-#include <tommath.h>
+#include "tommath_private.h"
#ifdef BN_S_MP_ADD_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://libtom.org
- */
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
/* 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_err s_mp_add(const mp_int *a, const 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;
-
- {
- register mp_digit u, *tmpa, *tmpb, *tmpc;
- register 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] */
- *tmpc++ &= MP_MASK;
- }
-
- /* 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++ &= MP_MASK;
+ 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;
}
- }
+ }
- /* add carry */
- *tmpc++ = u;
+ /* get old used digit count and set new one */
+ olduse = c->used;
+ c->used = max + 1;
- /* clear digits above oldused */
- for (i = c->used; i < olduse; i++) {
- *tmpc++ = 0;
- }
- }
+ {
+ mp_digit u, *tmpa, *tmpb, *tmpc;
+ int i;
- mp_clamp (c);
- return MP_OKAY;
+ /* 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] */
+ *tmpc++ &= MP_MASK;
+ }
+
+ /* 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] */
+ *tmpc++ &= MP_MASK;
+ }
+ }
+
+ /* add carry */
+ *tmpc++ = u;
+
+ /* clear digits above oldused */
+ MP_ZERO_DIGITS(tmpc, olduse - c->used);
+ }
+
+ mp_clamp(c);
+ return MP_OKAY;
}
#endif
-
-/* $Source: /cvs/libtom/libtommath/bn_s_mp_add.c,v $ */
-/* $Revision: 1.4 $ */
-/* $Date: 2006/12/28 01:25:13 $ */
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