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/*
* Ouroboros - Copyright (C) 2016
*
* Bitmap implementation - taken partly from Linux kernel
*
* Sander Vrijders <sander.vrijders@intec.ugent.be>
* Francesco Salvestrini <f.salvestrini@nextworks.it>
*
* This program 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 of the License, or
* (at your option) any later version.
*
* This program 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; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#define OUROBOROS_PREFIX "bitmap"
#include <ouroboros/bitmap.h>
#include <ouroboros/logs.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#define BITS_PER_BYTE 8
#define BITS_PER_LONG (sizeof(long) * 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(long))
static unsigned long find_next_zero_bit(const unsigned long * addr,
unsigned long nbits)
{
unsigned long tmp;
unsigned long start = 0;
unsigned long pos = 0;
unsigned long mask;
/* First find correct word */
tmp = ~addr[start];
while (!tmp) {
start++;
if (start >= (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(unsigned long * dst,
unsigned int nbits)
{
unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
memset(dst, 0, len);
}
static void bitmap_clear(unsigned long * map,
unsigned int start)
{
unsigned long * p = map + BIT_WORD(start);
unsigned long mask = ~(1UL << (start % (BITS_PER_LONG)));
*p &= mask;
}
static void bitmap_set(unsigned long * map,
unsigned int start)
{
unsigned long * p = map + BIT_WORD(start);
unsigned long mask = 1UL << (start % (BITS_PER_LONG));
*p |= mask;
}
struct bmp {
ssize_t offset;
size_t size;
unsigned long * bitmap;
};
struct bmp * bmp_create(size_t bits, ssize_t offset)
{
struct bmp * tmp;
if (bits == 0)
return NULL;
tmp = malloc(sizeof(*tmp));
if (tmp == NULL)
return NULL;
tmp->bitmap = malloc(BITS_TO_LONGS(bits) * sizeof(unsigned long));
if (!tmp->bitmap) {
free(tmp);
return NULL;
}
tmp->size = bits;
tmp->offset = offset;
bitmap_zero(tmp->bitmap, bits);
return tmp;
}
int bmp_destroy(struct bmp * b)
{
if (b == NULL)
return -1;
if (b->bitmap == NULL) {
free(b);
return -1;
}
free(b->bitmap);
free(b);
return 0;
}
static ssize_t bad_id(struct bmp * b)
{
return b->offset - 1;
}
ssize_t bmp_allocate(struct bmp * b)
{
ssize_t id;
if (b == NULL)
return -1;
id = (ssize_t) find_next_zero_bit(b->bitmap,
b->size);
if (id >= b->size)
return bad_id(b);
bitmap_set(b->bitmap, id);
return id + b->offset;
}
static bool is_id_valid(struct bmp * b,
ssize_t id)
{
assert(b);
if ((id < b->offset) || (id > (b->offset + b->size)))
return false;
return true;
}
bool bmp_is_id_valid(struct bmp * b,
ssize_t id)
{
if (!b)
return false;
return is_id_valid(b, id);
}
int bmp_release(struct bmp * b,
ssize_t id)
{
ssize_t rid;
if (!b)
return -1;
if (!is_id_valid(b, id))
return -1;
rid = id - b->offset;
bitmap_clear(b->bitmap, rid);
return 0;
}
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