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