annotate bn_mp_mul.c @ 139:cc04b085e7dd libtommath

Pristine compilation works.
author Matt Johnston <matt@ucc.asn.au>
date Fri, 17 Dec 2004 06:27:22 +0000
parents 22d5cf7d4b1a
children a96ff234ff19
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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 /* high level multiplication (handles sign) */
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18 int mp_mul (mp_int * a, mp_int * b, mp_int * c)
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19 {
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20 int res, neg;
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21 neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
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22
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23 #ifndef NO_LTM_TOOM
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24
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25 /* use Toom-Cook? */
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26 if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) {
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27 res = mp_toom_mul(a, b, c);
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28 } else
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29 #endif
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30 #ifndef NO_LTM_KARATSUBA
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31 /* use Karatsuba? */
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32 if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
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33 res = mp_karatsuba_mul (a, b, c);
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34 } else
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35 #endif
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36 {
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37 /* can we use the fast multiplier?
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38 *
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39 * The fast multiplier can be used if the output will
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40 * have less than MP_WARRAY digits and the number of
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41 * digits won't affect carry propagation
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42 */
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43 int digs = a->used + b->used + 1;
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44
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45 if ((digs < MP_WARRAY) &&
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46 MIN(a->used, b->used) <=
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47 (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) {
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48 res = fast_s_mp_mul_digs (a, b, c, digs);
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49 } else {
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50 res = s_mp_mul (a, b, c);
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51 }
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52 }
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53 c->sign = neg;
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54 return res;
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55 }