denyhosts/clamscan/libclamav/tomsfastmath/addsub/s_fp_sub.c
2022-10-22 18:41:00 +08:00

41 lines
1008 B
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 "bignum_fast.h"
/* unsigned subtraction ||a|| >= ||b|| ALWAYS! */
void s_fp_sub(fp_int *a, fp_int *b, fp_int *c)
{
int x, oldbused, oldused;
fp_word t;
oldused = c->used;
oldbused = b->used;
c->used = a->used;
t = 0;
for (x = 0; x < oldbused; x++) {
t = ((fp_word)a->dp[x]) - (((fp_word)b->dp[x]) + t);
c->dp[x] = (fp_digit)t;
t = (t >> DIGIT_BIT)&1;
}
for (; x < a->used; x++) {
t = ((fp_word)a->dp[x]) - t;
c->dp[x] = (fp_digit)t;
t = (t >> DIGIT_BIT);
}
for (; x < oldused; x++) {
c->dp[x] = 0;
}
fp_clamp(c);
}
/* $Source: /cvs/libtom/tomsfastmath/src/addsub/s_fp_sub.c,v $ */
/* $Revision: 1.1 $ */
/* $Date: 2006/12/31 21:25:53 $ */