annotate bn_s_mp_add.c @ 387:4663ced4968f libtommath-dropbear

propagate from branch 'au.asn.ucc.matt.ltm.orig' (head 1c2b7d389d0682caf980235dad97493e3206389c) to branch 'au.asn.ucc.matt.ltm.dropbear' (head 40ab3795de3a6157f34e52ed3f0be3eebe9a2eaa)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 03:13:04 +0000
parents 97db060d0ef5
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
282
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
1 #include <tommath.h>
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
2 #ifdef BN_S_MP_ADD_C
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
4 *
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
5 * LibTomMath is a library that provides multiple-precision
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
6 * integer arithmetic as well as number theoretic functionality.
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
7 *
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
8 * The library was designed directly after the MPI library by
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
9 * Michael Fromberger but has been written from scratch with
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
10 * additional optimizations in place.
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
11 *
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
12 * The library is free for all purposes without any express
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
13 * guarantee it works.
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
14 *
386
97db060d0ef5 Update to LibTomMath 0.40
Matt Johnston <matt@ucc.asn.au>
parents: 282
diff changeset
15 * Tom St Denis, [email protected], http://math.libtomcrypt.com
282
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
16 */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
17
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
18 /* low level addition, based on HAC pp.594, Algorithm 14.7 */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
19 int
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
20 s_mp_add (mp_int * a, mp_int * b, mp_int * c)
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
21 {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
22 mp_int *x;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
23 int olduse, res, min, max;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
24
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
25 /* find sizes, we let |a| <= |b| which means we have to sort
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
26 * them. "x" will point to the input with the most digits
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
27 */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
28 if (a->used > b->used) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
29 min = b->used;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
30 max = a->used;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
31 x = a;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
32 } else {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
33 min = a->used;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
34 max = b->used;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
35 x = b;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
36 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
37
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
38 /* init result */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
39 if (c->alloc < max + 1) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
40 if ((res = mp_grow (c, max + 1)) != MP_OKAY) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
41 return res;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
42 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
43 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
44
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
45 /* get old used digit count and set new one */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
46 olduse = c->used;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
47 c->used = max + 1;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
48
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
49 {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
50 register mp_digit u, *tmpa, *tmpb, *tmpc;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
51 register int i;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
52
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
53 /* alias for digit pointers */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
54
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
55 /* first input */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
56 tmpa = a->dp;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
57
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
58 /* second input */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
59 tmpb = b->dp;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
60
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
61 /* destination */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
62 tmpc = c->dp;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
63
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
64 /* zero the carry */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
65 u = 0;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
66 for (i = 0; i < min; i++) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
67 /* Compute the sum at one digit, T[i] = A[i] + B[i] + U */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
68 *tmpc = *tmpa++ + *tmpb++ + u;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
69
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
70 /* U = carry bit of T[i] */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
71 u = *tmpc >> ((mp_digit)DIGIT_BIT);
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
72
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
73 /* take away carry bit from T[i] */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
74 *tmpc++ &= MP_MASK;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
75 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
76
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
77 /* now copy higher words if any, that is in A+B
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
78 * if A or B has more digits add those in
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
79 */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
80 if (min != max) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
81 for (; i < max; i++) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
82 /* T[i] = X[i] + U */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
83 *tmpc = x->dp[i] + u;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
84
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
85 /* U = carry bit of T[i] */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
86 u = *tmpc >> ((mp_digit)DIGIT_BIT);
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
87
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
88 /* take away carry bit from T[i] */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
89 *tmpc++ &= MP_MASK;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
90 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
91 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
92
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
93 /* add carry */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
94 *tmpc++ = u;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
95
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
96 /* clear digits above oldused */
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
97 for (i = c->used; i < olduse; i++) {
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
98 *tmpc++ = 0;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
99 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
100 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
101
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
102 mp_clamp (c);
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
103 return MP_OKAY;
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
104 }
91fbc376f010 Import of libtommath 0.35
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
105 #endif
386
97db060d0ef5 Update to LibTomMath 0.40
Matt Johnston <matt@ucc.asn.au>
parents: 282
diff changeset
106
97db060d0ef5 Update to LibTomMath 0.40
Matt Johnston <matt@ucc.asn.au>
parents: 282
diff changeset
107 /* $Source: /cvs/libtom/libtommath/bn_s_mp_add.c,v $ */
97db060d0ef5 Update to LibTomMath 0.40
Matt Johnston <matt@ucc.asn.au>
parents: 282
diff changeset
108 /* $Revision: 1.3 $ */
97db060d0ef5 Update to LibTomMath 0.40
Matt Johnston <matt@ucc.asn.au>
parents: 282
diff changeset
109 /* $Date: 2006/03/31 14:18:44 $ */