1 # Copyright (C) 2001-2007 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 from functools import partial 13 14 import email.base64mime 15 import email.quoprimime 16 17 from email import errors 18 from email.encoders import encode_7or8bit 19 20 21 22 # Flags for types of header encodings 23 QP = 1 # Quoted-Printable 24 BASE64 = 2 # Base64 25 SHORTEST = 3 # the shorter of QP and base64, but only for headers 26 27 # In "=?charset?q?hello_world?=", the =?, ?q?, and ?= add up to 7 28 RFC2047_CHROME_LEN = 7 29 30 DEFAULT_CHARSET = 'us-ascii' 31 UNKNOWN8BIT = 'unknown-8bit' 32 EMPTYSTRING = '' 33 34 35 36 # Defaults 37 CHARSETS = { 38 # input header enc body enc output conv 39 'iso-8859-1': (QP, QP, None), 40 'iso-8859-2': (QP, QP, None), 41 'iso-8859-3': (QP, QP, None), 42 'iso-8859-4': (QP, QP, None), 43 # iso-8859-5 is Cyrillic, and not especially used 44 # iso-8859-6 is Arabic, also not particularly used 45 # iso-8859-7 is Greek, QP will not make it readable 46 # iso-8859-8 is Hebrew, QP will not make it readable 47 'iso-8859-9': (QP, QP, None), 48 'iso-8859-10': (QP, QP, None), 49 # iso-8859-11 is Thai, QP will not make it readable 50 'iso-8859-13': (QP, QP, None), 51 'iso-8859-14': (QP, QP, None), 52 'iso-8859-15': (QP, QP, None), 53 'iso-8859-16': (QP, QP, None), 54 'windows-1252':(QP, QP, None), 55 'viscii': (QP, QP, None), 56 'us-ascii': (None, None, None), 57 'big5': (BASE64, BASE64, None), 58 'gb2312': (BASE64, BASE64, None), 59 'euc-jp': (BASE64, None, 'iso-2022-jp'), 60 'shift_jis': (BASE64, None, 'iso-2022-jp'), 61 'iso-2022-jp': (BASE64, None, None), 62 'koi8-r': (BASE64, BASE64, None), 63 'utf-8': (SHORTEST, BASE64, 'utf-8'), 64 } 65 66 # Aliases for other commonly-used names for character sets. Map 67 # them to the real ones used in email. 68 ALIASES = { 69 'latin_1': 'iso-8859-1', 70 'latin-1': 'iso-8859-1', 71 'latin_2': 'iso-8859-2', 72 'latin-2': 'iso-8859-2', 73 'latin_3': 'iso-8859-3', 74 'latin-3': 'iso-8859-3', 75 'latin_4': 'iso-8859-4', 76 'latin-4': 'iso-8859-4', 77 'latin_5': 'iso-8859-9', 78 'latin-5': 'iso-8859-9', 79 'latin_6': 'iso-8859-10', 80 'latin-6': 'iso-8859-10', 81 'latin_7': 'iso-8859-13', 82 'latin-7': 'iso-8859-13', 83 'latin_8': 'iso-8859-14', 84 'latin-8': 'iso-8859-14', 85 'latin_9': 'iso-8859-15', 86 'latin-9': 'iso-8859-15', 87 'latin_10':'iso-8859-16', 88 'latin-10':'iso-8859-16', 89 'cp949': 'ks_c_5601-1987', 90 'euc_jp': 'euc-jp', 91 'euc_kr': 'euc-kr', 92 'ascii': 'us-ascii', 93 } 94 95 96 # Map charsets to their Unicode codec strings. 97 CODEC_MAP = { 98 'gb2312': 'eucgb2312_cn', 99 'big5': 'big5_tw', 100 # Hack: We don't want *any* conversion for stuff marked us-ascii, as all 101 # sorts of garbage might be sent to us in the guise of 7-bit us-ascii. 102 # Let that stuff pass through without conversion to/from Unicode. 103 'us-ascii': None, 104 } 105 106 107 108 # Convenience functions for extending the above mappings 109 def add_charset(charset, header_enc=None, body_enc=None, output_charset=None): 110 """Add character set properties to the global registry. 111 112 charset is the input character set, and must be the canonical name of a 113 character set. 114 115 Optional header_enc and body_enc is either Charset.QP for 116 quoted-printable, Charset.BASE64 for base64 encoding, Charset.SHORTEST for 117 the shortest of qp or base64 encoding, or None for no encoding. SHORTEST 118 is only valid for header_enc. It describes how message headers and 119 message bodies in the input charset are to be encoded. Default is no 120 encoding. 121 122 Optional output_charset is the character set that the output should be 123 in. Conversions will proceed from input charset, to Unicode, to the 124 output charset when the method Charset.convert() is called. The default 125 is to output in the same character set as the input. 