[25] | 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, tomstdenis@gmail.com, http://math.libtomcrypt.com |
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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 |
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| 50 | |
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| 51 | /* $Source: /cvsroot/tcl/libtommath/bn_mp_add.c,v $ */ |
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| 52 | /* $Revision: 1.3 $ */ |
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| 53 | /* $Date: 2006/12/01 19:45:38 $ */ |
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