bitfield.c revision 4b06059785b935dd1f4f09314e4e12c417d2c6a4 
1/*
2 * Bitfield
3 * Copyright (c) 2013, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9#include "includes.h"
10
11#include "common.h"
12#include "bitfield.h"
13
14
15struct bitfield {
16	u8 *bits;
17	size_t max_bits;
18};
19
20
21struct bitfield * bitfield_alloc(size_t max_bits)
22{
23	struct bitfield *bf;
24
25	bf = os_zalloc(sizeof(*bf) + (max_bits + 7) / 8);
26	if (bf == NULL)
27		return NULL;
28	bf->bits = (u8 *) (bf + 1);
29	bf->max_bits = max_bits;
30	return bf;
31}
32
33
34void bitfield_free(struct bitfield *bf)
35{
36	os_free(bf);
37}
38
39
40void bitfield_set(struct bitfield *bf, size_t bit)
41{
42	if (bit >= bf->max_bits)
43		return;
44	bf->bits[bit / 8] |= BIT(bit % 8);
45}
46
47
48void bitfield_clear(struct bitfield *bf, size_t bit)
49{
50	if (bit >= bf->max_bits)
51		return;
52	bf->bits[bit / 8] &= ~BIT(bit % 8);
53}
54
55
56int bitfield_is_set(struct bitfield *bf, size_t bit)
57{
58	if (bit >= bf->max_bits)
59		return 0;
60	return !!(bf->bits[bit / 8] & BIT(bit % 8));
61}
62
63
64static int first_zero(u8 val)
65{
66	int i;
67	for (i = 0; i < 8; i++) {
68		if (!(val & 0x01))
69			return i;
70		val >>= 1;
71	}
72	return -1;
73}
74
75
76int bitfield_get_first_zero(struct bitfield *bf)
77{
78	size_t i;
79	for (i = 0; i <= (bf->max_bits + 7) / 8; i++) {
80		if (bf->bits[i] != 0xff)
81			break;
82	}
83	if (i > (bf->max_bits + 7) / 8)
84		return -1;
85	i = i * 8 + first_zero(bf->bits[i]);
86	if (i >= bf->max_bits)
87		return -1;
88	return i;
89}
90