126 127 Both input_charset and output_charset must have Unicode codec entries in 128 the module's charset-to-codec mapping; use add_codec(charset, codecname) 129 to add codecs the module does not know about. See the codecs module's 130 documentation for more information. 131 """ 132 if body_enc == SHORTEST: 133 raise ValueError('SHORTEST not allowed for body_enc') 134 CHARSETS[charset] = (header_enc, body_enc, output_charset) 135 136 137 def add_alias(alias, canonical): 138 """Add a character set alias. 139 140 alias is the alias name, e.g. latin-1 141 canonical is the character set's canonical name, e.g. iso-8859-1 142 """ 143 ALIASES[alias] = canonical 144 145 146 def add_codec(charset, codecname): 147 """Add a codec that map characters in the given charset to/from Unicode. 148 149 charset is the canonical name of a character set. codecname is the name 150 of a Python codec, as appropriate for the second argument to the unicode() 151 built-in, or to the encode() method of a Unicode string. 152 """ 153 CODEC_MAP[charset] = codecname 154 155 156 157 # Convenience function for encoding strings, taking into account 158 # that they might be unknown-8bit (ie: have surrogate-escaped bytes) 159 def _encode(string, codec): 160 if codec == UNKNOWN8BIT: 161 return string.encode('ascii', 'surrogateescape') 162 else: 163 return string.encode(codec) 164 165 166 167 class Charset: 168 """Map character sets to their email properties. 169 170 This class provides information about the requirements imposed on email 171 for a specific character set. It also provides convenience routines for 172 converting between character sets, given the availability of the 173 applicable codecs. Given a character set, it will do its best to provide 174 information on how to use that character set in an email in an 175 RFC-compliant way. 176 177 Certain character sets must be encoded with quoted-printable or base64 178 when used in email headers or bodies. Certain character sets must be 179 converted outright, and are not allowed in email. Instances of this 180 module expose the following information about a character set: 181 182 input_charset: The initial character set specified. Common aliases 183 are converted to their `official' email names (e.g. latin_1 184 is converted to iso-8859-1). Defaults to 7-bit us-ascii. 185 186 header_encoding: If the character set must be encoded before it can be 187 used in an email header, this attribute will be set to 188 Charset.QP (for quoted-printable), Charset.BASE64 (for 189 base64 encoding), or Charset.SHORTEST for the shortest of 190 QP or BASE64 encoding. Otherwise, it will be None. 191 192 body_encoding: Same as header_encoding, but describes the encoding for the 193 mail message's body, which indeed may be different than the 194 header encoding. Charset.SHORTEST is not allowed for 195 body_encoding. 196 197 output_charset: Some character sets must be converted before they can be 198 used in email headers or bodies. If the input_charset is 199 one of them, this attribute will contain the name of the 200 charset output will be converted to. Otherwise, it will 201 be None. 202 203 input_codec: The name of the Python codec used to convert the 204 input_charset to Unicode. If no conversion codec is 205 necessary, this attribute will be None. 206 207 output_codec: The name of the Python codec used to convert Unicode 208 to the output_charset. If no conversion codec is necessary, 209 this attribute will have the same value as the input_codec. 210 """ 211 def __init__(self, input_charset=DEFAULT_CHARSET): 212 # RFC 2046, $4.1.2 says charsets are not case sensitive. We coerce to 213 # unicode because its .lower() is locale insensitive. If the argument 214 # is already a unicode, we leave it at that, but ensure that the 215 # charset is ASCII, as the standard (RFC XXX) requires. 