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gh-146192: Add base32 support to binascii#146193

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Merged
serhiy-storchaka merged 8 commits intopython:mainfromkangtastic:base32-accel
Mar 22, 2026
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46 changes: 46 additions & 0 deletionsDoc/library/binascii.rst
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Original file line numberDiff line numberDiff line change
Expand Up@@ -183,6 +183,38 @@ The :mod:`!binascii` module defines the following functions:
.. versionadded:: 3.15


.. function:: a2b_base32(string, /, *, alphabet=BASE32_ALPHABET)

Convert base32 data back to binary and return the binary data.

Valid base32 data contains characters from the base32 alphabet specified
in :rfc:`4648` in groups of eight (if necessary, the final group is padded
to eight characters with ``=``). Each group encodes 40 bits of binary data
in the range from ``0`` to ``2 ** 40 - 1``, inclusive.

.. note::
This function does not map lowercase characters (which are invalid in
standard base32) to their uppercase counterparts, nor does it
contextually map ``0`` to ``O`` and ``1`` to ``I``/``L`` as :rfc:`4648`
allows.

Optional *alphabet* must be a :class:`bytes` object of length 32 which
specifies an alternative alphabet.

Invalid base32 data will raise :exc:`binascii.Error`.

.. versionadded:: next

.. function:: b2a_base32(data, /, *, alphabet=BASE32_ALPHABET)

Convert binary data to a line of ASCII characters in base32 coding,
as specified in :rfc:`4648`. The return value is the converted line.

Optional *alphabet* must be a :term:`bytes-like object` of length 32 which
specifies an alternative alphabet.

.. versionadded:: next

.. function:: a2b_qp(data, header=False)

Convert a block of quoted-printable data back to binary and return the binary
Expand DownExpand Up@@ -327,6 +359,20 @@ The :mod:`!binascii` module defines the following functions:

.. versionadded:: next

.. data:: BASE32_ALPHABET

The Base 32 alphabet according to :rfc:`4648`.

.. versionadded:: next

.. data:: BASE32HEX_ALPHABET

The "Extended Hex" Base 32 alphabet according to :rfc:`4648`.
Data encoded with this alphabet maintains its sort order during bitwise
comparisons.

.. versionadded:: next


.. seealso::

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10 changes: 10 additions & 0 deletionsDoc/whatsnew/3.15.rst
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Expand Up@@ -662,6 +662,12 @@ binascii
* Added the *ignorechars* parameter in :func:`~binascii.a2b_base64`.
(Contributed by Serhiy Storchaka in :gh:`144001`.)

* Added functions for Base32 encoding:

- :func:`~binascii.b2a_base32` and :func:`~binascii.a2b_base32`

(Contributed by James Seo in :gh:`146192`.)


calendar
--------
Expand DownExpand Up@@ -1279,6 +1285,10 @@ base64 & binascii
two orders of magnitude less memory.
(Contributed by James Seo and Serhiy Storchaka in :gh:`101178`.)

* Implementation for Base32 has been rewritten in C.
Encoding and decoding is now two orders of magnitude faster.
(Contributed by James Seo in :gh:`146192`)


csv
---
Expand Down
96 changes: 12 additions & 84 deletionsLib/base64.py
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Expand Up@@ -206,54 +206,13 @@ def urlsafe_b64decode(s):
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)}

def b32encode(s):
return binascii.b2a_base32(s)
b32encode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32')

def b32decode(s, casefold=False, map01=None):
s = _bytes_from_decode_data(s)

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This is only needed if map01 is not None.

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Correction: it is also needed if casefold is true, for input like 'ß' or 'ffi'.

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).
Expand All@@ -263,51 +222,20 @@ def _b32decode(alphabet, s, casefold=False, map01=None):
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)
return binascii.a2b_base32(s)
b32decode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32',
extra_args=_B32_DECODE_MAP01_DOCSTRING)

def b32hexencode(s):
return_b32encode(_b32hexalphabet, s)
returnbinascii.b2a_base32(s, alphabet=binascii.BASE32HEX_ALPHABET)
b32hexencode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32hex')

def b32hexdecode(s, casefold=False):
s = _bytes_from_decode_data(s)
# base32hex does not have the 01 mapping
return _b32decode(_b32hexalphabet, s, casefold)
if casefold:
s = s.upper()
return binascii.a2b_base32(s, alphabet=binascii.BASE32HEX_ALPHABET)
b32hexdecode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32hex',
extra_args='')

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