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comparison libtommath/bn_mp_mul.c @ 284:eed26cff980b

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propagate from branch 'au.asn.ucc.matt.ltm.dropbear' (head 6c790cad5a7fa866ad062cb3a0c279f7ba788583) to branch 'au.asn.ucc.matt.dropbear' (head fff0894a0399405a9410ea1c6d118f342cf2aa64)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 08 Mar 2006 13:23:49 +0000
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children 5ff8218bcee9
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283:bd240aa12ba7 284:eed26cff980b
1 #include <tommath.h>
2 #ifdef BN_MP_MUL_C
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
16 */
17
18 /* high level multiplication (handles sign) */
19 int mp_mul (mp_int * a, mp_int * b, mp_int * c)
20 {
21 int res, neg;
22 neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
23
24 /* use Toom-Cook? */
25 #ifdef BN_MP_TOOM_MUL_C
26 if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) {
27 res = mp_toom_mul(a, b, c);
28 } else
29 #endif
30 #ifdef BN_MP_KARATSUBA_MUL_C
31 /* use Karatsuba? */
32 if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
33 res = mp_karatsuba_mul (a, b, c);
34 } else
35 #endif
36 {
37 /* can we use the fast multiplier?
38 *
39 * The fast multiplier can be used if the output will
40 * have less than MP_WARRAY digits and the number of
41 * digits won't affect carry propagation
42 */
43 int digs = a->used + b->used + 1;
44
45 #ifdef BN_FAST_S_MP_MUL_DIGS_C
46 if ((digs < MP_WARRAY) &&
47 MIN(a->used, b->used) <=
48 (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) {
49 res = fast_s_mp_mul_digs (a, b, c, digs);
50 } else
51 #endif
52 #ifdef BN_S_MP_MUL_DIGS_C
53 res = s_mp_mul (a, b, c); /* uses s_mp_mul_digs */
54 #else
55 res = MP_VAL;
56 #endif
57
58 }
59 c->sign = (c->used > 0) ? neg : MP_ZPOS;
60 return res;
61 }
62 #endif