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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: mpscan.h,v 1.4 2000/07/29 17:03:31 mdw Exp $ |
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4 | * |
5 | * Sequential bit scan of multiprecision integers |
6 | * |
7 | * (c) 1999 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: mpscan.h,v $ |
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33 | * Revision 1.4 2000/07/29 17:03:31 mdw |
34 | * Add support for left-to-right bitscanning, for use in modular |
35 | * exponentiation. |
36 | * |
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37 | * Revision 1.3 1999/12/10 23:29:48 mdw |
38 | * Change header file guard names. |
39 | * |
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40 | * Revision 1.2 1999/11/13 01:55:10 mdw |
41 | * Fixed so that they compile. Minor interface changes. |
42 | * |
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43 | * Revision 1.1 1999/09/03 08:41:12 mdw |
44 | * Initial import. |
45 | * |
46 | */ |
47 | |
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48 | #ifndef CATACOMB_MPSCAN_H |
49 | #define CATACOMB_MPSCAN_H |
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50 | |
51 | #ifdef __cplusplus |
52 | extern "C" { |
53 | #endif |
54 | |
55 | /*----- Header files ------------------------------------------------------*/ |
56 | |
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57 | #ifndef CATACOMB_MPW_H |
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58 | # include "mpw.h" |
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59 | #endif |
60 | |
61 | /*----- Data structures ---------------------------------------------------*/ |
62 | |
63 | typedef struct mpscan { |
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64 | const mpw *v, *vl; /* Vector of words to scan */ |
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65 | mpw w; /* Current word to scan */ |
66 | int bits; /* Number of bits left in @w@ */ |
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67 | } mpscan; |
68 | |
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69 | /*----- Right-to-left scanning --------------------------------------------*/ |
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70 | |
71 | /* --- @mpscan_initx@ --- * |
72 | * |
73 | * Arguments: @mpscan *m@ = pointer to bitscanner structure |
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74 | * @const mpw *v, *vl@ = vector of words to scan |
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75 | * |
76 | * Returns: --- |
77 | * |
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78 | * Use: Initializes a bitscanner from a low-level base-and-limit |
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79 | * representation of an integer. Initially no bit is ready; you |
80 | * must call @mpscan_step@ before anything useful will come |
81 | * out. |
82 | */ |
83 | |
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84 | #define MPSCAN_INITX(m_, v_, vl_) do { \ |
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85 | mpscan *_m = (m_); \ |
86 | _m->v = (v_); \ |
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87 | _m->vl = (vl_); \ |
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88 | _m->bits = 0; \ |
89 | } while (0) |
90 | |
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91 | extern void mpscan_initx(mpscan */*m*/, const mpw */*v*/, const mpw */*vl*/); |
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92 | |
93 | /* --- @mpscan_step@ --- * |
94 | * |
95 | * Arguments: @mpscan *m@ = pointer to bitscanner |
96 | * |
97 | * Returns: Nonzero if there is another bit to read. |
98 | * |
99 | * Use: Steps on to the next bit in the integer. The macro version |
100 | * evaluates its argument multiple times. |
101 | */ |
102 | |
103 | #define MPSCAN_STEP(m) \ |
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104 | ((m)->bits ? ((m)->w >>= 1, (m)->bits--, 1) : \ |
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105 | (m)->v < (m)->vl ? ((m)->w = *(m)->v++, \ |
106 | (m)->bits = MPW_BITS - 1, 1) : \ |
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107 | 0) |
108 | |
109 | extern int mpscan_step(mpscan */*m*/); |
110 | |
111 | /* --- @mpscan_bit@ --- * |
112 | * |
113 | * Arguments: @const mpscan *m@ = pointer to bitscanner |
114 | * |
115 | * Returns: The value of the current bit. |
116 | * |
117 | * Use: Reads the value of the current bit looked at by a |
118 | * bitscanner. |
119 | */ |
120 | |
121 | #define MPSCAN_BIT(m) ((m)->w & 1) |
122 | |
123 | extern int mpscan_bit(const mpscan */*m*/); |
124 | |
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125 | /*----- Left-to right-scanning --------------------------------------------*/ |
126 | |
127 | /* --- @mpscan_rinitx@ --- * |
128 | * |
129 | * Arguments: @mpscan *m@ = pointer to bitscanner structure |
130 | * @const mpw *v, *vl@ = vector of words to scan |
131 | * |
132 | * Returns: --- |
133 | * |
134 | * Use: Initializes a reverse bitscanner from a low-level |
135 | * vector-and-length representation of an integer. Initially no |
136 | * bit is ready; you must call @mpscan_rstep@ before anything |
137 | * useful will come out. |
138 | */ |
139 | |
140 | #define MPSCAN_RINITX(m_, v_, vl_) do { \ |
141 | mpscan *_m = (m_); \ |
142 | _m->v = (v_); \ |
143 | _m->vl = (vl_); \ |
144 | while (_m->vl > _m->v && !_m->vl[-1]) \ |
145 | _m->vl--; \ |
146 | _m->bits = 0; \ |
147 | } while (0) |
148 | |
149 | extern void mpscan_rinitx(mpscan */*m*/, |
150 | const mpw */*v*/, const mpw */*vl*/); |
151 | |
152 | /* --- @mpscan_rstep@ --- * |
153 | * |
154 | * Arguments: @mpscan *m@ = pointer to bitscanner |
155 | * |
156 | * Returns: Nonzero if there is another bit to read. |
157 | * |
158 | * Use: Steps on to the next bit in the integer. The macro version |
159 | * evaluates its argument multiple times. |
160 | */ |
161 | |
162 | #define MPSCAN_RSTEP(m) \ |
163 | ((m)->bits ? ((m)->w <<= 1, (m)->bits--, 1) : \ |
164 | (m)->vl > (m)->v ? ((m)->w = *--(m)->vl, \ |
165 | (m)->bits = MPW_BITS - 1, 1) : \ |
166 | 0) |
167 | |
168 | extern int mpscan_rstep(mpscan */*m*/); |
169 | |
170 | /* --- @mpscan_rbit@ --- * |
171 | * |
172 | * Arguments: @const mpscan *m@ = pointer to bitscanner |
173 | * |
174 | * Returns: The value of the current bit. |
175 | * |
176 | * Use: Reads the value of the current bit looked at by a |
177 | * reverse bitscanner. |
178 | */ |
179 | |
180 | #define MPSCAN_RBIT(m) (((m)->w >> (MPW_BITS - 1)) & 1) |
181 | |
182 | extern int mpscan_rbit(const mpscan */*m*/); |
183 | |
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184 | /*----- That's all, folks -------------------------------------------------*/ |
185 | |
186 | #ifdef __cplusplus |
187 | } |
188 | #endif |
189 | |
190 | #endif |