def load_classes(self) -> Iterable[Tuple[int, DXFClass]]:
sentinel = self.data[:SENTINEL_SIZE]
if (
sentinel
!= b"\x8D\xA1\xC4\xB8\xC4\xA9\xF8\xC5\xC0\xDC\xF4\x5F\xE7\xCF\xB6\x8A"
):
raise DwgCorruptedClassesSection(
"Sentinel for start of CLASSES section not found."
)
start_index = SENTINEL_SIZE
bs = BitStream(
self.data[start_index:],
dxfversion=self.specs.version,
encoding=self.specs.encoding,
)
class_data_size = bs.read_unsigned_long() # data size in bytes
end_sentinel_index = SENTINEL_SIZE + 6 + class_data_size
end_index = end_sentinel_index - 2
end_bit_index = (3 + class_data_size) << 3
while bs.bit_index < end_bit_index:
class_num = bs.read_bit_short()
dxfattribs = {
"flags": bs.read_bit_short(), # version?
"app_name": bs.read_text(),
"cpp_class_name": bs.read_text(),
"name": bs.read_text(),
"was_a_proxy": bs.read_bit(),
"is_an_entity": int(bs.read_bit_short() == 0x1F2),
}
yield class_num, DXFClass.new(dxfattribs=dxfattribs)
if self.crc_check and False:
check = struct.unpack_from("<H", self.data, end_index)[0]
# TODO: classes crc check
# Which data should be checked? This is not correct:
crc = crc8(self.data[start_index:end_index])
if check != crc:
raise CRCError("CRC error in classes section.")
sentinel = self.data[
end_sentinel_index : end_sentinel_index + SENTINEL_SIZE
]
if (
sentinel
!= b"\x72\x5E\x3B\x47\x3B\x56\x07\x3A\x3F\x23\x0B\xA0\x18\x30\x49\x75"
):
raise DwgCorruptedClassesSection(
"Sentinel for end of CLASSES section not found."
)
def classes_R2000(self) -> None:
seeker, section_size = self.specs.sections[CLASSES_ID]
sentinel = self.data[seeker:seeker + SENTINEL_SIZE]
if sentinel != b'\x8D\xA1\xC4\xB8\xC4\xA9\xF8\xC5\xC0\xDC\xF4\x5F\xE7\xCF\xB6\x8A':
raise DwgCorruptedClassesSection(
'Sentinel for start of section not found.')
cls_tag = DXFTag(0, 'CLASS')
classes = self.sections['CLASSES']
bs = BitStream(
self.data[seeker + SENTINEL_SIZE:seeker + section_size],
dxfversion=self.specs.version,
encoding=self.specs.encoding,
)
class_data_size = bs.read_unsigned_long() # data size in bytes
end_index = (3 + class_data_size) << 3
while bs.bit_index < end_index:
class_num = bs.read_bit_short()
flags = bs.read_bit_short() # version?
app_name = bs.read_text()
cpp_class_name = bs.read_text()
class_dxf_name = bs.read_text()
was_a_zombie = bs.read_bit()
item_class_id = bs.read_bit_short()
# print((class_num, flags, app_name, class_dxf_name, cpp_class_name, was_a_zombie, item_class_id))
classes.append(
Tags([
cls_tag,
DXFTag(1, class_dxf_name),
DXFTag(2, cpp_class_name),
DXFTag(3, app_name),
DXFTag(90, flags),
DXFTag(280, was_a_zombie),
DXFTag(281, 1 if item_class_id == 0x1f2 else 0)
]))
self.dxf_object_types[class_num] = class_dxf_name
# Ignore crc for the sake of speed.
# _index = index + (20 + class_data_size)
# crc = struct.unpack_from('<h', self.data, index)
_index = seeker + (SENTINEL_SIZE + 6 + class_data_size)
sentinel = self.data[_index:_index + SENTINEL_SIZE]
if sentinel != b'\x72\x5E\x3B\x47\x3B\x56\x07\x3A\x3F\x23\x0B\xA0\x18\x30\x49\x75':
raise DwgCorruptedClassesSection(
'Sentinel for end of section not found.')