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quopri.py
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"""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()