denyhosts/clamscan/libclamav/tomsfastmath/addsub/fp_sub.c

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2022-10-22 18:41:00 +08:00
/* 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 "bignum_fast.h"
/* c = a - b */
void fp_sub(fp_int *a, fp_int *b, fp_int *c)
{
int sa, sb;
sa = a->sign;
sb = b->sign;
if (sa != sb) {
/* subtract a negative from a positive, OR */
/* subtract a positive from a negative. */
/* In either case, ADD their magnitudes, */
/* and use the sign of the first number. */
c->sign = sa;
s_fp_add (a, b, c);
} else {
/* subtract a positive from a positive, OR */
/* subtract a negative from a negative. */
/* First, take the difference between their */
/* magnitudes, then... */
if (fp_cmp_mag (a, b) != FP_LT) {
/* Copy the sign from the first */
c->sign = sa;
/* The first has a larger or equal magnitude */
s_fp_sub (a, b, c);
} else {
/* The result has the *opposite* sign from */
/* the first number. */
c->sign = (sa == FP_ZPOS) ? FP_NEG : FP_ZPOS;
/* The second has a larger magnitude */
s_fp_sub (b, a, c);
}
}
}
/* $Source: /cvs/libtom/tomsfastmath/src/addsub/fp_sub.c,v $ */
/* $Revision: 1.1 $ */
/* $Date: 2006/12/31 21:25:53 $ */