def unpad_and_checksum(s, compact, checksum):
"""Check length padding and checksum for a string
return the string without length padding or checksum
raise ValueError if either are wrong"""
assert isinstance(s, bytes)
if checksum:
if compact:
checksum_length = ord(s[-1])
consumed = 1
length = len(s) - checksum_length - consumed
else:
(length, consumed) = decode_varint(s, endian='little')
checksum_length = max(1, (length-1).bit_length())
s = s[:-consumed]
s, checksum = s[:-checksum_length], s[-checksum_length:]
if len(s) != length:
raise ValueError("Invalid length")
k = Keccak()
k.absorb(s)
if k.squeeze(checksum_length) != checksum:
raise ValueError("Invalid checksum")
return s
else:
if compact:
return s[:-1]
else:
(length, consumed) = decode_varint(s, endian='little')
s = s[:-consumed]
if len(s) != length:
raise ValueError("Invalid length")
return s
def unpad_and_checksum(s, compact, checksum):
"""Check length padding and checksum for a string
return the string without length padding or checksum
raise ValueError if either are wrong"""
assert isinstance(s, bytes)
if checksum:
if compact:
checksum_length = ord(s[-1])
consumed = 1
length = len(s) - checksum_length - consumed
else:
(length, consumed) = decode_varint(s, endian='little')
checksum_length = max(1, (length - 1).bit_length())
s = s[:-consumed]
s, checksum = s[:-checksum_length], s[-checksum_length:]
if len(s) != length:
raise ValueError("Invalid length")
k = Keccak()
k.absorb(s)
if k.squeeze(checksum_length) != checksum:
raise ValueError("Invalid checksum")
return s
else:
if compact:
return s[:-1]
else:
(length, consumed) = decode_varint(s, endian='little')
s = s[:-consumed]
if len(s) != length:
raise ValueError("Invalid length")
return s
def deserialize(cls, s):
if s[0] != cls.tag_byte:
raise ValueError('Attempting to deserialize a stream with the wrong tag byte')
s = s[1:]
(length, consumed) = decode_varint(s,endian='big')
s = s[consumed:]
return (cls(s[:length]), 1+consumed+length)
def decode(w, compact=False, permissive=False):
"""From a list of words, or a whitespace-separated string of words, produce
the original string that was encoded.
w: the list of words, or whitespace delimited words to be decoded
compact: compact encoding was used instead of length encoding
permissive: if there are spelling errors, correct them instead of throwing
an error (will still throw ValueError if spelling can't be corrected)
Raises ValueError if the encoding is invalid.
"""
if isinstance(w, bytes):
w = w.split()
indexes = [None] * len(w)
for i, word in enumerate(w):
if word in rwords:
indexes[i] = rwords[word]
elif permissive:
for nearby in dldist(word, 1):
if nearby in rwords:
indexes[i] = rwords[nearby]
break
if indexes[i] is None:
raise ValueError('Unrecognized word %s' % repr(word))
# because we don't directly encode the mantissas, we have to extract them
values = reduce(
lambda (last_index, accum), index:
(index, accum + [(index - last_index) % len(words)]), indexes,
(0, []))[1]
i = sum(mantissa * len(words)**radix
for radix, mantissa in enumerate(values))
# we don't need to worry about truncating null bytes because of the encoded length on the end
s = int2bytes(i)
if compact:
checksum_length = ord(s[-1])
consumed = 1
length = len(s) - checksum_length - consumed
else:
(length, consumed) = decode_varint(s, endian='little')
checksum_length = max(1, (length - 1).bit_length())
s = s[:-consumed]
s, checksum = s[:-checksum_length], s[-checksum_length:]
if len(s) != length:
raise ValueError("Invalid length")
k = Keccak()
k.absorb(s)
if k.squeeze(checksum_length) != checksum:
raise ValueError("Invalid checksum")
return s
def decode(w, compact=False, permissive=False):
"""From a list of words, or a whitespace-separated string of words, produce
the original string that was encoded.
w: the list of words, or whitespace delimited words to be decoded
compact: compact encoding was used instead of length encoding
permissive: if there are spelling errors, correct them instead of throwing
an error (will still throw ValueError if spelling can't be corrected)
Raises ValueError if the encoding is invalid.
"""
if isinstance(w, bytes):
w = w.split()
indexes = [None]*len(w)
for i,word in enumerate(w):
if word in rwords:
indexes[i] = rwords[word]
elif permissive:
for nearby in dldist(word, 1):
if nearby in rwords:
indexes[i] = rwords[nearby]
break
if indexes[i] is None:
raise ValueError('Unrecognized word %s' % repr(word))
# because we don't directly encode the mantissas, we have to extract them
values = reduce(lambda (last_index, accum), index: (index,
accum + [(index - last_index) % len(words)]),
indexes,
(0, []))[1]
i = sum(mantissa * len(words)**radix for radix, mantissa in enumerate(values))
# we don't need to worry about truncating null bytes because of the encoded length on the end
s = int2bytes(i)
if compact:
checksum_length = ord(s[-1])
consumed = 1
length = len(s) - checksum_length - consumed
else:
(length, consumed) = decode_varint(s, endian='little')
checksum_length = max(1, (length-1).bit_length())
s = s[:-consumed]
s, checksum = s[:-checksum_length], s[-checksum_length:]
if len(s) != length:
raise ValueError("Invalid length")
k = Keccak()
k.absorb(s)
if k.squeeze(checksum_length) != checksum:
raise ValueError("Invalid checksum")
return s
def deserialize(cls, s):
if s[0] != cls.tag_byte:
raise ValueError('Attempting to deserialize a stream with the wrong tag byte')
total_consumed = 1
s = s[1:]
length, consumed = decode_varint(s,endian='big')
total_consumed += consumed
s = s[consumed:]
temp = [None]*length
for i in xrange(length):
(temp[i], consumed) = deserialize(s)
total_consumed += consumed
s = s[consumed:]
return (cls(temp), total_consumed)
def element_to_string(element):
if not isinstance(element, Element):
raise TypeError("Attempted to convert a non-element to a message")
length, consumed = decode_varint(element, endian='little')
element = element[:length]
return element