139 lines
2.7 KiB
C
139 lines
2.7 KiB
C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is library that provides for multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library is designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtommath.iahu.ca
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*/
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#include <tommath.h>
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/* chars used in radix conversions */
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static const char *s_rmap = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/";
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/* read a string [ASCII] in a given radix */
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int
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mp_read_radix (mp_int * a, char *str, int radix)
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{
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int y, res, neg;
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char ch;
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if (radix < 2 || radix > 64) {
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return MP_VAL;
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}
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if (*str == '-') {
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++str;
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neg = MP_NEG;
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} else {
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neg = MP_ZPOS;
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}
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mp_zero (a);
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while (*str) {
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ch = (char) ((radix < 36) ? toupper (*str) : *str);
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for (y = 0; y < 64; y++) {
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if (ch == s_rmap[y]) {
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break;
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}
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}
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if (y < radix) {
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if ((res = mp_mul_d (a, (mp_digit) radix, a)) != MP_OKAY) {
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return res;
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}
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if ((res = mp_add_d (a, (mp_digit) y, a)) != MP_OKAY) {
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return res;
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}
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} else {
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break;
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}
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++str;
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}
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a->sign = neg;
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return MP_OKAY;
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}
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/* stores a bignum as a ASCII string in a given radix (2..64) */
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int
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mp_toradix (mp_int * a, char *str, int radix)
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{
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int res, digs;
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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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if (radix < 2 || radix > 64) {
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return MP_VAL;
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}
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if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
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return res;
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}
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if (t.sign == MP_NEG) {
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++_s;
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*str++ = '-';
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t.sign = MP_ZPOS;
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}
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digs = 0;
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while (mp_iszero (&t) == 0) {
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if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
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mp_clear (&t);
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return res;
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}
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*str++ = s_rmap[d];
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++digs;
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}
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bn_reverse ((unsigned char *) _s, digs);
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*str++ = '\0';
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mp_clear (&t);
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return MP_OKAY;
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}
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/* returns size of ASCII reprensentation */
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int
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mp_radix_size (mp_int * a, int radix)
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{
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int res, digs;
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mp_int t;
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mp_digit d;
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/* special case for binary */
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if (radix == 2) {
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return mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1;
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}
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if (radix < 2 || radix > 64) {
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return 0;
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}
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if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
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return 0;
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}
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digs = 0;
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if (t.sign == MP_NEG) {
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++digs;
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t.sign = MP_ZPOS;
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}
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while (mp_iszero (&t) == 0) {
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if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
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mp_clear (&t);
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return 0;
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}
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++digs;
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}
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mp_clear (&t);
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return digs + 1;
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}
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