Donatien Garnier / MiniTLS-GPL

A super trimmed down TLS stack, GPL licensed

Dependents:   MiniTLS-HTTPS-Example

MiniTLS - A super trimmed down TLS/SSL Library for embedded devices Author: Donatien Garnier Copyright (C) 2013-2014 AppNearMe Ltd

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

math/addsub/s_fp_sub.c

Committer:
MiniTLS
Date:
2014-06-06
Revision:
0:35aa5be3b78d

File content as of revision 0:35aa5be3b78d:

/* TomsFastMath, a fast ISO C bignum library.
 * 
 * This project is meant to fill in where LibTomMath
 * falls short.  That is speed ;-)
 *
 * This project is public domain and free for all purposes.
 * 
 * Tom St Denis, tomstdenis@gmail.com
 */
#include <tfm.h>

/* unsigned subtraction ||a|| >= ||b|| ALWAYS! */
void s_fp_sub(fp_int *a, fp_int *b, fp_int *c)
{
  int      x, oldbused, oldused;
  fp_word  t;

  oldused  = c->used;
  oldbused = b->used;
  c->used  = a->used;
  t       = 0;
  for (x = 0; x < oldbused; x++) {
     t         = ((fp_word)a->dp[x]) - (((fp_word)b->dp[x]) + t);
     c->dp[x]  = (fp_digit)t;
     t         = (t >> DIGIT_BIT)&1;
  }
  for (; x < a->used; x++) {
     t         = ((fp_word)a->dp[x]) - t;
     c->dp[x]  = (fp_digit)t;
     t         = (t >> DIGIT_BIT);
   }
  for (; x < oldused; x++) {
     c->dp[x] = 0;
  }
  fp_clamp(c);
}

/* $Source: /cvs/libtom/tomsfastmath/src/addsub/s_fp_sub.c,v $ */
/* $Revision: 1.1 $ */
/* $Date: 2006/12/31 21:25:53 $ */