cpython/Lib/base64.py at main · https-github-com-nzysoft/cpython · GitHub

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#! /usr/bin/env python3

"""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 re

import struct

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',

# 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',

]

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):

"""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.

"""

encoded = binascii.b2a_base64(s, 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=False):

"""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 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 binascii.Error.

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 altchars is not None:

altchars = _bytes_from_decode_data(altchars)

assert len(altchars) == 2, repr(altchars)

s = s.translate(bytes.maketrans(altchars, b'+/'))

return binascii.a2b_base64(s, strict_mode=validate)

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)

s = s.translate(_urlsafe_decode_translation)

return b64decode(s)

# 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):

global _b32tab2

# 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 bytes(encoded)

def _b32decode(alphabet, s, casefold=False, map01=None):

global _b32rev

# 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 bytes(decoded)

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 re.search(b'[^0-9A-F]', s):

raise binascii.Error('Non-base16 digit found')

return binascii.unhexlify(s)

# Ascii85 encoding/decoding

_a85chars = None

_a85chars2 = None

_A85START = b"<~"

_A85END = b"~>"

def _85encode(b, chars, chars2, pad=False, foldnuls=False, foldspaces=False):

# Helper function for a85encode and b85encode

if not isinstance(b, bytes_types):

b = memoryview(b).tobytes()

padding = (-len(b)) % 4

if padding:

b = b + b'\0' * padding

words = struct.Struct('!%dI' % (len(b) // 4)).unpack(b)

chunks = [b'z' if foldnuls and not word else

b'y' if foldspaces and word == 0x20202020 else

(chars2[word // 614125] +

chars2[word // 85 % 7225] +

chars[word % 85])

for word in words]

if padding and not pad:

if chunks[-1] == b'z':

chunks[-1] = chars[0] * 5

chunks[-1] = chunks[-1][:-padding]

return b''.join(chunks)

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.

wrapcol controls whether the output should have newline (b'\\n') characters

added to it. If this is non-zero, each output line will be at most this

many characters long.

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.

"""

global _a85chars, _a85chars2

# Delay the initialization of tables to not waste memory

# if the function is never called

if _a85chars2 is None:

_a85chars = [bytes((i,)) for i in range(33, 118)]

_a85chars2 = [(a + b) for a in _a85chars for b in _a85chars]

result = _85encode(b, _a85chars, _a85chars2, pad, True, foldspaces)

if adobe:

result = _A85START + result

if wrapcol:

wrapcol = max(2 if adobe else 1, wrapcol)

chunks = [result[i: i + wrapcol]

for i in range(0, len(result), wrapcol)]

if adobe:

if len(chunks[-1]) + 2 > wrapcol:

chunks.append(b'')

result = b'\n'.join(chunks)

if adobe:

result += _A85END

return result

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.

"""

b = _bytes_from_decode_data(b)

if adobe:

if not b.endswith(_A85END):

raise ValueError(

"Ascii85 encoded byte sequences must end "

"with {!r}".format(_A85END)

)

if b.startswith(_A85START):

b = b[2:-2] # Strip off start/end markers

else:

b = b[:-2]

# We have to go through this stepwise, so as to ignore spaces and handle

# special short sequences

packI = struct.Struct('!I').pack

decoded = []

decoded_append = decoded.append

curr = []

curr_append = curr.append

curr_clear = curr.clear

for x in b + b'u' * 4:

if b'!'[0] <= x <= b'u'[0]:

curr_append(x)

if len(curr) == 5:

acc = 0

for x in curr:

acc = 85 * acc + (x - 33)

try:

decoded_append(packI(acc))

except struct.error:

raise ValueError('Ascii85 overflow') from None

curr_clear()

elif x == b'z'[0]:

if curr:

raise ValueError('z inside Ascii85 5-tuple')

decoded_append(b'\0\0\0\0')

elif foldspaces and x == b'y'[0]:

if curr:

raise ValueError('y inside Ascii85 5-tuple')

decoded_append(b'\x20\x20\x20\x20')

elif x in ignorechars:

# Skip whitespace

continue

else:

raise ValueError('Non-Ascii85 digit found: %c' % x)

result = b''.join(decoded)

padding = 4 - len(curr)

if padding:

# Throw away the extra padding

result = result[:-padding]

return result

# The following code is originally taken (with permission) from Mercurial

_b85alphabet = (b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"

b"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~")

_b85chars = None

_b85chars2 = None

_b85dec = None

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.

"""

global _b85chars, _b85chars2

# Delay the initialization of tables to not waste memory

# if the function is never called

if _b85chars2 is None:

_b85chars = [bytes((i,)) for i in _b85alphabet]

_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars]

return _85encode(b, _b85chars, _b85chars2, pad)

def b85decode(b):

"""Decode the base85-encoded bytes-like object or ASCII string b

The result is returned as a bytes object.

"""

global _b85dec

# Delay the initialization of tables to not waste memory

# if the function is never called

if _b85dec is None:

_b85dec = [None] * 256

for i, c in enumerate(_b85alphabet):

_b85dec[c] = i

b = _bytes_from_decode_data(b)

padding = (-len(b)) % 5

b = b + b'~' * padding

out = []

packI = struct.Struct('!I').pack

for i in range(0, len(b), 5):

chunk = b[i:i + 5]

acc = 0

try:

for c in chunk:

acc = acc * 85 + _b85dec[c]

except TypeError:

for j, c in enumerate(chunk):

if _b85dec[c] is None:

raise ValueError('bad base85 character at position %d'

% (i + j)) from None

raise

try:

out.append(packI(acc))

except struct.error:

raise ValueError('base85 overflow in hunk starting at byte %d'

% i) from None

result = b''.join(out)

if padding:

result = result[:-padding]

return result

# 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)

pieces = []

for i in range(0, len(s), MAXBINSIZE):

chunk = s[i : i + MAXBINSIZE]

pieces.append(binascii.b2a_base64(chunk))

return b"".join(pieces)

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:

func(sys.stdin.buffer, sys.stdout.buffer)

if __name__ == '__main__':

main()

cpython/Lib/base64.py at main · https-github-com-nzysoft/cpython · GitHub

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