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Fix mp_mod(a, b, c) if b < 0 and a = n * b, n integer

it used to return b, now it return 0.
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1 parent abb79eb commit 265651b2c7e7800c8e8d257057d4494d78bded95 @moritz committed Jan 8, 2012
Showing with 4 additions and 4 deletions.
  1. +4 −4 bn_mp_mod.c
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8 bn_mp_mod.c
@@ -15,7 +15,7 @@
* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
*/
-/* c = a mod b, 0 <= c < b */
+/* c = a mod b, 0 <= c < b if b > 0, b < c <= 0 if b < 0 */
int
mp_mod (mp_int * a, mp_int * b, mp_int * c)
{
@@ -31,11 +31,11 @@ mp_mod (mp_int * a, mp_int * b, mp_int * c)
return res;
}
- if (t.sign != b->sign) {
- res = mp_add (b, &t, c);
- } else {
+ if (mp_iszero(&t) || t.sign == b->sign) {
res = MP_OKAY;
mp_exch (&t, c);
+ } else {
+ res = mp_add (b, &t, c);
}
mp_clear (&t);

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