btrfs_stream: Ruby parsing library

Btrfs is a copy on write file system based on B-trees focusing on fault tolerance, repair and easy administration. Btrfs is intended to address the lack of pooling, snapshots, checksums, and integral multi-device spanning in Linux file systems. Given any pair of subvolumes (or snapshots), Btrfs can generate a binary diff between them by using the btrfs send command that can be replayed later by using btrfs receive, possibly on a different Btrfs file system. The btrfs send command creates a set of data modifications required for converting one subvolume into another. This spec can be used to disassemble the binary diff created by the btrfs send command. If you want a text representation you may want to checkout btrfs receive --dump instead.

Application

Btrfs

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of btrfs_stream using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime 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-struct

Code

Parse a local file and get structure in memory:

data = BtrfsStream.from_file("path/to/local/file.btrfs_stream")

Or parse structure from a string of bytes:

bytes = "\x00\x01\x02..."
data = BtrfsStream.new(Kaitai::Struct::Stream.new(bytes))

After that, one can get various attributes from the structure by invoking getter methods like:

data.header # => get header

Ruby source code to parse btrfs_stream

btrfs_stream.rb

# 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


##
# Btrfs is a copy on write file system based on B-trees focusing on fault tolerance, repair and easy
# administration. Btrfs is intended to address the lack of pooling, snapshots, checksums, and
# integral multi-device spanning in Linux file systems.
# Given any pair of subvolumes (or snapshots), Btrfs can generate a binary diff between them by
# using the `btrfs send` command that can be replayed later by using `btrfs receive`, possibly on a
# different Btrfs file system. The `btrfs send` command creates a set of data modifications required
# for converting one subvolume into another.
# This spec can be used to disassemble the binary diff created by the `btrfs send` command.
# If you want a text representation you may want to checkout `btrfs receive --dump` instead.
# @see https://btrfs.wiki.kernel.org/index.php/Design_notes_on_Send/Receive Source
class BtrfsStream < Kaitai::Struct::Struct

  COMMAND = {
    0 => :command_unspec,
    1 => :command_subvol,
    2 => :command_snapshot,
    3 => :command_mkfile,
    4 => :command_mkdir,
    5 => :command_mknod,
    6 => :command_mkfifo,
    7 => :command_mksock,
    8 => :command_symlink,
    9 => :command_rename,
    10 => :command_link,
    11 => :command_unlink,
    12 => :command_rmdir,
    13 => :command_set_xattr,
    14 => :command_remove_xattr,
    15 => :command_write,
    16 => :command_clone,
    17 => :command_truncate,
    18 => :command_chmod,
    19 => :command_chown,
    20 => :command_utimes,
    21 => :command_end,
    22 => :command_update_extent,
  }
  I__COMMAND = COMMAND.invert

  ATTRIBUTE = {
    0 => :attribute_unspec,
    1 => :attribute_uuid,
    2 => :attribute_ctransid,
    3 => :attribute_ino,
    4 => :attribute_size,
    5 => :attribute_mode,
    6 => :attribute_uid,
    7 => :attribute_gid,
    8 => :attribute_rdev,
    9 => :attribute_ctime,
    10 => :attribute_mtime,
    11 => :attribute_atime,
    12 => :attribute_otime,
    13 => :attribute_xattr_name,
    14 => :attribute_xattr_data,
    15 => :attribute_path,
    16 => :attribute_path_to,
    17 => :attribute_path_link,
    18 => :attribute_file_offset,
    19 => :attribute_data,
    20 => :attribute_clone_uuid,
    21 => :attribute_clone_ctransid,
    22 => :attribute_clone_path,
    23 => :attribute_clone_offset,
    24 => :attribute_clone_len,
  }
  I__ATTRIBUTE = ATTRIBUTE.invert
  def initialize(_io, _parent = nil, _root = self)
    super(_io, _parent, _root)
    _read
  end

