root/include/linux/cramfs_fs.h

INCLUDED FROM

#ifndef __CRAMFS_H
#define __CRAMFS_H

#include <linux/types.h>

#define CRAMFS_MAGIC            0x28cd3d45      /* some random number */
#define CRAMFS_MAGIC_WEND       0x453dcd28      /* magic number with the wrong endianess */
#define CRAMFS_SIGNATURE        "Compressed ROMFS"

/*
 * Width of various bitfields in struct cramfs_inode.
 * Primarily used to generate warnings in mkcramfs.
 */
#define CRAMFS_MODE_WIDTH 16
#define CRAMFS_UID_WIDTH 16
#define CRAMFS_SIZE_WIDTH 24
#define CRAMFS_GID_WIDTH 8
#define CRAMFS_NAMELEN_WIDTH 6
#define CRAMFS_OFFSET_WIDTH 26

/*
 * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs
 * path length is 63 << 2 = 252.
 */
#define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)

/*
 * Reasonably terse representation of the inode data.
 */
struct cramfs_inode {
        __u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;
        /* SIZE for device files is i_rdev */
        __u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;
        /* NAMELEN is the length of the file name, divided by 4 and
           rounded up.  (cramfs doesn't support hard links.) */
        /* OFFSET: For symlinks and non-empty regular files, this
           contains the offset (divided by 4) of the file data in
           compressed form (starting with an array of block pointers;
           see README).  For non-empty directories it is the offset
           (divided by 4) of the inode of the first file in that
           directory.  For anything else, offset is zero. */
        __u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
};

struct cramfs_info {
        __u32 crc;
        __u32 edition;
        __u32 blocks;
        __u32 files;
};

/*
 * Superblock information at the beginning of the FS.
 */
struct cramfs_super {
        __u32 magic;                    /* 0x28cd3d45 - random number */
        __u32 size;                     /* length in bytes */
        __u32 flags;                    /* feature flags */
        __u32 future;                   /* reserved for future use */
        __u8 signature[16];             /* "Compressed ROMFS" */
        struct cramfs_info fsid;        /* unique filesystem info */
        __u8 name[16];                  /* user-defined name */
        struct cramfs_inode root;       /* root inode data */
};

/*
 * Feature flags
 *
 * 0x00000000 - 0x000000ff: features that work for all past kernels
 * 0x00000100 - 0xffffffff: features that don't work for past kernels
 */
#define CRAMFS_FLAG_FSID_VERSION_2      0x00000001      /* fsid version #2 */
#define CRAMFS_FLAG_SORTED_DIRS         0x00000002      /* sorted dirs */
#define CRAMFS_FLAG_HOLES               0x00000100      /* support for holes */
#define CRAMFS_FLAG_WRONG_SIGNATURE     0x00000200      /* reserved */
#define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400      /* shifted root fs */

/*
 * Valid values in super.flags.  Currently we refuse to mount
 * if (flags & ~CRAMFS_SUPPORTED_FLAGS).  Maybe that should be
 * changed to test super.future instead.
 */
#define CRAMFS_SUPPORTED_FLAGS  ( 0x000000ff \
                                | CRAMFS_FLAG_HOLES \
                                | CRAMFS_FLAG_WRONG_SIGNATURE \
                                | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET )

/* Uncompression interfaces to the underlying zlib */
int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen);
int cramfs_uncompress_init(void);
void cramfs_uncompress_exit(void);

#endif