source: MondoRescue/branches/2.2.9/mindi-busybox/e2fsprogs/old_e2fsprogs/ext2fs/sparse.c@ 3320

/* vi: set sw=4 ts=4: */
/*
 * sparse.c --- find the groups in an ext2 filesystem with metadata backups
 *
 * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
 * Copyright (C) 2002 Andreas Dilger.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>

#include "ext2_fs.h"
#include "ext2fsP.h"

static int test_root(int a, int b)
{
    if (a == 0)
        return 1;
    while (1) {
        if (a == 1)
            return 1;
        if (a % b)
            return 0;
        a = a / b;
    }
}

int ext2fs_bg_has_super(ext2_filsys fs, int group_block)
{
    if (!(fs->super->s_feature_ro_compat &
          EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
        return 1;

    if (test_root(group_block, 3) || (test_root(group_block, 5)) ||
        test_root(group_block, 7))
        return 1;

    return 0;
}

/*
 * Iterate through the groups which hold BACKUP superblock/GDT copies in an
 * ext3 filesystem.  The counters should be initialized to 1, 5, and 7 before
 * calling this for the first time.  In a sparse filesystem it will be the
 * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
 * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
 */
unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three,
                 unsigned int *five, unsigned int *seven)
{
    unsigned int *min = three;
    int mult = 3;
    unsigned int ret;

    if (!(fs->super->s_feature_ro_compat &
          EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
        ret = *min;
        *min += 1;
        return ret;
    }

    if (*five < *min) {
        min = five;
        mult = 5;
    }
    if (*seven < *min) {
        min = seven;
        mult = 7;
    }

    ret = *min;
    *min *= mult;

    return ret;
}