def encode_int12(self, value):
"""encodes 12-bit integer -> 2 char string"""
if value < 0 or value > 0xFFF:
raise ValueError("value out of range")
raw = [value & 0x3f, (value>>6) & 0x3f]
if self.big:
raw = reversed(raw)
return join_byte_elems(imap(self._encode64, raw))
def encode_bytes(self, source):
"""encode bytes to base64 string.
:arg source: byte string to encode.
:returns: byte string containing encoded data.
"""
if not isinstance(source, bytes):
raise TypeError("source must be bytes, not %s" % (type(source),))
chunks, tail = divmod(len(source), 3)
if PY3:
next_value = nextgetter(iter(source))
else:
next_value = nextgetter(ord(elem) for elem in source)
gen = self._encode_bytes(next_value, chunks, tail)
out = join_byte_elems(imap(self._encode64, gen))
##if tail:
## padding = self.padding
## if padding:
## out += padding * (3-tail)
return out
def _encode_int(self, value, bits):
"""encode integer into base64 format
:arg value: non-negative integer to encode
:arg bits: number of bits to encode
:returns:
a string of length ``int(ceil(bits/6.0))``.
"""
assert value >= 0, "caller did not sanitize input"
pad = -bits % 6
bits += pad
if self.big:
itr = irange(bits-6, -6, -6)
# shift to add lsb padding.
value <<= pad
else:
itr = irange(0, bits, 6)
# padding is msb, so no change needed.
return join_byte_elems(imap(self._encode64,
((value>>off) & 0x3f for off in itr)))
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],))