m$% odd).
 146  */
 147
 148 extern mp *gfreduce_halftrace(gfreduce */*r*/, mp */*d*/, mp */*x*/);
 149
 150 /* --- @gfreduce_quadsolve@ --- *
 151  *
 152  * Arguments:   @gfreduce *r@ = pointer to reduction context
 153  *              @mp *d@ = destination
 154  *              @mp *x@ = some polynomial
 155  *
 156  * Returns:     A polynomial @y@ such that %$y^2 + y = x$%, or null.
 157  */
 158
 159 extern mp *gfreduce_quadsolve(gfreduce */*r*/, mp */*d*/, mp */*x*/);
 160
 161 /* --- @gfreduce_exp@ --- *
 162  *
 163  * Arguments:   @gfreduce *gr@ = pointer to reduction context
 164  *              @mp *d@ = fake destination
 165  *              @mp *a@ = base
 166  *              @mp *e@ = exponent
 167  *
 168  * Returns:     Result, %$a^e \bmod m$%.
 169  */
 170
 171 extern mp *gfreduce_exp(gfreduce */*gr*/, mp */*d*/, mp */*a*/, mp */*e*/);
 172
 173 /*----- That's all, folks -------------------------------------------------*/
 174
 175 #ifdef __cplusplus
 176   }
 177 #endif
 178
 179 #endif