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cpython/Lib/base64.py
kangtastic 45d4a34720
gh-101178: Add Ascii85, Base85, and Z85 support to binascii (GH-102753) 
Add Ascii85, Base85, and Z85 encoders and decoders to binascii,
replacing the existing pure Python implementations in base64.

This makes the codecs two orders of magnitude faster and consume
two orders of magnitude less memory.

Note that attempting to decode Ascii85 or Base85 data of length 1 mod 5
(after accounting for Ascii85 quirks) now produces an error, as no
encoder would emit such data. This should be the only significant
externally visible difference compared to the old implementation.

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
2026-02-06 16:43:16 +02:00

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"""Base16, Base32, Base64 (RFC 3548), Base85 and Ascii85 data encodings"""
# Modified 04-Oct-1995 by Jack Jansen to use binascii module
# Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
# Modified 22-May-2007 by Guido van Rossum to use bytes everywhere
import binascii
__all__ = [
# Legacy interface exports traditional RFC 2045 Base64 encodings
'encode', 'decode', 'encodebytes', 'decodebytes',
# Generalized interface for other encodings
'b64encode', 'b64decode', 'b32encode', 'b32decode',
'b32hexencode', 'b32hexdecode', 'b16encode', 'b16decode',
# Base85 and Ascii85 encodings
'b85encode', 'b85decode', 'a85encode', 'a85decode', 'z85encode', 'z85decode',
# Standard Base64 encoding
'standard_b64encode', 'standard_b64decode',
# Some common Base64 alternatives. As referenced by RFC 3458, see thread
# starting at:
#
# http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html
'urlsafe_b64encode', 'urlsafe_b64decode',
]
_NOT_SPECIFIED = ['NOT SPECIFIED']
bytes_types = (bytes, bytearray) # Types acceptable as binary data
def _bytes_from_decode_data(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__) from None
# Base64 encoding/decoding uses binascii
def b64encode(s, altchars=None, *, wrapcol=0):
"""Encode the bytes-like object s using Base64 and return a bytes object.
Optional altchars should 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.
If wrapcol is non-zero, insert a newline (b'\\n') character after at most
every wrapcol characters.
"""
encoded = binascii.b2a_base64(s, wrapcol=wrapcol, newline=False)
if altchars is not None:
assert len(altchars) == 2, repr(altchars)
return encoded.translate(bytes.maketrans(b'+/', altchars))
return encoded
def b64decode(s, altchars=None, validate=_NOT_SPECIFIED, *, ignorechars=_NOT_SPECIFIED):
"""Decode the Base64 encoded bytes-like object or ASCII string s.
Optional altchars must be a bytes-like object or ASCII string of length 2
which specifies the alternative alphabet used instead of the '+' and '/'
characters.
The result is returned as a bytes object. A binascii.Error is raised if
s is incorrectly padded.
If ignorechars is specified, it should be a byte string containing
characters to ignore from the input. The default value of validate is
True if ignorechars is specified, False otherwise.
If validate is false, 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 binascii.Error if they are not in ignorechars.
For more information about the strict base64 check, see:
https://docs.python.org/3.11/library/binascii.html#binascii.a2b_base64
"""
s = _bytes_from_decode_data(s)
if validate is _NOT_SPECIFIED:
validate = ignorechars is not _NOT_SPECIFIED
badchar = None
if altchars is not None:
altchars = _bytes_from_decode_data(altchars)
if len(altchars) != 2:
raise ValueError(f'invalid altchars: {altchars!r}')
if ignorechars is _NOT_SPECIFIED:
for b in b'+/':
if b not in altchars and b in s:
badchar = b
break
s = s.translate(bytes.maketrans(altchars, b'+/'))
else:
trans = bytes.maketrans(b'+/' + altchars, altchars + b'+/')
s = s.translate(trans)
ignorechars = ignorechars.translate(trans)
if ignorechars is _NOT_SPECIFIED:
ignorechars = b''
result = binascii.a2b_base64(s, strict_mode=validate,
ignorechars=ignorechars)
if badchar is not None:
import warnings
if validate:
warnings.warn(f'invalid character {chr(badchar)!a} in Base64 data '
f'with altchars={altchars!r} and validate=True '
f'will be an error in future Python versions',
DeprecationWarning, stacklevel=2)
else:
warnings.warn(f'invalid character {chr(badchar)!a} in Base64 data '
f'with altchars={altchars!r} and validate=False '
f'will be discarded in future Python versions',
FutureWarning, stacklevel=2)
return result
def standard_b64encode(s):
"""Encode bytes-like object s using the standard Base64 alphabet.
