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1 #include <tommath_private.h> |
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2 #ifdef BN_MP_EXPORT_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://libtom.org |
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16 */ |
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17 |
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18 /* based on gmp's mpz_export. |
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19 * see http://gmplib.org/manual/Integer-Import-and-Export.html |
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20 */ |
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21 int mp_export(void* rop, size_t* countp, int order, size_t size, |
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22 int endian, size_t nails, mp_int* op) { |
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23 int result; |
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24 size_t odd_nails, nail_bytes, i, j, bits, count; |
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25 unsigned char odd_nail_mask; |
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26 |
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27 mp_int t; |
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28 |
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29 if ((result = mp_init_copy(&t, op)) != MP_OKAY) { |
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30 return result; |
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31 } |
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32 |
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33 if (endian == 0) { |
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34 union { |
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35 unsigned int i; |
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36 char c[4]; |
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37 } lint; |
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38 lint.i = 0x01020304; |
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39 |
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40 endian = (lint.c[0] == 4) ? -1 : 1; |
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41 } |
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42 |
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43 odd_nails = (nails % 8); |
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44 odd_nail_mask = 0xff; |
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45 for (i = 0; i < odd_nails; ++i) { |
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46 odd_nail_mask ^= (1 << (7 - i)); |
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47 } |
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48 nail_bytes = nails / 8; |
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49 |
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50 bits = mp_count_bits(&t); |
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51 count = (bits / ((size * 8) - nails)) + (((bits % ((size * 8) - nails)) != 0) ? 1 : 0); |
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52 |
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53 for (i = 0; i < count; ++i) { |
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54 for (j = 0; j < size; ++j) { |
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55 unsigned char* byte = ( |
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56 (unsigned char*)rop + |
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57 (((order == -1) ? i : ((count - 1) - i)) * size) + |
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58 ((endian == -1) ? j : ((size - 1) - j)) |
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59 ); |
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60 |
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61 if (j >= (size - nail_bytes)) { |
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62 *byte = 0; |
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63 continue; |
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64 } |
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65 |
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66 *byte = (unsigned char)((j == ((size - nail_bytes) - 1)) ? (t.dp[0] & odd_nail_mask) : (t.dp[0] & 0xFF)); |
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67 |
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68 if ((result = mp_div_2d(&t, ((j == ((size - nail_bytes) - 1)) ? (8 - odd_nails) : 8), &t, NULL)) != MP_OKAY) { |
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69 mp_clear(&t); |
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70 return result; |
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71 } |
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72 } |
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73 } |
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74 |
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75 mp_clear(&t); |
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76 |
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77 if (countp != NULL) { |
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78 *countp = count; |
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79 } |
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80 |
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81 return MP_OKAY; |
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82 } |
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83 |
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84 #endif |
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85 |
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86 /* $Source$ */ |
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87 /* $Revision$ */ |
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88 /* $Date$ */ |
