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from base64 import b64decode, b64encode
CONSTS = {
100: {},
101: '',
102: 0,
103: True,
104: False
}
def parse_const(b):
return CONSTS.get(b, None)
def parse(b):
assert type(b) == bytes().__class__
if len(b) == 1:
return parse_const(b[0])
return None
class ViewState(object):
def __init__(self, base64=''):
self.base64 = base64
self.raw = b64decode(self.base64)
self.decoded = None
@property
def preamble(self):
return self.raw[:2]
@property
def body(self):
return self.raw[2:]
def is_valid(self):
format_marker = b'\xff'
version_marker = b'\x01'
preamble = format_marker + version_marker
return self.preamble == preamble
def decode(self):
if not self.is_valid():
raise Exception('Cannot decode invalid viewstate, bad preamble')
self.decoded = parse(self.body)
return self.decoded
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