| [25] | 1 | #include <tommath.h> |
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| 2 | #ifdef BN_MP_MUL_2D_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 | /* shift left by a certain bit count */ |
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| 19 | int mp_mul_2d (mp_int * a, int b, mp_int * c) |
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| 20 | { |
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| 21 | mp_digit d; |
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| 22 | int res; |
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| 23 | |
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| 24 | /* copy */ |
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| 25 | if (a != c) { |
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| 26 | if ((res = mp_copy (a, c)) != MP_OKAY) { |
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| 27 | return res; |
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| 28 | } |
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| 29 | } |
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| 30 | |
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| 31 | if (c->alloc < (int)(c->used + b/DIGIT_BIT + 1)) { |
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| 32 | if ((res = mp_grow (c, c->used + b / DIGIT_BIT + 1)) != MP_OKAY) { |
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| 33 | return res; |
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| 34 | } |
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| 35 | } |
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| 36 | |
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| 37 | /* shift by as many digits in the bit count */ |
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| 38 | if (b >= (int)DIGIT_BIT) { |
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| 39 | if ((res = mp_lshd (c, b / DIGIT_BIT)) != MP_OKAY) { |
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| 40 | return res; |
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| 41 | } |
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| 42 | } |
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| 43 | |
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| 44 | /* shift any bit count < DIGIT_BIT */ |
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| 45 | d = (mp_digit) (b % DIGIT_BIT); |
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| 46 | if (d != 0) { |
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| 47 | register mp_digit *tmpc, shift, mask, r, rr; |
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| 48 | register int x; |
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| 49 | |
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| 50 | /* bitmask for carries */ |
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| 51 | mask = (((mp_digit)1) << d) - 1; |
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| 52 | |
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| 53 | /* shift for msbs */ |
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| 54 | shift = DIGIT_BIT - d; |
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| 55 | |
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| 56 | /* alias */ |
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| 57 | tmpc = c->dp; |
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| 58 | |
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| 59 | /* carry */ |
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| 60 | r = 0; |
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| 61 | for (x = 0; x < c->used; x++) { |
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| 62 | /* get the higher bits of the current word */ |
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| 63 | rr = (*tmpc >> shift) & mask; |
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| 64 | |
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| 65 | /* shift the current word and OR in the carry */ |
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| 66 | *tmpc = ((*tmpc << d) | r) & MP_MASK; |
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| 67 | ++tmpc; |
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| 68 | |
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| 69 | /* set the carry to the carry bits of the current word */ |
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| 70 | r = rr; |
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| 71 | } |
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| 72 | |
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| 73 | /* set final carry */ |
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| 74 | if (r != 0) { |
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| 75 | c->dp[(c->used)++] = r; |
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| 76 | } |
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| 77 | } |
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| 78 | mp_clamp (c); |
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| 79 | return MP_OKAY; |
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| 80 | } |
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| 81 | #endif |
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| 82 | |
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| 83 | /* $Source: /cvsroot/tcl/libtommath/bn_mp_mul_2d.c,v $ */ |
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| 84 | /* $Revision: 1.1.1.3 $ */ |
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| 85 | /* $Date: 2006/12/01 00:08:11 $ */ |
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