diff options
Diffstat (limited to 'io_blend_utils/blend/blendfile.py')
| -rw-r--r-- | io_blend_utils/blend/blendfile.py | 917 |
1 files changed, 917 insertions, 0 deletions
diff --git a/io_blend_utils/blend/blendfile.py b/io_blend_utils/blend/blendfile.py new file mode 100644 index 00000000..0739a1bc --- /dev/null +++ b/io_blend_utils/blend/blendfile.py @@ -0,0 +1,917 @@ +# ***** BEGIN GPL LICENSE BLOCK ***** +# +# This program is free software; you can redistribute it and/or +# modify it under the terms of the GNU General Public License +# as published by the Free Software Foundation; either version 2 +# of the License, or (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program; if not, write to the Free Software Foundation, +# Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. +# +# ***** END GPL LICENCE BLOCK ***** +# +# (c) 2009, At Mind B.V. - Jeroen Bakker +# (c) 2014, Blender Foundation - Campbell Barton + +import os +import struct +import logging +import gzip +import tempfile + +log = logging.getLogger("blendfile") +log.setLevel(logging.ERROR) + +FILE_BUFFER_SIZE = 1024 * 1024 + + +# ----------------------------------------------------------------------------- +# module global routines +# +# read routines +# open a filename +# determine if the file is compressed +# and returns a handle +def open_blend(filename, access="rb"): + """Opens a blend file for reading or writing pending on the access + supports 2 kind of blend files. Uncompressed and compressed. + Known issue: does not support packaged blend files + """ + handle = open(filename, access) + magic_test = b"BLENDER" + magic = handle.read(len(magic_test)) + if magic == magic_test: + log.debug("normal blendfile detected") + handle.seek(0, os.SEEK_SET) + bfile = BlendFile(handle) + bfile.is_compressed = False + bfile.filepath_orig = filename + return bfile + elif magic[:2] == b'\x1f\x8b': + log.debug("gzip blendfile detected") + handle.close() + log.debug("decompressing started") + fs = gzip.open(filename, "rb") + data = fs.read(FILE_BUFFER_SIZE) + magic = data[:len(magic_test)] + if magic == magic_test: + handle = tempfile.TemporaryFile() + while data: + handle.write(data) + data = fs.read(FILE_BUFFER_SIZE) + log.debug("decompressing finished") + fs.close() + log.debug("resetting decompressed file") + handle.seek(os.SEEK_SET, 0) + bfile = BlendFile(handle) + bfile.is_compressed = True + bfile.filepath_orig = filename + return bfile + else: + raise Exception("filetype inside gzip not a blend") + else: + raise Exception("filetype not a blend or a gzip blend") + + +def align(offset, by): + n = by - 1 + return (offset + n) & ~n + + +# ----------------------------------------------------------------------------- +# module classes + + +class BlendFile: + """ + Blend file. + """ + __slots__ = ( + # file (result of open()) + "handle", + # str (original name of the file path) + "filepath_orig", + # BlendFileHeader + "header", + # struct.Struct + "block_header_struct", + # BlendFileBlock + "blocks", + # [DNAStruct, ...] + "structs", + # dict {b'StructName': sdna_index} + # (where the index is an index into 'structs') + "sdna_index_from_id", + # dict {addr_old: block} + "block_from_offset", + # int + "code_index", + # bool (did we make a change) + "is_modified", + # bool (is file gzipped) + "is_compressed", + ) + + def __init__(self, handle): + log.debug("initializing reading blend-file") + self.handle = handle + self.header = BlendFileHeader(handle) + self.block_header_struct = self.header.create_block_header_struct() + self.blocks = [] + self.code_index = {} + + block = BlendFileBlock(handle, self) + while block.code != b'ENDB': + if block.code == b'DNA1': + (self.structs, + self.sdna_index_from_id, + ) = BlendFile.decode_structs(self.header, block, handle) + else: + handle.seek(block.size, os.SEEK_CUR) + + self.blocks.append(block) + self.code_index.setdefault(block.code, []).append(block) + + block = BlendFileBlock(handle, self) + self.is_modified = False + self.blocks.append(block) + + # cache (could lazy init, incase we never use?) + self.block_from_offset = {block.addr_old: block for block in self.blocks if block.code != b'ENDB'} + + def __enter__(self): + return self + + def __exit__(self, type, value, traceback): + self.close() + + def find_blocks_from_code(self, code): + assert(type(code) == bytes) + if code not in self.code_index: + return [] + return self.code_index[code] + + def find_block_from_offset(self, offset): + # same as looking looping over all blocks, + # then checking ``block.addr_old == offset`` + assert(type(offset) is int) + return self.block_from_offset.get(offset) + + def close(self): + """ + Close the blend file + writes the blend file to disk if changes has happened + """ + if not self.is_modified: + self.handle.close() + else: + handle = self.handle + if self.is_compressed: + log.debug("close compressed blend file") + handle.seek(os.SEEK_SET, 0) + log.debug("compressing started") + fs = gzip.open(self.filepath_orig, "wb") + data = handle.read(FILE_BUFFER_SIZE) + while data: + fs.write(data) + data = handle.read(FILE_BUFFER_SIZE) + fs.close() + log.debug("compressing finished") + + handle.close() + + def ensure_subtype_smaller(self, sdna_index_curr, sdna_index_next): + # never refine to a smaller type + if (self.structs[sdna_index_curr].size > + self.structs[sdna_index_next].size): + + raise RuntimeError("cant refine to smaller type (%s -> %s)" % + (self.structs[sdna_index_curr].dna_type_id.decode('ascii'), + self.structs[sdna_index_next].dna_type_id.decode('ascii'))) + + @staticmethod + def decode_structs(header, block, handle): + """ + DNACatalog is a catalog of all information in the DNA1 file-block + """ + log.debug("building DNA catalog") + shortstruct = DNA_IO.USHORT[header.endian_index] + shortstruct2 = struct.Struct(header.endian_str + b'HH') + intstruct = DNA_IO.UINT[header.endian_index] + + data = handle.read(block.size) + types = [] + names = [] + + structs = [] + sdna_index_from_id = {} + + offset = 8 + names_len = intstruct.unpack_from(data, offset)[0] + offset += 4 + + log.debug("building #%d names" % names_len) + for i in range(names_len): + tName = DNA_IO.read_data0_offset(data, offset) + offset = offset + len(tName) + 1 + names.append(DNAName(tName)) + del names_len + + offset = align(offset, 4) + offset += 4 + types_len = intstruct.unpack_from(data, offset)[0] + offset += 4 + log.debug("building #%d types" % types_len) + for i in range(types_len): + dna_type_id = DNA_IO.read_data0_offset(data, offset) + # None will be replaced by the DNAStruct, below + types.append(DNAStruct(dna_type_id)) + offset += len(dna_type_id) + 1 + + offset = align(offset, 4) + offset += 4 + log.debug("building #%d type-lengths" % types_len) + for i in range(types_len): + tLen = shortstruct.unpack_from(data, offset)[0] + offset = offset + 2 + types[i].size = tLen + del types_len + + offset = align(offset, 4) + offset += 4 + + structs_len = intstruct.unpack_from(data, offset)[0] + offset += 4 + log.debug("building #%d structures" % structs_len) + for sdna_index in range(structs_len): + d = shortstruct2.unpack_from(data, offset) + struct_type_index = d[0] + offset += 4 + dna_struct = types[struct_type_index] + sdna_index_from_id[dna_struct.dna_type_id] = sdna_index + structs.append(dna_struct) + + fields_len = d[1] + dna_offset = 0 + + for field_index in range(fields_len): + d2 = shortstruct2.unpack_from(data, offset) + field_type_index = d2[0] + field_name_index = d2[1] + offset += 4 + dna_type = types[field_type_index] + dna_name = names[field_name_index] + if dna_name.is_pointer or dna_name.is_method_pointer: + dna_size = header.pointer_size * dna_name.array_size + else: + dna_size = dna_type.size * dna_name.array_size + + field = DNAField(dna_type, dna_name, dna_size, dna_offset) + dna_struct.fields.append(field) + dna_struct.field_from_name[dna_name.name_only] = field + dna_offset += dna_size + + return structs, sdna_index_from_id + + +class BlendFileBlock: + """ + Instance of a struct. + """ + __slots__ = ( + # BlendFile + "file", + "code", + "size", + "addr_old", + "sdna_index", + "count", + "file_offset", + "user_data", + ) + + def __str__(self): + return ("<%s.