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class Varbit(object):
__slots__ = ('data', 'bits')
def from_bits(subtype, bits, data):
if bits == 1:
return (data[0] & (1 << 7)) and OneBit or ZeroBit
else:
rob = object.__new__(subtype)
rob.bits = bits
rob.data = data
return rob
from_bits = classmethod(from_bits)
def __new__(typ, data):
if isinstance(data, Varbit):
return data
if isinstance(data, bytes):
return typ.from_bits(len(data) * 8, data)
# str(), eg '00101100'
bits = len(data)
nbytes, remain = divmod(bits, 8)
bdata = [bytes((int(data[x:x+8], 2),)) for x in range(0, bits - remain, 8)]
if remain != 0:
bdata.append(bytes((int(data[nbytes*8:].ljust(8,'0'), 2),)))
return typ.from_bits(bits, b''.join(bdata))
def __str__(self):
if self.bits:
# cut off the remainder from the bits
blocks = [bin(x)[2:].rjust(8, '0') for x in self.data]
blocks[-1] = blocks[-1][0:(self.bits % 8) or 8]
return ''.join(blocks)
else:
return ''
def __repr__(self):
return '%s.%s(%r)' %(
type(self).__module__,
type(self).__name__,
str(self)
)
def __eq__(self, ob):
if not isinstance(ob, type(self)):
ob = type(self)(ob)
return ob.bits == self.bits and ob.data == self.data
def __len__(self):
return self.bits
def __add__(self, ob):
return Varbit(str(self) + str(ob))
def __mul__(self, ob):
return Varbit(str(self) * ob)
def getbit(self, bitoffset):
if bitoffset < 0:
idx = self.bits + bitoffset
else:
idx = bitoffset
if not 0 <= idx < self.bits:
raise IndexError("bit index %d out of range" %(bitoffset,))
byte, bitofbyte = divmod(idx, 8)
if ord(self.data[byte]) & (1 << (7 - bitofbyte)):
return OneBit
else:
return ZeroBit
def __getitem__(self, item):
if isinstance(item, slice):
return type(self)(str(self)[item])
else:
return self.getbit(item)
def __nonzero__(self):
for x in self.data:
if x != 0:
return True
return False
class Bit(Varbit):
def __new__(subtype, ob):
if ob is ZeroBit or ob is False or ob == '0':
return ZeroBit
elif ob is OneBit or ob is True or ob == '1':
return OneBit
raise ValueError('unknown bit value %r, 0 or 1' %(ob,))
def __nonzero__(self):
return self is OneBit
def __str__(self):
return self is OneBit and '1' or '0'
ZeroBit = object.__new__(Bit)
ZeroBit.data = b'\x00'
ZeroBit.bits = 1
OneBit = object.__new__(Bit)
OneBit.data = b'\x80'
OneBit.bits = 1
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