t7x/deps/libtommath/mp_read_radix.c
2023-12-06 17:43:39 -05:00

70 lines
1.7 KiB
C

#include "tommath_private.h"
#ifdef MP_READ_RADIX_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* read a string [ASCII] in a given radix */
mp_err mp_read_radix(mp_int *a, const char *str, int radix)
{
mp_err err;
mp_sign sign = MP_ZPOS;
/* make sure the radix is ok */
if ((radix < 2) || (radix > 64)) {
return MP_VAL;
}
/* if the leading digit is a
* minus set the sign to negative.
*/
if (*str == '-') {
++str;
sign = MP_NEG;
}
/* set the integer to the default of zero */
mp_zero(a);
/* process each digit of the string */
while (*str != '\0') {
/* if the radix <= 36 the conversion is case insensitive
* this allows numbers like 1AB and 1ab to represent the same value
* [e.g. in hex]
*/
uint8_t y;
char ch = (radix <= 36) ? (char)MP_TOUPPER((int)*str) : *str;
unsigned pos = (unsigned)(ch - '+');
if (MP_RADIX_MAP_REVERSE_SIZE <= pos) {
break;
}
y = s_mp_radix_map_reverse[pos];
/* if the char was found in the map
* and is less than the given radix add it
* to the number, otherwise exit the loop.
*/
if (y >= radix) {
break;
}
if ((err = mp_mul_d(a, (mp_digit)radix, a)) != MP_OKAY) {
return err;
}
if ((err = mp_add_d(a, y, a)) != MP_OKAY) {
return err;
}
++str;
}
/* if an illegal character was found, fail. */
if ((*str != '\0') && (*str != '\r') && (*str != '\n')) {
return MP_VAL;
}
/* set the sign only if a != 0 */
if (!mp_iszero(a)) {
a->sign = sign;
}
return MP_OKAY;
}
#endif