mirror of http://galexander.org/git/simplesshd.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
39 lines
971 B
39 lines
971 B
#include "tommath_private.h"
|
|
#ifdef BN_MP_MOD_2D_C
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
|
/* SPDX-License-Identifier: Unlicense */
|
|
|
|
/* calc a value mod 2**b */
|
|
mp_err mp_mod_2d(const mp_int *a, int b, mp_int *c)
|
|
{
|
|
int x;
|
|
mp_err err;
|
|
|
|
/* if b is <= 0 then zero the int */
|
|
if (b <= 0) {
|
|
mp_zero(c);
|
|
return MP_OKAY;
|
|
}
|
|
|
|
/* if the modulus is larger than the value than return */
|
|
if (b >= (a->used * MP_DIGIT_BIT)) {
|
|
return mp_copy(a, c);
|
|
}
|
|
|
|
/* copy */
|
|
if ((err = mp_copy(a, c)) != MP_OKAY) {
|
|
return err;
|
|
}
|
|
|
|
/* zero digits above the last digit of the modulus */
|
|
x = (b / MP_DIGIT_BIT) + (((b % MP_DIGIT_BIT) == 0) ? 0 : 1);
|
|
MP_ZERO_DIGITS(c->dp + x, c->used - x);
|
|
|
|
/* clear the digit that is not completely outside/inside the modulus */
|
|
c->dp[b / MP_DIGIT_BIT] &=
|
|
((mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT)) - (mp_digit)1;
|
|
mp_clamp(c);
|
|
return MP_OKAY;
|
|
}
|
|
#endif
|