tomsfastmath/fp_add.c

/* TomsFastMath, a fast ISO C bignum library.
 * 
 * This project is meant to fill in where LibTomMath
 * falls short.  That is speed ;-)
 *
 * This project is public domain and free for all purposes.
 * 
 * Tom St Denis, tomstdenis@gmail.com
 */
#include <tfm.h>

void fp_add(fp_int *a, fp_int *b, fp_int *c)
{
  int     sa, sb;

  /* get sign of both inputs */
  sa = a->sign;
  sb = b->sign;

  /* handle two cases, not four */
  if (sa == sb) {
    /* both positive or both negative */
    /* add their magnitudes, copy the sign */
    c->sign = sa;
    s_fp_add (a, b, c);
  } else {
    /* one positive, the other negative */
    /* subtract the one with the greater magnitude from */
    /* the one of the lesser magnitude.  The result gets */
    /* the sign of the one with the greater magnitude. */
    if (fp_cmp_mag (a, b) == FP_LT) {
      c->sign = sb;
      s_fp_sub (b, a, c);
    } else {
      c->sign = sa;
      s_fp_sub (a, b, c);
    }
  }
}

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/* $Date$ */