loop.h

这是linux内核C源代码58的源程序

#ifndef _LINUX_LOOP_H
#define _LINUX_LOOP_H

#include <linux/kdev_t.h>

/*
 * include/linux/loop.h
 *
 * Written by Theodore Ts'o, 3/29/93.
 *
 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
 * permitted under the GNU General Public License.
 */

#define LO_NAME_SIZE	64
#define LO_KEY_SIZE	32


/*
 * Loop flags
 */
#define LO_FLAGS_DO_BMAP	1
#define LO_FLAGS_READ_ONLY	2

/* 
 * Note that this structure gets the wrong offsets when directly used
 * from a glibc program, because glibc has a 32bit dev_t.
 * Prevent people from shooting in their own foot.  
 */
#if __GLIBC__ >= 2 && !defined(dev_t)
#error "Wrong dev_t in loop.h"
#endif 

/*
 *	This uses kdev_t because glibc currently has no appropiate
 *	conversion version for the loop ioctls. 
 * 	The situation is very unpleasant	
 */

struct loop_info {
	int		lo_number;	/* ioctl r/o */
	dev_t		lo_device; 	/* ioctl r/o */
	unsigned long	lo_inode; 	/* ioctl r/o */
	dev_t		lo_rdevice; 	/* ioctl r/o */
	int		lo_offset;
	int		lo_encrypt_type;
	int		lo_encrypt_key_size; 	/* ioctl w/o */
	int		lo_flags;	/* ioctl r/o */
	char		lo_name[LO_NAME_SIZE];
	unsigned char	lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
	unsigned long	lo_init[2];
	char		reserved[4];
};

/*
 * Loop filter types
 */

#define LO_CRYPT_NONE	  0
#define LO_CRYPT_XOR	  1
#define LO_CRYPT_DES	  2
#define LO_CRYPT_FISH2    3    /* Brand new Twofish encryption */
#define LO_CRYPT_BLOW     4
#define LO_CRYPT_CAST128  5
#define LO_CRYPT_IDEA     6
#define LO_CRYPT_DUMMY    9
#define LO_CRYPT_SKIPJACK 10
#define MAX_LO_CRYPT	20

/*
 * IOCTL commands --- we will commandeer 0x4C ('L')
 */

#define LOOP_SET_FD	0x4C00
#define LOOP_CLR_FD	0x4C01
#define LOOP_SET_STATUS	0x4C02
#define LOOP_GET_STATUS	0x4C03
#define LOOP_CHANGE_FD	0x4C04

#endif