1 /* mpi-add.c - MPI functions 1
2 * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3 * 2003 Free Software Foundation
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Note: This code is heavily based on the GNU
8 * Actually it's the same code with only
9 * way the data is stored; this is to su
10 * of an optional secure memory allocati
11 * to avoid revealing of sensitive data
12 */
13
14 #include "mpi-internal.h"
15
16 int mpi_add(MPI w, MPI u, MPI v)
17 {
18 mpi_ptr_t wp, up, vp;
19 mpi_size_t usize, vsize, wsize;
20 int usign, vsign, wsign;
21 int err;
22
23 if (u->nlimbs < v->nlimbs) { /* Swap U
24 usize = v->nlimbs;
25 usign = v->sign;
26 vsize = u->nlimbs;
27 vsign = u->sign;
28 wsize = usize + 1;
29 err = RESIZE_IF_NEEDED(w, wsiz
30 if (err)
31 return err;
32 /* These must be after realloc
33 up = v->d;
34 vp = u->d;
35 } else {
36 usize = u->nlimbs;
37 usign = u->sign;
38 vsize = v->nlimbs;
39 vsign = v->sign;
40 wsize = usize + 1;
41 err = RESIZE_IF_NEEDED(w, wsiz
42 if (err)
43 return err;
44 /* These must be after realloc
45 up = u->d;
46 vp = v->d;
47 }
48 wp = w->d;
49 wsign = 0;
50
51 if (!vsize) { /* simple */
52 MPN_COPY(wp, up, usize);
53 wsize = usize;
54 wsign = usign;
55 } else if (usign != vsign) { /* differ
56 /* This test is right since US
57 if (usize != vsize) {
58 mpihelp_sub(wp, up, us
59 wsize = usize;
60 MPN_NORMALIZE(wp, wsiz
61 wsign = usign;
62 } else if (mpihelp_cmp(up, vp,
63 mpihelp_sub_n(wp, vp,
64 wsize = usize;
65 MPN_NORMALIZE(wp, wsiz
66 if (!usign)
67 wsign = 1;
68 } else {
69 mpihelp_sub_n(wp, up,
70 wsize = usize;
71 MPN_NORMALIZE(wp, wsiz
72 if (usign)
73 wsign = 1;
74 }
75 } else { /* U and V have same sign. Ad
76 mpi_limb_t cy = mpihelp_add(wp
77 wp[usize] = cy;
78 wsize = usize + cy;
79 if (usign)
80 wsign = 1;
81 }
82
83 w->nlimbs = wsize;
84 w->sign = wsign;
85 return 0;
86 }
87 EXPORT_SYMBOL_GPL(mpi_add);
88
89 int mpi_sub(MPI w, MPI u, MPI v)
90 {
91 int err;
92 MPI vv;
93
94 vv = mpi_copy(v);
95 if (!vv)
96 return -ENOMEM;
97
98 vv->sign = !vv->sign;
99 err = mpi_add(w, u, vv);
100 mpi_free(vv);
101
102 return err;
103 }
104 EXPORT_SYMBOL_GPL(mpi_sub);
105
106 int mpi_addm(MPI w, MPI u, MPI v, MPI m)
107 {
108 return mpi_add(w, u, v) ?:
109 mpi_mod(w, w, m);
110 }
111 EXPORT_SYMBOL_GPL(mpi_addm);
112
113 int mpi_subm(MPI w, MPI u, MPI v, MPI m)
114 {
115 return mpi_sub(w, u, v) ?:
116 mpi_mod(w, w, m);
117 }
118 EXPORT_SYMBOL_GPL(mpi_subm);
119
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