fp_add.c

00001 /* TomsFastMath, a fast ISO C bignum library.
00002  * 
00003  * This project is meant to fill in where LibTomMath
00004  * falls short.  That is speed ;-)
00005  *
00006  * This project is public domain and free for all purposes.
00007  * 
00008  * Tom St Denis, tomstdenis@gmail.com
00009  */
00010 #include <tfm.h>
00011 
00012 void fp_add(fp_int *a, fp_int *b, fp_int *c)
00013 {
00014   int     sa, sb;
00015 
00016   /* get sign of both inputs */
00017   sa = a->sign;
00018   sb = b->sign;
00019 
00020   /* handle two cases, not four */
00021   if (sa == sb) {
00022     /* both positive or both negative */
00023     /* add their magnitudes, copy the sign */
00024     c->sign = sa;
00025     s_fp_add (a, b, c);
00026   } else {
00027     /* one positive, the other negative */
00028     /* subtract the one with the greater magnitude from */
00029     /* the one of the lesser magnitude.  The result gets */
00030     /* the sign of the one with the greater magnitude. */
00031     if (fp_cmp_mag (a, b) == FP_LT) {
00032       c->sign = sb;
00033       s_fp_sub (b, a, c);
00034     } else {
00035       c->sign = sa;
00036       s_fp_sub (a, b, c);
00037     }
00038   }
00039 }
00040 
00041 /* $Source: /cvs/libtom/tomsfastmath/src/addsub/fp_add.c,v $ */
00042 /* $Revision: 1.1 $ */
00043 /* $Date: 2006/12/31 21:25:53 $ */