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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 /* get the lower 32-bits of an mp_int */ |
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18 unsigned long mp_get_int(mp_int * a) |
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19 { |
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20 int i; |
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21 unsigned long res; |
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22 |
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23 if (a->used == 0) { |
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24 return 0; |
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25 } |
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26 |
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27 /* get number of digits of the lsb we have to read */ |
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28 i = MIN(a->used,(int)((sizeof(unsigned long)*CHAR_BIT+DIGIT_BIT-1)/DIGIT_BIT))-1; |
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29 |
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30 /* get most significant digit of result */ |
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31 res = DIGIT(a,i); |
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32 |
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33 while (--i >= 0) { |
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34 res = (res << DIGIT_BIT) | DIGIT(a,i); |
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35 } |
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36 |
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37 /* force result to 32-bits always so it is consistent on non 32-bit platforms */ |
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38 return res & 0xFFFFFFFFUL; |
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39 } |
