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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 /* read a string [ASCII] in a given radix */ |
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18 int mp_read_radix (mp_int * a, char *str, int radix) |
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19 { |
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20 int y, res, neg; |
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21 char ch; |
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22 |
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23 /* make sure the radix is ok */ |
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24 if (radix < 2 || radix > 64) { |
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25 return MP_VAL; |
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26 } |
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27 |
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28 /* if the leading digit is a |
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29 * minus set the sign to negative. |
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30 */ |
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31 if (*str == '-') { |
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32 ++str; |
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33 neg = MP_NEG; |
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34 } else { |
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35 neg = MP_ZPOS; |
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36 } |
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37 |
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38 /* set the integer to the default of zero */ |
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39 mp_zero (a); |
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40 |
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41 /* process each digit of the string */ |
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42 while (*str) { |
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43 /* if the radix < 36 the conversion is case insensitive |
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44 * this allows numbers like 1AB and 1ab to represent the same value |
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45 * [e.g. in hex] |
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46 */ |
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47 ch = (char) ((radix < 36) ? toupper (*str) : *str); |
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48 for (y = 0; y < 64; y++) { |
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49 if (ch == mp_s_rmap[y]) { |
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50 break; |
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51 } |
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52 } |
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53 |
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54 /* if the char was found in the map |
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55 * and is less than the given radix add it |
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56 * to the number, otherwise exit the loop. |
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57 */ |
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58 if (y < radix) { |
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59 if ((res = mp_mul_d (a, (mp_digit) radix, a)) != MP_OKAY) { |
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60 return res; |
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61 } |
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62 if ((res = mp_add_d (a, (mp_digit) y, a)) != MP_OKAY) { |
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63 return res; |
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64 } |
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65 } else { |
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66 break; |
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67 } |
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68 ++str; |
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69 } |
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70 |
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71 /* set the sign only if a != 0 */ |
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72 if (mp_iszero(a) != 1) { |
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73 a->sign = neg; |
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74 } |
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75 return MP_OKAY; |
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76 } |
