linux/include/linux/cramfs_fs.h
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   1#ifndef __CRAMFS_H
   2#define __CRAMFS_H
   3
   4#include <linux/types.h>
   5#include <linux/magic.h>
   6
   7#define CRAMFS_SIGNATURE        "Compressed ROMFS"
   8
   9/*
  10 * Width of various bitfields in struct cramfs_inode.
  11 * Primarily used to generate warnings in mkcramfs.
  12 */
  13#define CRAMFS_MODE_WIDTH 16
  14#define CRAMFS_UID_WIDTH 16
  15#define CRAMFS_SIZE_WIDTH 24
  16#define CRAMFS_GID_WIDTH 8
  17#define CRAMFS_NAMELEN_WIDTH 6
  18#define CRAMFS_OFFSET_WIDTH 26
  19
  20/*
  21 * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs
  22 * path length is 63 << 2 = 252.
  23 */
  24#define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)
  25
  26/*
  27 * Reasonably terse representation of the inode data.
  28 */
  29struct cramfs_inode {
  30        __u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;
  31        /* SIZE for device files is i_rdev */
  32        __u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;
  33        /* NAMELEN is the length of the file name, divided by 4 and
  34           rounded up.  (cramfs doesn't support hard links.) */
  35        /* OFFSET: For symlinks and non-empty regular files, this
  36           contains the offset (divided by 4) of the file data in
  37           compressed form (starting with an array of block pointers;
  38           see README).  For non-empty directories it is the offset
  39           (divided by 4) of the inode of the first file in that
  40           directory.  For anything else, offset is zero. */
  41        __u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
  42};
  43
  44struct cramfs_info {
  45        __u32 crc;
  46        __u32 edition;
  47        __u32 blocks;
  48        __u32 files;
  49};
  50
  51/*
  52 * Superblock information at the beginning of the FS.
  53 */
  54struct cramfs_super {
  55        __u32 magic;                    /* 0x28cd3d45 - random number */
  56        __u32 size;                     /* length in bytes */
  57        __u32 flags;                    /* feature flags */
  58        __u32 future;                   /* reserved for future use */
  59        __u8 signature[16];             /* "Compressed ROMFS" */
  60        struct cramfs_info fsid;        /* unique filesystem info */
  61        __u8 name[16];                  /* user-defined name */
  62        struct cramfs_inode root;       /* root inode data */
  63};
  64
  65/*
  66 * Feature flags
  67 *
  68 * 0x00000000 - 0x000000ff: features that work for all past kernels
  69 * 0x00000100 - 0xffffffff: features that don't work for past kernels
  70 */
  71#define CRAMFS_FLAG_FSID_VERSION_2      0x00000001      /* fsid version #2 */
  72#define CRAMFS_FLAG_SORTED_DIRS         0x00000002      /* sorted dirs */
  73#define CRAMFS_FLAG_HOLES               0x00000100      /* support for holes */
  74#define CRAMFS_FLAG_WRONG_SIGNATURE     0x00000200      /* reserved */
  75#define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400      /* shifted root fs */
  76
  77/*
  78 * Valid values in super.flags.  Currently we refuse to mount
  79 * if (flags & ~CRAMFS_SUPPORTED_FLAGS).  Maybe that should be
  80 * changed to test super.future instead.
  81 */
  82#define CRAMFS_SUPPORTED_FLAGS  ( 0x000000ff \
  83                                | CRAMFS_FLAG_HOLES \
  84                                | CRAMFS_FLAG_WRONG_SIGNATURE \
  85                                | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET )
  86
  87#ifdef __KERNEL__
  88/* Uncompression interfaces to the underlying zlib */
  89int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen);
  90int cramfs_uncompress_init(void);
  91void cramfs_uncompress_exit(void);
  92#endif /* __KERNEL__ */
  93
  94#endif
  95
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