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

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Arithmetic on binary polynomials
   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_GF_H
  31 #define CATACOMB_GF_H
  32
  33 #ifdef __cplusplus
  34   extern "C" {
  35 #endif
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #ifndef CATACOMB_MP_H
  40 #  include "mp.h"
  41 #endif
  42
  43 #ifndef CATACOMB_GFX_H
  44 #  include "gfx.h"
  45 #endif
  46
  47 /*----- Functions provided ------------------------------------------------*/
  48
  49 /* --- @gf_add@ --- *
  50  *
  51  * Arguments:   @mp *d@ = destination
  52  *              @mp *a, *b@ = sources
  53  *
  54  * Returns:     Result, @a@ added to @b@.
  55  */
  56
  57 extern mp *gf_add(mp */*d*/, mp */*a*/, mp */*b*/);
  58 #define gf_sub gf_add
  59
  60 /* --- @gf_mul@ --- *
  61  *
  62  * Arguments:   @mp *d@ = destination
  63  *              @mp *a, *b@ = sources
  64  *
  65  * Returns:     Result, @a@ multiplied by @b@.
  66  */
  67
  68 extern mp *gf_mul(mp */*d*/, mp */*a*/, mp */*b*/);
  69
  70 /* --- @gf_sqr@ --- *
  71  *
  72  * Arguments:   @mp *d@ = destination
  73  *              @mp *a@ = source
  74  *
  75  * Returns:     Result, @a@ squared.
  76  */
  77
  78 extern mp *gf_sqr(mp */*d*/, mp */*a*/);
  79
  80 /* --- @gf_div@ --- *
  81  *
  82  * Arguments:   @mp **qq, **rr@ = destination, quotient and remainder
  83  *              @mp *a, *b@ = sources
  84  *
  85  * Use:         Calculates the quotient and remainder when @a@ is divided by
  86  *              @b@.  The destinations @*qq@ and @*rr@ must be distinct.
  87  *              Either of @qq@ or @rr@ may be null to indicate that the
  88  *              result is irrelevant.  (Discarding both results is silly.)
  89  *              There is a performance advantage if @a == *rr@.
  90  */
  91
  92 extern void gf_div(mp **/*qq*/, mp **/*rr*/, mp */*a*/, mp */*b*/);
  93
  94 /* --- @gf_exp@ --- *
  95  *
  96  * Arguments:   @mp *d@ = fake destination
  97  *              @mp *a@ = base
  98  *              @mp *e@ = exponent
  99  *
 100  * Returns:     Result, %$a^e$%.
 101  */
 102
 103 extern mp *gf_exp(mp */*d*/, mp */*a*/, mp */*e*/);
 104
 105 /* --- @gf_irreduciblep@ --- *
 106  *
 107  * Arguments:   @mp *f@ = a polynomial
 108  *
 109  * Returns:     Nonzero if the polynomial is irreducible; otherwise zero.
 110  */
 111
 112 extern int gf_irreduciblep(mp */*f*/);
 113
 114 /* --- @gf_gcd@ --- *
 115  *
 116  * Arguments:   @mp **gcd, **xx, **yy@ = where to write the results
 117  *              @mp *a, *b@ = sources (must be nonzero)
 118  *
 119  *
 120  * Returns:     ---
 121  *
 122  * Use:         Calculates @gcd(a, b)@, and two numbers @x@ and @y@ such that
 123  *              @ax + by = gcd(a, b)@.  This is useful for computing modular
 124  *              inverses.
 125  */
 126
 127 extern void gf_gcd(mp **/*gcd*/, mp **/*xx*/, mp **/*yy*/,
 128                    mp */*a*/, mp */*b*/);
 129
 130 /* -- @gf_modinv@ --- *
 131  *
 132  * Arguments:   @mp *d@ = destination
 133  *              @mp *x@ = argument
 134  *              @mp *p@ = modulus
 135  *
 136  * Returns:     The inverse %$x^{-1} \bmod p$%.
 137  *
 138  * Use:         Computes a modular inverse, the catch being that the
 139  *              arguments and results are binary polynomials.  An assertion
 140  *              fails if %$p$% has no inverse.
 141  */
 142
 143 extern mp *gf_modinv(mp */*d*/, mp */*x*/, mp */*p*/);
 144
 145 /*----- That's all, folks -------------------------------------------------*/
 146
 147 #ifdef __cplusplus
 148   }
 149 #endif
 150
 151 #endif