git.distorted.org.uk Git - u/mdw/catacomb/blob - math/gf-exp.c

   1 /* -*-c-*-
   2  *
   3  * Exponentiation for 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 /*----- Header files ------------------------------------------------------*/
  29
  30 #include <assert.h>
  31
  32 #include "gf.h"
  33 #include "gf-exp.h"
  34
  35 /*----- Main code ---------------------------------------------------------*/
  36
  37 /* --- @gf_exp@ --- *
  38  *
  39  * Arguments:   @mp *d@ = fake destination
  40  *              @mp *a@ = base
  41  *              @mp *e@ = exponent
  42  *
  43  * Returns:     Result, %$a^e$%.
  44  */
  45
  46 mp *gf_exp(mp *d, mp *a, mp *e)
  47 {
  48   mp *x = MP_ONE;
  49   mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
  50   assert(!MP_NEGP(e));
  51
  52   MP_COPY(a);
  53   if (MP_ZEROP(e))
  54     ;
  55   else if (MP_LEN(e) < EXP_THRESH)
  56     EXP_SIMPLE(x, a, e);
  57   else
  58     EXP_WINDOW(x, a, e);
  59   mp_drop(d);
  60   mp_drop(spare);
  61   mp_drop(a);
  62   return (x);
  63 }
  64
  65 /*----- That's all, folks -------------------------------------------------*/