getlabel.vfat.c

来自「linux下的一个mount工具」· C语言 代码 · 共 82 行

/*
 *  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 Library 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */
/*
 *$Id: getlabel.vfat.c,v 1.1.1.1 2000/09/13 19:36:45 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>

/* From inspection of a few FAT filesystems - aeb */
/* Unfortunately I find almost the same thing on an extended partition;
 *    it looks like a primary has some directory entries where the extended
 *       has a partition table: IO.SYS, MSDOS.SYS, WINBOOT.SYS */
struct vfat_super_block_struct {
		    u_char    s_dummy[3];
		    u_char    s_os[8];      /* "MSDOS5.0" or "MSWIN4.0" or "MSWIN4.1" */
				                /* mtools-3.9.4 writes "MTOOL394" */
		    u_char    s_dummy2[32];
		    u_char    s_label[11];  /* for DOS? */
		    u_char    s_fs[8];      /* "FAT12   " or "FAT16   " or all zero   */
	                                /* OS/2 BM has "FAT * " here. */
		    u_char    s_dummy3[9];
		    u_char    s_label2[11]; /* for Windows? */
		    u_char    s_fs2[8];         /* garbage or "FAT32   " */
};
typedef struct vfat_super_block_struct vfat_super_block;

int vfat_getlabel(int fd, char *label) {

	/* start with a test for ext2, taken from mount_guess_fstype */
	int i;
	vfat_super_block vfatsb;

	if (fd < 0)
		return 0;

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

	if ((strncmp(vfatsb.s_os, "MSDOS", 5) &&
		 strncmp(vfatsb.s_os, "MSWIN", 5) &&
		 strncmp(vfatsb.s_os, "MTOOL", 5) &&
		 strncmp(vfatsb.s_os, "mkdosfs", 7) &&
		 strncmp(vfatsb.s_os, "kmkdosfs", 8))&&
		 strncmp(vfatsb.s_fs, "FAT12   ", 8) &&
	     strncmp(vfatsb.s_fs, "FAT16   ", 8) &&
	     strncmp(vfatsb.s_fs2, "FAT32   ", 8))
			return 0;

	for(i=10; i>=0; i--)
			if(vfatsb.s_label[i] == ' ') vfatsb.s_label[i] = '\0';
			else break;

	strncpy(label, vfatsb.s_label, sizeof(vfatsb.s_label));
	return 1;
}