  def _read
    @header = SendStreamHeader.new(@_io, self, @_root)
    @commands = []
    i = 0
    while not @_io.eof?
      @commands << SendCommand.new(@_io, self, @_root)
      i += 1
    end
    self
  end
  class SendStreamHeader < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @magic = @_io.read_bytes(13)
      raise Kaitai::Struct::ValidationNotEqualError.new([98, 116, 114, 102, 115, 45, 115, 116, 114, 101, 97, 109, 0].pack('C*'), magic, _io, "/types/send_stream_header/seq/0") if not magic == [98, 116, 114, 102, 115, 45, 115, 116, 114, 101, 97, 109, 0].pack('C*')
      @version = @_io.read_u4le
      self
    end
    attr_reader :magic
    attr_reader :version
  end
  class SendCommand < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @len_data = @_io.read_u4le
      @type = Kaitai::Struct::Stream::resolve_enum(BtrfsStream::COMMAND, @_io.read_u2le)
      @checksum = @_io.read_bytes(4)
      @_raw_data = @_io.read_bytes(len_data)
      _io__raw_data = Kaitai::Struct::Stream.new(@_raw_data)
      @data = Tlvs.new(_io__raw_data, self, @_root)
      self
    end
    class Tlv < Kaitai::Struct::Struct
      def initialize(_io, _parent = nil, _root = self)
        super(_io, _parent, _root)
        _read
      end

      def _read
        @type = Kaitai::Struct::Stream::resolve_enum(BtrfsStream::ATTRIBUTE, @_io.read_u2le)
        @length = @_io.read_u2le
        case type
        when :attribute_ctransid
          @value = @_io.read_u8le
        when :attribute_size
          @value = @_io.read_u8le
        when :attribute_clone_uuid
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = Uuid.new(_io__raw_value, self, @_root)
        when :attribute_file_offset
          @value = @_io.read_u8le
        when :attribute_otime
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = Timespec.new(_io__raw_value, self, @_root)
        when :attribute_uid
          @value = @_io.read_u8le
        when :attribute_atime
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = Timespec.new(_io__raw_value, self, @_root)
        when :attribute_ctime
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = Timespec.new(_io__raw_value, self, @_root)
        when :attribute_uuid
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = Uuid.new(_io__raw_value, self, @_root)
        when :attribute_clone_len
          @value = @_io.read_u8le
        when :attribute_xattr_name
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = String.new(_io__raw_value, self, @_root)
        when :attribute_clone_ctransid
          @value = @_io.read_u8le
        when :attribute_mode
          @value = @_io.read_u8le
        when :attribute_mtime
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = Timespec.new(_io__raw_value, self, @_root)
        when :attribute_path_link
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = String.new(_io__raw_value, self, @_root)
        when :attribute_rdev
          @value = @_io.read_u8le
        when :attribute_path_to
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = String.new(_io__raw_value, self, @_root)
        when :attribute_path
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = String.new(_io__raw_value, self, @_root)
        when :attribute_clone_offset
          @value = @_io.read_u8le
        when :attribute_gid
          @value = @_io.read_u8le
        when :attribute_clone_path
          @_raw_value = @_io.read_bytes(length)
          _io__raw_value = Kaitai::Struct::Stream.new(@_raw_value)
          @value = String.new(_io__raw_value, self, @_root)
        else
          @value = @_io.read_bytes(length)
        end
        self
      end
      attr_reader :type
      attr_reader :length
      attr_reader :value
      attr_reader :_raw_value
    end
    class Uuid < Kaitai::Struct::Struct
      def initialize(_io, _parent = nil, _root = self)
        super(_io, _parent, _root)
        _read
      end

      def _read
        @uuid = @_io.read_bytes(16)
        self
      end
      attr_reader :uuid
    end
    class Tlvs < Kaitai::Struct::Struct
      def initialize(_io, _parent = nil, _root = self)
        super(_io, _parent, _root)
        _read
      end

      def _read
        @tlv = []
        i = 0
        while not @_io.eof?
          @tlv << Tlv.new(@_io, self, @_root)
          i += 1
        end
        self
      end
      attr_reader :tlv
    end
    class String < Kaitai::Struct::Struct
      def initialize(_io, _parent = nil, _root = self)
        super(_io, _parent, _root)
        _read
      end

      def _read
        @string = (@_io.read_bytes_full).force_encoding("UTF-8")
        self
      end
      attr_reader :string
    end
    class Timespec < Kaitai::Struct::Struct
      def initialize(_io, _parent = nil, _root = self)
        super(_io, _parent, _root)
        _read
      end

      def _read
        @ts_sec = @_io.read_s8le
        @ts_nsec = @_io.read_s4le
        self
      end
      attr_reader :ts_sec
      attr_reader :ts_nsec
    end
    attr_reader :len_data
    attr_reader :type

    ##
    # CRC32 checksum of a whole send command, including the header, with this attribute set to 0.
    attr_reader :checksum
    attr_reader :data
    attr_reader :_raw_data
  end
  attr_reader :header
  attr_reader :commands
end