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/* Bitfields
* Copyright (C) 2016 Cumulus Networks, Inc.
*
* This file is part of Quagga.
*
* Quagga is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* Quagga is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; see the file COPYING; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* 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)
/*
* 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)))
/*
* 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 = 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 = 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)
/*
* Free the allocated memory for data
* @v: an instance of bitfield_t struct.
*/
#define bf_free(v) \
do { \
if ((v).data) { \
free((v).data); \
} \
} while (0)
#endif
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