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acddc0ed | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
50e24903 DS |
2 | /* Bitfields |
3 | * Copyright (C) 2016 Cumulus Networks, Inc. | |
50e24903 | 4 | */ |
c3c0ac83 DS |
5 | /** |
6 | * A simple bit array implementation to allocate and free IDs. An example | |
7 | * of its usage is in allocating link state IDs for OSPFv3 as OSPFv3 has | |
8 | * removed all address semantics from LS ID. Another usage can be in | |
9 | * allocating IDs for BGP neighbors (and dynamic update groups) for | |
10 | * efficient storage of adj-rib-out. | |
11 | * | |
12 | * An example: | |
13 | * #include "bitfield.h" | |
14 | * | |
15 | * bitfield_t bitfield; | |
16 | * | |
17 | * bf_init(bitfield, 32); | |
18 | * ... | |
19 | * bf_assign_index(bitfield, id1); | |
20 | * bf_assign_index(bitfield, id2); | |
21 | * ... | |
22 | * bf_release_index(bitfield, id1); | |
23 | */ | |
24 | ||
25 | #ifndef _BITFIELD_H | |
26 | #define _BITFIELD_H | |
27 | ||
28 | #include <stdio.h> | |
29 | #include <string.h> | |
30 | #include <stdlib.h> | |
31 | ||
5e244469 RW |
32 | #ifdef __cplusplus |
33 | extern "C" { | |
34 | #endif | |
35 | ||
c3c0ac83 DS |
36 | typedef unsigned int word_t; |
37 | #define WORD_MAX 0xFFFFFFFF | |
38 | #define WORD_SIZE (sizeof(word_t) * 8) | |
39 | ||
40 | /** | |
41 | * The bitfield structure. | |
42 | * @data: the bits to manage. | |
43 | * @n: The current word number that is being used. | |
44 | * @m: total number of words in 'data' | |
45 | */ | |
89fbf168 | 46 | typedef struct {word_t *data; size_t n, m; } bitfield_t; |
c3c0ac83 | 47 | |
0e2deb58 PR |
48 | DECLARE_MTYPE(BITFIELD); |
49 | ||
c3c0ac83 DS |
50 | /** |
51 | * Initialize the bits. | |
52 | * @v: an instance of bitfield_t struct. | |
53 | * @N: number of bits to start with, which equates to how many | |
54 | * IDs can be allocated. | |
55 | */ | |
d62a17ae | 56 | #define bf_init(v, N) \ |
57 | do { \ | |
58 | (v).n = 0; \ | |
59 | (v).m = ((N) / WORD_SIZE + 1); \ | |
0e2deb58 | 60 | (v).data = XCALLOC(MTYPE_BITFIELD, ((v).m * sizeof(word_t))); \ |
d62a17ae | 61 | } while (0) |
c3c0ac83 DS |
62 | |
63 | /** | |
64 | * allocate and assign an id from bitfield v. | |
65 | */ | |
d62a17ae | 66 | #define bf_assign_index(v, id) \ |
67 | do { \ | |
68 | bf_find_bit(v, id); \ | |
69 | bf_set_bit(v, id); \ | |
70 | } while (0) | |
c3c0ac83 | 71 | |
4e9da201 | 72 | /* |
73 | * allocate and assign 0th bit in the bitfiled. | |
74 | */ | |
d62a17ae | 75 | #define bf_assign_zero_index(v) \ |
76 | do { \ | |
77 | int id = 0; \ | |
78 | bf_assign_index(v, id); \ | |
79 | } while (0) | |
4e9da201 | 80 | |
81 | /* | |
c3c0ac83 DS |
82 | * return an id to bitfield v |
83 | */ | |
d62a17ae | 84 | #define bf_release_index(v, id) \ |
85 | (v).data[bf_index(id)] &= ~(1 << (bf_offset(id))) | |
c3c0ac83 | 86 | |
89fbf168 AK |
87 | /* check if an id is in use */ |
88 | #define bf_test_index(v, id) \ | |
