Update LibTomMath to 1.2.0 (#84) * update C files * update other files * update headers * update makefiles * remove mp_set/get_double() * use ltm 1.2.0 API * update ltm_desc * use bundled tommath if system-tommath is too old * XMALLOC etc. were changed to MP_MALLOC etc.
author Steffen Jaeckel Tue, 26 May 2020 17:36:47 +0200 f52919ffd3b1
line wrap: on
line source
#include "tommath_private.h"
/* LibTomMath, multiple-precision integer library -- Tom St Denis */

/* low level addition, based on HAC pp.594, Algorithm 14.7 */
mp_err s_mp_add(const mp_int *a, const mp_int *b, mp_int *c)
{
const mp_int *x;
mp_err err;
int     olduse, 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 ((err = mp_grow(c, max + 1)) != MP_OKAY) {
return err;
}
}

/* 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)MP_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)MP_DIGIT_BIT;

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