The result is returned as a bytes object.
"""
return b64encode(s)
def standard_b64decode(s):
"""Decode bytes encoded with the standard Base64 alphabet.
Argument s is a bytes-like object or ASCII string to decode. The result
is returned as a bytes object. A binascii.Error is raised if the input
is incorrectly padded. Characters that are not in the standard alphabet
are discarded prior to the padding check.
"""
return b64decode(s)
_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')
_urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')
def urlsafe_b64encode(s):
"""Encode bytes using the URL- and filesystem-safe Base64 alphabet.
Argument s is a bytes-like object to encode. The result is returned as a
bytes object. The alphabet uses '-' instead of '+' and '_' instead of
'/'.
"""
return b64encode(s).translate(_urlsafe_encode_translation)
def urlsafe_b64decode(s):
"""Decode bytes using the URL- and filesystem-safe Base64 alphabet.
Argument s is a bytes-like object or ASCII string to decode. The result
is returned as a bytes object. A binascii.Error is raised if the input
is incorrectly padded. Characters that are not in the URL-safe base-64
alphabet, and are not a plus '+' or slash '/', are discarded prior to the
padding check.
The alphabet uses '-' instead of '+' and '_' instead of '/'.
"""
s = _bytes_from_decode_data(s)
badchar = None
for b in b'+/':
if b in s:
badchar = b
break
s = s.translate(_urlsafe_decode_translation)
result = binascii.a2b_base64(s, strict_mode=False)
if badchar is not None:
import warnings
warnings.warn(f'invalid character {chr(badchar)!a} in URL-safe Base64 data '
f'will be discarded in future Python versions',
FutureWarning, stacklevel=2)
return result
# Base32 encoding/decoding must be done in Python
_B32_ENCODE_DOCSTRING = '''
Encode the bytes-like objects using {encoding} and return a bytes object.
'''
_B32_DECODE_DOCSTRING = '''
Decode the {encoding} encoded bytes-like object or ASCII string s.
Optional casefold is a flag specifying whether a lowercase alphabet is
acceptable as input. For security purposes, the default is False.
{extra_args}
The result is returned as a bytes object. A binascii.Error is raised if
the input is incorrectly padded or if there are non-alphabet
characters present in the input.
'''
_B32_DECODE_MAP01_DOCSTRING = '''
RFC 3548 allows for optional mapping of the digit 0 (zero) to the
letter O (oh), and for optional mapping of the digit 1 (one) to
either the letter I (eye) or letter L (el). The optional argument
map01 when not None, specifies which letter the digit 1 should be
mapped to (when map01 is not None, the digit 0 is always mapped to
the letter O). For security purposes the default is None, so that
0 and 1 are not allowed in the input.
'''
_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
_b32hexalphabet = b'0123456789ABCDEFGHIJKLMNOPQRSTUV'
_b32tab2 = {}
_b32rev = {}
def _b32encode(alphabet, s):
# Delay the initialization of the table to not waste memory
# if the function is never called
if alphabet not in _b32tab2:
b32tab = [bytes((i,)) for i in alphabet]
_b32tab2[alphabet] = [a + b for a in b32tab for b in b32tab]
b32tab = None
if not isinstance(s, bytes_types):
s = memoryview(s).tobytes()
leftover = len(s) % 5
# Pad the last quantum with zero bits if necessary
if leftover:
s = s + b'\0' * (5 - leftover) # Don't use += !
