def _cipher(cls, data, salt):
"""xor static key against data - encrypts & decrypts"""
key = cls._key
key_size = len(key)
return join_byte_values(
value ^ ord(key[(salt + idx) % key_size])
for idx, value in enumerate(iter_byte_values(data)))
def getrandbytes(rng, count):
"""return byte-string containing *count* number of randomly generated bytes, using specified rng"""
# NOTE: would be nice if this was present in stdlib Random class
###just in case rng provides this...
##meth = getattr(rng, "getrandbytes", None)
##if meth:
## return meth(count)
if not count:
return _BEMPTY
def helper():
# XXX: break into chunks for large number of bits?
value = rng.getrandbits(count<<3)
i = 0
while i < count:
yield value & 0xff
value >>= 3
i += 1
return join_byte_values(helper())
def decode_bytes(self, source):
"""decode bytes from base64 string.
:arg source: byte string to decode.
:returns: byte string containing decoded data.
"""
if not isinstance(source, bytes):
raise TypeError("source must be bytes, not %s" % (type(source),))
##padding = self.padding
##if padding:
## # TODO: add padding size check?
## source = source.rstrip(padding)
chunks, tail = divmod(len(source), 4)
if tail == 1:
# only 6 bits left, can't encode a whole byte!
raise ValueError("input string length cannot be == 1 mod 4")
next_value = nextgetter(imap(self._decode64, source))
try:
return join_byte_values(self._decode_bytes(next_value, chunks, tail))
except KeyError as err:
raise ValueError("invalid character: %r" % (err.args[0],))
#: all hex chars
HEX_CHARS = u("0123456789abcdefABCDEF")
#: upper case hex chars
UPPER_HEX_CHARS = u("0123456789ABCDEF")
#: lower case hex chars
LOWER_HEX_CHARS = u("0123456789abcdef")
#-------------------------------------------------------------
# byte strings
#-------------------------------------------------------------
#: special byte string containing all possible byte values
#: NOTE: for efficiency, this is treated as singleton by some of the code
ALL_BYTE_VALUES = join_byte_values(irange(256))
#: some string constants we reuse
B_EMPTY = b''
B_NULL = b'\x00'
B_EQUAL = b'='
#=============================================================================
# byte translation
#=============================================================================
#: base list used to compile byte translations
_TRANSLATE_SOURCE = list(iter_byte_chars(ALL_BYTE_VALUES))
def compile_byte_translation(mapping, source=None):
"""