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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: gfx-sqr.c,v 1.1.4.1 2004/03/21 22:39:46 mdw Exp $ |
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4 | * |
5 | * Sqaring binary polynomials |
6 | * |
7 | * (c) 2000 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: gfx-sqr.c,v $ |
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33 | * Revision 1.1.4.1 2004/03/21 22:39:46 mdw |
34 | * Elliptic curves on binary fields work. |
35 | * |
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36 | * Revision 1.1 2000/10/08 15:49:37 mdw |
37 | * First glimmerings of binary polynomial arithmetic. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include "mpx.h" |
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44 | #include "gfx.h" |
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45 | #include "gfx-sqr-tab.h" |
46 | |
47 | /*----- Static variables --------------------------------------------------*/ |
48 | |
49 | static uint16 tab[256] = GFX_SQRTAB; |
50 | |
51 | /*----- Main code ---------------------------------------------------------*/ |
52 | |
53 | /* --- @gfx_sqr@ --- * |
54 | * |
55 | * Arguments: @mpw *dv, *dvl@ = destination vector base and limit |
56 | * @const mpw *av, *avl@ = argument vector base and limit |
57 | * |
58 | * Returns: --- |
59 | * |
60 | * Use: Performs squaring of binary polynomials. |
61 | */ |
62 | |
63 | void gfx_sqr(mpw *dv, mpw *dvl, const mpw *av, const mpw *avl) |
64 | { |
65 | mpd a = 0, aa = 0; |
66 | unsigned b = 0, bb = 0; |
67 | |
68 | /* --- Simple stuff --- */ |
69 | |
70 | if (dv >= dvl) |
71 | return; |
72 | MPX_SHRINK(av, avl); |
73 | |
74 | /* --- The main algorithm --- * |
75 | * |
76 | * Our method depends on the fact that, in a field of characteristic 2, we |
77 | * have that %$(a + b)^2 = a^2 + b^2$%. Thus, to square a polynomial, it's |
78 | * sufficient just to put a zero bit between each of the bits of the |
79 | * original argument. We use a precomputed table for this, and work on |
80 | * entire octets at a time. Life is more complicated because we've got to |
81 | * be careful of bizarre architectures which don't have words with a |
82 | * multiple of 8 bits in them. |
83 | */ |
84 | |
85 | for (;;) { |
86 | |
87 | /* --- Input buffering --- */ |
88 | |
89 | if (b < 8) { |
90 | if (av >= avl) |
91 | break; |
92 | a |= *av++ << b; |
93 | b += MPW_BITS; |
94 | } |
95 | |
96 | /* --- Do the work in the middle --- */ |
97 | |
98 | aa |= (mpd)(tab[U8(a)]) << bb; |
99 | bb += 16; |
100 | a >>= 8; |
101 | b -= 8; |
102 | |
103 | /* --- Output buffering --- */ |
104 | |
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105 | if (bb >= MPW_BITS) { |
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106 | *dv++ = MPW(aa); |
107 | if (dv >= dvl) |
108 | return; |
109 | aa >>= MPW_BITS; |
110 | bb -= MPW_BITS; |
111 | } |
112 | } |
113 | |
114 | /* --- Flush the input buffer --- */ |
115 | |
116 | if (b) for (;;) { |
117 | aa |= (mpd)(tab[U8(a)]) << bb; |
118 | bb += 16; |
119 | if (bb > MPW_BITS) { |
120 | *dv++ = MPW(aa); |
121 | if (dv >= dvl) |
122 | return; |
123 | aa >>= MPW_BITS; |
124 | bb -= MPW_BITS; |
125 | } |
126 | a >>= 8; |
127 | if (b <= 8) |
128 | break; |
129 | else |
130 | b -= 8; |
131 | } |
132 | |
133 | /* --- Flush the output buffer --- */ |
134 | |
135 | if (bb) for (;;) { |
136 | *dv++ = MPW(aa); |
137 | if (dv >= dvl) |
138 | return; |
139 | aa >>= MPW_BITS; |
140 | if (bb <= MPW_BITS) |
141 | break; |
142 | else |
143 | bb -= MPW_BITS; |
144 | } |
145 | |
146 | /* --- Zero the rest of everything --- */ |
147 | |
148 | MPX_ZERO(dv, dvl); |
149 | } |
150 | |
151 | /*----- Test rig ----------------------------------------------------------*/ |
152 | |
153 | #ifdef TEST_RIG |
154 | |
155 | #include <mLib/alloc.h> |
156 | #include <mLib/dstr.h> |
157 | #include <mLib/quis.h> |
158 | #include <mLib/testrig.h> |
159 | |
160 | #define ALLOC(v, vl, sz) do { \ |
161 | size_t _sz = (sz); \ |
162 | mpw *_vv = xmalloc(MPWS(_sz)); \ |
163 | mpw *_vvl = _vv + _sz; \ |
164 | (v) = _vv; \ |
165 | (vl) = _vvl; \ |
166 | } while (0) |
167 | |
168 | #define LOAD(v, vl, d) do { \ |
169 | const dstr *_d = (d); \ |
170 | mpw *_v, *_vl; \ |
171 | ALLOC(_v, _vl, MPW_RQ(_d->len)); \ |
172 | mpx_loadb(_v, _vl, _d->buf, _d->len); \ |
173 | (v) = _v; \ |
174 | (vl) = _vl; \ |
175 | } while (0) |
176 | |
177 | #define MAX(x, y) ((x) > (y) ? (x) : (y)) |
178 | |
179 | static void dumpmp(const char *msg, const mpw *v, const mpw *vl) |
180 | { |
181 | fputs(msg, stderr); |
182 | MPX_SHRINK(v, vl); |
183 | while (v < vl) |
184 | fprintf(stderr, " %08lx", (unsigned long)*--vl); |
185 | fputc('\n', stderr); |
186 | } |
187 | |
188 | static int vsqr(dstr *v) |
189 | { |
190 | mpw *a, *al; |
191 | mpw *b, *bl; |
192 | mpw *d, *dl; |
193 | int ok = 1; |
194 | |
195 | LOAD(a, al, &v[0]); |
196 | LOAD(b, bl, &v[1]); |
197 | ALLOC(d, dl, 2 * (al - a)); |
198 | |
199 | gfx_sqr(d, dl, a, al); |
200 | if (!mpx_ueq(d, dl, b, bl)) { |
201 | fprintf(stderr, "\n*** vsqr failed\n"); |
202 | dumpmp(" a", a, al); |
203 | dumpmp("expected", b, bl); |
204 | dumpmp(" result", d, dl); |
205 | ok = 0; |
206 | } |
207 | |
208 | free(a); free(b); free(d); |
209 | return (ok); |
210 | } |
211 | |
212 | static test_chunk defs[] = { |
213 | { "sqr", vsqr, { &type_hex, &type_hex, 0 } }, |
214 | { 0, 0, { 0 } } |
215 | }; |
216 | |
217 | int main(int argc, char *argv[]) |
218 | { |
219 | test_run(argc, argv, defs, SRCDIR"/tests/gfx"); |
220 | return (0); |
221 | } |
222 | |
223 | #endif |
224 | |
225 | /*----- That's all, folks -------------------------------------------------*/ |