def parse_swf(input_: Union[memoryview, bytes]) -> Iterable[Tag]:
"""
Parse SWF file and get an iterable of its tags.
"""
reader = MemoryViewReader(input_)
signature = Signature(reader.read_u8())
assert reader.read_u16() == 0x5357
reader.skip(1) # version
reader.skip(4) # file length
reader = decompress(reader, signature)
reader.skip_rect()
reader.skip(4) # frame rate and frame count
return read_tags(reader)
def read_tags(reader: MemoryViewReader) -> Iterable[Tag]:
"""
Read tags from the stream and get an iterable of tags.
"""
while not reader.is_eof():
code_length = reader.read_u16()
length = code_length & 0b111111
if length == 0x3F:
# Long tag header.
length = reader.read_u32()
try:
type_ = TagType(code_length >> 6)
except ValueError:
# Unknown tag type. Skip the tag.
reader.skip(length)
else:
yield Tag(type_=type_, raw=reader.read(length))
def decompress(reader: MemoryViewReader,
signature: Signature) -> MemoryViewReader:
"""
Decompress the rest of an SWF file, depending on its signature.
"""
if signature == Signature.UNCOMPRESSED:
return reader
if signature == Signature.LZMA:
# https://stackoverflow.com/a/39777419/359730
reader.skip(4) # skip compressed length
return MemoryViewReader(
lzma.decompress(
reader.read(5).tobytes() +
b'\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF' +
reader.read_all().tobytes()))
if signature == Signature.ZLIB:
return MemoryViewReader(zlib.decompress(reader.read_all()))
assert False, 'unreachable code'