Mercurial > dropbear

comparison bn_mp_mul.c @ 2:86e0b50a9b58 libtommath-orig ltm-0.30-orig

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
ltm 0.30 orig import
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:25:22 +0000
parents
children d29b64170cf0
comparison
equal deleted inserted replaced
-1:000000000000 2:86e0b50a9b58
1 /* LibTomMath, multiple-precision integer library -- Tom St Denis
2 *
3 * LibTomMath is a library that provides multiple-precision
4 * integer arithmetic as well as number theoretic functionality.
5 *
6 * The library was designed directly after the MPI library by
7 * Michael Fromberger but has been written from scratch with
8 * additional optimizations in place.
9 *
10 * The library is free for all purposes without any express
11 * guarantee it works.
12 *
13 * Tom St Denis, [email protected], http://math.libtomcrypt.org
14 */
15 #include <tommath.h>
16
17 /* high level multiplication (handles sign) */
18 int mp_mul (mp_int * a, mp_int * b, mp_int * c)
19 {
20 int res, neg;
21 neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
22
23 /* use Toom-Cook? */
24 if (MIN (a->used, b->used) >= TOOM_MUL_CUTOFF) {
25 res = mp_toom_mul(a, b, c);
26 /* use Karatsuba? */
27 } else if (MIN (a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
28 res = mp_karatsuba_mul (a, b, c);
29 } else {
30 /* can we use the fast multiplier?
31 *
32 * The fast multiplier can be used if the output will
33 * have less than MP_WARRAY digits and the number of
34 * digits won't affect carry propagation
35 */
36 int digs = a->used + b->used + 1;
37
38 if ((digs < MP_WARRAY) &&
39 MIN(a->used, b->used) <=
40 (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) {
41 res = fast_s_mp_mul_digs (a, b, c, digs);
42 } else {
43 res = s_mp_mul (a, b, c);
44 }
45 }
46 c->sign = neg;
47 return res;
48 }