libtommath/bn_mp_incr.c

#include "tommath_private.h"
#ifdef BN_MP_INCR_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.
 *
 * SPDX-License-Identifier: Unlicense
 */

/* Increment "a" by one like "a++". Changes input! */
int mp_incr(mp_int *a)
{
   int e = MP_OKAY;
   if (IS_ZERO(a)) {
      mp_set(a,1uL);
      return MP_OKAY;
   } else if (a->sign == MP_NEG) {
      a->sign = MP_ZPOS;
      if ((e = mp_decr(a)) != MP_OKAY) {
         return e;
      }
      /* There is no -0 in LTM */
      if (!IS_ZERO(a)) {
         a->sign = MP_NEG;
      }
      return MP_OKAY;
   } else if (a->dp[0] < MP_MASK) {
      a->dp[0]++;
      return MP_OKAY;
   }
   return mp_add_d(a, 1uL,a);
}
#endif