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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: mpscan.h,v 1.5 2004/04/08 01:36:15 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 | |
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30 | #ifndef CATACOMB_MPSCAN_H |
31 | #define CATACOMB_MPSCAN_H |
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32 | |
33 | #ifdef __cplusplus |
34 | extern "C" { |
35 | #endif |
36 | |
37 | /*----- Header files ------------------------------------------------------*/ |
38 | |
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39 | #ifndef CATACOMB_MPW_H |
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40 | # include "mpw.h" |
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41 | #endif |
42 | |
43 | /*----- Data structures ---------------------------------------------------*/ |
44 | |
45 | typedef struct mpscan { |
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46 | const mpw *v, *vl; /* Vector of words to scan */ |
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47 | mpw w; /* Current word to scan */ |
48 | int bits; /* Number of bits left in @w@ */ |
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49 | } mpscan; |
50 | |
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51 | /*----- Right-to-left scanning --------------------------------------------*/ |
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52 | |
53 | /* --- @mpscan_initx@ --- * |
54 | * |
55 | * Arguments: @mpscan *m@ = pointer to bitscanner structure |
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56 | * @const mpw *v, *vl@ = vector of words to scan |
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57 | * |
58 | * Returns: --- |
59 | * |
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60 | * Use: Initializes a bitscanner from a low-level base-and-limit |
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61 | * representation of an integer. Initially no bit is ready; you |
62 | * must call @mpscan_step@ before anything useful will come |
63 | * out. |
64 | */ |
65 | |
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66 | #define MPSCAN_INITX(m_, v_, vl_) do { \ |
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67 | mpscan *_m = (m_); \ |
68 | _m->v = (v_); \ |
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69 | _m->vl = (vl_); \ |
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70 | _m->bits = 0; \ |
71 | } while (0) |
72 | |
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73 | extern void mpscan_initx(mpscan */*m*/, const mpw */*v*/, const mpw */*vl*/); |
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74 | |
75 | /* --- @mpscan_step@ --- * |
76 | * |
77 | * Arguments: @mpscan *m@ = pointer to bitscanner |
78 | * |
79 | * Returns: Nonzero if there is another bit to read. |
80 | * |
81 | * Use: Steps on to the next bit in the integer. The macro version |
82 | * evaluates its argument multiple times. |
83 | */ |
84 | |
85 | #define MPSCAN_STEP(m) \ |
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86 | ((m)->bits ? ((m)->w >>= 1, (m)->bits--, 1) : \ |
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87 | (m)->v < (m)->vl ? ((m)->w = *(m)->v++, \ |
88 | (m)->bits = MPW_BITS - 1, 1) : \ |
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89 | 0) |
90 | |
91 | extern int mpscan_step(mpscan */*m*/); |
92 | |
93 | /* --- @mpscan_bit@ --- * |
94 | * |
95 | * Arguments: @const mpscan *m@ = pointer to bitscanner |
96 | * |
97 | * Returns: The value of the current bit. |
98 | * |
99 | * Use: Reads the value of the current bit looked at by a |
100 | * bitscanner. |
101 | */ |
102 | |
103 | #define MPSCAN_BIT(m) ((m)->w & 1) |
104 | |
105 | extern int mpscan_bit(const mpscan */*m*/); |
106 | |
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107 | /*----- Left-to right-scanning --------------------------------------------*/ |
108 | |
109 | /* --- @mpscan_rinitx@ --- * |
110 | * |
111 | * Arguments: @mpscan *m@ = pointer to bitscanner structure |
112 | * @const mpw *v, *vl@ = vector of words to scan |
113 | * |
114 | * Returns: --- |
115 | * |
116 | * Use: Initializes a reverse bitscanner from a low-level |
117 | * vector-and-length representation of an integer. Initially no |
118 | * bit is ready; you must call @mpscan_rstep@ before anything |
119 | * useful will come out. |
120 | */ |
121 | |
122 | #define MPSCAN_RINITX(m_, v_, vl_) do { \ |
123 | mpscan *_m = (m_); \ |
124 | _m->v = (v_); \ |
125 | _m->vl = (vl_); \ |
126 | while (_m->vl > _m->v && !_m->vl[-1]) \ |
127 | _m->vl--; \ |
128 | _m->bits = 0; \ |
129 | } while (0) |
130 | |
131 | extern void mpscan_rinitx(mpscan */*m*/, |
132 | const mpw */*v*/, const mpw */*vl*/); |
133 | |
134 | /* --- @mpscan_rstep@ --- * |
135 | * |
136 | * Arguments: @mpscan *m@ = pointer to bitscanner |
137 | * |
138 | * Returns: Nonzero if there is another bit to read. |
139 | * |
140 | * Use: Steps on to the next bit in the integer. The macro version |
141 | * evaluates its argument multiple times. |
142 | */ |
143 | |
144 | #define MPSCAN_RSTEP(m) \ |
145 | ((m)->bits ? ((m)->w <<= 1, (m)->bits--, 1) : \ |
146 | (m)->vl > (m)->v ? ((m)->w = *--(m)->vl, \ |
147 | (m)->bits = MPW_BITS - 1, 1) : \ |
148 | 0) |
149 | |
150 | extern int mpscan_rstep(mpscan */*m*/); |
151 | |
152 | /* --- @mpscan_rbit@ --- * |
153 | * |
154 | * Arguments: @const mpscan *m@ = pointer to bitscanner |
155 | * |
156 | * Returns: The value of the current bit. |
157 | * |
158 | * Use: Reads the value of the current bit looked at by a |
159 | * reverse bitscanner. |
160 | */ |
161 | |
162 | #define MPSCAN_RBIT(m) (((m)->w >> (MPW_BITS - 1)) & 1) |
163 | |
164 | extern int mpscan_rbit(const mpscan */*m*/); |
165 | |
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166 | /*----- That's all, folks -------------------------------------------------*/ |
167 | |
168 | #ifdef __cplusplus |
169 | } |
170 | #endif |
171 | |
172 | #endif |