56 lines
1.7 KiB
Python
56 lines
1.7 KiB
Python
import logging
|
|
import pathlib
|
|
import struct
|
|
import typing
|
|
|
|
from . import dna_io, exceptions
|
|
|
|
log = logging.getLogger(__name__)
|
|
|
|
|
|
class BlendFileHeader:
|
|
"""
|
|
BlendFileHeader represents the first 12 bytes of a blend file.
|
|
|
|
it contains information about the hardware architecture, which is relevant
|
|
to the structure of the rest of the file.
|
|
"""
|
|
structure = struct.Struct(b'7s1s1s3s')
|
|
|
|
def __init__(self, fileobj: typing.BinaryIO, path: pathlib.Path):
|
|
log.debug("reading blend-file-header %s", path)
|
|
header = fileobj.read(self.structure.size)
|
|
values = self.structure.unpack(header)
|
|
|
|
self.magic = values[0]
|
|
|
|
pointer_size_id = values[1]
|
|
if pointer_size_id == b'-':
|
|
self.pointer_size = 8
|
|
elif pointer_size_id == b'_':
|
|
self.pointer_size = 4
|
|
else:
|
|
raise exceptions.BlendFileError('invalid pointer size %r' % pointer_size_id, path)
|
|
|
|
endian_id = values[2]
|
|
if endian_id == b'v':
|
|
self.endian = dna_io.LittleEndianTypes
|
|
self.endian_str = b'<' # indication for struct.Struct()
|
|
elif endian_id == b'V':
|
|
self.endian = dna_io.BigEndianTypes
|
|
self.endian_str = b'>' # indication for struct.Struct()
|
|
else:
|
|
raise exceptions.BlendFileError('invalid endian indicator %r' % endian_id, path)
|
|
|
|
version_id = values[3]
|
|
self.version = int(version_id)
|
|
|
|
def create_block_header_struct(self) -> struct.Struct:
|
|
"""Create a Struct instance for parsing data block headers."""
|
|
return struct.Struct(b''.join((
|
|
self.endian_str,
|
|
b'4sI',
|
|
b'I' if self.pointer_size == 4 else b'Q',
|
|
b'II',
|
|
)))
|