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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 /* determines if mp_reduce_2k can be used */ |
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18 int mp_reduce_is_2k(mp_int *a) |
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19 { |
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20 int ix, iy, iz, iw; |
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21 |
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22 if (a->used == 0) { |
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23 return 0; |
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24 } else if (a->used == 1) { |
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25 return 1; |
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26 } else if (a->used > 1) { |
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27 iy = mp_count_bits(a); |
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28 iz = 1; |
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29 iw = 1; |
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30 |
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31 /* Test every bit from the second digit up, must be 1 */ |
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32 for (ix = DIGIT_BIT; ix < iy; ix++) { |
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33 if ((a->dp[iw] & iz) == 0) { |
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34 return 0; |
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35 } |
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36 iz <<= 1; |
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37 if (iz > (int)MP_MASK) { |
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38 ++iw; |
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39 iz = 1; |
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40 } |
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41 } |
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42 } |
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43 return 1; |
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44 } |
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45 |
