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// SPDX-License-Identifier: GPL-2.0-or-later
/* Bitfields
* Copyright (C) 2016 Cumulus Networks, Inc.
*/
/**
* 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;
DECLARE_MTYPE(BITFIELD);
/**
* 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 = (word_t *)XCALLOC(MTYPE_BITFIELD, \
((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 = XREALLOC(MTYPE_BITFIELD, (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)
/*
* Find a clear bit in v and return it
* Start looking in the word containing bit position start_index.
* If necessary, wrap around after bit position max_index.
*/
static inline unsigned int
bf_find_next_clear_bit_wrap(bitfield_t *v, word_t start_index, word_t max_index)
{
int start_bit;
unsigned long i, offset, scanbits, wordcount_max, index_max;
if (start_index > max_index)
start_index = 0;
start_bit = start_index & (WORD_SIZE - 1);
wordcount_max = bf_index(max_index) + 1;
scanbits = WORD_SIZE;
for (i = bf_index(start_index); i < v->m; ++i) {
if (v->data[i] == WORD_MAX) {
/* if the whole word is full move to the next */
start_bit = 0;
continue;
}
/* scan one word for clear bits */
if ((i == v->m - 1) && (v->m >= wordcount_max))
/* max index could be only part of word */
scanbits = (max_index % WORD_SIZE) + 1;
for (offset = start_bit; offset < scanbits; ++offset) {
if (!((v->data[i] >> offset) & 1))
return ((i * WORD_SIZE) + offset);
}
/* move to the next word */
start_bit = 0;
}
if (v->m < wordcount_max) {
/*
* We can expand bitfield, so no need to wrap.
* Return the index of the first bit of the next word.
* Assumption is that caller will call bf_set_bit which
* will allocate additional space.
*/
v->m += 1;
v->data = (word_t *)XREALLOC(MTYPE_BITFIELD, v->data,
v->m * sizeof(word_t));
v->data[v->m - 1] = 0;
return v->m * WORD_SIZE;
}
/*
* start looking for a clear bit at the start of the bitfield and
* stop when we reach start_index
*/
scanbits = WORD_SIZE;
index_max = bf_index(start_index - 1);
for (i = 0; i <= index_max; ++i) {
if (i == index_max)
scanbits = ((start_index - 1) % WORD_SIZE) + 1;
for (offset = start_bit; offset < scanbits; ++offset) {
if (!((v->data[i] >> offset) & 1))
return ((i * WORD_SIZE) + offset);
}
/* move to the next word */
start_bit = 0;
}
return WORD_MAX;
}
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 { \
XFREE(MTYPE_BITFIELD, (v).data); \
(v).data = NULL; \
} while (0)
static inline bitfield_t bf_copy(bitfield_t src)
{
bitfield_t dst;
assert(bf_is_inited(src));
bf_init(dst, WORD_SIZE * (src.m - 1));
for (size_t i = 0; i < src.m; i++)
dst.data[i] = src.data[i];
dst.n = src.n;
return dst;
}
#ifdef __cplusplus
}
#endif
#endif
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