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