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