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, tomstdenis@gmail.com, http://math.libtomcrypt.com
16 */
17
18/* high level multiplication (handles sign) */
19int 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
63
64/* $Source: /cvs/libtom/libtommath/bn_mp_mul.c,v $ */
65/* $Revision: 1.3 $ */
66/* $Date: 2006/03/31 14:18:44 $ */
67