216 try: 217 if isinstance(input_charset, str): 218 input_charset.encode('ascii') 219 else: 220 input_charset = str(input_charset, 'ascii') 221 except UnicodeError: 222 raise errors.CharsetError(input_charset) 223 input_charset = input_charset.lower() 224 # Set the input charset after filtering through the aliases 225 self.input_charset = ALIASES.get(input_charset, input_charset) 226 # We can try to guess which encoding and conversion to use by the 227 # charset_map dictionary. Try that first, but let the user override 228 # it. 229 henc, benc, conv = CHARSETS.get(self.input_charset, 230 (SHORTEST, BASE64, None)) 231 if not conv: 232 conv = self.input_charset 233 # Set the attributes, allowing the arguments to override the default. 234 self.header_encoding = henc 235 self.body_encoding = benc 236 self.output_charset = ALIASES.get(conv, conv) 237 # Now set the codecs. If one isn't defined for input_charset, 238 # guess and try a Unicode codec with the same name as input_codec. 239 self.input_codec = CODEC_MAP.get(self.input_charset, 240 self.input_charset) 241 self.output_codec = CODEC_MAP.get(self.output_charset, 242 self.output_charset) 243 244 def __str__(self): 245 return self.input_charset.lower() 246 247 __repr__ = __str__ 248 249 def __eq__(self, other): 250 return str(self) == str(other).lower() 251 252 def __ne__(self, other): 253 return not self.__eq__(other) 254 255 def get_body_encoding(self): 256 """Return the content-transfer-encoding used for body encoding. 257 258 This is either the string `quoted-printable' or `base64' depending on 259 the encoding used, or it is a function in which case you should call 260 the function with a single argument, the Message object being 261 encoded. The function should then set the Content-Transfer-Encoding 262 header itself to whatever is appropriate. 263 264 Returns "quoted-printable" if self.body_encoding is QP. 265 Returns "base64" if self.body_encoding is BASE64. 266 Returns conversion function otherwise. 267 """ 268 assert self.body_encoding != SHORTEST 269 if self.body_encoding == QP: 270 return 'quoted-printable' 271 elif self.body_encoding == BASE64: 272 return 'base64' 273 else: 274 return encode_7or8bit 275 276 def get_output_charset(self): 277 """Return the output character set. 278 279 This is self.output_charset if that is not None, otherwise it is 280 self.input_charset. 281 """ 282 return self.output_charset or self.input_charset 283 284 def header_encode(self, string): 285 """Header-encode a string by converting it first to bytes. 286 287 The type of encoding (base64 or quoted-printable) will be based on 288 this charset's `header_encoding`. 289 290 :param string: A unicode string for the header. It must be possible 291 to encode this string to bytes using the character set's 292 output codec. 293 :return: The encoded string, with RFC 2047 chrome. 294 """ 295 codec = self.output_codec or 'us-ascii' 296 header_bytes = _encode(string, codec) 297 # 7bit/8bit encodings return the string unchanged (modulo conversions) 298 encoder_module = self._get_encoder(header_bytes) 299 if encoder_module is None: 300 return string 301 return encoder_module.header_encode(header_bytes, codec) 302 303 def header_encode_lines(self, string, maxlengths): 304 """Header-encode a string by converting it first to bytes. 305 306 This is similar to `header_encode()` except that the string is fit 307 into maximum line lengths as given by the argument. 308 309 :param string: A unicode string for the header. It must be possible 310 to encode this string to bytes using the character set's 311 output codec. 312 :param maxlengths: Maximum line length iterator. Each element 313 returned from this iterator will provide the next maximum line 314 length. This parameter is used as an argument to built-in next() 315 and should never be exhausted. The maximum line lengths should 316 not count the RFC 2047 chrome. These line lengths are only a 317 hint; the splitter does the best it can. 318 :return: Lines of encoded strings, each with RFC 2047 chrome. 