source: branches/samba-3.3.x/source/lib/bitmap.c

/*
   Unix SMB/CIFS implementation.
   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"

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

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

        bm = SMB_MALLOC_P(struct bitmap);

        if (!bm) return NULL;
        
        bm->n = n;
        bm->b = SMB_MALLOC_ARRAY(uint32, (n+31)/32);
        if (!bm->b) {
                SAFE_FREE(bm);
                return NULL;
        }

        memset(bm->b, 0, sizeof(uint32)*((n+31)/32));

        return bm;
}

/****************************************************************************
free a bitmap.
****************************************************************************/

void bitmap_free(struct bitmap *bm)
{
        if (!bm)
                return;

        SAFE_FREE(bm->b);
        SAFE_FREE(bm);
}

/****************************************************************************
talloc a bitmap
****************************************************************************/
struct bitmap *bitmap_talloc(TALLOC_CTX *mem_ctx, int n)
{
        struct bitmap *bm;

        if (!mem_ctx) return NULL;

        bm = TALLOC_P(mem_ctx, struct bitmap);

        if (!bm) return NULL;
        
        bm->n = n;
        bm->b = TALLOC_ARRAY(mem_ctx, uint32, (n+31)/32);
        if (!bm->b) {
                return NULL;
        }

        memset(bm->b, 0, sizeof(uint32)*((n+31)/32));

        return bm;
}

/****************************************************************************
copy as much of the source bitmap as will fit in the destination bitmap.
****************************************************************************/

int bitmap_copy(struct bitmap * const dst, const struct bitmap * const src)
{
        int count = MIN(dst->n, src->n);

        SMB_ASSERT(dst->b != src->b);
        memcpy(dst->b, src->b, sizeof(uint32)*((count+31)/32));

        return count;
}

/****************************************************************************
set a bit in a bitmap
****************************************************************************/
bool bitmap_set(struct bitmap *bm, unsigned i)
{
        if (i >= bm->n) {
                DEBUG(0,("Setting invalid bitmap entry %d (of %d)\n",
                      i, bm->n));
                return False;
        }
        bm->b[i/32] |= (1<<(i%32));
        return True;
}

/****************************************************************************
clear a bit in a bitmap
****************************************************************************/
bool bitmap_clear(struct bitmap *bm, unsigned i)
{
        if (i >= bm->n) {
                DEBUG(0,("clearing invalid bitmap entry %d (of %d)\n",
                      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)
{
        unsigned 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;
}