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1 #include <tommath.h> |
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2 #ifdef BN_MP_ADD_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://math.libtomcrypt.org |
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16 */ |
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17 |
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18 /* high level addition (handles signs) */ |
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19 int mp_add (mp_int * a, mp_int * b, mp_int * c) |
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20 { |
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21 int sa, sb, res; |
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22 |
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23 /* get sign of both inputs */ |
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24 sa = a->sign; |
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25 sb = b->sign; |
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26 |
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27 /* handle two cases, not four */ |
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28 if (sa == sb) { |
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29 /* both positive or both negative */ |
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30 /* add their magnitudes, copy the sign */ |
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31 c->sign = sa; |
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32 res = s_mp_add (a, b, c); |
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33 } else { |
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34 /* one positive, the other negative */ |
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35 /* subtract the one with the greater magnitude from */ |
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36 /* the one of the lesser magnitude. The result gets */ |
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37 /* the sign of the one with the greater magnitude. */ |
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38 if (mp_cmp_mag (a, b) == MP_LT) { |
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39 c->sign = sb; |
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40 res = s_mp_sub (b, a, c); |
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41 } else { |
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42 c->sign = sa; |
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43 res = s_mp_sub (a, b, c); |
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44 } |
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45 } |
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46 return res; |
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47 } |
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48 |
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49 #endif |
