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#! /usr/bin/env python3
"""Conversions to/from quoted-printable transport encoding as per RFC 1521."""
# (Dec 1991 version).
__all__ = ["encode", "decode", "encodestring", "decodestring"]
ESCAPE = b'='
MAXLINESIZE = 76
HEX = b'0123456789ABCDEF'
EMPTYSTRING = b''
try:
from binascii import a2b_qp, b2a_qp
except ImportError:
a2b_qp = None
b2a_qp = None
def needsquoting(c, quotetabs, header):
"""Decide whether a particular byte ordinal needs to be quoted.
The 'quotetabs' flag indicates whether embedded tabs and spaces should be
quoted. Note that line-ending tabs and spaces are always encoded, as per
RFC 1521.
"""
assert isinstance(c, bytes)
if c in b' \t':
return quotetabs
# if header, we have to escape _ because _ is used to escape space
if c == b'_':
return header
return c == ESCAPE or not (b' ' <= c <= b'~')
def quote(c):
"""Quote a single character."""
assert isinstance(c, bytes) and len(c)==1
c = ord(c)
return ESCAPE + bytes((HEX[c//16], HEX[c%16]))
def encode(input, output, quotetabs, header=False):
"""Read 'input', apply quoted-printable encoding, and write to 'output'.
'input' and 'output' are binary file objects. The 'quotetabs' flag
indicates whether embedded tabs and spaces should be quoted. Note that
line-ending tabs and spaces are always encoded, as per RFC 1521.
The 'header' flag indicates whether we are encoding spaces as _ as per RFC
1522."""
if b2a_qp is not None:
data = input.read()
odata = b2a_qp(data, quotetabs=quotetabs, header=header)
output.write(odata)
return
def write(s, output=output, lineEnd=b'\n'):
# RFC 1521 requires that the line ending in a space or tab must have
# that trailing character encoded.
if s and s[-1:] in b' \t':
output.write(s[:-1] + quote(s[-1:]) + lineEnd)
elif s == b'.':
output.write(quote(s) + lineEnd)
else:
output.write(s + lineEnd)
prevline = None
while line := input.readline():
outline = []
# Strip off any readline induced trailing newline
stripped = b''
if line[-1:] == b'\n':
line = line[:-1]
stripped = b'\n'
# Calculate the un-length-limited encoded line
for c in line:
c = bytes((c,))
if needsquoting(c, quotetabs, header):
c = quote(c)
if header and c == b' ':
outline.append(b'_')
else:
outline.append(c)
# First, write out the previous line
if prevline is not None:
write(prevline)
# Now see if we need any soft line breaks because of RFC-imposed
# length limitations. Then do the thisline->prevline dance.
thisline = EMPTYSTRING.join(outline)
while len(thisline) > MAXLINESIZE:
# Don't forget to include the soft line break `=' sign in the
# length calculation!
write(thisline[:MAXLINESIZE-1], lineEnd=b'=\n')
thisline = thisline[MAXLINESIZE-1:]
# Write out the current line
prevline = thisline
# Write out the last line, without a trailing newline
if prevline is not None:
write(prevline, lineEnd=stripped)
def encodestring(s, quotetabs=False, header=False):
if b2a_qp is not None:
return b2a_qp(s, quotetabs=quotetabs, header=header)
from io import BytesIO
infp = BytesIO(s)
outfp = BytesIO()
encode(infp, outfp, quotetabs, header)
return outfp.getvalue()
def decode(input, output, header=False):
"""Read 'input', apply quoted-printable decoding, and write to 'output'.
'input' and 'output' are binary file objects.
If 'header' is true, decode underscore as space (per RFC 1522)."""
if a2b_qp is not None:
data = input.read()
odata = a2b_qp(data, header=header)
output.write(odata)
return
new = b''
while line := input.readline():
i, n = 0, len(line)
if n > 0 and line[n-1:n] == b'\n':
partial = 0; n = n-1
# Strip trailing whitespace
while n > 0 and line[n-1:n] in b" \t\r":
n = n-1
else:
partial = 1
while i < n:
c = line[i:i+1]
if c == b'_' and header:
new = new + b' '; i = i+1
elif c != ESCAPE:
new = new + c; i = i+1
elif i+1 == n and not partial:
partial = 1; break
elif i+1 < n and line[i+1:i+2] == ESCAPE:
new = new + ESCAPE; i = i+2
elif i+2 < n and ishex(line[i+1:i+2]) and ishex(line[i+2:i+3]):
new = new + bytes((unhex(line[i+1:i+3]),)); i = i+3
else: # Bad escape sequence -- leave it in
new = new + c; i = i+1
if not partial:
output.write(new + b'\n')
new = b''
if new:
output.write(new)
def decodestring(s, header=False):
if a2b_qp is not None:
return a2b_qp(s, header=header)
from io import BytesIO
infp = BytesIO(s)
outfp = BytesIO()
decode(infp, outfp, header=header)
return outfp.getvalue()
# Other helper functions
def ishex(c):
"""Return true if the byte ordinal 'c' is a hexadecimal digit in ASCII."""
assert isinstance(c, bytes)
return b'0' <= c <= b'9' or b'a' <= c <= b'f' or b'A' <= c <= b'F'
def unhex(s):
"""Get the integer value of a hexadecimal number."""
bits = 0
for c in s:
c = bytes((c,))
if b'0' <= c <= b'9':
i = ord('0')
elif b'a' <= c <= b'f':
i = ord('a')-10
elif b'A' <= c <= b'F':
i = ord(b'A')-10
else:
assert False, "non-hex digit "+repr(c)
bits = bits*16 + (ord(c) - i)
return bits
def main():
import sys
import getopt
try:
opts, args = getopt.getopt(sys.argv[1:], 'td')
except getopt.error as msg:
sys.stdout = sys.stderr
print(msg)
print("usage: quopri [-t | -d] [file] ...")
print("-t: quote tabs")
print("-d: decode; default encode")
sys.exit(2)
deco = False
tabs = False
for o, a in opts:
if o == '-t': tabs = True
if o == '-d': deco = True
if tabs and deco:
sys.stdout = sys.stderr
print("-t and -d are mutually exclusive")
sys.exit(2)
if not args: args = ['-']
sts = 0
for file in args:
if file == '-':
fp = sys.stdin.buffer
else:
try:
fp = open(file, "rb")
except OSError as msg:
sys.stderr.write("%s: can't open (%s)\n" % (file, msg))
sts = 1
continue
try:
if deco:
decode(fp, sys.stdout.buffer)
else:
encode(fp, sys.stdout.buffer, tabs)
finally:
if file != '-':
fp.close()
if sts:
sys.exit(sts)
if __name__ == '__main__':
main()
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