This page hosts a formal specification of cramfs 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 = Cramfs.from_file("path/to/local/file.bin")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = Cramfs.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.super_block # => get super block
# 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 Cramfs < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@super_block = SuperBlockStruct.new(@_io, self, @_root)
self
end
class SuperBlockStruct < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@magic = @_io.read_bytes(4)
raise Kaitai::Struct::ValidationNotEqualError.new([69, 61, 205, 40].pack('C*'), magic, _io, "/types/super_block_struct/seq/0") if not magic == [69, 61, 205, 40].pack('C*')
@size = @_io.read_u4le
@flags = @_io.read_u4le
@future = @_io.read_u4le
@signature = @_io.read_bytes(16)
raise Kaitai::Struct::ValidationNotEqualError.new([67, 111, 109, 112, 114, 101, 115, 115, 101, 100, 32, 82, 79, 77, 70, 83].pack('C*'), signature, _io, "/types/super_block_struct/seq/4") if not signature == [67, 111, 109, 112, 114, 101, 115, 115, 101, 100, 32, 82, 79, 77, 70, 83].pack('C*')
@fsid = Info.new(@_io, self, @_root)
@name = (@_io.read_bytes(16)).force_encoding("ASCII")
@root = Inode.new(@_io, self, @_root)
self
end
def flag_fsid_v2
return @flag_fsid_v2 unless @flag_fsid_v2.nil?
@flag_fsid_v2 = ((flags >> 0) & 1)
@flag_fsid_v2
end
def flag_holes
return @flag_holes unless @flag_holes.nil?
@flag_holes = ((flags >> 8) & 1)
@flag_holes
end
def flag_wrong_signature
return @flag_wrong_signature unless @flag_wrong_signature.nil?
@flag_wrong_signature = ((flags >> 9) & 1)
@flag_wrong_signature
end
def flag_sorted_dirs
return @flag_sorted_dirs unless @flag_sorted_dirs.nil?
@flag_sorted_dirs = ((flags >> 1) & 1)
@flag_sorted_dirs
end
def flag_shifted_root_offset
return @flag_shifted_root_offset unless @flag_shifted_root_offset.nil?
@flag_shifted_root_offset = ((flags >> 10) & 1)
@flag_shifted_root_offset
end
attr_reader :magic
attr_reader :size
attr_reader :flags
attr_reader :future
attr_reader :signature
attr_reader :fsid
attr_reader :name
attr_reader :root
end
class ChunkedDataInode < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@block_end_index = []
((((_parent.size + _root.page_size) - 1) / _root.page_size)).times { |i|
@block_end_index << @_io.read_u4le
}
@raw_blocks = @_io.read_bytes_full
self
end
attr_reader :block_end_index
attr_reader :raw_blocks
end
class Inode < Kaitai::Struct::Struct
FILE_TYPE = {
1 => :file_type_fifo,
2 => :file_type_chrdev,
4 => :file_type_dir,
6 => :file_type_blkdev,
8 => :file_type_reg_file,
10 => :file_type_symlink,
12 => :file_type_socket,
}
I__FILE_TYPE = FILE_TYPE.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@mode = @_io.read_u2le
@uid = @_io.read_u2le
@size_gid = @_io.read_u4le
@namelen_offset = @_io.read_u4le
@name = (@_io.read_bytes(namelen)).force_encoding("utf-8")
self
end
def attr
return @attr unless @attr.nil?
@attr = ((mode >> 9) & 7)
@attr
end
def as_reg_file
return @as_reg_file unless @as_reg_file.nil?
io = _root._io
_pos = io.pos
io.seek(offset)
@as_reg_file = ChunkedDataInode.new(io, self, @_root)
io.seek(_pos)
@as_reg_file
end
def perm_u
return @perm_u unless @perm_u.nil?
@perm_u = ((mode >> 6) & 7)
@perm_u
end
def as_symlink
return @as_symlink unless @as_symlink.nil?
io = _root._io
_pos = io.pos
io.seek(offset)
@as_symlink = ChunkedDataInode.new(io, self, @_root)
io.seek(_pos)
@as_symlink
end
def perm_o
return @perm_o unless @perm_o.nil?
@perm_o = (mode & 7)
@perm_o
end
def size
return @size unless @size.nil?
@size = (size_gid & 16777215)
@size
end
def gid
return @gid unless @gid.nil?
@gid = (size_gid >> 24)
@gid
end
def perm_g
return @perm_g unless @perm_g.nil?
@perm_g = ((mode >> 3) & 7)
@perm_g
end
def namelen
return @namelen unless @namelen.nil?
@namelen = ((namelen_offset & 63) << 2)
@namelen
end
def as_dir
return @as_dir unless @as_dir.nil?
io = _root._io
_pos = io.pos
io.seek(offset)
@_raw_as_dir = io.read_bytes(size)
_io__raw_as_dir = Kaitai::Struct::Stream.new(@_raw_as_dir)
@as_dir = DirInode.new(_io__raw_as_dir, self, @_root)
io.seek(_pos)
@as_dir
end
def type
return @type unless @type.nil?
@type = Kaitai::Struct::Stream::resolve_enum(FILE_TYPE, ((mode >> 12) & 15))
@type
end
def offset
return @offset unless @offset.nil?
@offset = (((namelen_offset >> 6) & 67108863) << 2)
@offset
end
attr_reader :mode
attr_reader :uid
attr_reader :size_gid
attr_reader :namelen_offset
attr_reader :name
attr_reader :_raw_as_dir
end
class DirInode < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
if _io.size > 0
@children = []
i = 0
while not @_io.eof?
@children << Inode.new(@_io, self, @_root)
i += 1
end
end
self
end
attr_reader :children
end
class Info < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@crc = @_io.read_u4le
@edition = @_io.read_u4le
@blocks = @_io.read_u4le
@files = @_io.read_u4le
self
end
attr_reader :crc
attr_reader :edition
attr_reader :blocks
attr_reader :files
end
def page_size
return @page_size unless @page_size.nil?
@page_size = 4096
@page_size
end
attr_reader :super_block
end