1 files changed, 147 insertions, 0 deletions

diff --git a/Mailman/EncWord.py b/Mailman/EncWord.py
new file mode 100644
index 000000000..fdcd2ff4b
--- /dev/null
+++ b/Mailman/EncWord.py
@@ -0,0 +1,147 @@
+"""Decode encoded-words as defined by RFC 2047"""
+
+import base64
+
+class DecodeError(ValueError):
+    __super_init = ValueError.__init__
+    def __init__(self, msg):
+        self.__super_init("invalid encoded-word: %s" % msg)
+
+class Decoder:
+    """Decode mail header encoded-word format defined by RFC 2047"""
+    
+    offset = 0
+
+    def decode(self, s):
+        """Decode an encoded-word
+
+        Returns the charset of the encoded-word, the decoded text, and
+        the position of the first character following the
+        encoded-word.
+
+        The first position of the input string must by the first
+        character of the encoded-word.
+        """
+        if not s.startswith('=?'):
+            raise DecodeError("must start with '=?', not %s" % repr(s[:2]))
+        charset = self._get_charset(s)
+        encoding = self._get_encoding(s)
+        _text = self._get_text(s)
+
+        if encoding == 'q':
+            text = self._decode_q(_text)
+        else:
+            text = self._decode_b(_text)
+        
+        return charset, text, self.offset
+
+    # XXX technically the charset and encoding can't contain SPACE,
+    # CTLs, or especials; do not currently check this
+
+    def _get_charset(self, s):
+        i = s.find('?', 2)
+        if i == -1:
+            raise DecodeError("can't find of charset")
+        self.offset = i + 1
+        return s[2:i]
+
+    _valid_encodings = ('q', 'b')
+
+    def _get_encoding(self, s):
+        i = s.find('?', self.offset)
+        if i == -1:
+            raise DecodeError("can't find encoding")
+        enc = s[self.offset:i].lower()
+        self.offset = i + 1
+        if enc not in Decoder._valid_encodings:
+            raise DecodeError("'%s' is not a valid encoding" % enc)
+        return enc
+
+    def _get_text(self, s):
+        i = s.find('?=', self.offset)
+        if i == -1:
+            raise DecodeError("can't find end of encoded text")
+        text = s[self.offset:i]
+        self.offset = i + 2
+        return text
+
+    SPACE = chr(0x20)
+
+    def _decode_q(self, s):
+        """Q encoding defined by RFC 2047"""
+        chunks = []
+        offset = 0
+        end = len(s)
+        import sys
+        while offset < end:
+            i = s.find('=', offset)
+            j = s.find('_', offset)
+            if j == i == -1:
+                chunks.append(s[offset:])
+                break
+            if (j < i and j != -1) or i == -1:
+                chunks.append(s[offset:j])
+                chunks.append(Decoder.SPACE)
+                offset = j + 1
+            else:
+                chunks.append(s[offset:i])
+                hexdig = s[i+1:i+3]
+                chunks.append(chr(int(hexdig, 16)))
+                offset = i + 3
+        return "".join(chunks)
+
+    def _decode_b(self, s):
+        """B encoding == base64 encoding defined by RFC 2045"""
+        import sys
+        return base64.decodestring(s)
+
+def decode(s):
+    """Decode a string containing encoded words"""
+    _decode = Decoder().decode
+
+    chunks = []
+    offset = 0
+    charset = None
+    while 1:
+        i = s.find('=?', offset)
+        if i == -1:
+            chunks.append(s[offset:])
+            break
+        chunks.append(s[offset:i])
+        _charset, text, offset = _decode(s[i:])
+        offset = offset + i
+        if charset is None:
+            charset = _charset
+        elif charset != _charset:
+            raise ValueError, "can not decode string with multiple charsets"
+        chunks.append(text)
+    return "".join(chunks), charset
+
+def test():
+    examples = [
+        # valid
+        '=?US-ASCII?Q?Keith_Moore?= <moore@cs.utk.edu>',
+        '=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld@dkuug.dk>',
+        '=?ISO-8859-1?Q?Andr=E9_?= Pirard <PIRARD@vm1.ulg.ac.be>',
+        '=?ISO-8859-1?B?SWYgeW91IGNhbiByZWFkIHRoaXMgeW8=?=',
+        '=?ISO-8859-2?B?dSB1bmRlcnN0YW5kIHRoZSBleGFtcGxlLg==?=',
+        '=?US-ASCII?Q?.._cool!?=',
+        '=?ISO-8859-1?Q?Olle_J=E4rnefors?= <ojarnef@admin.kth.se>',
+        '(=?iso-8859-8?b?7eXs+SDv4SDp7Oj08A==?=)',
+        # invalid
+        'abc',
+        '=?abc',
+        '=?abc?abc',
+        '=?ISO-8859-1?abc?text',
+        ]
+    for s in examples:
+        try:
+            text, charset = decode(s)
+        except ValueError, msg:
+            print "error:", msg
+        else:
+            print text, charset
+
+if __name__ == "__main__":
+    test()
+