getlabel.ext2.c

linux下的一个mount工具

/*
 * $Id: getlabel.ext2.c,v 1.1.1.1 2000/09/13 19:36:41 lyonel Exp $
 *
 * Copyright (c) 2000, Lyonel VINCENT <[e-mail]>
 *
 * This file may be redistributed under the terms of the GNU Public
 * License.
 *
 * Taken from aeb's mount, 990619
 */

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <unistd.h>

#define EXT2_SUPER_MAGIC    0xEF53
struct ext2_super_block_struct {
        unsigned char   s_dummy1[56];
        unsigned char   s_magic[2];
        unsigned char   s_dummy2[46];
        unsigned char   s_uuid[16];
        unsigned char   s_volume_name[16];
};
typedef struct ext2_super_block_struct ext2_super_block;
#define ext2magic(s)    ((unsigned int) s.s_magic[0] + (((unsigned int) s.s_magic[1]) << 8))

int ext2_getlabel(int fd, char *label) {

	/* start with a test for ext2, taken from mount_guess_fstype */
	ext2_super_block e2sb;

	if (lseek(fd, 1024, SEEK_SET) != 1024
	    || read(fd, (char *) &e2sb, sizeof(e2sb)) != sizeof(e2sb)
	    || (ext2magic(e2sb) != EXT2_SUPER_MAGIC)) {
		return 0;
	}

	strncpy(label, e2sb.s_volume_name, sizeof(e2sb.s_volume_name));
	return 1;
}