s1-mod/deps/libtommath/mp_reduce_2k_setup.c
2024-02-27 03:09:30 -05:00

31 lines
596 B
C

#include "tommath_private.h"
#ifdef MP_REDUCE_2K_SETUP_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* determines the setup value */
mp_err mp_reduce_2k_setup(const mp_int *a, mp_digit *d)
{
mp_err err;
mp_int tmp;
if ((err = mp_init(&tmp)) != MP_OKAY) {
return err;
}
if ((err = mp_2expt(&tmp, mp_count_bits(a))) != MP_OKAY) {
goto LBL_ERR;
}
if ((err = s_mp_sub(&tmp, a, &tmp)) != MP_OKAY) {
goto LBL_ERR;
}
*d = tmp.dp[0];
LBL_ERR:
mp_clear(&tmp);
return err;
}
#endif