1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
/* Bitfields
* Copyright (C) 2016 Cumulus Networks, Inc.
*
* This file is part of Quagga.
*
* Quagga is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* Quagga is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; see the file COPYING; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* A simple bit array implementation to allocate and free IDs. An example
* of its usage is in allocating link state IDs for OSPFv3 as OSPFv3 has
* removed all address semantics from LS ID. Another usage can be in
* allocating IDs for BGP neighbors (and dynamic update groups) for
* efficient storage of adj-rib-out.
*
* An example:
* #include "bitfield.h"
*
* bitfield_t bitfield;
*
* bf_init(bitfield, 32);
* ...
* bf_assign_index(bitfield, id1);
* bf_assign_index(bitfield, id2);
* ...
* bf_release_index(bitfield, id1);
*/
#ifndef _BITFIELD_H
#define _BITFIELD_H
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#ifdef __cplusplus
extern "C" {
#endif
typedef unsigned int word_t;
#define WORD_MAX 0xFFFFFFFF
#define WORD_SIZE (sizeof(word_t) * 8)
/**
* The bitfield structure.
* @data: the bits to manage.
* @n: The current word number that is being used.
* @m: total number of words in 'data'
*/
typedef struct {word_t *data; size_t n, m; } bitfield_t;
/**
* Initialize the bits.
* @v: an instance of bitfield_t struct.
* @N: number of bits to start with, which equates to how many
* IDs can be allocated.
*/
#define bf_init(v, N) \
do { \
(v).n = 0; \
(v).m = ((N) / WORD_SIZE + 1); \
(v).data = calloc(1, ((v).m * sizeof(word_t))); \
} while (0)
/**
* allocate and assign an id from bitfield v.
*/
#define bf_assign_index(v, id) \
do { \
bf_find_bit(v, id); \
bf_set_bit(v, id); \
} while (0)
/*
* allocate and assign 0th bit in the bitfiled.
*/
#define bf_assign_zero_index(v) \
do { \
int id = 0; \
bf_assign_index(v, id); \
} while (0)
/*
* return an id to bitfield v
*/
#define bf_release_index(v, id) \
(v).data[bf_index(id)] &= ~(1 << (bf_offset(id)))
/* check if an id is in use */
#define bf_test_index(v, id) \
((v).data[bf_index(id)] & (1 << (bf_offset(id))))
/* check if the bit field has been setup */
#define bf_is_inited(v) ((v).data)
/* compare two bitmaps of the same length */
#define bf_cmp(v1, v2) (memcmp((v1).data, (v2).data, ((v1).m * sizeof(word_t))))
/*
* return 0th index back to bitfield
*/
#define bf_release_zero_index(v) bf_release_index(v, 0)
#define bf_index(b) ((b) / WORD_SIZE)
#define bf_offset(b) ((b) % WORD_SIZE)
/**
* Set a bit in the array. If it fills up that word and we are
* out of words, extend it by one more word.
*/
#define bf_set_bit(v, b) \
do { \
size_t w = bf_index(b); \
(v).data[w] |= 1 << (bf_offset(b)); \
(v).n += ((v).data[w] == WORD_MAX); \
if ((v).n == (v).m) { \
(v).m = (v).m + 1; \
(v).data = realloc((v).data, (v).m * sizeof(word_t)); \
} \
} while (0)
/* Find a clear bit in v and assign it to b. */
#define bf_find_bit(v, b) \
do { \
word_t word = 0; \
unsigned int w, sh; \
for (w = 0; w <= (v).n; w++) { \
if ((word = (v).data[w]) != WORD_MAX) \
break; \
} \
(b) = ((word & 0xFFFF) == 0xFFFF) << 4; \
word >>= (b); \
sh = ((word & 0xFF) == 0xFF) << 3; \
word >>= sh; \
(b) |= sh; \
sh = ((word & 0xF) == 0xF) << 2; \
word >>= sh; \
(b) |= sh; \
sh = ((word & 0x3) == 0x3) << 1; \
word >>= sh; \
(b) |= sh; \
sh = ((word & 0x1) == 0x1) << 0; \
word >>= sh; \
(b) |= sh; \
(b) += (w * WORD_SIZE); \
} while (0)
static inline unsigned int bf_find_next_set_bit(bitfield_t v,
word_t start_index)
{
int start_bit;
unsigned long i, offset;
start_bit = start_index & (WORD_SIZE - 1);
for (i = bf_index(start_index); i < v.m; ++i) {
if (v.data[i] == 0) {
/* if the whole word is empty move to the next */
start_bit = 0;
continue;
}
/* scan one word for set bits */
for (offset = start_bit; offset < WORD_SIZE; ++offset) {
if ((v.data[i] >> offset) & 1)
return ((i * WORD_SIZE) + offset);
}
/* move to the next word */
start_bit = 0;
}
return WORD_MAX;
}
/* iterate through all the set bits */
#define bf_for_each_set_bit(v, b, max) \
for ((b) = bf_find_next_set_bit((v), 0); \
(b) < max; \
(b) = bf_find_next_set_bit((v), (b) + 1))
/*
* Free the allocated memory for data
* @v: an instance of bitfield_t struct.
*/
#define bf_free(v) \
do { \
free((v).data); \
(v).data = NULL; \
} while (0)
#ifdef __cplusplus
}
#endif
#endif
|
