mirror of
http://galexander.org/git/simplesshd.git
synced 2024-11-15 19:48:56 +00:00
113 lines
2.4 KiB
C
113 lines
2.4 KiB
C
#include <tommath.h>
|
|
#ifdef BN_MP_ADD_D_C
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis
|
|
*
|
|
* LibTomMath is a library that provides multiple-precision
|
|
* integer arithmetic as well as number theoretic functionality.
|
|
*
|
|
* The library was designed directly after the MPI library by
|
|
* Michael Fromberger but has been written from scratch with
|
|
* additional optimizations in place.
|
|
*
|
|
* The library is free for all purposes without any express
|
|
* guarantee it works.
|
|
*
|
|
* Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com
|
|
*/
|
|
|
|
/* single digit addition */
|
|
int
|
|
mp_add_d (mp_int * a, mp_digit b, mp_int * c)
|
|
{
|
|
int res, ix, oldused;
|
|
mp_digit *tmpa, *tmpc, mu;
|
|
|
|
/* grow c as required */
|
|
if (c->alloc < a->used + 1) {
|
|
if ((res = mp_grow(c, a->used + 1)) != MP_OKAY) {
|
|
return res;
|
|
}
|
|
}
|
|
|
|
/* if a is negative and |a| >= b, call c = |a| - b */
|
|
if (a->sign == MP_NEG && (a->used > 1 || a->dp[0] >= b)) {
|
|
/* temporarily fix sign of a */
|
|
a->sign = MP_ZPOS;
|
|
|
|
/* c = |a| - b */
|
|
res = mp_sub_d(a, b, c);
|
|
|
|
/* fix sign */
|
|
a->sign = c->sign = MP_NEG;
|
|
|
|
/* clamp */
|
|
mp_clamp(c);
|
|
|
|
return res;
|
|
}
|
|
|
|
/* old number of used digits in c */
|
|
oldused = c->used;
|
|
|
|
/* sign always positive */
|
|
c->sign = MP_ZPOS;
|
|
|
|
/* source alias */
|
|
tmpa = a->dp;
|
|
|
|
/* destination alias */
|
|
tmpc = c->dp;
|
|
|
|
/* if a is positive */
|
|
if (a->sign == MP_ZPOS) {
|
|
/* add digit, after this we're propagating
|
|
* the carry.
|
|
*/
|
|
*tmpc = *tmpa++ + b;
|
|
mu = *tmpc >> DIGIT_BIT;
|
|
*tmpc++ &= MP_MASK;
|
|
|
|
/* now handle rest of the digits */
|
|
for (ix = 1; ix < a->used; ix++) {
|
|
*tmpc = *tmpa++ + mu;
|
|
mu = *tmpc >> DIGIT_BIT;
|
|
*tmpc++ &= MP_MASK;
|
|
}
|
|
/* set final carry */
|
|
ix++;
|
|
*tmpc++ = mu;
|
|
|
|
/* setup size */
|
|
c->used = a->used + 1;
|
|
} else {
|
|
/* a was negative and |a| < b */
|
|
c->used = 1;
|
|
|
|
/* the result is a single digit */
|
|
if (a->used == 1) {
|
|
*tmpc++ = b - a->dp[0];
|
|
} else {
|
|
*tmpc++ = b;
|
|
}
|
|
|
|
/* setup count so the clearing of oldused
|
|
* can fall through correctly
|
|
*/
|
|
ix = 1;
|
|
}
|
|
|
|
/* now zero to oldused */
|
|
while (ix++ < oldused) {
|
|
*tmpc++ = 0;
|
|
}
|
|
mp_clamp(c);
|
|
|
|
return MP_OKAY;
|
|
}
|
|
|
|
#endif
|
|
|
|
/* $Source: /cvs/libtom/libtommath/bn_mp_add_d.c,v $ */
|
|
/* $Revision: 1.4 $ */
|
|
/* $Date: 2006/03/31 14:18:44 $ */
|