libtommath/mp_radix_size.c

35 lines
769 B
C

#include "tommath_private.h"
#ifdef MP_RADIX_SIZE_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* returns size of ASCII representation */
mp_err mp_radix_size(const mp_int *a, int radix, size_t *size)
{
mp_err err;
mp_int a_;
int b;
/* make sure the radix is in range */
if ((radix < 2) || (radix > 64)) {
return MP_VAL;
}
if (mp_iszero(a)) {
*size = 2;
return MP_OKAY;
}
a_ = *a;
a_.sign = MP_ZPOS;
if ((err = mp_log_n(&a_, radix, &b)) != MP_OKAY) {
return err;
}
/* mp_ilogb truncates to zero, hence we need one extra put on top and one for `\0`. */
*size = (size_t)b + 2U + (mp_isneg(a) ? 1U : 0U);
return MP_OKAY;
}
#endif