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85 lines
1.9 KiB
C
85 lines
1.9 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_TO_RADIX_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/* stores a bignum as a ASCII string in a given radix (2..64)
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*
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* Stores upto "size - 1" chars and always a NULL byte, puts the number of characters
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* written, including the '\0', in "written".
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*/
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mp_err mp_to_radix(const mp_int *a, char *str, size_t maxlen, size_t *written, int radix)
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{
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size_t digs;
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mp_err err;
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mp_int t;
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mp_digit d;
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char *_s = str;
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/* check range of radix and size*/
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if (maxlen < 2u) {
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return MP_BUF;
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}
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if ((radix < 2) || (radix > 64)) {
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return MP_VAL;
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}
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/* quick out if its zero */
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if (MP_IS_ZERO(a)) {
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*str++ = '0';
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*str = '\0';
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if (written != NULL) {
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*written = 2u;
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}
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return MP_OKAY;
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}
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if ((err = mp_init_copy(&t, a)) != MP_OKAY) {
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return err;
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}
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/* if it is negative output a - */
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if (t.sign == MP_NEG) {
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/* we have to reverse our digits later... but not the - sign!! */
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++_s;
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/* store the flag and mark the number as positive */
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*str++ = '-';
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t.sign = MP_ZPOS;
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/* subtract a char */
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--maxlen;
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}
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digs = 0u;
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while (!MP_IS_ZERO(&t)) {
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if (--maxlen < 1u) {
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/* no more room */
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err = MP_BUF;
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goto LBL_ERR;
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}
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if ((err = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
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goto LBL_ERR;
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}
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*str++ = mp_s_rmap[d];
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++digs;
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}
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/* reverse the digits of the string. In this case _s points
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* to the first digit [exluding the sign] of the number
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*/
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s_mp_reverse((unsigned char *)_s, digs);
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/* append a NULL so the string is properly terminated */
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*str = '\0';
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digs++;
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if (written != NULL) {
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*written = (a->sign == MP_NEG) ? (digs + 1u): digs;
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}
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LBL_ERR:
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mp_clear(&t);
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return err;
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}
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#endif
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