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
|
/**
* 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>
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'
*/
#define bitfield_t struct { word_t *data; size_t n, m; }
/**
* 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)
/**
* return an id to bitfield v
*/
#define bf_release_index(v, id) \
(v).data[bf_index(id)] &= ~(1 << (bf_offset(id)))
#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; \
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)
#endif
|
