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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: exp.c,v 1.2 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * Generalized exponentiation |
6 | * |
7 | * (c) 2001 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 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #define EXP_TYPE /* Hack */ |
33 | #include "exp.h" |
34 | |
35 | /*----- Main code ---------------------------------------------------------*/ |
36 | |
37 | /* --- @exp_simulnext@ --- * |
38 | * |
39 | * Arguments: @exp_simul *e@ = pointer to state structure |
40 | * @size_t x@ = a current accumulator |
41 | * |
42 | * Returns: The next column of bits. |
43 | * |
44 | * Use: Scans the next column of bits for a simultaneous |
45 | * exponentiation. |
46 | */ |
47 | |
48 | size_t exp_simulnext(exp_simul *e, size_t x) |
49 | { |
50 | size_t i; |
51 | |
52 | /* --- Move to the next word along --- */ |
53 | |
54 | if (!e->b) { |
55 | e->o--; |
56 | for (i = 0; i < e->n; i++) |
57 | e->s[i].w = e->o < e->s[i].len ? e->s[i].v[e->o] : 0; |
58 | e->b = MPW_BITS; |
59 | } |
60 | |
61 | /* --- Scan out a column of bits --- */ |
62 | |
63 | for (i = 0; i < e->n; i++) { |
64 | x = (x << 1) | ((e->s[i].w >> (MPW_BITS - 1)) & 1u); |
65 | e->s[i].w <<= 1; |
66 | } |
67 | e->b--; |
68 | return (x); |
69 | } |
70 | |
71 | /*----- That's all, folks -------------------------------------------------*/ |