encoded = bytearray()
from_bytes = int.from_bytes
b32tab2 = _b32tab2[alphabet]
for i in range(0, len(s), 5):
c = from_bytes(s[i: i + 5]) # big endian
encoded += (b32tab2[c >> 30] + # bits 1 - 10
b32tab2[(c >> 20) & 0x3ff] + # bits 11 - 20
b32tab2[(c >> 10) & 0x3ff] + # bits 21 - 30
b32tab2[c & 0x3ff] # bits 31 - 40
)
# Adjust for any leftover partial quanta
if leftover == 1:
encoded[-6:] = b'======'
elif leftover == 2:
encoded[-4:] = b'===='
elif leftover == 3:
encoded[-3:] = b'==='
elif leftover == 4:
encoded[-1:] = b'='
return encoded.take_bytes()
def _b32decode(alphabet, s, casefold=False, map01=None):
# Delay the initialization of the table to not waste memory
# if the function is never called
if alphabet not in _b32rev:
_b32rev[alphabet] = {v: k for k, v in enumerate(alphabet)}
s = _bytes_from_decode_data(s)
if len(s) % 8:
raise binascii.Error('Incorrect padding')
# Handle section 2.4 zero and one mapping. The flag map01 will be either
# False, or the character to map the digit 1 (one) to. It should be
# either L (el) or I (eye).
if map01 is not None:
map01 = _bytes_from_decode_data(map01)
assert len(map01) == 1, repr(map01)
s = s.translate(bytes.maketrans(b'01', b'O' + map01))
if casefold:
s = s.upper()
# Strip off pad characters from the right. We need to count the pad
# characters because this will tell us how many null bytes to remove from
# the end of the decoded string.
l = len(s)
s = s.rstrip(b'=')
padchars = l - len(s)
# Now decode the full quanta
decoded = bytearray()
b32rev = _b32rev[alphabet]
for i in range(0, len(s), 8):
quanta = s[i: i + 8]
acc = 0
try:
for c in quanta:
acc = (acc << 5) + b32rev[c]
except KeyError:
raise binascii.Error('Non-base32 digit found') from None
decoded += acc.to_bytes(5) # big endian
# Process the last, partial quanta
if l % 8 or padchars not in {0, 1, 3, 4, 6}:
raise binascii.Error('Incorrect padding')
if padchars and decoded:
acc <<= 5 * padchars
last = acc.to_bytes(5) # big endian
leftover = (43 - 5 * padchars) // 8 # 1: 4, 3: 3, 4: 2, 6: 1
decoded[-5:] = last[:leftover]
return decoded.take_bytes()
def b32encode(s):
return _b32encode(_b32alphabet, s)
b32encode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32')
def b32decode(s, casefold=False, map01=None):
return _b32decode(_b32alphabet, s, casefold, map01)
b32decode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32',
extra_args=_B32_DECODE_MAP01_DOCSTRING)
def b32hexencode(s):
return _b32encode(_b32hexalphabet, s)
b32hexencode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32hex')
def b32hexdecode(s, casefold=False):
# base32hex does not have the 01 mapping
return _b32decode(_b32hexalphabet, s, casefold)
b32hexdecode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32hex',
extra_args='')
# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
# lowercase. The RFC also recommends against accepting input case
# insensitively.
def b16encode(s):
"""Encode the bytes-like object s using Base16 and return a bytes object.
"""
return binascii.hexlify(s).upper()
def b16decode(s, casefold=False):
"""Decode the Base16 encoded bytes-like object or ASCII string s.
Optional casefold is a flag specifying whether a lowercase alphabet is
acceptable as input. For security purposes, the default is False.
The result is returned as a bytes object. A binascii.Error is raised if
s is incorrectly padded or if there are non-alphabet characters present
in the input.
"""
s = _bytes_from_decode_data(s)
if casefold:
s = s.upper()
if s.translate(None, delete=b'0123456789ABCDEF'):
raise binascii.Error('Non-base16 digit found')
return binascii.unhexlify(s)
#
# Ascii85 encoding/decoding
#
def a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False):
"""Encode bytes-like object b using Ascii85 and return a bytes object.
foldspaces is an optional flag that uses the special short sequence 'y'
instead of 4 consecutive spaces (ASCII 0x20) as supported by 'btoa'. This
feature is not supported by the "standard" Adobe encoding.
If wrapcol is non-zero, insert a newline (b'\\n') character after at most
every wrapcol characters.
pad controls whether the input is padded to a multiple of 4 before
encoding. Note that the btoa implementation always pads.
adobe controls whether the encoded byte sequence is framed with <~ and ~>,
which is used by the Adobe implementation.
