bn_mp_add_factored_factorials.c

#include <tommath.h>
#ifdef BN_MP_ADD_FACTORED_FACTORIALS_C
int mp_add_factored_factorials(long *summand_1,
                               unsigned long l_summand_1,
                               long *summand_2,
                               unsigned long l_summand_2,
                               long **sum,
                               unsigned long *l_sum)
{
   unsigned long k, counter=0;
   unsigned long max_length = MAX(l_summand_1,l_summand_2);
   unsigned long min_length = MIN(l_summand_1,l_summand_2);
   long s,p, s_1,s_2;
   /* For more detailed comments see mp_subtract_factored_factorials() */
   *sum = malloc(sizeof(unsigned long)*(max_length+1));
   if (*sum == NULL) {
      return MP_MEM;
   }
   for (k=0; k<min_length; k+=2) {
      p = summand_1[k];
      /* Over/underflow possible! */
      /*s = summand_1[k+1] + summand_2[k+1];*/
      s_1 = summand_1[k+1];
      s_2 = summand_2[k+1];

      if ((s_2 > 0) && (s_1 > LONG_MAX - s_2)) {
         /* overflow */
         return MP_VAL;
      }
      if ((s_2 < 0) && (s_1 < LONG_MIN - s_2)) {
         /* underflow */
         return MP_VAL;
      }
      s = s_1 + s_2;
      (*sum)[counter]   = p;
      (*sum)[counter+1] = s;
      counter += 2;
   }
   if (l_summand_1 >= l_summand_2) {
      for (; k<max_length; k+=2) {
         p = summand_1[k];
         s = summand_1[k+1];
         (*sum)[counter]   = p;
         (*sum)[counter+1] = s;
         counter += 2;
      }
   } else {
      for (; k<max_length; k+=2) {
         p = summand_2[k];
         s = summand_2[k+1];
         (*sum)[counter]   = p;
         (*sum)[counter+1] = s;
         counter += 2;
      }
   }
   *l_sum = counter;
   return MP_OKAY;
}

#endif