squashfs_fs.h

一款linux的文件系统

#ifndef SQUASHFS_FS
#define SQUASHFS_FS
/*
 * Squashfs
 *
 * Copyright (c) 2002, 2003, 2004 Phillip Lougher <[e-mail]>
 *
 * 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,
 * 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 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * squashfs_fs.h
 */

#define SQUASHFS_MAJOR			2
#define SQUASHFS_MINOR			1
#define SQUASHFS_MAGIC			0x73717368
#define SQUASHFS_MAGIC_SWAP		0x68737173
#define SQUASHFS_START			0

/* size of metadata (inode and directory) blocks */
#define SQUASHFS_METADATA_SIZE		8192
#define SQUASHFS_METADATA_LOG		13

/* default size of data blocks */
#define SQUASHFS_FILE_SIZE		65536
#define SQUASHFS_FILE_LOG		16

#define SQUASHFS_FILE_MAX_SIZE		65536

/* Max number of uids and gids */
#define SQUASHFS_UIDS			256
#define SQUASHFS_GUIDS			255

/* Max length of filename (not 255) */
#define SQUASHFS_NAME_LEN		256

#define SQUASHFS_INVALID		((long long) 0xffffffffffff)
#define SQUASHFS_INVALID_BLK		((long long) 0xffffffff)
#define SQUASHFS_USED_BLK		((long long) 0xfffffffe)

/* Filesystem flags */
#define SQUASHFS_NOI			0
#define SQUASHFS_NOD			1
#define SQUASHFS_CHECK			2
#define SQUASHFS_NOF			3
#define SQUASHFS_NO_FRAG		4
#define SQUASHFS_ALWAYS_FRAG		5
#define SQUASHFS_DUPLICATE		6
#define SQUASHFS_BIT(flag, bit)		((flag >> bit) & 1)
#define SQUASHFS_UNCOMPRESSED_INODES(flags)	SQUASHFS_BIT(flags, SQUASHFS_NOI)
#define SQUASHFS_UNCOMPRESSED_DATA(flags)	SQUASHFS_BIT(flags, SQUASHFS_NOD)
#define SQUASHFS_UNCOMPRESSED_FRAGMENTS(flags)	SQUASHFS_BIT(flags, SQUASHFS_NOF)
#define SQUASHFS_NO_FRAGMENTS(flags)		SQUASHFS_BIT(flags, SQUASHFS_NO_FRAG)
#define SQUASHFS_ALWAYS_FRAGMENTS(flags)	SQUASHFS_BIT(flags, SQUASHFS_ALWAYS_FRAG)
#define SQUASHFS_DUPLICATES(flags)		SQUASHFS_BIT(flags, SQUASHFS_DUPLICATE)
#define SQUASHFS_CHECK_DATA(flags)		SQUASHFS_BIT(flags, SQUASHFS_CHECK)
#define SQUASHFS_MKFLAGS(noi, nod, check_data, nof, no_frag, always_frag, duplicate_checking)	(noi | (nod << 1) | (check_data << 2) | (nof << 3) | (no_frag << 4) | (always_frag << 5) | (duplicate_checking << 6))

/* Max number of types and file types */
#define SQUASHFS_DIR_TYPE		1
#define SQUASHFS_FILE_TYPE		2
#define SQUASHFS_SYMLINK_TYPE		3
#define SQUASHFS_BLKDEV_TYPE		4
#define SQUASHFS_CHRDEV_TYPE		5
#define SQUASHFS_FIFO_TYPE		6
#define SQUASHFS_SOCKET_TYPE		7
#define SQUASHFS_LDIR_TYPE		8

/* 1.0 filesystem type definitions */
#define SQUASHFS_TYPES			5
#define SQUASHFS_IPC_TYPE		0

/* Flag whether block is compressed or uncompressed, bit is set if block is uncompressed */
#define SQUASHFS_COMPRESSED_BIT		(1 << 15)
#define SQUASHFS_COMPRESSED_SIZE(B)	(((B) & ~SQUASHFS_COMPRESSED_BIT) ? \
					(B) & ~SQUASHFS_COMPRESSED_BIT : SQUASHFS_COMPRESSED_BIT)

#define SQUASHFS_COMPRESSED(B)		(!((B) & SQUASHFS_COMPRESSED_BIT))

#define SQUASHFS_COMPRESSED_BIT_BLOCK		(1 << 24)
#define SQUASHFS_COMPRESSED_SIZE_BLOCK(B)	(((B) & ~SQUASHFS_COMPRESSED_BIT_BLOCK) ? \
					(B) & ~SQUASHFS_COMPRESSED_BIT_BLOCK : SQUASHFS_COMPRESSED_BIT_BLOCK)

#define SQUASHFS_COMPRESSED_BLOCK(B)		(!((B) & SQUASHFS_COMPRESSED_BIT_BLOCK))

/*
 * Inode number ops.  Inodes consist of a compressed block number, and an uncompressed
 * offset within that block
 */
#define SQUASHFS_INODE_BLK(a)		((unsigned int) ((a) >> 16))
#define SQUASHFS_INODE_OFFSET(a)	((unsigned int) ((a) & 0xffff))
#define SQUASHFS_MKINODE(A, B)		((squashfs_inode)(((squashfs_inode) (A) << 16)\
					+ (B)))

/* Compute 32 bit VFS inode number from squashfs inode number */
#define SQUASHFS_MK_VFS_INODE(a, b)	((unsigned int) (((a) << 8) + ((b) >> 2) + 1))

/* Translate between VFS mode and squashfs mode */
#define SQUASHFS_MODE(a)		((a) & 0xfff)