"""
return binascii.b2a_ascii85(b, foldspaces=foldspaces,
adobe=adobe, wrapcol=wrapcol, pad=pad)
def a85decode(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v'):
"""Decode the Ascii85 encoded bytes-like object or ASCII string b.
foldspaces is a flag that specifies whether the 'y' short sequence should be
accepted as shorthand for 4 consecutive spaces (ASCII 0x20). This feature is
not supported by the "standard" Adobe encoding.
adobe controls whether the input sequence is in Adobe Ascii85 format (i.e.
is framed with <~ and ~>).
ignorechars should be a byte string containing characters to ignore from the
input. This should only contain whitespace characters, and by default
contains all whitespace characters in ASCII.
The result is returned as a bytes object.
"""
return binascii.a2b_ascii85(b, foldspaces=foldspaces,
adobe=adobe, ignorechars=ignorechars)
def b85encode(b, pad=False):
"""Encode bytes-like object b in base85 format and return a bytes object.
If pad is true, the input is padded with b'\\0' so its length is a multiple of
4 bytes before encoding.
"""
return binascii.b2a_base85(b, pad=pad)
def b85decode(b):
"""Decode the base85-encoded bytes-like object or ASCII string b
The result is returned as a bytes object.
"""
return binascii.a2b_base85(b)
def z85encode(s, pad=False):
"""Encode bytes-like object b in z85 format and return a bytes object."""
return binascii.b2a_z85(s, pad=pad)
def z85decode(s):
"""Decode the z85-encoded bytes-like object or ASCII string b
The result is returned as a bytes object.
"""
return binascii.a2b_z85(s)
# Legacy interface. This code could be cleaned up since I don't believe
# binascii has any line length limitations. It just doesn't seem worth it
# though. The files should be opened in binary mode.
MAXLINESIZE = 76 # Excluding the CRLF
MAXBINSIZE = (MAXLINESIZE//4)*3
def encode(input, output):
"""Encode a file; input and output are binary files."""
while s := input.read(MAXBINSIZE):
while len(s) < MAXBINSIZE and (ns := input.read(MAXBINSIZE-len(s))):
s += ns
line = binascii.b2a_base64(s)
output.write(line)
def decode(input, output):
"""Decode a file; input and output are binary files."""
while line := input.readline():
s = binascii.a2b_base64(line)
output.write(s)
def _input_type_check(s):
try:
m = memoryview(s)
except TypeError as err:
msg = "expected bytes-like object, not %s" % s.__class__.__name__
raise TypeError(msg) from err
if m.format not in ('c', 'b', 'B'):
msg = ("expected single byte elements, not %r from %s" %
(m.format, s.__class__.__name__))
raise TypeError(msg)
if m.ndim != 1:
msg = ("expected 1-D data, not %d-D data from %s" %
(m.ndim, s.__class__.__name__))
raise TypeError(msg)
def encodebytes(s):
"""Encode a bytestring into a bytes object containing multiple lines
of base-64 data."""
_input_type_check(s)
result = binascii.b2a_base64(s, wrapcol=MAXLINESIZE)
if result == b'\n':
return b''
return result
def decodebytes(s):
"""Decode a bytestring of base-64 data into a bytes object."""
_input_type_check(s)
return binascii.a2b_base64(s)
# Usable as a script...
def main():
"""Small main program"""
import sys, getopt
usage = f"""usage: {sys.argv[0]} [-h|-d|-e|-u] [file|-]
-h: print this help message and exit
-d, -u: decode
-e: encode (default)"""
try:
opts, args = getopt.getopt(sys.argv[1:], 'hdeu')
except getopt.error as msg:
sys.stdout = sys.stderr
print(msg)
print(usage)
sys.exit(2)
func = encode
for o, a in opts:
if o == '-e': func = encode
if o == '-d': func = decode
if o == '-u': func = decode
if o == '-h': print(usage); return
if args and args[0] != '-':
with open(args[0], 'rb') as f:
func(f, sys.stdout.buffer)
else:
if sys.stdin.isatty():
# gh-138775: read terminal input data all at once to detect EOF
import io
data = sys.stdin.buffer.read()
buffer = io.BytesIO(data)
else:
buffer = sys.stdin.buffer
func(buffer, sys.stdout.buffer)
if __name__ == '__main__':
main()
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