source: MondoRescue/branches/3.2/mindi-busybox/libbb/find_root_device.c@ 3232

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"

/* Find block device /dev/XXX which contains specified file
 * We handle /dev/dir/dir/dir too, at a cost of ~80 more bytes code */

/* Do not reallocate all this stuff on each recursion */
enum { DEVNAME_MAX = 256 };
struct arena {
    struct stat st;
    dev_t dev;
    /* Was PATH_MAX, but we recurse _/dev_. We can assume
     * people are not crazy enough to have mega-deep tree there */
    char devpath[DEVNAME_MAX];
};

static char *find_block_device_in_dir(struct arena *ap)
{
    DIR *dir;
    struct dirent *entry;
    char *retpath = NULL;
    int len, rem;

    len = strlen(ap->devpath);
    rem = DEVNAME_MAX-2 - len;
    if (rem <= 0)
        return NULL;

    dir = opendir(ap->devpath);
    if (!dir)
        return NULL;

    ap->devpath[len++] = '/';

    while ((entry = readdir(dir)) != NULL) {
        safe_strncpy(ap->devpath + len, entry->d_name, rem);
        /* lstat: do not follow links */
        if (lstat(ap->devpath, &ap->st) != 0)
            continue;
        if (S_ISBLK(ap->st.st_mode) && ap->st.st_rdev == ap->dev) {
            retpath = xstrdup(ap->devpath);
            break;
        }
        if (S_ISDIR(ap->st.st_mode)) {
            /* Do not recurse for '.' and '..' */
            if (DOT_OR_DOTDOT(entry->d_name))
                continue;
            retpath = find_block_device_in_dir(ap);
            if (retpath)
                break;
        }
    }
    closedir(dir);

    return retpath;
}

char* FAST_FUNC find_block_device(const char *path)
{
    struct arena a;

    if (stat(path, &a.st) != 0)
        return NULL;
    a.dev = S_ISBLK(a.st.st_mode) ? a.st.st_rdev : a.st.st_dev;
    strcpy(a.devpath, "/dev");
    return find_block_device_in_dir(&a);
}