from base64 import b64decode as builtin_decode
from base64 import b64encode as builtin_encode
from base64 import encodebytes as builtin_encodebytes
from binascii import Error as BinAsciiError
__all__ = ['b64decode', 'b64encode', 'encodebytes']
_bytes_types = (bytes, bytearray) # Types acceptable as binary data
def _get_bytes(s):
if isinstance(s, str):
try:
return s.encode('ascii')
except UnicodeEncodeError:
raise ValueError('string argument should contain only ASCII '
'characters')
if isinstance(s, _bytes_types):
return s
try:
return memoryview(s).tobytes()
except TypeError:
raise TypeError('argument should be a bytes-like object or ASCII '
'string, not %r' % s.__class__.__name__)
[docs]def b64decode(s, altchars=None, validate=False):
"""Decode bytes encoded with the standard Base64 alphabet.
Argument ``s`` is a :term:`bytes-like object` or ASCII string to
decode.
Optional ``altchars`` must be a :term:`bytes-like object` or ASCII
string of length 2 which specifies the alternative alphabet used instead
of the '+' and '/' characters.
If ``validate`` is ``False`` (the default), characters that are neither in
the normal base-64 alphabet nor the alternative alphabet are discarded
prior to the padding check.
If ``validate`` is ``True``, these non-alphabet characters in the input
result in a :exc:`binascii.Error`.
The result is returned as a :class:`bytes` object.
A :exc:`binascii.Error` is raised if ``s`` is incorrectly padded.
"""
if validate:
if len(s) % 4 != 0:
raise BinAsciiError('Incorrect padding')
s = _get_bytes(s)
if altchars is not None:
altchars = _get_bytes(altchars)
assert len(altchars) == 2, repr(altchars)
map = bytes.maketrans(altchars, b'+/')
s = s.translate(map)
try:
result = builtin_decode(s, altchars, validate=False)
except TypeError as e:
raise BinAsciiError(str(e))
# check length of result vs length of input
padding = 0
if len(s) > 1 and s[-2] in (b'=', 61):
padding = padding + 1
if len(s) > 0 and s[-1] in (b'=', 61):
padding = padding + 1
if 3 * (len(s) / 4) - padding != len(result):
raise BinAsciiError('Non-base64 digit found')
return result
return builtin_decode(s, altchars, validate=False)
[docs]def b64encode(s, altchars=None):
"""Encode bytes using the standard Base64 alphabet.
Argument ``s`` is a :term:`bytes-like object` to encode.
Optional ``altchars`` must be a byte string of length 2 which specifies
an alternative alphabet for the '+' and '/' characters. This allows an
application to e.g. generate url or filesystem safe Base64 strings.
The result is returned as a :class:`bytes` object.
"""
if altchars is not None:
altchars = _get_bytes(altchars)
assert len(altchars) == 2, repr(altchars)
return builtin_encode(s, altchars)
[docs]def encodebytes(s):
"""Encode bytes into a bytes object with newlines (b'\n') inserted after
every 76 bytes of output, and ensuring that there is a trailing newline,
as per :rfc:`2045` (MIME).
Argument ``s`` is a :term:`bytes-like object` to encode.
The result is returned as a :class:`bytes` object.
"""
return builtin_encodebytes(s)