Update to libtommath v1.0
author Matt Johnston Sat, 24 Jun 2017 22:37:14 +0800 5ff8218bcee9 8bba51a55704
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#include <tommath_private.h>
/* 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
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], http://libtom.org
*/

/* low level addition, based on HAC pp.594, Algorithm 14.7 */
int
s_mp_add (mp_int * a, mp_int * b, mp_int * c)
{
mp_int *x;
int     olduse, res, min, max;

/* find sizes, we let |a| <= |b| which means we have to sort
* them.  "x" will point to the input with the most digits
*/
if (a->used > b->used) {
min = b->used;
max = a->used;
x = a;
} else {
min = a->used;
max = b->used;
x = b;
}

/* init result */
if (c->alloc < (max + 1)) {
if ((res = mp_grow (c, max + 1)) != MP_OKAY) {
return res;
}
}

/* get old used digit count and set new one */
olduse = c->used;
c->used = max + 1;

{
mp_digit u, *tmpa, *tmpb, *tmpc;
int i;

/* alias for digit pointers */

/* first input */
tmpa = a->dp;

/* second input */
tmpb = b->dp;

/* destination */
tmpc = c->dp;

/* zero the carry */
u = 0;
for (i = 0; i < min; i++) {
/* Compute the sum at one digit, T[i] = A[i] + B[i] + U */
*tmpc = *tmpa++ + *tmpb++ + u;

/* U = carry bit of T[i] */
u = *tmpc >> ((mp_digit)DIGIT_BIT);

/* take away carry bit from T[i] */
}

/* now copy higher words if any, that is in A+B
* if A or B has more digits add those in
*/
if (min != max) {
for (; i < max; i++) {
/* T[i] = X[i] + U */
*tmpc = x->dp[i] + u;

/* U = carry bit of T[i] */
u = *tmpc >> ((mp_digit)DIGIT_BIT);

/* take away carry bit from T[i] */
}
}

*tmpc++ = u;

/* clear digits above oldused */
for (i = c->used; i < olduse; i++) {
*tmpc++ = 0;
}
}

mp_clamp (c);
return MP_OKAY;
}
#endif

/* \$Source\$ */
/* \$Revision\$ */
/* \$Date\$ */