This page hosts a formal specification of ext2 filesystem using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.
The Ruby runtime library can be installed from RubyGems:
gem install kaitai-structParse a local file and get structure in memory:
data = Ext2.from_file("path/to/local/file.bin")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = Ext2.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.bg1 # => get bg1
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
require 'kaitai/struct/struct'
unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end
class Ext2 < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
self
end
class SuperBlockStruct < Kaitai::Struct::Struct
STATE_ENUM = {
1 => :state_enum_valid_fs,
2 => :state_enum_error_fs,
}
I__STATE_ENUM = STATE_ENUM.invert
ERRORS_ENUM = {
1 => :errors_enum_act_continue,
2 => :errors_enum_act_ro,
3 => :errors_enum_act_panic,
}
I__ERRORS_ENUM = ERRORS_ENUM.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@inodes_count = @_io.read_u4le
@blocks_count = @_io.read_u4le
@r_blocks_count = @_io.read_u4le
@free_blocks_count = @_io.read_u4le
@free_inodes_count = @_io.read_u4le
@first_data_block = @_io.read_u4le
@log_block_size = @_io.read_u4le
@log_frag_size = @_io.read_u4le
@blocks_per_group = @_io.read_u4le
@frags_per_group = @_io.read_u4le
@inodes_per_group = @_io.read_u4le
@mtime = @_io.read_u4le
@wtime = @_io.read_u4le
@mnt_count = @_io.read_u2le
@max_mnt_count = @_io.read_u2le
@magic = @_io.read_bytes(2)
raise Kaitai::Struct::ValidationNotEqualError.new([83, 239].pack('C*'), magic, _io, "/types/super_block_struct/seq/15") if not magic == [83, 239].pack('C*')
@state = Kaitai::Struct::Stream::resolve_enum(STATE_ENUM, @_io.read_u2le)
@errors = Kaitai::Struct::Stream::resolve_enum(ERRORS_ENUM, @_io.read_u2le)
@minor_rev_level = @_io.read_u2le
@lastcheck = @_io.read_u4le
@checkinterval = @_io.read_u4le
@creator_os = @_io.read_u4le
@rev_level = @_io.read_u4le
@def_resuid = @_io.read_u2le
@def_resgid = @_io.read_u2le
@first_ino = @_io.read_u4le
@inode_size = @_io.read_u2le
@block_group_nr = @_io.read_u2le
@feature_compat = @_io.read_u4le
@feature_incompat = @_io.read_u4le
@feature_ro_compat = @_io.read_u4le
@uuid = @_io.read_bytes(16)
@volume_name = @_io.read_bytes(16)
@last_mounted = @_io.read_bytes(64)
@algo_bitmap = @_io.read_u4le
@prealloc_blocks = @_io.read_u1
@prealloc_dir_blocks = @_io.read_u1
@padding1 = @_io.read_bytes(2)
@journal_uuid = @_io.read_bytes(16)
@journal_inum = @_io.read_u4le
@journal_dev = @_io.read_u4le
@last_orphan = @_io.read_u4le
@hash_seed = []
(4).times { |i|
@hash_seed << @_io.read_u4le
}
@def_hash_version = @_io.read_u1
self
end
def block_size
return @block_size unless @block_size.nil?
@block_size = (1024 << log_block_size)
@block_size
end
def block_group_count
return @block_group_count unless @block_group_count.nil?
@block_group_count = (blocks_count / blocks_per_group)
@block_group_count
end
attr_reader :inodes_count
attr_reader :blocks_count
attr_reader :r_blocks_count
attr_reader :free_blocks_count
attr_reader :free_inodes_count
attr_reader :first_data_block
attr_reader :log_block_size
attr_reader :log_frag_size
attr_reader :blocks_per_group
attr_reader :frags_per_group
attr_reader :inodes_per_group
attr_reader :mtime
attr_reader :wtime
attr_reader :mnt_count
attr_reader :max_mnt_count
attr_reader :magic
attr_reader :state
attr_reader :errors
attr_reader :minor_rev_level
attr_reader :lastcheck
attr_reader :checkinterval
attr_reader :creator_os
attr_reader :rev_level
attr_reader :def_resuid
attr_reader :def_resgid
attr_reader :first_ino
attr_reader :inode_size
attr_reader :block_group_nr
attr_reader :feature_compat
attr_reader :feature_incompat
attr_reader :feature_ro_compat
attr_reader :uuid
attr_reader :volume_name
attr_reader :last_mounted
attr_reader :algo_bitmap
attr_reader :prealloc_blocks
attr_reader :prealloc_dir_blocks
attr_reader :padding1
attr_reader :journal_uuid
attr_reader :journal_inum
attr_reader :journal_dev
attr_reader :last_orphan
attr_reader :hash_seed
attr_reader :def_hash_version
end
class DirEntry < Kaitai::Struct::Struct
FILE_TYPE_ENUM = {
0 => :file_type_enum_unknown,
1 => :file_type_enum_reg_file,
2 => :file_type_enum_dir,
3 => :file_type_enum_chrdev,
4 => :file_type_enum_blkdev,
5 => :file_type_enum_fifo,
6 => :file_type_enum_sock,
7 => :file_type_enum_symlink,
}
I__FILE_TYPE_ENUM = FILE_TYPE_ENUM.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@inode_ptr = @_io.read_u4le
@rec_len = @_io.read_u2le
@name_len = @_io.read_u1
@file_type = Kaitai::Struct::Stream::resolve_enum(FILE_TYPE_ENUM, @_io.read_u1)
@name = (@_io.read_bytes(name_len)).force_encoding("UTF-8")
@padding = @_io.read_bytes(((rec_len - name_len) - 8))
self
end
def inode
return @inode unless @inode.nil?
