int n, BN_ULONG *t)
{
int i,j,n2=n*2;
- unsigned int c1;
+ unsigned int c1,c2,neg,zero;
BN_ULONG ln,lo,*p;
# ifdef BN_COUNT
}
/* r=(a[0]-a[1])*(b[1]-b[0]) */
- bn_sub_words(t, a, &(a[n]),n); /* + */
- bn_sub_words(&(t[n]),b, &(b[n]),n); /* - */
-
+ c1=bn_cmp_words(a,&(a[n]),n);
+ c2=bn_cmp_words(&(b[n]),b,n);
+ zero=neg=0;
+ switch (c1*3+c2)
+ {
+ case -4:
+ bn_sub_words(t, &(a[n]),a, n); /* - */
+ bn_sub_words(&(t[n]),b, &(b[n]),n); /* - */
+ break;
+ case -3:
+ zero=1;
+ /* break; */
+ case -2:
+ bn_sub_words(t, &(a[n]),a, n); /* - */
+ bn_sub_words(&(t[n]),&(b[n]),b, n); /* + */
+ neg=1;
+ break;
+ case -1:
+ case 0:
+ case 1:
+ zero=1;
+ /* break; */
+ case 2:
+ bn_sub_words(t, a, &(a[n]),n); /* + */
+ bn_sub_words(&(t[n]),b, &(b[n]),n); /* - */
+ neg=1;
+ break;
+ case 3:
+ zero=1;
+ /* break; */
+ case 4:
+ bn_sub_words(t, a, &(a[n]),n);
+ bn_sub_words(&(t[n]),&(b[n]),b, n);
+ break;
+ }
+ /* The zero case isn't yet implemented here. The speedup
+ would probably be negligible. */
# if 0
if (n == 4)
{
*/
c1=(int)(bn_add_words(t,r,&(r[n2]),n2));
- c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
+
+ if (neg) /* if t[32] is negative */
+ {
+ c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
+ }
+ else
+ {
+ /* Might have a carry */
+ c1+=(int)(bn_add_words(&(t[n2]),&(t[n2]),t,n2));
+ }
/* t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
* r[10] holds (a[0]*b[0])
}
}
#endif /* BN_RECURSION */
-
if (bn_wexpand(rr,top) == NULL) goto err;
rr->top=top;
bn_mul_normal(rr->d,a->d,al,b->d,bl);