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/*
* Ouroboros - Copyright (C) 2016 - 2021
*
* Bitmap implementation
*
* Dimitri Staessens <dimitri.staessens@ugent.be>
* Sander Vrijders <sander.vrijders@ugent.be>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* version 2.1 as published by the Free Software Foundation.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., http://www.fsf.org/about/contact/.
*/
#include <ouroboros/bitmap.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#define BITS_PER_BYTE CHAR_BIT
#define BITS_PER_LONG (sizeof(size_t) * BITS_PER_BYTE)
#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
#define BITS_TO_LONGS(nr) \
DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(size_t))
static size_t find_next_zero_bit(const size_t * addr,
size_t nbits)
{
size_t tmp;
size_t start = 0;
size_t pos = 0;
size_t mask;
/* First find correct word */
tmp = ~addr[start];
while (!tmp) {
start++;
if (start >= DIV_ROUND_UP(nbits, BITS_PER_LONG))
return nbits;
tmp = ~addr[start];
}
/* Find the free bit in the word */
mask = 1UL;
while (!(tmp & mask)) {
pos++;
mask = 1UL << pos;
}
return (start * BITS_PER_LONG) + pos;
}
static void bitmap_zero(size_t * dst,
size_t nbits)
{
memset(dst, 0, BITS_TO_LONGS(nbits) * sizeof(size_t));
}
static void bitmap_clear(size_t * map,
size_t start)
{
size_t * p = map + BIT_WORD(start);
size_t mask = ~(1UL << (start % (BITS_PER_LONG)));
*p &= mask;
}
static void bitmap_set(size_t * map,
size_t start)
{
size_t * p = map + BIT_WORD(start);
size_t mask = 1UL << (start % (BITS_PER_LONG));
*p |= mask;
}
struct bmp {
ssize_t offset;
size_t size;
size_t * bitmap;
};
struct bmp * bmp_create(size_t bits,
ssize_t offset)
{
struct bmp * bmp;
assert(bits);
bmp = malloc(sizeof(*bmp));
if (bmp == NULL)
return NULL;
bmp->bitmap = malloc(BITS_TO_LONGS(bits) * sizeof(size_t));
if (bmp->bitmap == NULL) {
free(bmp);
return NULL;
}
bmp->size = bits;
bmp->offset = offset;
bitmap_zero(bmp->bitmap, bits);
return bmp;
}
void bmp_destroy(struct bmp * bmp)
{
assert(bmp);
if (bmp->bitmap != NULL)
free(bmp->bitmap);
free(bmp);
}
static ssize_t bad_id(struct bmp * bmp)
{
assert(bmp);
return bmp->offset - 1;
}
ssize_t bmp_allocate(struct bmp * bmp)
{
size_t id;
assert(bmp);
id = find_next_zero_bit(bmp->bitmap, bmp->size);
if (id >= bmp->size)
return bad_id(bmp);
bitmap_set(bmp->bitmap, id);
return id + bmp->offset;
}
static bool is_id_valid(struct bmp * bmp,
ssize_t id)
{
assert(bmp);
if ((id < bmp->offset) || (id > (ssize_t) (bmp->offset + bmp->size)))
return false;
return true;
}
static bool is_id_used(size_t * map,
size_t start)
{
size_t * p = map + BIT_WORD(start);
size_t mask = 1UL << (start % (BITS_PER_LONG));
return (*p & mask) != 0;
}
bool bmp_is_id_valid(struct bmp * bmp,
ssize_t id)
{
assert(bmp);
return is_id_valid(bmp, id);
}
int bmp_release(struct bmp * bmp,
ssize_t id)
{
assert(bmp);
if (!is_id_valid(bmp, id))
return -1;
bitmap_clear(bmp->bitmap, id - bmp->offset);
return 0;
}
bool bmp_is_id_used(struct bmp * bmp,
ssize_t id)
{
assert(bmp);
return is_id_used(bmp->bitmap, id - bmp->offset);
}
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