Move file set parsing into the udf module.

This just moves more of the parsing where it should be.

Signed-off-by: Chris Lalancette <clalancette@openrobotics.org>

Author: clalancette

pycdlib/pycdlib.py

@@ -22,7 +22,6 @@
 import collections
 import inspect
 import io
-import logging
 import os
 import struct
 import sys
@@ -69,7 +68,6 @@
 # We allow A-Z, 0-9, and _ as "d1" characters.  The below is the fastest way to
 # build that list as integers.
 _allowed_d1_characters = set(tuple(range(65, 91)) + tuple(range(48, 58)) + tuple((ord(b'_'),)))
-_logger = logging.getLogger(__name__)
 
 
 def _check_d1_characters(name):
@@ -2064,28 +2062,9 @@ def _parse_udf_descriptors(self):
         # Read the data for the File Set and File Terminator together
         file_set_and_term_data = self._cdfp.read(2 * self.logical_block_size)
 
-        desc_tag = udfmod.UDFTag()
-        desc_tag.parse(file_set_and_term_data[:self.logical_block_size], 0)
-        if desc_tag.tag_ident != 256:
-            raise pycdlibexception.PyCdlibInvalidISO('UDF File Set Tag identifier not 256')
-        self.udf_file_set.parse(file_set_and_term_data[:self.logical_block_size],
-                                current_extent, desc_tag)
-
-        current_extent += 1
-        (tag_ident,) = struct.unpack_from('<H', file_set_and_term_data, self.logical_block_size)
-        self.udf_file_set_terminator = udfmod.UDFTerminatingDescriptor()
-        if tag_ident == 8:
-            desc_tag = udfmod.UDFTag()
-            desc_tag.parse(file_set_and_term_data[self.logical_block_size:],
-                           current_extent - self.udf_main_descs.partitions[0].part_start_location)
-            self.udf_file_set_terminator.parse(current_extent, desc_tag)
-        else:
-            # In this case, the UDF ISO had an invalid File Set Terminator Tag.
-            # But this isn't fatal, so log a warning and continue on.
-            _logger.warning('Missing UDF File Set Terminator, continuing')
-            self.udf_file_set_terminator.new()
-            self.udf_file_set_terminator.orig_extent_loc = current_extent
-            self.udf_file_set_terminator.desc_tag.tag_location = current_extent - self.udf_main_descs.partitions[0].part_start_location
+        self.udf_file_set, self.udf_file_set_terminator = udfmod.parse_file_set(file_set_and_term_data,
+                                                                                current_extent,
+                                                                                self.logical_block_size)
 
     def _walk_udf_directories(self, extent_to_inode):
         # type: (Dict[int, inode.Inode]) -> None

pycdlib/udf.py

@@ -18,6 +18,7 @@
 
 from __future__ import absolute_import
 
+import logging
 import random
 import struct
 import sys
@@ -92,6 +93,9 @@
     have_py_3 = False
 
 
+_logger = logging.getLogger('pycdlib')
+
+
 def crc_ccitt(data):
     # type: (bytes) -> int
     """
@@ -5822,6 +5826,44 @@ def parse_logical_volume_integrity(integrity_data, current_extent, logical_block
     return logical_volume_integrity, logical_volume_integrity_terminator
 
 
+def parse_file_set(file_set_and_term_data, current_extent, logical_block_size):
+    # type: (bytes, int, int) -> Tuple[UDFFileSetDescriptor, UDFTerminatingDescriptor]
+    """
+    An internal method to parse File Set data, and the File Set Terminator.
+
+    Parameters:
+     file_set_and_term_data - The data to parse.
+     current_extent - The extent location of the data.
+     logical_block_size - The logical block size of the ISO.
+    Returns:
+     A tuple where the first item is a UDFFileSetDescriptor, and the second item
+     is a UDFTerminatorDescriptor.
+    """
+    desc_tag = UDFTag()
+    desc_tag.parse(file_set_and_term_data[:logical_block_size], 0)
+    if desc_tag.tag_ident != 256:
+        raise pycdlibexception.PyCdlibInvalidISO('UDF File Set Tag identifier not 256')
+    file_set = UDFFileSetDescriptor()
+    file_set.parse(file_set_and_term_data[:logical_block_size],
+                   current_extent, desc_tag)
+
+    (tag_ident,) = struct.unpack_from('<H', file_set_and_term_data, logical_block_size)
+    file_set_terminator = UDFTerminatingDescriptor()
+    if tag_ident == 8:
+        desc_tag = UDFTag()
+        desc_tag.parse(file_set_and_term_data[logical_block_size:], 1)
+        file_set_terminator.parse(current_extent + 1, desc_tag)
+    else:
+        # In this case, the UDF ISO had an invalid File Set Terminator Tag.
+        # But this isn't fatal, so log a warning and continue on.
+        _logger.warning('Missing UDF File Set Terminator, continuing')
+        file_set_terminator.new()
+        file_set_terminator.orig_extent_loc = current_extent + 1
+        file_set_terminator.desc_tag.tag_location = 1
+
+    return file_set, file_set_terminator
+
+
 def parse_file_entry(icbdata, abs_file_entry_extent, icb_log_block_num, parent):
     # type: (bytes, int, int, Optional[UDFFileEntry]) -> Optional[UDFFileEntry]
     """