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#include "tommath_private.h"
#ifdef BN_MP_EXPT_N_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* calculate c = a**b using a square-multiply algorithm */
mp_err mp_expt_n(const mp_int *a, int b, mp_int *c)
{
mp_err err;
mp_int g;
if ((err = mp_init_copy(&g, a)) != MP_OKAY) {
return err;
}
/* set initial result */
mp_set(c, 1uL);
while (b > 0) {
/* if the bit is set multiply */
if ((b & 1) != 0) {
if ((err = mp_mul(c, &g, c)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* square */
if (b > 1) {
if ((err = mp_sqr(&g, &g)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* shift to next bit */
b >>= 1;
}
LBL_ERR:
mp_clear(&g);
return err;
}
#endif
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