89 | ((v).data[bf_index(id)] & (1 << (bf_offset(id)))) | |
90 | ||
91 | /* check if the bit field has been setup */ | |
92 | #define bf_is_inited(v) ((v).data) | |
93 | ||
94 | /* compare two bitmaps of the same length */ | |
95 | #define bf_cmp(v1, v2) (memcmp((v1).data, (v2).data, ((v1).m * sizeof(word_t)))) | |
96 | ||
4e9da201 | 97 | /* |
98 | * return 0th index back to bitfield | |
99 | */ | |
d62a17ae | 100 | #define bf_release_zero_index(v) bf_release_index(v, 0) |
4e9da201 | 101 | |
c3c0ac83 DS |
102 | #define bf_index(b) ((b) / WORD_SIZE) |
103 | #define bf_offset(b) ((b) % WORD_SIZE) | |
104 | ||
105 | /** | |
106 | * Set a bit in the array. If it fills up that word and we are | |
107 | * out of words, extend it by one more word. | |
108 | */ | |
d62a17ae | 109 | #define bf_set_bit(v, b) \ |
110 | do { \ | |
111 | size_t w = bf_index(b); \ | |
112 | (v).data[w] |= 1 << (bf_offset(b)); \ | |
113 | (v).n += ((v).data[w] == WORD_MAX); \ | |
114 | if ((v).n == (v).m) { \ | |
115 | (v).m = (v).m + 1; \ | |
116 | (v).data = realloc((v).data, (v).m * sizeof(word_t)); \ | |
117 | } \ | |
118 | } while (0) | |
c3c0ac83 DS |
119 | |
120 | /* Find a clear bit in v and assign it to b. */ | |
d62a17ae | 121 | #define bf_find_bit(v, b) \ |
122 | do { \ | |
123 | word_t word = 0; \ | |
124 | unsigned int w, sh; \ | |
125 | for (w = 0; w <= (v).n; w++) { \ | |
126 | if ((word = (v).data[w]) != WORD_MAX) \ | |
127 | break; \ | |
128 | } \ | |
129 | (b) = ((word & 0xFFFF) == 0xFFFF) << 4; \ | |
130 | word >>= (b); \ | |
131 | sh = ((word & 0xFF) == 0xFF) << 3; \ | |
132 | word >>= sh; \ | |
133 | (b) |= sh; \ | |
134 | sh = ((word & 0xF) == 0xF) << 2; \ | |
135 | word >>= sh; \ | |
136 | (b) |= sh; \ | |
137 | sh = ((word & 0x3) == 0x3) << 1; \ | |
138 | word >>= sh; \ | |
139 | (b) |= sh; \ | |
140 | sh = ((word & 0x1) == 0x1) << 0; \ | |
141 | word >>= sh; \ | |
142 | (b) |= sh; \ | |
143 | (b) += (w * WORD_SIZE); \ | |
144 | } while (0) | |
c3c0ac83 | 145 | |
80853c2e PZ |
146 | /* |
147 | * Find a clear bit in v and return it | |
148 | * Start looking in the word containing bit position start_index. | |
149 | * If necessary, wrap around after bit position max_index. | |
150 | */ | |
151 | static inline unsigned int | |
152 | bf_find_next_clear_bit_wrap(bitfield_t *v, word_t start_index, word_t max_index) | |
153 | { | |
154 | int start_bit; | |
155 | unsigned long i, offset, scanbits, wordcount_max, index_max; | |
156 | ||
157 | if (start_index > max_index) | |
158 | start_index = 0; | |
159 | ||
160 | start_bit = start_index & (WORD_SIZE - 1); | |
161 | wordcount_max = bf_index(max_index) + 1; | |
162 | ||
163 | scanbits = WORD_SIZE; | |
164 | for (i = bf_index(start_index); i < v->m; ++i) { | |
165 | if (v->data[i] == WORD_MAX) { | |
166 | /* if the whole word is full move to the next */ | |
167 | start_bit = 0; | |
168 | continue; | |
169 | } | |
170 | /* scan one word for clear bits */ | |
171 | if ((i == v->m - 1) && (v->m >= wordcount_max)) | |
