### view libtommath/bn_mp_div_d.c @ 1938:77bc00dcc19fdefaulttipmainmaster

Bump version to 2022.82
author Matt Johnston Fri, 01 Apr 2022 14:43:27 +0800 1051e4eea25a
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```#include "tommath_private.h"
#ifdef BN_MP_DIV_D_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */

/* single digit division (based on routine from MPI) */
mp_err 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;
mp_err err;
int ix;

/* cannot divide by zero */
if (b == 0u) {
return MP_VAL;
}

/* quick outs */
if ((b == 1u) || MP_IS_ZERO(a)) {
if (d != NULL) {
*d = 0;
}
if (c != NULL) {
return mp_copy(a, c);
}
return MP_OKAY;
}

/* power of two ? */
if ((b & (b - 1u)) == 0u) {
ix = 1;
while ((ix < MP_DIGIT_BIT) && (b != (((mp_digit)1)<<ix))) {
ix++;
}
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;
}

/* three? */
if (MP_HAS(MP_DIV_3) && (b == 3u)) {
return mp_div_3(a, c, d);
}

/* no easy answer [c'est la vie].  Just division */
if ((err = mp_init_size(&q, a->used)) != MP_OKAY) {
return err;
}

q.used = a->used;
q.sign = a->sign;
w = 0;
for (ix = a->used - 1; ix >= 0; ix--) {
w = (w << (mp_word)MP_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 err;
}

#endif
```