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1 | /* -*-c-*- |
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2 | * |
3 | * Sequential bit scan of multiprecision integers |
4 | * |
5 | * (c) 1999 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 | #ifndef CATACOMB_MPSCAN_H |
29 | #define CATACOMB_MPSCAN_H |
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30 | |
31 | #ifdef __cplusplus |
32 | extern "C" { |
33 | #endif |
34 | |
35 | /*----- Header files ------------------------------------------------------*/ |
36 | |
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37 | #ifndef CATACOMB_MPW_H |
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38 | # include "mpw.h" |
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39 | #endif |
40 | |
41 | /*----- Data structures ---------------------------------------------------*/ |
42 | |
43 | typedef struct mpscan { |
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44 | const mpw *v, *vl; /* Vector of words to scan */ |
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45 | mpw w; /* Current word to scan */ |
46 | int bits; /* Number of bits left in @w@ */ |
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47 | } mpscan; |
48 | |
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49 | /*----- Right-to-left scanning --------------------------------------------*/ |
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50 | |
51 | /* --- @mpscan_initx@ --- * |
52 | * |
53 | * Arguments: @mpscan *m@ = pointer to bitscanner structure |
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54 | * @const mpw *v, *vl@ = vector of words to scan |
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55 | * |
56 | * Returns: --- |
57 | * |
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58 | * Use: Initializes a bitscanner from a low-level base-and-limit |
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59 | * representation of an integer. Initially no bit is ready; you |
60 | * must call @mpscan_step@ before anything useful will come |
61 | * out. |
62 | */ |
63 | |
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64 | #define MPSCAN_INITX(m_, v_, vl_) do { \ |
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65 | mpscan *_m = (m_); \ |
66 | _m->v = (v_); \ |
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67 | _m->vl = (vl_); \ |
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68 | _m->bits = 0; \ |
69 | } while (0) |
70 | |
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71 | extern void mpscan_initx(mpscan */*m*/, const mpw */*v*/, const mpw */*vl*/); |
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72 | |
73 | /* --- @mpscan_step@ --- * |
74 | * |
75 | * Arguments: @mpscan *m@ = pointer to bitscanner |
76 | * |
77 | * Returns: Nonzero if there is another bit to read. |
78 | * |
79 | * Use: Steps on to the next bit in the integer. The macro version |
80 | * evaluates its argument multiple times. |
81 | */ |
82 | |
83 | #define MPSCAN_STEP(m) \ |
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84 | ((m)->bits ? ((m)->w >>= 1, (m)->bits--, 1) : \ |
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85 | (m)->v < (m)->vl ? ((m)->w = *(m)->v++, \ |
86 | (m)->bits = MPW_BITS - 1, 1) : \ |
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87 | 0) |
88 | |
89 | extern int mpscan_step(mpscan */*m*/); |
90 | |
91 | /* --- @mpscan_bit@ --- * |
92 | * |
93 | * Arguments: @const mpscan *m@ = pointer to bitscanner |
94 | * |
95 | * Returns: The value of the current bit. |
96 | * |
97 | * Use: Reads the value of the current bit looked at by a |
98 | * bitscanner. |
99 | */ |
100 | |
101 | #define MPSCAN_BIT(m) ((m)->w & 1) |
102 | |
103 | extern int mpscan_bit(const mpscan */*m*/); |
104 | |
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105 | /*----- Left-to right-scanning --------------------------------------------*/ |
106 | |
107 | /* --- @mpscan_rinitx@ --- * |
108 | * |
109 | * Arguments: @mpscan *m@ = pointer to bitscanner structure |
110 | * @const mpw *v, *vl@ = vector of words to scan |
111 | * |
112 | * Returns: --- |
113 | * |
114 | * Use: Initializes a reverse bitscanner from a low-level |
115 | * vector-and-length representation of an integer. Initially no |
116 | * bit is ready; you must call @mpscan_rstep@ before anything |
117 | * useful will come out. |
118 | */ |
119 | |
120 | #define MPSCAN_RINITX(m_, v_, vl_) do { \ |
121 | mpscan *_m = (m_); \ |
122 | _m->v = (v_); \ |
123 | _m->vl = (vl_); \ |
124 | while (_m->vl > _m->v && !_m->vl[-1]) \ |
125 | _m->vl--; \ |
126 | _m->bits = 0; \ |
127 | } while (0) |
128 | |
129 | extern void mpscan_rinitx(mpscan */*m*/, |
130 | const mpw */*v*/, const mpw */*vl*/); |
131 | |
132 | /* --- @mpscan_rstep@ --- * |
133 | * |
134 | * Arguments: @mpscan *m@ = pointer to bitscanner |
135 | * |
136 | * Returns: Nonzero if there is another bit to read. |
137 | * |
138 | * Use: Steps on to the next bit in the integer. The macro version |
139 | * evaluates its argument multiple times. |
140 | */ |
141 | |
142 | #define MPSCAN_RSTEP(m) \ |
143 | ((m)->bits ? ((m)->w <<= 1, (m)->bits--, 1) : \ |
144 | (m)->vl > (m)->v ? ((m)->w = *--(m)->vl, \ |
145 | (m)->bits = MPW_BITS - 1, 1) : \ |
146 | 0) |
147 | |
148 | extern int mpscan_rstep(mpscan */*m*/); |
149 | |
150 | /* --- @mpscan_rbit@ --- * |
151 | * |
152 | * Arguments: @const mpscan *m@ = pointer to bitscanner |
153 | * |
154 | * Returns: The value of the current bit. |
155 | * |
156 | * Use: Reads the value of the current bit looked at by a |
157 | * reverse bitscanner. |
158 | */ |
159 | |
160 | #define MPSCAN_RBIT(m) (((m)->w >> (MPW_BITS - 1)) & 1) |
161 | |
162 | extern int mpscan_rbit(const mpscan */*m*/); |
163 | |
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164 | /*----- That's all, folks -------------------------------------------------*/ |
165 | |
166 | #ifdef __cplusplus |
167 | } |
168 | #endif |
169 | |
170 | #endif |