+from .utils import (
+ compat_str,
+ ExtractorError,
+ struct_unpack,
+)
+
+
+def _extract_tags(file_contents):
+ if file_contents[1:3] != b'WS':
+ raise ExtractorError(
+ 'Not an SWF file; header is %r' % file_contents[:3])
+ if file_contents[:1] == b'C':
+ content = zlib.decompress(file_contents[8:])
+ else:
+ raise NotImplementedError(
+ 'Unsupported compression format %r' %
+ file_contents[:1])
+
+ # Determine number of bits in framesize rectangle
+ framesize_nbits = struct_unpack('!B', content[:1])[0] >> 3
+ framesize_len = (5 + 4 * framesize_nbits + 7) // 8
+
+ pos = framesize_len + 2 + 2