%s (%s), size=%d at %s>" % + # fields=[%s] + (self.__class__.__name__, + self.dna_type.dna_type_id.decode('ascii'), + self.code.decode(), + self.size, + # b", ".join(f.dna_name.name_only for f in self.dna_type.fields).decode('ascii'), + hex(self.addr_old), + )) + + def __init__(self, handle, bfile): + OLDBLOCK = struct.Struct(b'4sI') + + self.file = bfile + self.user_data = None + + data = handle.read(bfile.block_header_struct.size) + # 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) + 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.file_offset = handle.tell() + else: + self.size = 0 + self.addr_old = 0 + self.sdna_index = 0 + self.count = 0 + self.file_offset = 0 + else: + blockheader = OLDBLOCK.unpack(data) + self.code = blockheader[0].partition(b'\0')[0] + self.code = DNA_IO.read_data0(blockheader[0]) + self.size = 0 + self.addr_old = 0 + self.sdna_index = 0 + self.count = 0 + self.file_offset = 0 + + @property + def dna_type(self): + return self.file.structs[self.sdna_index] + + def refine_type_from_index(self, sdna_index_next): + assert(type(sdna_index_next) is int) + sdna_index_curr = self.sdna_index + self.file.ensure_subtype_smaller(sdna_index_curr, sdna_index_next) + self.sdna_index = sdna_index_next + + def refine_type(self, dna_type_id): + assert(type(dna_type_id) is bytes) + self.refine_type_from_index(self.file.sdna_index_from_id[dna_type_id]) + + def get_file_offset(self, path, + default=..., + sdna_index_refine=None, + base_index=0, + ): + """ + Return (offset, length) + """ + assert(type(path) is bytes) + + ofs = self.file_offset + if base_index != 0: + assert(base_index < self.count) + ofs += (self.size // self.count) * base_index + self.file.handle.seek(ofs, os.SEEK_SET) + + if sdna_index_refine is None: + sdna_index_refine = self.sdna_index + else: + self.file.ensure_subtype_smaller(self.sdna_index, sdna_index_refine) + + dna_struct = self.file.structs[sdna_index_refine] + field = dna_struct.field_from_path( + self.file.header, self.file.handle, path) + + return (self.file.handle.tell(), field.dna_name.array_size) + + def get(self, path, + default=..., + sdna_index_refine=None, + use_nil=True, use_str=True, + base_index=0, + ): + + ofs = self.file_offset + if base_index != 0: + assert(base_index < self.count) + ofs += (self.size // self.count) * base_index + self.file.handle.seek(ofs, os.SEEK_SET) + + if sdna_index_refine is None: + sdna_index_refine = self.sdna_index + else: + self.file.ensure_subtype_smaller(self.sdna_index, sdna_index_refine) + + dna_struct = self.file.structs[sdna_index_refine] + return dna_struct.field_get( + self.file.header, self.file.handle, path, + default=default, + use_nil=use_nil, use_str=use_str, + ) + + def get_recursive_iter(self, path, path_root=b"", + default=..., + sdna_index_refine=None, + use_nil=True, use_str=True, + base_index=0, + ): + if path_root: + path_full = ( + (path_root if type(path_root) is tuple else (path_root, )) + + (path if type(path) is tuple else (path, ))) + else: + path_full = path + + try: + yield (path_full, self.get(path_full, default, sdna_index_refine, use_nil, use_str, base_index)) + except NotImplementedError as ex: + msg, dna_name, dna_type = ex.args + struct_index = self.file.sdna_index_from_id.get(dna_type.dna_type_id, None) + if struct_index is None: + yield (path_full, "<%s>" % dna_type.dna_type_id.decode('ascii')) + else: + struct = self.file.structs[struct_index] + for f in struct.fields: + yield from self.get_recursive_iter( + f.dna_name.name_only, path_full, default, None, use_nil, use_str, 0) + + def items_recursive_iter(self): + for k in self.keys(): + yield from self.get_recursive_iter(k, use_str=False) + + def