Current File : //opt/rh/rh-python35/root/lib64/python3.5/base64.py
#! /opt/rh/rh-python35/root/usr/bin/python3.5
"""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 1521 Base64 encodings
'encode', 'decode', 'encodebytes', 'decodebytes',
# Generalized interface for other encodings
'b64encode', 'b64decode', 'b32encode', 'b32decode',
'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 a byte string using Base64.
s is the byte string 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 encoded byte string is returned.
"""
# Strip off the trailing newline
encoded = binascii.b2a_base64(s)[:-1]
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 a Base64 encoded byte string.
s is the byte string to decode. Optional altchars must be a
string of length 2 which specifies the alternative alphabet used
instead of the '+' and '/' characters.
The decoded string is returned. A binascii.Error is raised if s is
incorrectly padded.
If validate is False (the default), non-base64-alphabet characters are
discarded prior to the padding check. If validate is True,
non-base64-alphabet characters in the input result in a binascii.Error.
"""
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'+/'))
if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):
raise binascii.Error('Non-base64 digit found')
return binascii.a2b_base64(s)
def standard_b64encode(s):
"""Encode a byte string using the standard Base64 alphabet.
s is the byte string to encode. The encoded byte string is returned.
"""
return b64encode(s)
def standard_b64decode(s):
"""Decode a byte string encoded with the standard Base64 alphabet.
s is the byte string to decode. The decoded byte string is
returned. binascii.Error is raised if the input is incorrectly
padded or if there are non-alphabet characters present in the
input.
"""
return b64decode(s)
_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')
_urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')
def urlsafe_b64encode(s):
"""Encode a byte string using a url-safe Base64 alphabet.
s is the byte string to encode. The encoded byte string is
returned. The alphabet uses '-' instead of '+' and '_' instead of
'/'.
"""
return b64encode(s).translate(_urlsafe_encode_translation)
def urlsafe_b64decode(s):
"""Decode a byte string encoded with the standard Base64 alphabet.
s is the byte string to decode. The decoded byte string is
returned. binascii.Error is raised if the input is incorrectly
padded or if there are non-alphabet characters present in the
input.
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
_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
_b32tab2 = None
_b32rev = None
def b32encode(s):
"""Encode a byte string using Base32.
s is the byte string to encode. The encoded byte string is returned.
"""
global _b32tab2
# Delay the initialization of the table to not waste memory
# if the function is never called
if _b32tab2 is None:
b32tab = [bytes((i,)) for i in _b32alphabet]
_b32tab2 = [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 + bytes(5 - leftover) # Don't use += !
encoded = bytearray()
from_bytes = int.from_bytes
b32tab2 = _b32tab2
for i in range(0, len(s), 5):
c = from_bytes(s[i: i + 5], 'big')
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(s, casefold=False, map01=None):
"""Decode a Base32 encoded byte string.
s is the byte string to decode. Optional casefold is a flag
specifying whether a lowercase alphabet is acceptable as input.
For security purposes, the default is False.
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.
The decoded byte string is returned. binascii.Error is raised if
the input is incorrectly padded or if there are non-alphabet
characters present in the input.
"""
global _b32rev
# Delay the initialization of the table to not waste memory
# if the function is never called
if _b32rev is None:
_b32rev = {v: k for k, v in enumerate(_b32alphabet)}
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
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')
# Process the last, partial quanta
if padchars:
acc <<= 5 * padchars
last = acc.to_bytes(5, 'big')
if padchars == 1:
decoded[-5:] = last[:-1]
elif padchars == 3:
decoded[-5:] = last[:-2]
elif padchars == 4:
decoded[-5:] = last[:-3]
elif padchars == 6:
decoded[-5:] = last[:-4]
else:
raise binascii.Error('Incorrect padding')
return bytes(decoded)
# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
# lowercase. The RFC also recommends against accepting input case
# insensitively.
def b16encode(s):
"""Encode a byte string using Base16.
s is the byte string to encode. The encoded byte string is returned.
"""
return binascii.hexlify(s).upper()
def b16decode(s, casefold=False):
"""Decode a Base16 encoded byte string.
s is the byte string to decode. Optional casefold is a flag
specifying whether a lowercase alphabet is acceptable as input.
For security purposes, the default is False.
The decoded byte string is returned. binascii.Error is raised if
s were incorrectly padded or if there are non-alphabet characters
present in the string.
"""
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 a byte string using Ascii85.
b is the byte string to encode. The encoded byte string is returned.
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 ('\\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 string 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 _a85chars 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 an Ascii85 encoded byte string.
s is the byte string to decode.
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.
"""
b = _bytes_from_decode_data(b)
if adobe:
if not (b.startswith(_A85START) and b.endswith(_A85END)):
raise ValueError("Ascii85 encoded byte sequences must be bracketed "
"by {!r} and {!r}".format(_A85START, _A85END))
b = b[2:-2] # Strip off start/end markers
#
# 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 an ASCII-encoded byte array in base85 format.
If pad is true, the input is padded with "\\0" so its length is a multiple of
4 characters before encoding.
"""
global _b85chars, _b85chars2
# Delay the initialization of tables to not waste memory
# if the function is never called
if _b85chars 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 base85-encoded byte array"""
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 True:
s = input.read(MAXBINSIZE)
if not s:
break
while len(s) < MAXBINSIZE:
ns = input.read(MAXBINSIZE-len(s))
if not ns:
break
s += ns
line = binascii.b2a_base64(s)
output.write(line)
def decode(input, output):
"""Decode a file; input and output are binary files."""
while True:
line = input.readline()
if not line:
break
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 bytestring 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 encodestring(s):
"""Legacy alias of encodebytes()."""
import warnings
warnings.warn("encodestring() is a deprecated alias, use encodebytes()",
DeprecationWarning, 2)
return encodebytes(s)
def decodebytes(s):
"""Decode a bytestring of base-64 data into a bytestring."""
_input_type_check(s)
return binascii.a2b_base64(s)
def decodestring(s):
"""Legacy alias of decodebytes()."""
import warnings
warnings.warn("decodestring() is a deprecated alias, use decodebytes()",
DeprecationWarning, 2)
return decodebytes(s)
# Usable as a script...
def main():
"""Small main program"""
import sys, getopt
try:
opts, args = getopt.getopt(sys.argv[1:], 'deut')
except getopt.error as msg:
sys.stdout = sys.stderr
print(msg)
print("""usage: %s [-d|-e|-u|-t] [file|-]
-d, -u: decode
-e: encode (default)
-t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0])
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 == '-t': test(); 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)
def test():
s0 = b"Aladdin:open sesame"
print(repr(s0))
s1 = encodebytes(s0)
print(repr(s1))
s2 = decodebytes(s1)
print(repr(s2))
assert s0 == s2
if __name__ == '__main__':
main()
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He has been blogging regularly for the past 35 years on this subject. Having taught media studies at Columbia University, NYU and now the University of Oxford, he is considered an expert on this subject.
Continue reading this post or look back at previous posts.
