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#include "tommath_private.h"
#ifdef BN_MP_MOD_2D_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
/* calc a value mod 2**b */
int mp_mod_2d(const mp_int *a, int b, mp_int *c)
{
int x, res;
/* 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 * DIGIT_BIT)) {
res = mp_copy(a, c);
return res;
}
/* copy */
if ((res = mp_copy(a, c)) != MP_OKAY) {
return res;
}
/* zero digits above the last digit of the modulus */
for (x = (b / DIGIT_BIT) + (((b % DIGIT_BIT) == 0) ? 0 : 1); x < c->used; x++) {
c->dp[x] = 0;
}
/* clear the digit that is not completely outside/inside the modulus */
c->dp[b / DIGIT_BIT] &=
((mp_digit)1 << (mp_digit)(b % DIGIT_BIT)) - (mp_digit)1;
mp_clamp(c);
return MP_OKAY;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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