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Core: support LargeBHead8 in blendfile.py

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This indirectly also fixes `blend2json.py` because it's build on top of
`blendfile.py`.

Main changes:
* Update .blend file header parsing to support the different header types.
* Support unpacking `LargeBHead8`.
* Use `namedtuple` instead of index access when accessing block header because
  the order of items is different now.
* Update comments that were either fully redundant or already outdated.

Pull Request: https://projects.blender.org/blender/blender/pulls/140195
This commit is contained in:
Jacques Lucke
2025-06-11 14:30:37 +02:00
parent 4df037e582
commit d83bfee347
1 changed files with 114 additions and 57 deletions
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165
tools/modules/blendfile.py
View File

@@ -19,6 +19,7 @@ __all__ = (
)
from collections import namedtuple
import gzip
import logging
import os
@@ -56,6 +57,8 @@ class BlendFile:
"header",
# struct.Struct
"block_header_struct",
# namedtuple
"block_header_fields",
# BlendFileBlock
"blocks",
# [DNAStruct, ...]
@@ -77,7 +80,7 @@ class BlendFile:
log.debug("initializing reading blend-file")
self.handle = handle
self.header = BlendFileHeader(handle)
self.block_header_struct = self.header.create_block_header_struct()
self.block_header_struct, self.block_header_fields = self.header.create_block_header_struct()
self.blocks = []
self.code_index = {}
self.structs = []
@@ -270,8 +273,6 @@ class BlendFileBlock:
))
def __init__(self, handle, bfile):
OLDBLOCK = struct.Struct(b'4sI')
self.file = bfile
self.user_data = None
@@ -286,18 +287,15 @@ class BlendFileBlock:
self.count = 0
self.file_offset = 0
return
# header size can be 8, 20, or 24 bytes long
# 8: old blend files ENDB block (exception)
# 20: normal headers 32 bit platform
# 24: normal headers 64 bit platform
if len(data) > 15:
blockheader = bfile.block_header_struct.unpack(data)
# Header can be just 8 byte because of ENDB block in old .blend files.
if len(data) > 8:
blockheader = bfile.block_header_fields(*bfile.block_header_struct.unpack(data))
self.code = blockheader[0].partition(b'\0')[0]
if self.code != b'ENDB':
self.size = blockheader[1]
self.addr_old = blockheader[2]
self.sdna_index = blockheader[3]
self.count = blockheader[4]
self.size = blockheader.len
self.addr_old = blockheader.old
self.sdna_index = blockheader.SDNAnr
self.count = blockheader.nr
self.file_offset = handle.tell()
else:
self.size = 0
@@ -306,6 +304,7 @@ class BlendFileBlock:
self.count = 0
self.file_offset = 0
else:
OLDBLOCK = struct.Struct(b'4sI')
blockheader = OLDBLOCK.unpack(data)
self.code = blockheader[0].partition(b'\0')[0]
self.code = DNA_IO.read_data0(blockheader[0])
@@ -567,6 +566,8 @@ class BlendFileRaw:
"header",
# struct.Struct
"block_header_struct",
# namedtuple
"block_header_fields",
# BlendFileBlock
"blocks",
# dict {addr_old: block}
@@ -583,7 +584,7 @@ class BlendFileRaw:
log.debug("initializing reading blend-file")
self.handle = handle
self.header = BlendFileHeader(handle)
self.block_header_struct = self.header.create_block_header_struct()
self.block_header_struct, self.block_header_fields = self.header.create_block_header_struct()
self.blocks = []
self.code_index = {}
@@ -681,8 +682,6 @@ class BlendFileBlockRaw:
))
def __init__(self, handle, bfile):
OLDBLOCK = struct.Struct(b'4sI')
self.file = bfile
self.user_data = None
@@ -697,18 +696,15 @@ class BlendFileBlockRaw:
self.count = 0
self.file_offset = 0
return
# header size can be 8, 20, or 24 bytes long
# 8: old blend files ENDB block (exception)
# 20: normal headers 32 bit platform
# 24: normal headers 64 bit platform
if len(data) > 15:
blockheader = bfile.block_header_struct.unpack(data)
# Header can be just 8 byte because of ENDB block in old .blend files.
if len(data) > 8:
blockheader = bfile.block_header_fields(*bfile.block_header_struct.unpack(data))
