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.
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.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = BtrfsStream.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = BtrfsStream(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.header # => get header
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class BtrfsStream(KaitaiStruct):
"""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.
.. seealso::
Source - https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/index.php/Design_notes_on_Send/Receive.html
"""
class Command(Enum):
unspec = 0
subvol = 1
snapshot = 2
mkfile = 3
mkdir = 4
mknod = 5
mkfifo = 6
mksock = 7
symlink = 8
rename = 9
link = 10
unlink = 11
rmdir = 12
set_xattr = 13
remove_xattr = 14
write = 15
clone = 16
truncate = 17
chmod = 18
chown = 19
utimes = 20
end = 21
update_extent = 22
class Attribute(Enum):
unspec = 0
uuid = 1
ctransid = 2
ino = 3
size = 4
mode = 5
uid = 6
gid = 7
rdev = 8
ctime = 9
mtime = 10
atime = 11
otime = 12
xattr_name = 13
xattr_data = 14
path = 15
path_to = 16
path_link = 17
file_offset = 18
data = 19
clone_uuid = 20
clone_ctransid = 21
clone_path = 22
clone_offset = 23
clone_len = 24
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.header = BtrfsStream.SendStreamHeader(self._io, self, self._root)
self.commands = []
i = 0
while not self._io.is_eof():
self.commands.append(BtrfsStream.SendCommand(self._io, self, self._root))
i += 1
class SendStreamHeader(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.magic = self._io.read_bytes(13)
if not self.magic == b"\x62\x74\x72\x66\x73\x2D\x73\x74\x72\x65\x61\x6D\x00":
raise kaitaistruct.ValidationNotEqualError(b"\x62\x74\x72\x66\x73\x2D\x73\x74\x72\x65\x61\x6D\x00", self.magic, self._io, u"/types/send_stream_header/seq/0")
self.version = self._io.read_u4le()
class SendCommand(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.len_data = self._io.read_u4le()
self.type = KaitaiStream.resolve_enum(BtrfsStream.Command, self._io.read_u2le())
self.checksum = self._io.read_bytes(4)
self._raw_data = self._io.read_bytes(self.len_data)
_io__raw_data = KaitaiStream(BytesIO(self._raw_data))
self.data = BtrfsStream.SendCommand.Tlvs(_io__raw_data, self, self._root)
class Tlv(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.type = KaitaiStream.resolve_enum(BtrfsStream.Attribute, self._io.read_u2le())
self.length = self._io.read_u2le()
_on = self.type
if _on == BtrfsStream.Attribute.ctransid:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.size:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.clone_uuid:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.Uuid(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.file_offset:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.otime:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.Timespec(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.uid:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.atime:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.Timespec(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.ctime:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.Timespec(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.uuid:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.Uuid(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.clone_len:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.xattr_name:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.String(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.clone_ctransid:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.mode:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.mtime:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.Timespec(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.path_link:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.String(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.rdev:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.path_to:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.String(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.path:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.String(_io__raw_value, self, self._root)
elif _on == BtrfsStream.Attribute.clone_offset:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.gid:
self.value = self._io.read_u8le()
elif _on == BtrfsStream.Attribute.clone_path:
self._raw_value = self._io.read_bytes(self.length)
_io__raw_value = KaitaiStream(BytesIO(self._raw_value))
self.value = BtrfsStream.SendCommand.String(_io__raw_value, self, self._root)
else:
self.value = self._io.read_bytes(self.length)
class Uuid(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.uuid = self._io.read_bytes(16)
class Tlvs(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.tlv = []
i = 0
while not self._io.is_eof():
self.tlv.append(BtrfsStream.SendCommand.Tlv(self._io, self, self._root))
i += 1
class String(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.string = (self._io.read_bytes_full()).decode(u"UTF-8")
class Timespec(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.ts_sec = self._io.read_s8le()
self.ts_nsec = self._io.read_s4le()