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1 | /* mpi-add.c - MPI functions |
2 | * Copyright (C) 1994, 1996, 1998, 2001, 2002, | |
3 | * 2003 Free Software Foundation, Inc. | |
4 | * | |
5 | * This file is part of Libgcrypt. | |
6 | * | |
7 | * Note: This code is heavily based on the GNU MP Library. | |
8 | * Actually it's the same code with only minor changes in the | |
9 | * way the data is stored; this is to support the abstraction | |
10 | * of an optional secure memory allocation which may be used | |
11 | * to avoid revealing of sensitive data due to paging etc. | |
12 | */ | |
13 | ||
14 | #include "mpi-internal.h" | |
15 | ||
16 | /**************** | |
17 | * Add the unsigned integer V to the mpi-integer U and store the | |
18 | * result in W. U and V may be the same. | |
19 | */ | |
20 | void mpi_add_ui(MPI w, MPI u, unsigned long v) | |
21 | { | |
22 | mpi_ptr_t wp, up; | |
23 | mpi_size_t usize, wsize; | |
24 | int usign, wsign; | |
25 | ||
26 | usize = u->nlimbs; | |
27 | usign = u->sign; | |
28 | wsign = 0; | |
29 | ||
30 | /* If not space for W (and possible carry), increase space. */ | |
31 | wsize = usize + 1; | |
32 | if (w->alloced < wsize) | |
33 | mpi_resize(w, wsize); | |
34 | ||
35 | /* These must be after realloc (U may be the same as W). */ | |
36 | up = u->d; | |
37 | wp = w->d; | |
38 | ||
39 | if (!usize) { /* simple */ | |
40 | wp[0] = v; | |
41 | wsize = v ? 1:0; | |
42 | } else if (!usign) { /* mpi is not negative */ | |
43 | mpi_limb_t cy; | |
44 | cy = mpihelp_add_1(wp, up, usize, v); | |
45 | wp[usize] = cy; | |
46 | wsize = usize + cy; | |
47 | } else { | |
48 | /* The signs are different. Need exact comparison to determine | |
49 | * which operand to subtract from which. | |
50 | */ | |
51 | if (usize == 1 && up[0] < v) { | |
52 | wp[0] = v - up[0]; | |
53 | wsize = 1; | |
54 | } else { | |
55 | mpihelp_sub_1(wp, up, usize, v); | |
56 | /* Size can decrease with at most one limb. */ | |
57 | wsize = usize - (wp[usize-1] == 0); | |
58 | wsign = 1; | |
59 | } | |
60 | } | |
61 | ||
62 | w->nlimbs = wsize; | |
63 | w->sign = wsign; | |
64 | } | |
65 | ||
66 | ||
67 | void mpi_add(MPI w, MPI u, MPI v) | |
68 | { | |
69 | mpi_ptr_t wp, up, vp; | |
70 | mpi_size_t usize, vsize, wsize; | |
71 | int usign, vsign, wsign; | |
72 | ||
73 | if (u->nlimbs < v->nlimbs) { /* Swap U and V. */ | |
74 | usize = v->nlimbs; | |
75 | usign = v->sign; | |
76 | vsize = u->nlimbs; | |
77 | vsign = u->sign; | |
78 | wsize = usize + 1; | |
79 | RESIZE_IF_NEEDED(w, wsize); | |
80 | /* These must be after realloc (u or v may be the same as w). */ | |
81 | up = v->d; | |
82 | vp = u->d; | |
83 | } else { | |
84 | usize = u->nlimbs; | |
85 | usign = u->sign; | |
86 | vsize = v->nlimbs; | |
87 | vsign = v->sign; | |
88 | wsize = usize + 1; | |
89 | RESIZE_IF_NEEDED(w, wsize); | |
90 | /* These must be after realloc (u or v may be the same as w). */ | |
91 | up = u->d; | |
92 | vp = v->d; | |
93 | } | |
94 | wp = w->d; | |
95 | wsign = 0; | |
96 | ||
97 | if (!vsize) { /* simple */ | |
98 | MPN_COPY(wp, up, usize); | |
99 | wsize = usize; | |
100 | wsign = usign; | |
101 | } else if (usign != vsign) { /* different sign */ | |
102 | /* This test is right since USIZE >= VSIZE */ | |
103 | if (usize != vsize) { | |
104 | mpihelp_sub(wp, up, usize, vp, vsize); | |
105 | wsize = usize; | |
106 | MPN_NORMALIZE(wp, wsize); | |
107 | wsign = usign; | |
108 | } else if (mpihelp_cmp(up, vp, usize) < 0) { | |
109 | mpihelp_sub_n(wp, vp, up, usize); | |
110 | wsize = usize; | |
111 | MPN_NORMALIZE(wp, wsize); | |
112 | if (!usign) | |
113 | wsign = 1; | |
114 | } else { | |
115 | mpihelp_sub_n(wp, up, vp, usize); | |
116 | wsize = usize; | |
117 | MPN_NORMALIZE(wp, wsize); | |
118 | if (usign) | |
119 | wsign = 1; | |
120 | } | |
121 | } else { /* U and V have same sign. Add them. */ | |
122 | mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize); | |
123 | wp[usize] = cy; | |
124 | wsize = usize + cy; | |
125 | if (usign) | |
126 | wsign = 1; | |
127 | } | |
128 | ||
129 | w->nlimbs = wsize; | |
130 | w->sign = wsign; | |
131 | } | |
132 | EXPORT_SYMBOL_GPL(mpi_add); | |
133 | ||
134 | void mpi_sub(MPI w, MPI u, MPI v) | |
135 | { | |
136 | MPI vv = mpi_copy(v); | |
137 | vv->sign = !vv->sign; | |
138 | mpi_add(w, u, vv); | |
139 | mpi_free(vv); | |
140 | } | |
f145d411 | 141 | EXPORT_SYMBOL_GPL(mpi_sub); |
a8ea8bdd TZ |
142 | |
143 | void mpi_addm(MPI w, MPI u, MPI v, MPI m) | |
144 | { | |
145 | mpi_add(w, u, v); | |
146 | mpi_mod(w, w, m); | |
147 | } | |
148 | EXPORT_SYMBOL_GPL(mpi_addm); | |
149 | ||
150 | void mpi_subm(MPI w, MPI u, MPI v, MPI m) | |
151 | { | |
152 | mpi_sub(w, u, v); | |
153 | mpi_mod(w, w, m); | |
154 | } | |
155 | EXPORT_SYMBOL_GPL(mpi_subm); |