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# Conversions to/from base64 transport encoding as per RFC-MIME (Dec 1991
# version).
# Parameters set by RFX-XXXX.
MAXLINESIZE = 76 # Excluding the CRLF
INVAR = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
PAD = '='
# Check that I typed that string correctly...
if len(INVAR) <> 64: raise RuntimeError, 'wrong INVAR string!?!?'
# Compute the inverse table, for decode().
inverse = {}
for i in range(64): inverse[INVAR[i]] = i
del i
inverse[PAD] = 0
# Encode a file.
def encode(input, output):
line = ''
BUFSIZE = 8192
leftover = ''
while 1:
s = input.read(BUFSIZE)
if not s: break
s = leftover + s
i = 0
while i+3 <= len(s):
quad = makequad(s[i:i+3])
i = i+3
if len(line) + 4 > MAXLINESIZE:
output.write(line + '\n')
line = ''
line = line + quad
leftover = s[i:]
if leftover:
quad = makeshortquad(leftover)
if len(line) + 4 > MAXLINESIZE:
output.write(line + '\n')
line = ''
line = line + quad
if line:
output.write(line + '\n')
def makequad(s): # Return the quad for a 3 character string
x = ord(s[0])*0x10000 + ord(s[1])*0x100 + ord(s[2])
x, c4 = divmod(x, 64)
x, c3 = divmod(x, 64)
c1, c2 = divmod(x, 64)
return INVAR[c1] + INVAR[c2] +INVAR[c3] + INVAR[c4]
def makeshortquad(s): # Return the quad value for a 1 or 2 character string
n = len(s)
while len(s) < 3:
s = s + '\0'
quad = makequad(s)
if n == 2:
quad = quad[:3] + PAD
elif n == 1:
quad = quad[:2] + 2*PAD
return quad
# Decode a file.
def decode(input, output):
BUFSIZE = 8192
bits, n, bytes, prev = 0, 0, '', ''
while 1:
line = input.readline()
if not line: break
for c in line:
if inverse.has_key(c):
bits = bits*64 + inverse[c]
n = n+6
if n == 24:
triplet = decodequad(bits)
if c == PAD:
if prev == PAD:
triplet = triplet[:1]
else:
triplet = triplet[:2]
bits, n = 0, 0
bytes = bytes + triplet
if len(bytes) > BUFSIZE:
output.write(bytes[:BUFSIZE])
bytes = bytes[BUFSIZE:]
prev = c
if bytes:
output.write(bytes)
def decodequad(bits): # Turn 24 bits into 3 characters
bits, c3 = divmod(bits, 256)
c1, c2 = divmod(bits, 256)
return chr(c1) + chr(c2) + chr(c3)
def encodestring(s):
import StringIO
f = StringIO.StringIO(s)
g = StringIO.StringIO()
encode(f, g)
return g.getvalue()
def decodestring(s):
import StringIO
f = StringIO.StringIO(s)
g = StringIO.StringIO()
decode(f, g)
return g.getvalue()
# Small test program, reads stdin, writes stdout.
# no arg: encode, any arg: decode.
def test():
import sys, getopt
try:
opts, args = getopt.getopt(sys.argv[1:], 'deut')
except getopt.error, msg:
print msg
print """usage: basd64 [-d] [-e] [-u] [-t] [file|-]
-d, -u: decode
-e: encode (default)
-t: decode string 'Aladdin:open sesame'"""
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': test1(); return
if args and args[0] != '-':
func(open(args[0]), sys.stdout)
else:
func(sys.stdin, sys.stdout)
def test1():
s0 = "Aladdin:open sesame"
s1 = encodestring(s0)
s2 = decodestring(s1)
print s0, `s1`, s2
if __name__ == '__main__':
test()
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