h2-mod/deps/libtommath/mp_reduce_is_2k.c
2024-03-07 03:33:59 -05:00

35 lines
801 B
C

#include "tommath_private.h"
#ifdef MP_REDUCE_IS_2K_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* determines if mp_reduce_2k can be used */
bool mp_reduce_is_2k(const mp_int *a)
{
if (mp_iszero(a)) {
return false;
} else if (a->used == 1) {
return true;
} else if (a->used > 1) {
int ix, iy = mp_count_bits(a), iw = 1;
mp_digit iz = 1;
/* Test every bit from the second digit up, must be 1 */
for (ix = MP_DIGIT_BIT; ix < iy; ix++) {
if ((a->dp[iw] & iz) == 0u) {
return false;
}
iz <<= 1;
if (iz > MP_DIGIT_MAX) {
++iw;
iz = 1;
}
}
return true;
} else {
return true;
}
}
#endif