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math/mpint.[ch]: Consolidate the list of supplied conversions in header.
[catacomb] / math / mpint.h
1 /* -*-c-*-
2 *
3 * Conversion between MPs and standard C integers
4 *
5 * (c) 1999 Straylight/Edgeware
6 */
7
8 /*----- Licensing notice --------------------------------------------------*
9 *
10 * This file is part of Catacomb.
11 *
12 * Catacomb is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
16 *
17 * Catacomb is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
21 *
22 * You should have received a copy of the GNU Library General Public
23 * License along with Catacomb; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
25 * MA 02111-1307, USA.
26 */
27
28 #ifndef CATACOMB_MPINT_H
29 #define CATACOMB_MPINT_H
30
31 #ifdef __cplusplus
32 extern "C" {
33 #endif
34
35 /*----- Header files ------------------------------------------------------*/
36
37 #include <limits.h>
38
39 #include <mLib/macros.h>
40
41 #ifndef CATACOMB_MP_H
42 # include "mp.h"
43 #endif
44
45 /*----- Generic translation macros ----------------------------------------*/
46
47 /* --- Warning damage control --- *
48 *
49 * GCC (at least) isn't clever enough to work out that the division in
50 * @MP_FROMINT@ is actually safe (since it will only be executed if @_i >
51 * MPW_MAX@, which would prove that @(type)MPW_MAX + 1 != 0@).
52 */
53
54 /* --- @MP_FROMINT@ --- *
55 *
56 * Arguments: @d@ = destination multiprecision integer
57 * @type@ = type of integer which @i@ is
58 * @i@ = a standard C integer
59 *
60 * Use: Stores the value of @i@ in @d@. This macro is actually
61 * rather subtle in places. Be careful what you change.
62 */
63
64 #define MP_FROMINT(d, type, i) do { \
65 type _i = (i); \
66 size_t _o = 0; \
67 mp *_d = (d); \
68 size_t _sz = 4; \
69 \
70 MP_DEST(_d, _sz, 0); \
71 _d->f &= ~(MP_NEG | MP_UNDEF); \
72 \
73 if (_i >= 0) { \
74 while (_i) { \
75 if (_o == _sz) { \
76 _sz <<= 1; \
77 MP_ENSURE(_d, _sz); \
78 } \
79 _d->v[_o++] = MPW(_i); \
80 if (_i <= MPW_MAX) \
81 break; \
82 else \
83 MUFFLE_WARNINGS_STMT(GCC_WARNING("-Wdiv-by-zero"), { \
84 _i /= (type)MPW_MAX + 1; \
85 }); \
86 } \
87 } else { \
88 _d->f |= MP_NEG; \
89 while (_i) { \
90 if (_o == _sz) { \
91 _sz <<= 1; \
92 MP_ENSURE(_d, _sz); \
93 } \
94 _d->v[_o++] = MPW(-_i); \
95 if (_i >= -MPW_MAX) \
96 break; \
97 else \
98 MUFFLE_WARNINGS_STMT(GCC_WARNING("-Wdiv-by-zero"), { \
99 _i /= (type)MPW_MAX + 1; \
100 }); \
101 } \
102 } \
103 \
104 _d->vl = _d->v + _o; \
105 (d) = _d; \
106 } while (0)
107
108 /* --- @MP_TOINT@ --- *
109 *
110 * Arguments: @m@ = a multiprecision integer
111 * @type@ = the type of @i@
112 * @max@ = the largest value @i@ can represent
113 * @i@ = an integer variable
114 *
115 * Use: Stores the value of a multiprecision integer in a standard C
116 * integer. If the value won't fit, the behaviour is determined
117 * by the type of @i@: if @i@ is unsigned, the value of the
118 * multiprecision integer modulo @max + 1@ is stored; if @i@ is
119 * signed, the behaviour is undefined.
120 *
121 * If you don't want to be bitten by these sorts of things, keep
122 * copies of @INT_MAX@ or whatever is appropriate in
123 * multiprecision form and compare before conversion.
124 */
125
126 #define MP_TOINT(m, type, max, i) do { \
127 type _i = 0; \
128 type _max = (max); \
129 unsigned _s = 0; \
130 const mp *_m = (m); \
131 const mpw *_v = _m->v, *_vl = _m->vl; \
132 \
133 /* --- Do all the arithmetic in negative numbers --- */ \
134 \
135 while (_v < _vl && _max > 0) { \
136 _i -= *_v << _s; \
137 _s += MPW_BITS; \
138 _v++; \
139 _max /= (mpd)MPW_MAX + 1; \
140 } \
141 if (!MP_NEGP(_m)) \
142 _i = -_i; \
143 (i) = _i; \
144 } while (0)
145
146 /*----- Functions provided ------------------------------------------------*/
147
148 /* --- Build up the list of conversions to be supplied --- */
149
150 #define MPINT_CONVERSIONS(_) \
151 _(short, short, SHRT_MAX) \
152 _(ushort, unsigned short, USHRT_MAX) \
153 _(int, int, INT_MAX) \
154 _(uint, unsigned, UINT_MAX) \
155 _(long, long, LONG_MAX) \
156 _(ulong, unsigned long, ULONG_MAX) \
157 _(uint32, uint32, MASK32)
158
159 /* --- @mp_fromINT@ --- *
160 *
161 * Arguments: @mp *d@ = pointer to destination multiprecision integer
162 * @INT i@ = standard C integer to convert
163 *
164 * Returns: The resulting multiprecision integer.
165 *
166 * Use: Converts a standard C integer to a multiprecision integer.
167 */
168
169 #define mp_fromINT(name, type, max) \
170 extern mp *mp_from##name(mp */*d*/, type /*i*/);
171 MPINT_CONVERSIONS(mp_fromINT)
172 #undef mp_fromINT
173
174 /* --- @mp_toINT@ --- *
175 *
176 * Arguments: @const mp *m@ = pointer to a multiprecision integer
177 *
178 * Returns: The value of the integer @m@ as a C integer.
179 *
180 * Use: Converts a multiprecision integer to a standard C integer.
181 * If the value of the multiprecision integer cannot be
182 * represented in the return type, and the return type is
183 * unsigned, it is reduced modulo @TYPE_MAX + 1@; if the return
184 * type is signed, the behaviour is undefined.
185 */
186
187 #define mp_toINT(name, type, max) \
188 extern type mp_to##name(const mp */*m*/);
189 MPINT_CONVERSIONS(mp_toINT)
190 #undef mp_toINT
191
192 /*----- That's all, folks -------------------------------------------------*/
193
194 #ifdef __cplusplus
195 }
196 #endif
197
198 #endif
Catacomb cryptographic library