@inode = _root.bg1.block_groups[((inode_ptr - 1) / _root.bg1.super_block.inodes_per_group)].inodes[((inode_ptr - 1) % _root.bg1.super_block.inodes_per_group)]
@inode
end
attr_reader :inode_ptr
attr_reader :rec_len
attr_reader :name_len
attr_reader :file_type
attr_reader :name
attr_reader :padding
end
class Inode < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@mode = @_io.read_u2le
@uid = @_io.read_u2le
@size = @_io.read_u4le
@atime = @_io.read_u4le
@ctime = @_io.read_u4le
@mtime = @_io.read_u4le
@dtime = @_io.read_u4le
@gid = @_io.read_u2le
@links_count = @_io.read_u2le
@blocks = @_io.read_u4le
@flags = @_io.read_u4le
@osd1 = @_io.read_u4le
@block = []
(15).times { |i|
@block << BlockPtr.new(@_io, self, @_root)
}
@generation = @_io.read_u4le
@file_acl = @_io.read_u4le
@dir_acl = @_io.read_u4le
@faddr = @_io.read_u4le
@osd2 = @_io.read_bytes(12)
self
end
def as_dir
return @as_dir unless @as_dir.nil?
io = block[0].body._io
_pos = io.pos
io.seek(0)
@as_dir = Dir.new(io, self, @_root)
io.seek(_pos)
@as_dir
end
attr_reader :mode
attr_reader :uid
attr_reader :size
attr_reader :atime
attr_reader :ctime
attr_reader :mtime
attr_reader :dtime
attr_reader :gid
attr_reader :links_count
attr_reader :blocks
attr_reader :flags
attr_reader :osd1
attr_reader :block
attr_reader :generation
attr_reader :file_acl
attr_reader :dir_acl
attr_reader :faddr
attr_reader :osd2
end
class BlockPtr < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@ptr = @_io.read_u4le
self
end
def body
return @body unless @body.nil?
_pos = @_io.pos
@_io.seek((ptr * _root.bg1.super_block.block_size))
@_raw_body = @_io.read_bytes(_root.bg1.super_block.block_size)
_io__raw_body = Kaitai::Struct::Stream.new(@_raw_body)
@body = RawBlock.new(_io__raw_body, self, @_root)
@_io.seek(_pos)
@body
end
attr_reader :ptr
attr_reader :_raw_body
end
class Dir < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@entries = []
i = 0
while not @_io.eof?
@entries << DirEntry.new(@_io, self, @_root)
i += 1
end
self
end
attr_reader :entries
end
class BlockGroup < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@_raw_super_block = @_io.read_bytes(1024)
_io__raw_super_block = Kaitai::Struct::Stream.new(@_raw_super_block)
@super_block = SuperBlockStruct.new(_io__raw_super_block, self, @_root)
@block_groups = []
(super_block.block_group_count).times { |i|
@block_groups << Bgd.new(@_io, self, @_root)
}
self
end
attr_reader :super_block
attr_reader :block_groups
attr_reader :_raw_super_block
end
class Bgd < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@block_bitmap_block = @_io.read_u4le
@inode_bitmap_block = @_io.read_u4le
@inode_table_block = @_io.read_u4le
@free_blocks_count = @_io.read_u2le
@free_inodes_count = @_io.read_u2le
@used_dirs_count = @_io.read_u2le
@pad_reserved = @_io.read_bytes((2 + 12))
self
end
def block_bitmap
return @block_bitmap unless @block_bitmap.nil?
_pos = @_io.pos
@_io.seek((block_bitmap_block * _root.bg1.super_block.block_size))
@block_bitmap = @_io.read_bytes(1024)
@_io.seek(_pos)
@block_bitmap
end
def inode_bitmap
return @inode_bitmap unless @inode_bitmap.nil?
_pos = @_io.pos
@_io.seek((inode_bitmap_block * _root.bg1.super_block.block_size))
@inode_bitmap = @_io.read_bytes(1024)
@_io.seek(_pos)
@inode_bitmap
end
def inodes
return @inodes unless @inodes.nil?
_pos = @_io.pos
@_io.seek((inode_table_block * _root.bg1.super_block.block_size))
@inodes = []
(_root.bg1.super_block.inodes_per_group).times { |i|
@inodes << Inode.new(@_io, self, @_root)
}
@_io.seek(_pos)
@inodes
end
attr_reader :block_bitmap_block
attr_reader :inode_bitmap_block
attr_reader :inode_table_block
attr_reader :free_blocks_count
attr_reader :free_inodes_count
attr_reader :used_dirs_count
attr_reader :pad_reserved
end
class RawBlock < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@body = @_io.read_bytes(_root.bg1.super_block.block_size)
self
end
attr_reader :body
end
def bg1
return @bg1 unless @bg1.nil?
_pos = @_io.pos
@_io.seek(1024)
@bg1 = BlockGroup.new(@_io, self, @_root)
@_io.seek(_pos)
@bg1
end
def root_dir
return @root_dir unless @root_dir.nil?
@root_dir = bg1.block_groups[0].inodes[1].as_dir
@root_dir
end
end