code.kerkeslager.com Git - sandbox/blob - serial/binary.py

   1 import collections
   2 import functools
   3 import io
   4 import struct
   5
   6 TAG_NULL = 0x00
   7 TAG_TRUE = 0x01
   8 TAG_FALSE = 0x02
   9 TAG_UINT8 = 0x03
  10 TAG_UINT16 = 0x04
  11 TAG_UINT32 = 0x05
  12 TAG_UINT64 = 0x06
  13
  14 TaggedObject = collections.namedtuple(
  15     'TaggedObject',
  16     [
  17         'tag',
  18         'instance',
  19     ],
  20 )
  21
  22 def _make_tag_only_serializer(tag, expected_value):
  23     tag = bytes([tag])
  24
  25     def serializer(to):
  26         assert to.instance == expected_value
  27         return tag
  28
  29     return serializer
  30
  31 def _make_struct_serializer(fmt):
  32     fmt = '!B' + fmt
  33     packer = functools.partial(struct.pack, fmt)
  34
  35     def serializer(to):
  36         return packer(to.tag, to.instance)
  37
  38     return serializer
  39
  40 _TAGS_TO_SERIALIZERS = {
  41     TAG_NULL: _make_tag_only_serializer(TAG_NULL, None),
  42     TAG_TRUE: _make_tag_only_serializer(TAG_TRUE, True),
  43     TAG_FALSE: _make_tag_only_serializer(TAG_FALSE, False),
  44     TAG_UINT8: _make_struct_serializer('B'),
  45     TAG_UINT16: _make_struct_serializer('H'),
  46     TAG_UINT32: _make_struct_serializer('I'),
  47     TAG_UINT64: _make_struct_serializer('Q'),
  48 }
  49
  50 def serialize(to):
  51     return _TAGS_TO_SERIALIZERS[to.tag](to)
  52
  53 def _make_tag_only_parser(tag, value):
  54     def parser(b):
  55         return TaggedObject(tag = tag, instance = value)
  56
  57     return parser
  58
  59 _TAGS_TO_PARSERS = {
  60     TAG_NULL: _make_tag_only_parser(TAG_NULL, None),
  61     TAG_TRUE: _make_tag_only_parser(TAG_TRUE, True),
  62     TAG_FALSE: _make_tag_only_parser(TAG_FALSE, False),
  63 }
  64
  65 def deserialize(b):
  66     if isinstance(b, bytes):
  67         b = io.BytesIO(b)
  68
  69     tag = b.read(1)[0]
  70
  71     result = _TAGS_TO_PARSERS[tag](b)
  72
  73     remainder = b.read()
  74
  75     if len(remainder) == 0:
  76         return result
  77
  78     raise Exception('Unable to parse remainder: {}'.format(remainder))