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1 | /* -*-c-*- |
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2 | * |
3 | * Sqaring binary polynomials |
4 | * |
5 | * (c) 2000 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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16 | * |
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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. |
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21 | * |
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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 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include "mpx.h" |
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31 | #include "gfx.h" |
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32 | |
33 | /*----- Static variables --------------------------------------------------*/ |
34 | |
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35 | extern const uint16 gfx_sqrtab[256]; |
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36 | |
37 | /*----- Main code ---------------------------------------------------------*/ |
38 | |
39 | /* --- @gfx_sqr@ --- * |
40 | * |
41 | * Arguments: @mpw *dv, *dvl@ = destination vector base and limit |
42 | * @const mpw *av, *avl@ = argument vector base and limit |
43 | * |
44 | * Returns: --- |
45 | * |
46 | * Use: Performs squaring of binary polynomials. |
47 | */ |
48 | |
49 | void gfx_sqr(mpw *dv, mpw *dvl, const mpw *av, const mpw *avl) |
50 | { |
51 | mpd a = 0, aa = 0; |
52 | unsigned b = 0, bb = 0; |
53 | |
54 | /* --- Simple stuff --- */ |
55 | |
56 | if (dv >= dvl) |
57 | return; |
58 | MPX_SHRINK(av, avl); |
59 | |
60 | /* --- The main algorithm --- * |
61 | * |
62 | * Our method depends on the fact that, in a field of characteristic 2, we |
63 | * have that %$(a + b)^2 = a^2 + b^2$%. Thus, to square a polynomial, it's |
64 | * sufficient just to put a zero bit between each of the bits of the |
65 | * original argument. We use a precomputed table for this, and work on |
66 | * entire octets at a time. Life is more complicated because we've got to |
67 | * be careful of bizarre architectures which don't have words with a |
68 | * multiple of 8 bits in them. |
69 | */ |
70 | |
71 | for (;;) { |
72 | |
73 | /* --- Input buffering --- */ |
74 | |
75 | if (b < 8) { |
76 | if (av >= avl) |
77 | break; |
78 | a |= *av++ << b; |
79 | b += MPW_BITS; |
80 | } |
81 | |
82 | /* --- Do the work in the middle --- */ |
83 | |
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84 | aa |= (mpd)(gfx_sqrtab[U8(a)]) << bb; |
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85 | bb += 16; |
86 | a >>= 8; |
87 | b -= 8; |
88 | |
89 | /* --- Output buffering --- */ |
90 | |
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91 | if (bb >= MPW_BITS) { |
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92 | *dv++ = MPW(aa); |
93 | if (dv >= dvl) |
94 | return; |
95 | aa >>= MPW_BITS; |
96 | bb -= MPW_BITS; |
97 | } |
98 | } |
99 | |
100 | /* --- Flush the input buffer --- */ |
101 | |
102 | if (b) for (;;) { |
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103 | aa |= (mpd)(gfx_sqrtab[U8(a)]) << bb; |
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104 | bb += 16; |
105 | if (bb > MPW_BITS) { |
106 | *dv++ = MPW(aa); |
107 | if (dv >= dvl) |
108 | return; |
109 | aa >>= MPW_BITS; |
110 | bb -= MPW_BITS; |
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111 | } |
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112 | a >>= 8; |
113 | if (b <= 8) |
114 | break; |
115 | else |
116 | b -= 8; |
117 | } |
118 | |
119 | /* --- Flush the output buffer --- */ |
120 | |
121 | if (bb) for (;;) { |
122 | *dv++ = MPW(aa); |
123 | if (dv >= dvl) |
124 | return; |
125 | aa >>= MPW_BITS; |
126 | if (bb <= MPW_BITS) |
127 | break; |
128 | else |
129 | bb -= MPW_BITS; |
130 | } |
131 | |
132 | /* --- Zero the rest of everything --- */ |
133 | |
134 | MPX_ZERO(dv, dvl); |
135 | } |
136 | |
137 | /*----- Test rig ----------------------------------------------------------*/ |
138 | |
139 | #ifdef TEST_RIG |
140 | |
141 | #include <mLib/alloc.h> |
142 | #include <mLib/dstr.h> |
143 | #include <mLib/quis.h> |
144 | #include <mLib/testrig.h> |
145 | |
146 | #define ALLOC(v, vl, sz) do { \ |
147 | size_t _sz = (sz); \ |
148 | mpw *_vv = xmalloc(MPWS(_sz)); \ |
149 | mpw *_vvl = _vv + _sz; \ |
150 | (v) = _vv; \ |
151 | (vl) = _vvl; \ |
152 | } while (0) |
153 | |
154 | #define LOAD(v, vl, d) do { \ |
155 | const dstr *_d = (d); \ |
156 | mpw *_v, *_vl; \ |
157 | ALLOC(_v, _vl, MPW_RQ(_d->len)); \ |
158 | mpx_loadb(_v, _vl, _d->buf, _d->len); \ |
159 | (v) = _v; \ |
160 | (vl) = _vl; \ |
161 | } while (0) |
162 | |
163 | #define MAX(x, y) ((x) > (y) ? (x) : (y)) |
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164 | |
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165 | static void dumpmp(const char *msg, const mpw *v, const mpw *vl) |
166 | { |
167 | fputs(msg, stderr); |
168 | MPX_SHRINK(v, vl); |
169 | while (v < vl) |
170 | fprintf(stderr, " %08lx", (unsigned long)*--vl); |
171 | fputc('\n', stderr); |
172 | } |
173 | |
174 | static int vsqr(dstr *v) |
175 | { |
176 | mpw *a, *al; |
177 | mpw *b, *bl; |
178 | mpw *d, *dl; |
179 | int ok = 1; |
180 | |
181 | LOAD(a, al, &v[0]); |
182 | LOAD(b, bl, &v[1]); |
183 | ALLOC(d, dl, 2 * (al - a)); |
184 | |
185 | gfx_sqr(d, dl, a, al); |
186 | if (!mpx_ueq(d, dl, b, bl)) { |
187 | fprintf(stderr, "\n*** vsqr failed\n"); |
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188 | dumpmp(" a", a, al); |
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189 | dumpmp("expected", b, bl); |
190 | dumpmp(" result", d, dl); |
191 | ok = 0; |
192 | } |
193 | |
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194 | xfree(a); xfree(b); xfree(d); |
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195 | return (ok); |
196 | } |
197 | |
198 | static test_chunk defs[] = { |
199 | { "sqr", vsqr, { &type_hex, &type_hex, 0 } }, |
200 | { 0, 0, { 0 } } |
201 | }; |
202 | |
203 | int main(int argc, char *argv[]) |
204 | { |
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205 | test_run(argc, argv, defs, SRCDIR"/t/gfx"); |
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206 | return (0); |
207 | } |
208 | |
209 | #endif |
210 | |
211 | /*----- That's all, folks -------------------------------------------------*/ |