1# This file is part of Xpra. 

2# Copyright (C) 2011-2019 Antoine Martin <antoine@xpra.org> 

3# Xpra is released under the terms of the GNU GPL v2, or, at your option, any 

4# later version. See the file COPYING for details. 

5 

6import struct 

7 

8#Note: since encoding flags and compression flags are all mutually exclusive, 

9# (ie: only one encoder and at most one compressor can be used at a time) 

10# we could theoretically add many more values here, 

11# not necessarily limitting ourselves to the ones that land on a bit. 

12 

13#packet encoding flags: 

14FLAGS_BENCODE = 0x0 #assume bencode if not other flag is set 

15FLAGS_RENCODE = 0x1 

16FLAGS_CIPHER = 0x2 

17FLAGS_YAML = 0x4 

18FLAGS_FLUSH = 0x8 

19 

20#compression flags are carried in the "level" field, 

21#the low bits contain the compression level, the high bits the compression algo: 

22ZLIB_FLAG = 0x0 #assume zlib if no other compression flag is set 

23LZ4_FLAG = 0x10 

24LZO_FLAG = 0x20 

25BROTLI_FLAG = 0x40 

26FLAGS_NOHEADER = 0x10000 #never encoded, so we can use a value bigger than a byte 

27 

28 

29_header_unpack_struct = struct.Struct(b'!cBBBL') 

30HEADER_SIZE = _header_unpack_struct.size 

31assert HEADER_SIZE==8 

32 

33def unpack_header(buf): 

34 return _header_unpack_struct.unpack_from(buf) 

35 

36#'P' + protocol-flags + compression_level + packet_index + data_size 

37_header_pack_struct = struct.Struct(b'!BBBBL') 

38assert ord("P") == 80 

39def pack_header(proto_flags, level, index, payload_size) -> bytes: 

40 return _header_pack_struct.pack(80, proto_flags, level, index, payload_size)