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#include "tommath_private.h"
#ifdef BN_MP_DIV_D_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.
*
* SPDX-License-Identifier: Unlicense
*/
static int s_is_power_of_two(mp_digit b, int *p)
{
int x;
/* fast return if no power of two */
if ((b == 0u) || ((b & (b-1u)) != 0u)) {
return 0;
}
for (x = 0; x < DIGIT_BIT; x++) {
if (b == ((mp_digit)1<<(mp_digit)x)) {
*p = x;
return 1;
}
}
return 0;
}
/* single digit division (based on routine from MPI) */
int mp_div_d(const mp_int *a, mp_digit b, mp_int *c, mp_digit *d)
{
mp_int q;
mp_word w;
mp_digit t;
int res, ix;
/* cannot divide by zero */
if (b == 0u) {
return MP_VAL;
}
/* quick outs */
if ((b == 1u) || (mp_iszero(a) == MP_YES)) {
if (d != NULL) {
*d = 0;
}
if (c != NULL) {
return mp_copy(a, c);
}
return MP_OKAY;
}
/* power of two ? */
if (s_is_power_of_two(b, &ix) == 1) {
if (d != NULL) {
*d = a->dp[0] & (((mp_digit)1<<(mp_digit)ix) - 1uL);
}
if (c != NULL) {
return mp_div_2d(a, ix, c, NULL);
}
return MP_OKAY;
}
#ifdef BN_MP_DIV_3_C
/* three? */
if (b == 3u) {
return mp_div_3(a, c, d);
}
#endif
/* no easy answer [c'est la vie]. Just division */
if ((res = mp_init_size(&q, a->used)) != MP_OKAY) {
return res;
}
q.used = a->used;
q.sign = a->sign;
w = 0;
for (ix = a->used - 1; ix >= 0; ix--) {
w = (w << (mp_word)DIGIT_BIT) | (mp_word)a->dp[ix];
if (w >= b) {
t = (mp_digit)(w / b);
w -= (mp_word)t * (mp_word)b;
} else {
t = 0;
}
q.dp[ix] = t;
}
if (d != NULL) {
*d = (mp_digit)w;
}
if (c != NULL) {
mp_clamp(&q);
mp_exch(&q, c);
}
mp_clear(&q);
return res;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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