mirror of
https://github.com/XLabsProject/s1x-client.git
synced 2023-08-02 15:02:12 +02:00
39 lines
797 B
C
39 lines
797 B
C
#include "tommath_private.h"
|
|
#ifdef MP_CNT_LSB_C
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
|
/* SPDX-License-Identifier: Unlicense */
|
|
|
|
static const char lnz[16] = {
|
|
4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0
|
|
};
|
|
|
|
/* Counts the number of lsbs which are zero before the first zero bit */
|
|
int mp_cnt_lsb(const mp_int *a)
|
|
{
|
|
int x;
|
|
mp_digit q;
|
|
|
|
/* easy out */
|
|
if (mp_iszero(a)) {
|
|
return 0;
|
|
}
|
|
|
|
/* scan lower digits until non-zero */
|
|
for (x = 0; (x < a->used) && (a->dp[x] == 0u); x++) {}
|
|
q = a->dp[x];
|
|
x *= MP_DIGIT_BIT;
|
|
|
|
/* now scan this digit until a 1 is found */
|
|
if ((q & 1u) == 0u) {
|
|
mp_digit p;
|
|
do {
|
|
p = q & 15u;
|
|
x += lnz[p];
|
|
q >>= 4;
|
|
} while (p == 0u);
|
|
}
|
|
return x;
|
|
}
|
|
|
|
#endif
|