319 """ 320 # See which encoding we should use. 321 codec = self.output_codec or 'us-ascii' 322 header_bytes = _encode(string, codec) 323 encoder_module = self._get_encoder(header_bytes) 324 encoder = partial(encoder_module.header_encode, charset=codec) 325 # Calculate the number of characters that the RFC 2047 chrome will 326 # contribute to each line. 327 charset = self.get_output_charset() 328 extra = len(charset) + RFC2047_CHROME_LEN 329 # Now comes the hard part. We must encode bytes but we can't split on 330 # bytes because some character sets are variable length and each 331 # encoded word must stand on its own. So the problem is you have to 332 # encode to bytes to figure out this word's length, but you must split 333 # on characters. This causes two problems: first, we don't know how 334 # many octets a specific substring of unicode characters will get 335 # encoded to, and second, we don't know how many ASCII characters 336 # those octets will get encoded to. Unless we try it. Which seems 337 # inefficient. In the interest of being correct rather than fast (and 338 # in the hope that there will be few encoded headers in any such 339 # message), brute force it. :( 340 lines = [] 341 current_line = [] 342 maxlen = next(maxlengths) - extra 343 for character in string: 344 current_line.append(character) 345 this_line = EMPTYSTRING.join(current_line) 346 length = encoder_module.header_length(_encode(this_line, charset)) 347 if length > maxlen: 348 # This last character doesn't fit so pop it off. 349 current_line.pop() 350 # Does nothing fit on the first line? 351 if not lines and not current_line: 352 lines.append(None) 353 else: 354 separator = (' ' if lines else '') 355 joined_line = EMPTYSTRING.join(current_line) 356 header_bytes = _encode(joined_line, codec) 357 lines.append(encoder(header_bytes)) 358 current_line = [character] 359 maxlen = next(maxlengths) - extra 360 joined_line = EMPTYSTRING.join(current_line) 361 header_bytes = _encode(joined_line, codec) 362 lines.append(encoder(header_bytes)) 363 return lines 364 365 def _get_encoder(self, header_bytes): 366 if self.header_encoding == BASE64: 367 return email.base64mime 368 elif self.header_encoding == QP: 369 return email.quoprimime 370 elif self.header_encoding == SHORTEST: 371 len64 = email.base64mime.header_length(header_bytes) 372 lenqp = email.quoprimime.header_length(header_bytes) 373 if len64 < lenqp: 374 return email.base64mime 375 else: 376 return email.quoprimime 377 else: 378 return None 379 380 def body_encode(self, string): 381 """Body-encode a string by converting it first to bytes. 382 383 The type of encoding (base64 or quoted-printable) will be based on 384 self.body_encoding. If body_encoding is None, we assume the 385 output charset is a 7bit encoding, so re-encoding the decoded 386 string using the ascii codec produces the correct string version 387 of the content. 388 """ 389 # 7bit/8bit encodings return the string unchanged (module conversions) 390 if self.body_encoding is BASE64: 391 if isinstance(string, str): 392 string = string.encode(self.output_charset) 393 return email.base64mime.body_encode(string) 394 elif self.body_encoding is QP: 395 # quopromime.body_encode takes a string, but operates on it as if 396 # it were a list of byte codes. For a (minimal) history on why 397 # this is so, see changeset 0cf700464177. To correctly encode a 398 # character set, then, we must turn it into pseudo bytes via the 399 # latin1 charset, which will encode any byte as a single code point 400 # between 0 and 255, which is what body_encode is expecting. 401 # 402 # Note that this clause doesn't handle the case of a _payload that 403 # is already bytes. It never did, and the semantics of _payload 404 # being bytes has never been nailed down, so fixing that is a 405 # longer term TODO. 406 if isinstance(string, str): 407 string = string.encode(self.output_charset).decode('latin1') 408 return email.quoprimime.body_encode(string) 409 else: 410 if isinstance(string, str): 411 string = string.encode(self.output_charset).decode('ascii') 412 return string |