get_data_hash(self): + """ + Generates a 'hash' that can be used instead of addr_old as block id, and that should be 'stable' across .blend + file load & save (i.e. it does not changes due to pointer addresses variations). + """ + # TODO This implementation is most likely far from optimal... and CRC32 is not renown as the best hashing + # algo either. But for now does the job! + import zlib + def _is_pointer(self, k): + return self.file.structs[self.sdna_index].field_from_path( + self.file.header, self.file.handle, k).dna_name.is_pointer + + hsh = 1 + for k, v in self.items_recursive_iter(): + if not _is_pointer(self, k): + hsh = zlib.adler32(str(v).encode(), hsh) + return hsh + + def set(self, path, value, + sdna_index_refine=None, + ): + + if sdna_index_refine is None: + sdna_index_refine = self.sdna_index + else: + self.file.ensure_subtype_smaller(self.sdna_index, sdna_index_refine) + + dna_struct = self.file.structs[sdna_index_refine] + self.file.handle.seek(self.file_offset, os.SEEK_SET) + self.file.is_modified = True + return dna_struct.field_set( + self.file.header, self.file.handle, path, value) + + # --------------- + # Utility get/set + # + # avoid inline pointer casting + def get_pointer( + self, path, + default=..., + sdna_index_refine=None, + base_index=0, + ): + if sdna_index_refine is None: + sdna_index_refine = self.sdna_index + result = self.get(path, default, sdna_index_refine=sdna_index_refine, base_index=base_index) + + # default + if type(result) is not int: + return result + + assert(self.file.structs[sdna_index_refine].field_from_path( + self.file.header, self.file.handle, path).dna_name.is_pointer) + if result != 0: + # possible (but unlikely) + # that this fails and returns None + # maybe we want to raise some exception in this case + return self.file.find_block_from_offset(result) + else: + return None + + # ---------------------- + # Python convenience API + + # dict like access + def __getitem__(self, item): + return self.get(item, use_str=False) + + def __setitem__(self, item, value): + self.set(item, value) + + def keys(self): + return (f.dna_name.name_only for f in self.dna_type.fields) + + def values(self): + for k in self.keys(): + try: + yield self[k] + except NotImplementedError as ex: + msg, dna_name, dna_type = ex.args + yield "<%s>" % dna_type.dna_type_id.decode('ascii') + + def items(self): + for k in self.keys(): + try: + yield (k, self[k]) + except NotImplementedError as ex: + msg, dna_name, dna_type = ex.args + yield (k, "<%s>" % dna_type.dna_type_id.decode('ascii')) + + +# ----------------------------------------------------------------------------- +# 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 + it contains information about the hardware architecture + """ + __slots__ = ( + # str + "magic", + # int 4/8 + "pointer_size", + # bool + "is_little_endian", + # int + "version", + # str, used to pass to 'struct' + "endian_str", + # int, used to index common types + "endian_index", + ) + + 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'_': + self.pointer_size = 4 + else: + assert(0) + endian_id = values[2] + if endian_id == b'v': + self.is_little_endian = True + self.endian_str = b'<' + self.endian_index = 0 + elif endian_id == b'V': + self.is_little_endian = False + self.endian_index = 1 + self.endian_str = b'>' + else: + assert(0) + + version_id = values[3] + self.version = int(version_id) + + def create_block_header_struct(self): + return struct.Struct(b''.join(( + self.endian_str, + b'4sI', + b'I' if self.pointer_size == 4 else b'Q', + b'II', + ))) + + +class DNAName: + """ + DNAName is a C-type name stored in the DNA + """ + __slots__ = ( + "name_full", + "name_only", + "is_pointer", + "is_method_pointer", + "array_size", + ) + + def __init__(self, name_full): + self.name_full = name_full + self.name_only = self.calc_name_only() + self.is_pointer = self.calc_is_pointer() + self.is_method_pointer = self.calc_is_method_pointer() + self.array_size = self.calc_array_size() + + def as_reference(self, parent): + if parent is None: + result = b'' + else: + result = parent + b'.' + + result = result + self.name_only + return result + + def calc_name_only(self): + result = self.name_full.strip(b'*()') + index = result.find(b'[') + if index != -1: + result = result[:index] + return result + + def calc_is_pointer(self): + return (b'*' in self.name_full) + + def calc_is_method_pointer(self): + return (b'(*' in self.name_full) + + def calc_array_size(self): + result = 1 + temp = self.name_full + index = temp.find(b'[') + + while index != -1: + index_2 = temp.find(b']') + result *= int(temp[index + 1:index_2]) + temp = temp[index_2 + 1:] + index = temp.find(b'[') + + return result + + +class DNAField: + """ + DNAField is a coupled DNAStruct and DNAName + and cache offset for reuse + """ + __slots__ = ( + # DNAName + "dna_name", + # tuple of 3 items + # [bytes (struct name), int (struct size), DNAStruct] + "dna_type", + # size on-disk + "dna_size", + # cached info (avoid looping over fields each time) + "dna_offset", + ) + + def __init__(self, dna_type, dna_name, dna_size, dna_offset): + self.dna_type = dna_type + self.dna_name = dna_name + self.dna_size = dna_size + self.dna_offset = dna_offset + + +class DNAStruct: + """ + DNAStruct is a C-type structure stored in the DNA + """ + __slots__ = ( + "dna_type_id", + "size", + "fields", + "field_from_name", + "user_data", + ) + + def __init__(self, dna_type_id): + self.dna_type_id = dna_type_id + self.fields = [] + self.field_from_name = {} + self.user_data = None + + def field_from_path(self, header, handle, path): + """ + Support lookups as bytes or a tuple of bytes and optional index. + + C style 'id.name' --> (b'id', b'name') + C style 'array[4]' --> ('array', 4) + """ + if type(path) is tuple: + name = path[0] + if len(path) >= 2 and type(path[1]) is not bytes: + name_tail = path[2:] + index = path[1] + assert(type(index) is int) + else: + name_tail = path[1:] + index = 0 + else: + name = path + name_tail = None + index = 0 + + assert(type(name) is bytes) + + field = self.field_from_name.get(name) + + if field is not None: + handle.seek(field.dna_offset, os.SEEK_CUR) + if index != 0: + if field.dna_name.is_pointer: + index_offset = header.pointer_size * index + else: + index_offset = field.dna_type.size * index + assert(index_offset < field.dna_size) + handle.seek(index_offset, os.SEEK_CUR) + if not name_tail: # None or () + return field + else: + return field.dna_type.field_from_path(header, handle, name_tail) + + def field_get(self, header, handle, path, + default=..., + use_nil=True, use_str=True, + ): + field = self.field_from_path(header, handle, path) + if field is None: + if default is not ...: + return default + else: + raise KeyError("%r not found in %r (%r)" % + (path, [f.dna_name.name_only for f in self.fields], self.dna_type_id)) + + dna_type = field.dna_type + dna_name = field.dna_name + + if dna_name.is_pointer: + return DNA_IO.read_pointer(handle, header) + elif dna_type.dna_type_id == b'int': + if dna_name.array_size > 1: + return [DNA_IO.read_int(handle, header) for i in range(dna_name.array_size)] + return DNA_IO.read_int(handle, header) + elif dna_type.dna_type_id == b'short': + if dna_name.array_size > 1: + return [DNA_IO.read_short(handle, header) for i in range(dna_name.array_size)] + return DNA_IO.read_short(handle, header) + elif dna_type.dna_type_id == b'uint64_t': + if dna_name.array_size > 1: + return [DNA_IO.read_ulong(handle, header) for i in range(dna_name.array_size)] + return DNA_IO.read_ulong(handle, header) + elif dna_type.dna_type_id == b'float': + if dna_name.array_size > 1: + return [DNA_IO.read_float(handle, header) for i in range(dna_name.array_size)] + return DNA_IO.read_float(handle, header) + elif dna_type.dna_type_id == b'char': + if use_str: + if use_nil: + return DNA_IO.read_string0(handle, dna_name.array_size) + else: + return DNA_IO.read_string(handle, dna_name.array_size) + else: + if use_nil: + return DNA_IO.read_bytes0(handle, dna_name.array_size) + else: + return DNA_IO.read_bytes(handle, dna_name.array_size) + else: + raise NotImplementedError("%r exists but isn't pointer, can't resolve field %r" % + (path, dna_name.name_only), dna_name, dna_type) + + def field_set(self, header, handle, path, value): + assert(type(path) == bytes) + + field = self.field_from_path(header, handle, path) + if field is None: + raise KeyError("%r not found in %r" % + (path, [f.dna_name.name_only for f in self.fields])) + + dna_type = field.dna_type + dna_name = field.dna_name + + if dna_type.dna_type_id == b'char': + if type(value) is str: + return DNA_IO.write_string(handle, value, dna_name.array_size) + else: + return DNA_IO.write_bytes(handle, value, dna_name.array_size) + else: + raise NotImplementedError("Setting %r is not yet supported" % + dna_type[0], dna_name, dna_type) + + +class DNA_IO: + """ + Module like class, for read-write utility functions. + + Only stores static methods & constants. + """ + + __slots__ = () + + def __new__(cls, *args, **kwargs): + raise RuntimeError("%s should not be instantiated" % cls) + + @staticmethod + def write_string(handle, astring, fieldlen): + assert(isinstance(astring, str)) + if len(astring) >= fieldlen: + stringw = astring[0:fieldlen] + else: + stringw = astring + '\0' + handle.write(stringw.encode('utf-8')) + + @staticmethod + def write_bytes(handle, astring, fieldlen): + assert(isinstance(astring, (bytes, bytearray))) + if len(astring) >= fieldlen: + stringw = astring[0:fieldlen] + else: + stringw = astring + b'\0' + + handle.write(stringw) + + @staticmethod + def read_bytes(handle, length): + data = handle.read(length) + return data + + @staticmethod + def read_bytes0(handle, length): + data = handle.read(length) + return DNA_IO.read_data0(data) + + @staticmethod + def read_string(handle, length): + return DNA_IO.read_bytes(handle, length).decode('utf-8') + + @staticmethod + def read_string0(handle, length): + return DNA_IO.read_bytes0(handle, length).decode('utf-8') + + @staticmethod + def read_data0_offset(data, offset): + add = data.find(b'\0', offset) - offset + return data[offset:offset + add] + + @staticmethod + def read_data0(data): + add = data.find(b'\0') + return data[:add] + + USHORT = struct.Struct(b'<H'), struct.Struct(b'>H') + + @staticmethod + def read_ushort(handle, fileheader): + st = DNA_IO.USHORT[fileheader.endian_index] + return st.unpack(handle.read(st.size))[0] + + SSHORT = struct.Struct(b'<h'), struct.Struct(b'>h') + + @staticmethod + def read_short(handle, fileheader): + st = DNA_IO.SSHORT[fileheader.endian_index] + return st.unpack(handle.read(st.size))[0] + + UINT = struct.Struct(b'<I'), struct.Struct(b'>I') + + @staticmethod + def read_uint(handle, fileheader): + st = DNA_IO.UINT[fileheader.endian_index] + return st.unpack(handle.read(st.size))[0] + + SINT = struct.Struct(b'<i'), struct.Struct(b'>i') + + @staticmethod + def read_int(handle, fileheader): + st = DNA_IO.SINT[fileheader.endian_index] + return st.unpack(handle.read(st.size))[0] + + FLOAT = struct.Struct(b'<f'), struct.Struct(b'>f') + + @staticmethod + def read_float(handle, fileheader): + st = DNA_IO.FLOAT[fileheader.endian_index] + return st.unpack(handle.read(st.size))[0] + + ULONG = struct.Struct(b'<Q'), struct.Struct(b'>Q') + + @staticmethod + def read_ulong(handle, fileheader): + st = DNA_IO.ULONG[fileheader.endian_index] + return st.unpack(handle.read(st.size))[0] + + @staticmethod + def read_pointer(handle, header): + """ + reads an pointer from a file handle + the pointer size is given by the header (BlendFileHeader) + """ + if header.pointer_size == 4: + st = DNA_IO.UINT[header.endian_index] + return st.unpack(handle.read(st.size))[0] + if header.pointer_size == 8: + st = DNA_IO.ULONG[header.endian_index] + return st.unpack(handle.read(st.size))[0] |