79 lines
2.7 KiB
Python
79 lines
2.7 KiB
Python
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# ***** BEGIN GPL LICENSE BLOCK *****
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public License
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# as published by the Free Software Foundation; either version 2
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# of the License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software Foundation,
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# Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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#
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# ***** END GPL LICENCE BLOCK *****
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#
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# (c) 2009, At Mind B.V. - Jeroen Bakker
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# (c) 2014, Blender Foundation - Campbell Barton
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# (c) 2018, Blender Foundation - Sybren A. Stüvel
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import logging
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import os
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import pathlib
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import struct
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import typing
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from . import dna_io, exceptions
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log = logging.getLogger(__name__)
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class BlendFileHeader:
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"""
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BlendFileHeader represents the first 12 bytes of a blend file.
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It contains information about the hardware architecture, which is relevant
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to the structure of the rest of the file.
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"""
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structure = struct.Struct(b'7s1s1s3s')
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def __init__(self, fileobj: typing.IO[bytes], path: pathlib.Path) -> None:
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log.debug("reading blend-file-header %s", path)
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fileobj.seek(0, os.SEEK_SET)
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header = fileobj.read(self.structure.size)
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values = self.structure.unpack(header)
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self.magic = values[0]
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pointer_size_id = values[1]
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if pointer_size_id == b'-':
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self.pointer_size = 8
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elif pointer_size_id == b'_':
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self.pointer_size = 4
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else:
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raise exceptions.BlendFileError('invalid pointer size %r' % pointer_size_id, path)
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endian_id = values[2]
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if endian_id == b'v':
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self.endian = dna_io.LittleEndianTypes
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self.endian_str = b'<' # indication for struct.Struct()
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elif endian_id == b'V':
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self.endian = dna_io.BigEndianTypes
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self.endian_str = b'>' # indication for struct.Struct()
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else:
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raise exceptions.BlendFileError('invalid endian indicator %r' % endian_id, path)
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version_id = values[3]
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self.version = int(version_id)
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def create_block_header_struct(self) -> struct.Struct:
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"""Create a Struct instance for parsing data block headers."""
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return struct.Struct(b''.join((
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self.endian_str,
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b'4sI',
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b'I' if self.pointer_size == 4 else b'Q',
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b'II',
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)))
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