172 | /* max index could be only part of word */ | |
173 | scanbits = (max_index % WORD_SIZE) + 1; | |
174 | for (offset = start_bit; offset < scanbits; ++offset) { | |
175 | if (!((v->data[i] >> offset) & 1)) | |
176 | return ((i * WORD_SIZE) + offset); | |
177 | } | |
178 | /* move to the next word */ | |
179 | start_bit = 0; | |
180 | } | |
181 | ||
182 | if (v->m < wordcount_max) { | |
183 | /* | |
184 | * We can expand bitfield, so no need to wrap. | |
185 | * Return the index of the first bit of the next word. | |
186 | * Assumption is that caller will call bf_set_bit which | |
187 | * will allocate additional space. | |
188 | */ | |
189 | v->m += 1; | |
190 | v->data = (word_t *)realloc(v->data, v->m * sizeof(word_t)); | |
191 | v->data[v->m - 1] = 0; | |
192 | return v->m * WORD_SIZE; | |
193 | } | |
194 | ||
195 | /* | |
196 | * start looking for a clear bit at the start of the bitfield and | |
197 | * stop when we reach start_index | |
198 | */ | |
199 | scanbits = WORD_SIZE; | |
200 | index_max = bf_index(start_index - 1); | |
201 | for (i = 0; i <= index_max; ++i) { | |
202 | if (i == index_max) | |
203 | scanbits = ((start_index - 1) % WORD_SIZE) + 1; | |
204 | for (offset = start_bit; offset < scanbits; ++offset) { | |
205 | if (!((v->data[i] >> offset) & 1)) | |
206 | return ((i * WORD_SIZE) + offset); | |
207 | } | |
208 | /* move to the next word */ | |
209 | start_bit = 0; | |
210 | } | |
211 | ||
212 | return WORD_MAX; | |
213 | } | |
214 | ||
89fbf168 AK |
215 | static inline unsigned int bf_find_next_set_bit(bitfield_t v, |
216 | word_t start_index) | |
217 | { | |
218 | int start_bit; | |
219 | unsigned long i, offset; | |
220 | ||
221 | start_bit = start_index & (WORD_SIZE - 1); | |
222 | ||
223 | for (i = bf_index(start_index); i < v.m; ++i) { | |
224 | if (v.data[i] == 0) { | |
225 | /* if the whole word is empty move to the next */ | |
226 | start_bit = 0; | |
227 | continue; | |
228 | } | |
229 | /* scan one word for set bits */ | |
230 | for (offset = start_bit; offset < WORD_SIZE; ++offset) { | |
231 | if ((v.data[i] >> offset) & 1) | |
232 | return ((i * WORD_SIZE) + offset); | |
233 | } | |
234 | /* move to the next word */ | |
235 | start_bit = 0; | |
236 | } | |
237 | return WORD_MAX; | |
238 | } | |
239 | ||
240 | /* iterate through all the set bits */ | |
241 | #define bf_for_each_set_bit(v, b, max) \ | |
242 | for ((b) = bf_find_next_set_bit((v), 0); \ | |
243 | (b) < max; \ | |
244 | (b) = bf_find_next_set_bit((v), (b) + 1)) | |
245 | ||
4e9da201 | 246 | /* |
247 | * Free the allocated memory for data | |
248 | * @v: an instance of bitfield_t struct. | |
249 | */ | |
d62a17ae | 250 | #define bf_free(v) \ |
251 | do { \ | |
0e2deb58 | 252 | XFREE(MTYPE_BITFIELD, (v).data); \ |
1ac10b15 | 253 | (v).data = NULL; \ |
d62a17ae | 254 | } while (0) |
4e9da201 | 255 | |
5e244469 RW |
256 | #ifdef __cplusplus |
257 | } | |
258 | #endif | |
259 | ||
c3c0ac83 | 260 | #endif |