Mercurial > dropbear

annotate libtommath/bn_mp_toradix_n.c @ 310:4b4478d0d2b9 ucc-axis-hack

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add a comment on usage
author Matt Johnston <matt@ucc.asn.au>
date Sun, 26 Mar 2006 08:28:16 +0000
parents eed26cff980b
children 5ff8218bcee9
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rev   line source
284
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diff changeset
1 #include <tommath.h>
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2 #ifdef BN_MP_TORADIX_N_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
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16 */
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17
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18 /* stores a bignum as a ASCII string in a given radix (2..64)
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19 *
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20 * Stores upto maxlen-1 chars and always a NULL byte
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21 */
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22 int mp_toradix_n(mp_int * a, char *str, int radix, int maxlen)
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23 {
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24 int res, digs;
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25 mp_int t;
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26 mp_digit d;
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27 char *_s = str;
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28
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29 /* check range of the maxlen, radix */
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30 if (maxlen < 3 || radix < 2 || radix > 64) {
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31 return MP_VAL;
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32 }
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33
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34 /* quick out if its zero */
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35 if (mp_iszero(a) == 1) {
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36 *str++ = '0';
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37 *str = '\0';
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38 return MP_OKAY;
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39 }
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40
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41 if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
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42 return res;
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43 }
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44
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45 /* if it is negative output a - */
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46 if (t.sign == MP_NEG) {
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47 /* we have to reverse our digits later... but not the - sign!! */
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48 ++_s;
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49
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50 /* store the flag and mark the number as positive */
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51 *str++ = '-';
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52 t.sign = MP_ZPOS;
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53
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54 /* subtract a char */
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55 --maxlen;
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56 }
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57
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58 digs = 0;
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59 while (mp_iszero (&t) == 0) {
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60 if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
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61 mp_clear (&t);
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62 return res;
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63 }
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64 *str++ = mp_s_rmap[d];
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65 ++digs;
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66
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67 if (--maxlen == 1) {
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68 /* no more room */
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69 break;
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70 }
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71 }
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72
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73 /* reverse the digits of the string. In this case _s points
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74 * to the first digit [exluding the sign] of the number]
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75 */
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76 bn_reverse ((unsigned char *)_s, digs);
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77
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78 /* append a NULL so the string is properly terminated */
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79 *str = '\0';
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80
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81 mp_clear (&t);
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82 return MP_OKAY;
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83 }
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84
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85 #endif