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# Copyright (C) 2015-2019 Chris Lalancette <clalancette@gmail.com>
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation;
# version 2.1 of the License.
# This library 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
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
'''
Class to support ISO9660 Path Table Records.
'''
from __future__ import absolute_import
import struct
from pycdlib import pycdlibexception
from pycdlib import utils
# For mypy annotations
if False: # pylint: disable=using-constant-test
from typing import Type # NOQA pylint: disable=unused-import
class PathTableRecord(object):
'''
A class that represents a single ISO9660 Path Table Record.
'''
__slots__ = ('_initialized', 'len_di', 'xattr_length', 'extent_location',
'parent_directory_num', 'directory_identifier', 'dirrecord')
FMT = '<BBLH'
def __init__(self):
# type: () -> None
self._initialized = False
def parse(self, data):
# type: (bytes) -> None
'''
Parse an ISO9660 Path Table Record out of a string.
Parameters:
data - The string to parse.
Returns:
Nothing.
'''
if self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record already initialized')
(self.len_di, self.xattr_length, self.extent_location,
self.parent_directory_num) = struct.unpack_from(self.FMT, data[:8], 0)
if self.len_di % 2 != 0:
self.directory_identifier = data[8:-1]
else:
self.directory_identifier = data[8:]
self.dirrecord = None
self._initialized = True
def _record(self, ext_loc, parent_dir_num):
# type: (int, int) -> bytes
'''
An internal method to generate a string representing this Path Table Record.
Parameters:
ext_loc - The extent location to place in this Path Table Record.
parent_dir_num - The parent directory number to place in this Path Table
Record.
Returns:
A string representing this Path Table Record.
'''
return struct.pack(self.FMT, self.len_di, self.xattr_length,
ext_loc, parent_dir_num) + self.directory_identifier + b'\x00' * (self.len_di % 2)
def record_little_endian(self):
# type: () -> bytes
'''
Generate a string representing the little endian version of this Path
Table Record.
Parameters:
None.
Returns:
A string representing the little endian version of this Path Table Record.
'''
if not self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record not initialized')
return self._record(self.extent_location, self.parent_directory_num)
def record_big_endian(self):
# type: () -> bytes
'''
Generate a string representing the big endian version of
this Path Table Record.
Parameters:
None.
Returns:
A string representing the big endian version of this Path Table Record.
'''
if not self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record not initialized')
return self._record(utils.swab_32bit(self.extent_location),
utils.swab_16bit(self.parent_directory_num))
@classmethod
def record_length(cls, len_di):
# type: (Type[PathTableRecord], int) -> int
'''
A class method to calculate the length of a Path Table Record.
Parameters:
len_di - The length of the name for this Path Directory Record.
Returns:
The total length that a Path Directory Record with this name would occupy.
'''
return struct.calcsize(cls.FMT) + len_di + (len_di % 2)
def _new(self, name, parent_dir_num):
# type: (bytes, int) -> None
'''
An internal method to create a new Path Table Record.
Parameters:
name - The name for this Path Table Record.
parent_dir_num - The directory number of the parent of this Path Table
Record.
Returns:
Nothing.
'''
self.len_di = len(name)
self.xattr_length = 0 # FIXME: we don't support xattr for now
self.parent_directory_num = parent_dir_num
self.directory_identifier = name
self._initialized = True
def new_root(self):
# type: () -> None
'''
Create a new root Path Table Record.
Parameters:
None.
Returns:
Nothing.
'''
if self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record already initialized')
self._new(b'\x00', 1)
def new_dir(self, name):
# type: (bytes) -> None
'''
Create a new Path Table Record.
Parameters:
name - The name for this Path Table Record.
Returns:
Nothing.
'''
if self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record already initialized')
# Zero for the parent dir num is bogus, but that will get fixed later.
self._new(name, 0)
def update_extent_location(self, extent_loc):
# type: (int) -> None
'''
Update the extent location for this Path Table Record.
Parameters:
extent_loc - The new extent location.
Returns:
Nothing.
'''
if not self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record not initialized')
self.extent_location = extent_loc
def update_parent_directory_number(self, parent_dir_num):
# type: (int) -> None
'''
Update the parent directory number for this Path Table Record.
Parameters:
parent_dir_num - The new parent directory number to assign to this PTR.
Returns:
Nothing.
'''
if not self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record not initialized')
self.parent_directory_num = parent_dir_num
def equal_to_be(self, be_record):
# type: (PathTableRecord) -> bool
'''
Compare a little-endian path table record to its big-endian counterpart.
This is used to ensure that the ISO is sane.
Parameters:
be_record - The big-endian object to compare with the little-endian
object.
Returns:
True if this record is equal to the big-endian record passed in,
False otherwise.
'''
if not self._initialized:
raise pycdlibexception.PyCdlibInternalError('Path Table Record not initialized')
if be_record.len_di != self.len_di or \
be_record.xattr_length != self.xattr_length or \
utils.swab_32bit(be_record.extent_location) != self.extent_location or \
utils.swab_16bit(be_record.parent_directory_num) != self.parent_directory_num or \
be_record.directory_identifier != self.directory_identifier:
return False
return True
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