samba-mirror/source3/lib/bitmap.c

/*
   Unix SMB/Netbios implementation.
   Version 1.9.
   simple bitmap functions
   Copyright (C) Andrew Tridgell 1992-1998

   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.
*/

#include "includes.h"

/* these functions provide a simple way to allocate integers from a
   pool without repitition */


/****************************************************************************
allocate a bitmap of the specified size
****************************************************************************/
struct bitmap *bitmap_allocate(int n)
{
	struct bitmap *bm;

	bm = (struct bitmap *)malloc(sizeof(*bm));
	bm->n = n;

	if (!bm) return NULL;
	
	bm->b = (uint32 *)malloc(sizeof(bm->b[0])*(n+31)/32);
	if (!bm->b) {
		free(bm);
		return NULL;
	}

	memset(bm->b, 0, sizeof(bm->b[0])*bm->n);

	return bm;
}

/****************************************************************************
free a bitmap structure
****************************************************************************/
void bitmap_free(struct bitmap *bm)
{
	free(bm->b);
	bm->b = NULL;
	free(bm);
}


/****************************************************************************
set a bit in a bitmap
****************************************************************************/
BOOL bitmap_set(struct bitmap *bm, unsigned i)
{
	if (i >= bm->n) return False;
	bm->b[i/32] |= (1<<(i%32));
	return True;
}

/****************************************************************************
query a bit in a bitmap
****************************************************************************/
BOOL bitmap_query(struct bitmap *bm, unsigned i)
{
	if (i >= bm->n) return False;
	if (bm->b[i/32] & (1<<(i%32))) {
		return True;
	}
	return False;
}

/****************************************************************************
find a zero bit in a bitmap starting at the specified offset, with
wraparound
****************************************************************************/
int bitmap_find(struct bitmap *bm, unsigned ofs)
{
	int i, j;

	if (ofs > bm->n) ofs = 0;

	i = ofs;
	while (i < bm->n) {
		if (~(bm->b[i/32])) {
			j = i;
			do {
				if (!bitmap_query(bm, j)) return j;
				j++;
			} while (j & 31 && j < bm->n);
		}
		i += 32;
		i &= ~31;
	}

	i = 0;
	while (i < ofs) {
		if (~(bm->b[i/32])) {
			j = i;
			do {
				if (!bitmap_query(bm, j)) return j;
				j++;
			} while (j & 31 && j < bm->n);
		}
		i += 32;
		i &= ~31;
	}

	return -1;
}