annotate bn_s_mp_mul_high_digs.c @ 190:d8254fc979e9 libtommath-orig LTM_0.35

Initial import of libtommath 0.35
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 08:59:30 +0000
parents d29b64170cf0
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
142
d29b64170cf0 import of libtommath 0.32
Matt Johnston <matt@ucc.asn.au>
parents: 2
diff changeset
1 #include <tommath.h>
d29b64170cf0 import of libtommath 0.32
Matt Johnston <matt@ucc.asn.au>
parents: 2
diff changeset
2 #ifdef BN_S_MP_MUL_HIGH_DIGS_C
2
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
4 *
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
5 * LibTomMath is a library that provides multiple-precision
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
6 * integer arithmetic as well as number theoretic functionality.
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
7 *
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
8 * The library was designed directly after the MPI library by
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
9 * Michael Fromberger but has been written from scratch with
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
10 * additional optimizations in place.
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
11 *
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
12 * The library is free for all purposes without any express
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
13 * guarantee it works.
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
14 *
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
16 */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
17
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
18 /* multiplies |a| * |b| and does not compute the lower digs digits
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
19 * [meant to get the higher part of the product]
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
20 */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
21 int
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
22 s_mp_mul_high_digs (mp_int * a, mp_int * b, mp_int * c, int digs)
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
23 {
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
24 mp_int t;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
25 int res, pa, pb, ix, iy;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
26 mp_digit u;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
27 mp_word r;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
28 mp_digit tmpx, *tmpt, *tmpy;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
29
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
30 /* can we use the fast multiplier? */
142
d29b64170cf0 import of libtommath 0.32
Matt Johnston <matt@ucc.asn.au>
parents: 2
diff changeset
31 #ifdef BN_FAST_S_MP_MUL_HIGH_DIGS_C
2
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
32 if (((a->used + b->used + 1) < MP_WARRAY)
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
33 && MIN (a->used, b->used) < (1 << ((CHAR_BIT * sizeof (mp_word)) - (2 * DIGIT_BIT)))) {
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
34 return fast_s_mp_mul_high_digs (a, b, c, digs);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
35 }
142
d29b64170cf0 import of libtommath 0.32
Matt Johnston <matt@ucc.asn.au>
parents: 2
diff changeset
36 #endif
2
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
37
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
38 if ((res = mp_init_size (&t, a->used + b->used + 1)) != MP_OKAY) {
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
39 return res;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
40 }
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
41 t.used = a->used + b->used + 1;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
42
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
43 pa = a->used;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
44 pb = b->used;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
45 for (ix = 0; ix < pa; ix++) {
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
46 /* clear the carry */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
47 u = 0;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
48
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
49 /* left hand side of A[ix] * B[iy] */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
50 tmpx = a->dp[ix];
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
51
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
52 /* alias to the address of where the digits will be stored */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
53 tmpt = &(t.dp[digs]);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
54
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
55 /* alias for where to read the right hand side from */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
56 tmpy = b->dp + (digs - ix);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
57
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
58 for (iy = digs - ix; iy < pb; iy++) {
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
59 /* calculate the double precision result */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
60 r = ((mp_word)*tmpt) +
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
61 ((mp_word)tmpx) * ((mp_word)*tmpy++) +
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
62 ((mp_word) u);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
63
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
64 /* get the lower part */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
65 *tmpt++ = (mp_digit) (r & ((mp_word) MP_MASK));
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
66
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
67 /* carry the carry */
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
68 u = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
69 }
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
70 *tmpt = u;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
71 }
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
72 mp_clamp (&t);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
73 mp_exch (&t, c);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
74 mp_clear (&t);
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
75 return MP_OKAY;
86e0b50a9b58 ltm 0.30 orig import
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
76 }
142
d29b64170cf0 import of libtommath 0.32
Matt Johnston <matt@ucc.asn.au>
parents: 2
diff changeset
77 #endif