self.code = blockheader[0].partition(b'\0')[0]
if self.code != b'ENDB':
self.size = blockheader[1]
self.addr_old = blockheader[2]
self.sdna_index = blockheader[3]
self.count = blockheader[4]
self.size = blockheader.len
self.addr_old = blockheader.old
self.sdna_index = blockheader.SDNAnr
self.count = blockheader.nr
self.file_offset = handle.tell()
else:
self.size = 0
@@ -717,6 +713,7 @@ class BlendFileBlockRaw:
self.count = 0
self.file_offset = 0
else:
OLDBLOCK = struct.Struct(b'4sI')
blockheader = OLDBLOCK.unpack(data)
self.code = blockheader[0].partition(b'\0')[0]
self.code = DNA_IO.read_data0(blockheader[0])
@@ -745,21 +742,18 @@ class BlendFileBlockRaw:
# -----------------------------------------------------------------------------
# Read Magic
#
# magic = str
# pointer_size = int
# is_little_endian = bool
# version = int
class BlendFileHeader:
"""
BlendFileHeader allocates the first 12 bytes of a blend file
BlendFileHeader allocates the first 12-17 bytes (depending on the file version) of a blend file
it contains information about the hardware architecture
"""
__slots__ = (
# str
"magic",
# int
"file_format_version",
# int 4/8
"pointer_size",
# bool
@@ -773,40 +767,103 @@ class BlendFileHeader:
)
def __init__(self, handle):
FILEHEADER = struct.Struct(b'7s1s1s3s')
log.debug("reading blend-file-header")
values = FILEHEADER.unpack(handle.read(FILEHEADER.size))
self.magic = values[0]
pointer_size_id = values[1]
if pointer_size_id == b'-':
self.pointer_size = 8
elif pointer_size_id == b'_':
bytes_0_6 = handle.read(7)
if bytes_0_6 != b'BLENDER':
raise BlendFileError("invalid first bytes")
self.magic = bytes_0_6
byte_7 = handle.read(1)
is_legacy_header = byte_7 in (b'_', b'-')
if is_legacy_header:
self.file_format_version = 0
if byte_7 == b'_':
self.pointer_size = 4
elif byte_7 == b'-':
self.pointer_size = 8
else:
assert False, "unreachable"
endian_id = values[2]
if endian_id == b'v':
raise BlendFileError("invalid file header")
byte_8 = handle.read(1)
if byte_8 == b'v':
self.is_little_endian = True
elif byte_8 == b'V':
self.is_little_endian = False
else:
raise BlendFileError("invalid file header")
bytes_9_11 = handle.read(3)
self.version = int(bytes_9_11)
else:
byte_8 = handle.read(1)
header_size = int(byte_7 + byte_8)
if header_size != 17:
raise BlendFileError("invalid file header")
byte_9 = handle.read(1)
if byte_9 != b'-':
raise BlendFileError("invalid file header")
self.pointer_size = 8
byte_10_11 = handle.read(2)
self.file_format_version = int(byte_10_11)
if self.file_format_version != 1:
raise BlendFileError("unsupported file format version")
byte_12 = handle.read(1)
if byte_12 != b'v':
raise BlendFileError("invalid file header")
self.is_little_endian = True
byte_13_16 = handle.read(4)
self.version = int(byte_13_16)
if self.is_little_endian:
self.endian_str = b'<'
self.endian_index = 0
elif endian_id == b'V':
self.is_little_endian = False
else:
self.endian_index = 1
self.endian_str = b'>'
else:
assert False, "unreachable"
version_id = values[3]
self.version = int(version_id)
def create_block_header_struct(self):
if self.file_format_version == 0:
if self.pointer_size == 4:
return struct.Struct(b''.join((
self.endian_str,
b'4sI',
b'I' if self.pointer_size == 4 else b'Q',
b'II',
)))
# BHead4.code
b'4s',
# BHead4.len
b'i',
# BHead4.old
b'I',
# BHead4.SDNAnr
b'i',
# BHead4.nr
b'i',
))), namedtuple('BHead4', ('code', 'len', 'old', 'SDNAnr', 'nr'))
else:
return struct.Struct(b''.join((
self.endian_str,
# SmallBHead8.code
b'4s',
# SmallBHead8.len
b'i',
# SmallBHead8.old
b'Q',
# SmallBHead8.SDNAnr
b'i',
# SmallBHead8.nr
b'i',
))), namedtuple('SmallBHead8', ('code', 'len', 'old', 'SDNAnr', 'nr'))
else:
return struct.Struct(b''.join((
self.endian_str,
# LargeBHead8.code
b'4s',
# LargeBHead8.SDNAnr
b'i',
# LargeBHead8.old
b'Q',
# LargeBHead8.len
b'q',
# LargeBHead8.nr
b'q',
))), namedtuple('LargeBHead8', ('code', 'SDNAnr', 'old', 'len', 'nr'))
class DNAName: