1 # Copyright (C) 2001-2006 Python Software Foundation
2 # Author: Ben Gertzfield, Barry Warsaw
3 # Contact: email-sig@python.org
4 
5 __all__ = [
6     'Charset',
7     'add_alias',
8     'add_charset',
9     'add_codec',
10     ]
11 
12 import email.base64mime
13 import email.quoprimime
14 
15 from email import errors
16 from email.encoders import encode_7or8bit
17 
18 
19 
20 # Flags for types of header encodings
21 QP          = 1 # Quoted-Printable
22 BASE64      = 2 # Base64
23 SHORTEST    = 3 # the shorter of QP and base64, but only for headers
24 
25 # In "=?charset?q?hello_world?=", the =?, ?q?, and ?= add up to 7
26 MISC_LEN = 7
27 
28 DEFAULT_CHARSET = 'us-ascii'
29 
30 
31 
32 # Defaults
33 CHARSETS = {
34     # input        header enc  body enc output conv
35     'iso-8859-1':  (QP,        QP,      None),
36     'iso-8859-2':  (QP,        QP,      None),
37     'iso-8859-3':  (QP,        QP,      None),
38     'iso-8859-4':  (QP,        QP,      None),
39     # iso-8859-5 is Cyrillic, and not especially used
40     # iso-8859-6 is Arabic, also not particularly used
41     # iso-8859-7 is Greek, QP will not make it readable
42     # iso-8859-8 is Hebrew, QP will not make it readable
43     'iso-8859-9':  (QP,        QP,      None),
44     'iso-8859-10': (QP,        QP,      None),
45     # iso-8859-11 is Thai, QP will not make it readable
46     'iso-8859-13': (QP,        QP,      None),
47     'iso-8859-14': (QP,        QP,      None),
48     'iso-8859-15': (QP,        QP,      None),
49     'windows-1252':(QP,        QP,      None),
50     'viscii':      (QP,        QP,      None),
51     'us-ascii':    (None,      None,    None),
52     'big5':        (BASE64,    BASE64,  None),
53     'gb2312':      (BASE64,    BASE64,  None),
54     'euc-jp':      (BASE64,    None,    'iso-2022-jp'),
55     'shift_jis':   (BASE64,    None,    'iso-2022-jp'),
56     'iso-2022-jp': (BASE64,    None,    None),
57     'koi8-r':      (BASE64,    BASE64,  None),
58     'utf-8':       (SHORTEST,  BASE64, 'utf-8'),
59     # We're making this one up to represent raw unencoded 8-bit
60     '8bit':        (None,      BASE64, 'utf-8'),
61     }
62 
63 # Aliases for other commonly-used names for character sets.  Map
64 # them to the real ones used in email.
65 ALIASES = {
66     'latin_1': 'iso-8859-1',
67     'latin-1': 'iso-8859-1',
68     'latin_2': 'iso-8859-2',
69     'latin-2': 'iso-8859-2',
70     'latin_3': 'iso-8859-3',
71     'latin-3': 'iso-8859-3',
72     'latin_4': 'iso-8859-4',
73     'latin-4': 'iso-8859-4',
74     'latin_5': 'iso-8859-9',
75     'latin-5': 'iso-8859-9',
76     'latin_6': 'iso-8859-10',
77     'latin-6': 'iso-8859-10',
78     'latin_7': 'iso-8859-13',
79     'latin-7': 'iso-8859-13',
80     'latin_8': 'iso-8859-14',
81     'latin-8': 'iso-8859-14',
82     'latin_9': 'iso-8859-15',
83     'latin-9': 'iso-8859-15',
84     'cp949':   'ks_c_5601-1987',
85     'euc_jp':  'euc-jp',
86     'euc_kr':  'euc-kr',
87     'ascii':   'us-ascii',
88     }
89 
90 
91 # Map charsets to their Unicode codec strings.
92 CODEC_MAP = {
93     'gb2312':      'eucgb2312_cn',
94     'big5':        'big5_tw',
95     # Hack: We don't want *any* conversion for stuff marked us-ascii, as all
96     # sorts of garbage might be sent to us in the guise of 7-bit us-ascii.
97     # Let that stuff pass through without conversion to/from Unicode.
98     'us-ascii':    None,
99     }
100 
101 
102 
103 # Convenience functions for extending the above mappings
104 def add_charset(charset, header_enc=None, body_enc=None, output_charset=None):
105     """Add character set properties to the global registry.
106 
107     charset is the input character set, and must be the canonical name of a
108     character set.
109 
110     Optional header_enc and body_enc is either Charset.QP for
111     quoted-printable, Charset.BASE64 for base64 encoding, Charset.SHORTEST for
112     the shortest of qp or base64 encoding, or None for no encoding.  SHORTEST
113     is only valid for header_enc.  It describes how message headers and
114     message bodies in the input charset are to be encoded.  Default is no
115     encoding.
116 
117     Optional output_charset is the character set that the output should be
118     in.  Conversions will proceed from input charset, to Unicode, to the
119     output charset when the method Charset.convert() is called.  The default
120     is to output in the same character set as the input.
121 
122     Both input_charset and output_charset must have Unicode codec entries in
123     the module's charset-to-codec mapping; use add_codec(charset, codecname)
124     to add codecs the module does not know about.  See the codecs module's
125     documentation for more information.
126     """
127     if body_enc == SHORTEST:
128         raise ValueError('SHORTEST not allowed for body_enc')
129     CHARSETS[charset] = (header_enc, body_enc, output_charset)
130 
131 
132 def add_alias(alias, canonical):
133     """Add a character set alias.
134 
135     alias is the alias name, e.g. latin-1
136     canonical is the character set's canonical name, e.g. iso-8859-1
137     """
138     ALIASES[alias] = canonical
139 
140 
141 def add_codec(charset, codecname):
142     """Add a codec that map characters in the given charset to/from Unicode.
143 
144     charset is the canonical name of a character set.  codecname is the name
145     of a Python codec, as appropriate for the second argument to the unicode()
146     built-in, or to the encode() method of a Unicode string.
147     """
148     CODEC_MAP[charset] = codecname
149 
150 
151 
152 class Charset:
153     """Map character sets to their email properties.
154 
155     This class provides information about the requirements imposed on email
156     for a specific character set.  It also provides convenience routines for
157     converting between character sets, given the availability of the
158     applicable codecs.  Given a character set, it will do its best to provide
159     information on how to use that character set in an email in an
160     RFC-compliant way.
161 
162     Certain character sets must be encoded with quoted-printable or base64
163     when used in email headers or bodies.  Certain character sets must be
164     converted outright, and are not allowed in email.  Instances of this
165     module expose the following information about a character set:
166 
167     input_charset: The initial character set specified.  Common aliases
168                    are converted to their `official' email names (e.g. latin_1
169                    is converted to iso-8859-1).  Defaults to 7-bit us-ascii.
170 
171     header_encoding: If the character set must be encoded before it can be
172                      used in an email header, this attribute will be set to
173                      Charset.QP (for quoted-printable), Charset.BASE64 (for
174                      base64 encoding), or Charset.SHORTEST for the shortest of
175                      QP or BASE64 encoding.  Otherwise, it will be None.
176 
177     body_encoding: Same as header_encoding, but describes the encoding for the
178                    mail message's body, which indeed may be different than the
179                    header encoding.  Charset.SHORTEST is not allowed for
180                    body_encoding.
181 
182     output_charset: Some character sets must be converted before the can be
183                     used in email headers or bodies.  If the input_charset is
184                     one of them, this attribute will contain the name of the
185                     charset output will be converted to.  Otherwise, it will
186                     be None.
187 
188     input_codec: The name of the Python codec used to convert the
189                  input_charset to Unicode.  If no conversion codec is
190                  necessary, this attribute will be None.
191 
192     output_codec: The name of the Python codec used to convert Unicode
193                   to the output_charset.  If no conversion codec is necessary,
194                   this attribute will have the same value as the input_codec.
195     """
196     def __init__(self, input_charset=DEFAULT_CHARSET):
197         # RFC 2046, $4.1.2 says charsets are not case sensitive.  We coerce to
198         # unicode because its .lower() is locale insensitive.  If the argument
199         # is already a unicode, we leave it at that, but ensure that the
200         # charset is ASCII, as the standard (RFC XXX) requires.
201         try:
202             if isinstance(input_charset, unicode):
203                 input_charset.encode('ascii')
204             else:
205                 input_charset = unicode(input_charset, 'ascii')
206         except UnicodeError:
207             raise errors.CharsetError(input_charset)
208         input_charset = input_charset.lower()
209         # Set the input charset after filtering through the aliases
210         self.input_charset = ALIASES.get(input_charset, input_charset)
211         # We can try to guess which encoding and conversion to use by the
212         # charset_map dictionary.  Try that first, but let the user override
213         # it.
214         henc, benc, conv = CHARSETS.get(self.input_charset,
215                                         (SHORTEST, BASE64, None))
216         if not conv:
217             conv = self.input_charset
218         # Set the attributes, allowing the arguments to override the default.
219         self.header_encoding = henc
220         self.body_encoding = benc
221         self.output_charset = ALIASES.get(conv, conv)
222         # Now set the codecs.  If one isn't defined for input_charset,
223         # guess and try a Unicode codec with the same name as input_codec.
224         self.input_codec = CODEC_MAP.get(self.input_charset,
225                                          self.input_charset)
226         self.output_codec = CODEC_MAP.get(self.output_charset,
227                                           self.output_charset)
228 
229     def __str__(self):
230         return self.input_charset.lower()
231 
232     __repr__ = __str__
233 
234     def __eq__(self, other):
235         return str(self) == str(other).lower()
236 
237     def __ne__(self, other):
238         return not self.__eq__(other)
239 
240     def get_body_encoding(self):
241         """Return the content-transfer-encoding used for body encoding.
242 
243         This is either the string `quoted-printable' or `base64' depending on
244         the encoding used, or it is a function in which case you should call
245         the function with a single argument, the Message object being
246         encoded.  The function should then set the Content-Transfer-Encoding
247         header itself to whatever is appropriate.
248 
249         Returns "quoted-printable" if self.body_encoding is QP.
250         Returns "base64" if self.body_encoding is BASE64.
251         Returns "7bit" otherwise.
252         """
253         assert self.body_encoding <> SHORTEST
254         if self.body_encoding == QP:
255             return 'quoted-printable'
256         elif self.body_encoding == BASE64:
257             return 'base64'
258         else:
259             return encode_7or8bit
260 
261     def convert(self, s):
262         """Convert a string from the input_codec to the output_codec."""
263         if self.input_codec <> self.output_codec:
264             return unicode(s, self.input_codec).encode(self.output_codec)
265         else:
266             return s
267 
268     def to_splittable(self, s):
269         """Convert a possibly multibyte string to a safely splittable format.
270 
271         Uses the input_codec to try and convert the string to Unicode, so it
272         can be safely split on character boundaries (even for multibyte
273         characters).
274 
275         Returns the string as-is if it isn't known how to convert it to
276         Unicode with the input_charset.
277 
278         Characters that could not be converted to Unicode will be replaced
279         with the Unicode replacement character U+FFFD.
280         """
281         if isinstance(s, unicode) or self.input_codec is None:
282             return s
283         try:
284             return unicode(s, self.input_codec, 'replace')
285         except LookupError:
286             # Input codec not installed on system, so return the original
287             # string unchanged.
288             return s
289 
290     def from_splittable(self, ustr, to_output=True):
291         """Convert a splittable string back into an encoded string.
292 
293         Uses the proper codec to try and convert the string from Unicode back
294         into an encoded format.  Return the string as-is if it is not Unicode,
295         or if it could not be converted from Unicode.
296 
297         Characters that could not be converted from Unicode will be replaced
298         with an appropriate character (usually '?').
299 
300         If to_output is True (the default), uses output_codec to convert to an
301         encoded format.  If to_output is False, uses input_codec.
302         """
303         if to_output:
304             codec = self.output_codec
305         else:
306             codec = self.input_codec
307         if not isinstance(ustr, unicode) or codec is None:
308             return ustr
309         try:
310             return ustr.encode(codec, 'replace')
311         except LookupError:
312             # Output codec not installed
313             return ustr
314 
315     def get_output_charset(self):
316         """Return the output character set.
317 
318         This is self.output_charset if that is not None, otherwise it is
319         self.input_charset.
320         """
321         return self.output_charset or self.input_charset
322 
323     def encoded_header_len(self, s):
324         """Return the length of the encoded header string."""
325         cset = self.get_output_charset()
326         # The len(s) of a 7bit encoding is len(s)
327         if self.header_encoding == BASE64:
328             return email.base64mime.base64_len(s) + len(cset) + MISC_LEN
329         elif self.header_encoding == QP:
330             return email.quoprimime.header_quopri_len(s) + len(cset) + MISC_LEN
331         elif self.header_encoding == SHORTEST:
332             lenb64 = email.base64mime.base64_len(s)
333             lenqp = email.quoprimime.header_quopri_len(s)
334             return min(lenb64, lenqp) + len(cset) + MISC_LEN
335         else:
336             return len(s)
337 
338     def header_encode(self, s, convert=False):
339         """Header-encode a string, optionally converting it to output_charset.
340 
341         If convert is True, the string will be converted from the input
342         charset to the output charset automatically.  This is not useful for
343         multibyte character sets, which have line length issues (multibyte
344         characters must be split on a character, not a byte boundary); use the
345         high-level Header class to deal with these issues.  convert defaults
346         to False.
347 
348         The type of encoding (base64 or quoted-printable) will be based on
349         self.header_encoding.
350         """
351         cset = self.get_output_charset()
352         if convert:
353             s = self.convert(s)
354         # 7bit/8bit encodings return the string unchanged (modulo conversions)
355         if self.header_encoding == BASE64:
356             return email.base64mime.header_encode(s, cset)
357         elif self.header_encoding == QP:
358             return email.quoprimime.header_encode(s, cset, maxlinelen=None)
359         elif self.header_encoding == SHORTEST:
360             lenb64 = email.base64mime.base64_len(s)
361             lenqp = email.quoprimime.header_quopri_len(s)
362             if lenb64 < lenqp:
363                 return email.base64mime.header_encode(s, cset)
364             else:
365                 return email.quoprimime.header_encode(s, cset, maxlinelen=None)
366         else:
367             return s
368 
369     def body_encode(self, s, convert=True):
370         """Body-encode a string and convert it to output_charset.
371 
372         If convert is True (the default), the string will be converted from
373         the input charset to output charset automatically.  Unlike
374         header_encode(), there are no issues with byte boundaries and
375         multibyte charsets in email bodies, so this is usually pretty safe.
376 
377         The type of encoding (base64 or quoted-printable) will be based on
378         self.body_encoding.
379         """
380         if convert:
381             s = self.convert(s)
382         # 7bit/8bit encodings return the string unchanged (module conversions)
383         if self.body_encoding is BASE64:
384             return email.base64mime.body_encode(s)
385         elif self.body_encoding is QP:
386             return email.quoprimime.body_encode(s)
387         else:
388             return s