| # Copyright (C) 2002 Python Software Foundation |
| # Author: che@debian.org (Ben Gertzfield) |
| |
| """Header encoding and decoding functionality.""" |
| |
| import re |
| import email.quopriMIME |
| import email.base64MIME |
| from email.Charset import Charset |
| |
| CRLFSPACE = '\r\n ' |
| CRLF = '\r\n' |
| NLSPACE = '\n ' |
| |
| MAXLINELEN = 76 |
| |
| ENCODE = 1 |
| DECODE = 2 |
| |
| # Match encoded-word strings in the form =?charset?q?Hello_World?= |
| ecre = re.compile(r''' |
| =\? # literal =? |
| (?P<charset>[^?]*?) # non-greedy up to the next ? is the charset |
| \? # literal ? |
| (?P<encoding>[qb]) # either a "q" or a "b", case insensitive |
| \? # literal ? |
| (?P<encoded>.*?) # non-greedy up to the next ?= is the encoded string |
| \?= # literal ?= |
| ''', re.VERBOSE | re.IGNORECASE) |
| |
| |
| |
| # Helpers |
| _max_append = email.quopriMIME._max_append |
| |
| |
| |
| def decode_header(header): |
| """Decode a message header value without converting charset. |
| |
| Returns a list of (decoded_string, charset) pairs containing each of the |
| decoded parts of the header. Charset is None for non-encoded parts of the |
| header, otherwise a lower-case string containing the name of the character |
| set specified in the encoded string. |
| """ |
| # If no encoding, just return the header |
| header = str(header) |
| if not ecre.search(header): |
| return [(header, None)] |
| |
| decoded = [] |
| dec = '' |
| for line in header.splitlines(): |
| # This line might not have an encoding in it |
| if not ecre.search(line): |
| decoded.append((line, None)) |
| continue |
| |
| parts = ecre.split(line) |
| while parts: |
| unenc = parts.pop(0).strip() |
| if unenc: |
| # Should we continue a long line? |
| if decoded and decoded[-1][1] is None: |
| decoded[-1] = (decoded[-1][0] + dec, None) |
| else: |
| decoded.append((unenc, None)) |
| if parts: |
| charset, encoding = [s.lower() for s in parts[0:2]] |
| encoded = parts[2] |
| dec = '' |
| if encoding == 'q': |
| dec = email.quopriMIME.header_decode(encoded) |
| elif encoding == 'b': |
| dec = email.base64MIME.decode(encoded) |
| else: |
| dec = encoded |
| |
| if decoded and decoded[-1][1] == charset: |
| decoded[-1] = (decoded[-1][0] + dec, decoded[-1][1]) |
| else: |
| decoded.append((dec, charset)) |
| del parts[0:3] |
| return decoded |
| |
| |
| |
| class Header: |
| def __init__(self, s, charset=None, maxlinelen=MAXLINELEN, |
| header_name=None): |
| """Create a MIME-compliant header that can contain many languages. |
| |
| Specify the initial header value in s. Specify its character set as a |
| Charset object in the charset argument. If none, a default Charset |
| instance will be used. |
| |
| You can later append to the header with append(s, charset) below; |
| charset does not have to be the same as the one initially specified |
| here. In fact, it's optional, and if not given, defaults to the |
| charset specified in the constructor. |
| |
| The maximum line length can either be specified by maxlinelen, or you |
| can pass in the name of the header field (e.g. "Subject") to let this |
| class guess the best line length to use to prevent wrapping. The |
| default maxlinelen is 76. |
| """ |
| if charset is None: |
| charset = Charset() |
| self._charset = charset |
| # BAW: I believe `chunks' and `maxlinelen' should be non-public. |
| self._chunks = [] |
| self.append(s, charset) |
| self._maxlinelen = maxlinelen |
| if header_name is not None: |
| self.guess_maxlinelen(header_name) |
| |
| def __str__(self): |
| """A synonym for self.encode().""" |
| return self.encode() |
| |
| def guess_maxlinelen(self, s=None): |
| """Guess the maximum length to make each header line. |
| |
| Given a header name (e.g. "Subject"), set this header's maximum line |
| length to an appropriate length to avoid line wrapping. If s is not |
| given, return the previous maximum line length and don't set it. |
| |
| Returns the new maximum line length. |
| """ |
| # BAW: is this semantic necessary? |
| if s is not None: |
| self._maxlinelen = MAXLINELEN - len(s) - 2 |
| return self._maxlinelen |
| |
| def append(self, s, charset=None): |
| """Append string s with Charset charset to the MIME header. |
| |
| charset defaults to the one given in the class constructor. |
| """ |
| if charset is None: |
| charset = self._charset |
| self._chunks.append((s, charset)) |
| |
| def _split(self, s, charset): |
| # Split up a header safely for use with encode_chunks. BAW: this |
| # appears to be a private convenience method. |
| splittable = charset.to_splittable(s) |
| encoded = charset.from_splittable(splittable) |
| |
| if charset.encoded_header_len(encoded) < self._maxlinelen: |
| return [(encoded, charset)] |
| else: |
| # Divide and conquer. BAW: halfway depends on integer division. |
| # When porting to Python 2.2, use the // operator. |
| halfway = len(splittable) // 2 |
| first = charset.from_splittable(splittable[:halfway], 0) |
| last = charset.from_splittable(splittable[halfway:], 0) |
| return self._split(first, charset) + self._split(last, charset) |
| |
| def encode(self): |
| """Encode a message header, possibly converting charset and encoding. |
| |
| There are many issues involved in converting a given string for use in |
| an email header. Only certain character sets are readable in most |
| email clients, and as header strings can only contain a subset of |
| 7-bit ASCII, care must be taken to properly convert and encode (with |
| Base64 or quoted-printable) header strings. In addition, there is a |
| 75-character length limit on any given encoded header field, so |
| line-wrapping must be performed, even with double-byte character sets. |
| |
| This method will do its best to convert the string to the correct |
| character set used in email, and encode and line wrap it safely with |
| the appropriate scheme for that character set. |
| |
| If the given charset is not known or an error occurs during |
| conversion, this function will return the header untouched. |
| """ |
| newchunks = [] |
| for s, charset in self._chunks: |
| newchunks += self._split(s, charset) |
| self._chunks = newchunks |
| return self.encode_chunks() |
| |
| def encode_chunks(self): |
| """MIME-encode a header with many different charsets and/or encodings. |
| |
| Given a list of pairs (string, charset), return a MIME-encoded string |
| suitable for use in a header field. Each pair may have different |
| charsets and/or encodings, and the resulting header will accurately |
| reflect each setting. |
| |
| Each encoding can be email.Utils.QP (quoted-printable, for ASCII-like |
| character sets like iso-8859-1), email.Utils.BASE64 (Base64, for |
| non-ASCII like character sets like KOI8-R and iso-2022-jp), or None |
| (no encoding). |
| |
| Each pair will be represented on a separate line; the resulting string |
| will be in the format: |
| |
| "=?charset1?q?Mar=EDa_Gonz=E1lez_Alonso?=\n |
| =?charset2?b?SvxyZ2VuIEL2aW5n?=" |
| """ |
| chunks = [] |
| for header, charset in self._chunks: |
| if charset is None: |
| _max_append(chunks, header, self._maxlinelen, ' ') |
| else: |
| _max_append(chunks, charset.header_encode(header, 0), |
| self._maxlinelen, ' ') |
| return NLSPACE.join(chunks) |