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assetbundle.py
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assetbundle.py
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import lzma
import struct
from io import BytesIO
from .asset import Asset
from .enums import CompressionType
from .utils import BinaryReader, lz4_decompress
SIGNATURE_RAW = "UnityRaw"
SIGNATURE_WEB = "UnityWeb"
SIGNATURE_FS = "UnityFS"
class AssetBundle:
def __init__(self, environment):
self.environment = environment
self.assets = []
def __repr__(self):
if hasattr(self, "name"):
return "<%s %r>" % (self.__class__.__name__, self.name)
return "<%s>" % (self.__class__.__name__)
@property
def is_unityfs(self):
return self.signature == SIGNATURE_FS
@property
def compressed(self):
return self.signature == SIGNATURE_WEB
def load(self, file):
buf = BinaryReader(file, endian=">")
self.path = file.name
# Verify that the format starts with b"Unity"
position = buf.tell()
if buf.read(5) != b"Unity":
raise NotImplementedError("File does not start with b'Unity': %r" % self.path)
buf.seek(position)
self.signature = buf.read_string()
self.format_version = buf.read_int()
self.unity_version = buf.read_string()
self.generator_version = buf.read_string()
if self.is_unityfs:
self.load_unityfs(buf)
elif self.signature in (SIGNATURE_RAW, SIGNATURE_WEB):
self.load_raw(buf)
else:
raise NotImplementedError("Unrecognized file signature %r in %r" % (self.signature, self.path))
def load_raw(self, buf):
self.file_size = buf.read_uint()
self.header_size = buf.read_int()
self.file_count = buf.read_int()
self.bundle_count = buf.read_int()
if self.format_version >= 2:
self.bundle_size = buf.read_uint() # without header_size
if self.format_version >= 3:
self.uncompressed_bundle_size = buf.read_uint() # without header_size
if self.header_size >= 60:
self.compressed_file_size = buf.read_uint() # with header_size
self.asset_header_size = buf.read_uint()
buf.read_int()
buf.read_byte()
self.name = buf.read_string()
# Preload assets
buf.seek(self.header_size)
if not self.compressed:
num_assets = buf.read_int()
else:
num_assets = 1
for i in range(num_assets):
asset = Asset.from_bundle(self, buf)
self.assets.append(asset)
def read_compressed_data(self, buf, compression):
data = buf.read(self.ciblock_size)
if compression == CompressionType.NONE:
return data
if compression in (CompressionType.LZ4, CompressionType.LZ4HC):
return lz4_decompress(data, self.uiblock_size)
raise NotImplementedError("Unimplemented compression method: %r" % (compression))
def load_unityfs(self, buf):
self.file_size = buf.read_int64()
self.ciblock_size = buf.read_uint()
self.uiblock_size = buf.read_uint()
flags = buf.read_uint()
compression = CompressionType(flags & 0x3F)
eof_metadata = flags & 0x80
if eof_metadata:
orig_pos = buf.tell()
buf.seek(-self.ciblock_size, 2)
data = self.read_compressed_data(buf, compression)
if eof_metadata:
buf.seek(orig_pos)
blk = BinaryReader(BytesIO(data), endian=">")
self.guid = blk.read(16)
num_blocks = blk.read_int()
blocks = []
for i in range(num_blocks):
busize, bcsize = blk.read_int(), blk.read_int()
bflags = blk.read_int16()
blocks.append(ArchiveBlockInfo(busize, bcsize, bflags))
num_nodes = blk.read_int()
nodes = []
for i in range(num_nodes):
ofs = blk.read_int64()
size = blk.read_int64()
status = blk.read_int()
name = blk.read_string()
nodes.append((ofs, size, status, name))
storage = ArchiveBlockStorage(blocks, buf)
for ofs, size, status, name in nodes:
storage.seek(ofs)
asset = Asset.from_bundle(self, storage)
asset.name = name
self.assets.append(asset)
# Hacky
self.name = self.assets[0].name
class ArchiveBlockInfo:
def __init__(self, usize, csize, flags):
self.uncompressed_size = usize
self.compressed_size = csize
self.flags = flags
def __repr__(self):
return "<%s: %d %d %r %r>" % (
self.__class__.__name__,
self.uncompressed_size, self.compressed_size,
self.compressed, self.compression_type
)
@property
def compressed(self):
return self.compression_type != CompressionType.NONE
@property
def compression_type(self):
return CompressionType(self.flags & 0x3f)
def decompress(self, buf):
if not self.compressed:
return buf
ty = self.compression_type
if ty == CompressionType.LZMA:
props, dict_size = struct.unpack("<BI", buf.read(5))
lc = props % 9
props = int(props / 9)
pb = int(props / 5)
lp = props % 5
dec = lzma.LZMADecompressor(format=lzma.FORMAT_RAW, filters=[{
"id": lzma.FILTER_LZMA1,
"dict_size": dict_size,
"lc": lc,
"lp": lp,
"pb": pb,
}])
res = dec.decompress(buf.read())
return BytesIO(res)
if ty in (CompressionType.LZ4, CompressionType.LZ4HC):
res = lz4_decompress(buf.read(self.compressed_size), self.uncompressed_size)
return BytesIO(res)
raise NotImplementedError("Unimplemented compression method: %r" % (ty))
class ArchiveBlockStorage:
def __init__(self, blocks, stream):
self.blocks = blocks
self.stream = stream
self.cursor = 0
self.basepos = stream.tell()
self.maxpos = sum([b.uncompressed_size for b in blocks])
self.sought = False
self.current_block = None
self.current_block_start = 0
self.current_stream = None
self._seek(0)
def read(self, size=-1):
buf = bytearray()
while size != 0 and self.cursor < self.maxpos:
if not self.in_current_block(self.cursor):
self.seek_to_block(self.cursor)
part = self.current_stream.read(size)
if size > 0:
if len(part) == 0:
raise EOFError()
size -= len(part)
self.cursor += len(part)
buf += part
return bytes(buf)
def seek(self, offset, whence=0):
new_cursor = 0
if whence == 1:
new_cursor = offset + self.cursor
elif whence == 2:
new_cursor = self.maxpos + offset
else:
new_cursor = offset
if self.cursor != new_cursor:
self._seek(new_cursor)
def tell(self):
return self.cursor
def _seek(self, new_cursor):
self.cursor = new_cursor
if not self.in_current_block(new_cursor):
self.seek_to_block(new_cursor)
self.current_stream.seek(new_cursor - self.current_block_start)
def in_current_block(self, pos):
if self.current_block is None:
return False
end = self.current_block_start + self.current_block.uncompressed_size
return self.current_block_start <= pos and pos < end
def seek_to_block(self, pos):
baseofs = 0
ofs = 0
for b in self.blocks:
if ofs + b.uncompressed_size > pos:
self.current_block = b
break
baseofs += b.compressed_size
ofs += b.uncompressed_size
else:
self.current_block = None
self.current_stream = BytesIO(b"")
return
self.current_block_start = ofs
self.stream.seek(self.basepos + baseofs)
buf = BytesIO(self.stream.read(self.current_block.compressed_size))
self.current_stream = self.current_block.decompress(buf)