/* fragment and fragment table defines */
typedef unsigned int			squashfs_fragment_index;
#define SQUASHFS_FRAGMENT_BYTES(A)	(A * sizeof(squashfs_fragment_entry))
#define SQUASHFS_FRAGMENT_INDEX(A)	(SQUASHFS_FRAGMENT_BYTES(A) / SQUASHFS_METADATA_SIZE)
#define SQUASHFS_FRAGMENT_INDEX_OFFSET(A)	(SQUASHFS_FRAGMENT_BYTES(A) % SQUASHFS_METADATA_SIZE)
#define SQUASHFS_FRAGMENT_INDEXES(A)	((SQUASHFS_FRAGMENT_BYTES(A) + SQUASHFS_METADATA_SIZE - 1) / SQUASHFS_METADATA_SIZE)
#define SQUASHFS_FRAGMENT_INDEX_BYTES(A)	(SQUASHFS_FRAGMENT_INDEXES(A) * sizeof(squashfs_fragment_index))
#define SQUASHFS_CACHED_FRAGMENTS	3

/* cached data constants for filesystem */
#define SQUASHFS_CACHED_BLKS		8

#define SQUASHFS_MAX_FILE_SIZE_LOG	32
#define SQUASHFS_MAX_FILE_SIZE		((long long) 1 << (SQUASHFS_MAX_FILE_SIZE_LOG - 1))

#define SQUASHFS_MARKER_BYTE		0xff


/*
 * definitions for structures on disk
 */

typedef unsigned int		squashfs_block;
typedef long long		squashfs_inode;

typedef unsigned int		squashfs_uid;

typedef struct squashfs_super_block {
	unsigned int		s_magic;
	unsigned int		inodes;
	unsigned int		bytes_used;
	unsigned int		uid_start;
	unsigned int		guid_start;
	unsigned int		inode_table_start;
	unsigned int		directory_table_start;
	unsigned int		s_major:16;
	unsigned int		s_minor:16;
	unsigned int		block_size_1:16;
	unsigned int		block_log:16;
	unsigned int		flags:8;
	unsigned int		no_uids:8;
	unsigned int		no_guids:8;
	unsigned int		mkfs_time /* time of filesystem creation */;
	squashfs_inode		root_inode;
	unsigned int		block_size;
	unsigned int		fragments;
	unsigned int		fragment_table_start;
} __attribute__ ((packed)) squashfs_super_block;

typedef struct {
	unsigned int		index:27;
	unsigned int		start_block:29;
	unsigned char		size;
	unsigned char		name[0];
} __attribute__ ((packed)) squashfs_dir_index;

typedef struct {
	unsigned int		inode_type:4;
	unsigned int		mode:12; /* protection */
	unsigned int		uid:8; /* index into uid table */
	unsigned int		guid:8; /* index into guid table */
} __attribute__ ((packed)) squashfs_base_inode_header;

typedef squashfs_base_inode_header squashfs_ipc_inode_header;

typedef struct {
	unsigned int		inode_type:4;
	unsigned int		mode:12; /* protection */
	unsigned int		uid:8; /* index into uid table */
	unsigned int		guid:8; /* index into guid table */
	unsigned short		rdev;
} __attribute__ ((packed)) squashfs_dev_inode_header;
	
typedef struct {
	unsigned int		inode_type:4;
	unsigned int		mode:12; /* protection */
	unsigned int		uid:8; /* index into uid table */
	unsigned int		guid:8; /* index into guid table */
	unsigned short		symlink_size;
	char			symlink[0];
} __attribute__ ((packed)) squashfs_symlink_inode_header;

typedef struct {
	unsigned int		inode_type:4;
	unsigned int		mode:12; /* protection */
	unsigned int		uid:8; /* index into uid table */
	unsigned int		guid:8; /* index into guid table */
	unsigned int		mtime;
	squashfs_block		start_block;
	unsigned int		fragment;
	unsigned int		offset;
	unsigned int		file_size:SQUASHFS_MAX_FILE_SIZE_LOG;
	unsigned short		block_list[0];
} __attribute__ ((packed)) squashfs_reg_inode_header;

typedef struct {
	unsigned int		inode_type:4;
	unsigned int		mode:12; /* protection */
	unsigned int		uid:8; /* index into uid table */
	unsigned int		guid:8; /* index into guid table */
	unsigned int		file_size:19;
	unsigned int		offset:13;
	unsigned int		mtime;
	unsigned int		start_block:24;
} __attribute__  ((packed)) squashfs_dir_inode_header;

typedef struct {
	unsigned int		inode_type:4;
	unsigned int		mode:12; /* protection */
	unsigned int		uid:8; /* index into uid table */
	unsigned int		guid:8; /* index into guid table */
	unsigned int		file_size:27;
	unsigned int		offset:13;
	unsigned int		mtime;
	unsigned int		start_block:24;
	unsigned int		i_count:16;
	squashfs_dir_index	index[0];
} __attribute__  ((packed)) squashfs_ldir_inode_header;

typedef union {
	squashfs_base_inode_header	base;
	squashfs_dev_inode_header	dev;
	squashfs_symlink_inode_header	symlink;
	squashfs_reg_inode_header	reg;
	squashfs_dir_inode_header	dir;
	squashfs_ldir_inode_header	ldir;
	squashfs_ipc_inode_header	ipc;
} squashfs_inode_header;
	
typedef struct {
	unsigned int		offset:13;
	unsigned int		type:3;
	unsigned int		size:8;
	char			name[0];
} __attribute__ ((packed)) squashfs_dir_entry;

typedef struct {
	unsigned int		count:8;
	unsigned int		start_block:24;
} __attribute__ ((packed)) squashfs_dir_header;

typedef struct {
	unsigned int		start_block;
	unsigned int		size;
} __attribute__ ((packed)) squashfs_fragment_entry;