]>
git.proxmox.com Git - mirror_frr.git/blob - lib/bitfield.h
2 * Copyright (C) 2016 Cumulus Networks, Inc.
4 * This file is part of Quagga.
6 * Quagga is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation; either version 2, or (at your option) any
11 * Quagga is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * General Public License for more details.
16 * You should have received a copy of the GNU General Public License along
17 * with this program; see the file COPYING; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
21 * A simple bit array implementation to allocate and free IDs. An example
22 * of its usage is in allocating link state IDs for OSPFv3 as OSPFv3 has
23 * removed all address semantics from LS ID. Another usage can be in
24 * allocating IDs for BGP neighbors (and dynamic update groups) for
25 * efficient storage of adj-rib-out.
28 * #include "bitfield.h"
30 * bitfield_t bitfield;
32 * bf_init(bitfield, 32);
34 * bf_assign_index(bitfield, id1);
35 * bf_assign_index(bitfield, id2);
37 * bf_release_index(bitfield, id1);
47 typedef unsigned int word_t
;
48 #define WORD_MAX 0xFFFFFFFF
49 #define WORD_SIZE (sizeof(word_t) * 8)
52 * The bitfield structure.
53 * @data: the bits to manage.
54 * @n: The current word number that is being used.
55 * @m: total number of words in 'data'
57 #define bitfield_t struct { word_t *data; size_t n, m; }
60 * Initialize the bits.
61 * @v: an instance of bitfield_t struct.
62 * @N: number of bits to start with, which equates to how many
63 * IDs can be allocated.
65 #define bf_init(v, N) \
68 (v).m = ((N) / WORD_SIZE + 1); \
69 (v).data = calloc(1, ((v).m * sizeof(word_t))); \
73 * allocate and assign an id from bitfield v.
75 #define bf_assign_index(v, id) \
82 * return an id to bitfield v
84 #define bf_release_index(v, id) \
85 (v).data[bf_index(id)] &= ~(1 << (bf_offset(id)))
87 #define bf_index(b) ((b) / WORD_SIZE)
88 #define bf_offset(b) ((b) % WORD_SIZE)
91 * Set a bit in the array. If it fills up that word and we are
92 * out of words, extend it by one more word.
94 #define bf_set_bit(v, b) \
96 size_t w = bf_index(b); \
97 (v).data[w] |= 1 << (bf_offset(b)); \
98 (v).n += ((v).data[w] == WORD_MAX); \
99 if ((v).n == (v).m) { \
101 (v).data = realloc((v).data, (v).m * sizeof(word_t)); \
105 /* Find a clear bit in v and assign it to b. */
106 #define bf_find_bit(v, b) \
109 unsigned int w, sh; \
110 for (w = 0; w <= (v).n; w++) { \
111 if ((word = (v).data[w]) != WORD_MAX) break; \
113 (b) = ((word & 0xFFFF) == 0xFFFF) << 4; word >>= (b); \
114 sh = ((word & 0xFF) == 0xFF) << 3; word >>= sh; (b) |= sh; \
115 sh = ((word & 0xF) == 0xF) << 2; word >>= sh; (b) |= sh; \
116 sh = ((word & 0x3) == 0x3) << 1; word >>= sh; (b) |= sh; \
117 sh = ((word & 0x1) == 0x1) << 0; word >>= sh; (b) |= sh; \
118 (b) += (w * WORD_SIZE); \