| # Copyright (C) 2002 Python Software Foundation |
| # Author: che@debian.org (Ben Gertzfield), barry@zope.com (Barry Warsaw) |
| |
| """Header encoding and decoding functionality.""" |
| |
| import re |
| from types import StringType, UnicodeType |
| |
| import email.quopriMIME |
| import email.base64MIME |
| from email.Charset import Charset |
| |
| try: |
| from email._compat22 import _floordiv |
| except SyntaxError: |
| # Python 2.1 spells integer division differently |
| from email._compat21 import _floordiv |
| |
| try: |
| True, False |
| except NameError: |
| True = 1 |
| False = 0 |
| |
| CRLFSPACE = '\r\n ' |
| CRLF = '\r\n' |
| NL = '\n' |
| SPACE8 = ' ' * 8 |
| EMPTYSTRING = '' |
| |
| MAXLINELEN = 76 |
| |
| ENCODE = 1 |
| DECODE = 2 |
| |
| USASCII = Charset('us-ascii') |
| UTF8 = Charset('utf-8') |
| |
| # 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 |
| |
| |
| |
| def make_header(decoded_seq, maxlinelen=None, header_name=None, |
| continuation_ws=' '): |
| """Create a Header from a sequence of pairs as returned by decode_header() |
| |
| decode_header() takes a header value string and returns a sequence of |
| pairs of the format (decoded_string, charset) where charset is the string |
| name of the character set. |
| |
| This function takes one of those sequence of pairs and returns a Header |
| instance. Optional maxlinelen, header_name, and continuation_ws are as in |
| the Header constructor. |
| """ |
| h = Header(maxlinelen=maxlinelen, header_name=header_name, |
| continuation_ws=continuation_ws) |
| for s, charset in decoded_seq: |
| # None means us-ascii but we can simply pass it on to h.append() |
| if charset is not None and not isinstance(charset, Charset): |
| charset = Charset(charset) |
| h.append(s, charset) |
| return h |
| |
| |
| |
| class Header: |
| def __init__(self, s=None, charset=None, maxlinelen=None, header_name=None, |
| continuation_ws=' ', errors='strict'): |
| """Create a MIME-compliant header that can contain many character sets. |
| |
| Optional s is the initial header value. If None, the initial header |
| value is not set. You can later append to the header with .append() |
| method calls. s may be a byte string or a Unicode string, but see the |
| .append() documentation for semantics. |
| |
| Optional charset serves two purposes: it has the same meaning as the |
| charset argument to the .append() method. It also sets the default |
| character set for all subsequent .append() calls that omit the charset |
| argument. If charset is not provided in the constructor, the us-ascii |
| charset is used both as s's initial charset and as the default for |
| subsequent .append() calls. |
| |
| The maximum line length can be specified explicit via maxlinelen. For |
| splitting the first line to a shorter value (to account for the field |
| header which isn't included in s, e.g. `Subject') pass in the name of |
| the field in header_name. The default maxlinelen is 76. |
| |
| continuation_ws must be RFC 2822 compliant folding whitespace (usually |
| either a space or a hard tab) which will be prepended to continuation |
| lines. |
| |
| errors is passed through to the .append() call. |
| """ |
| if charset is None: |
| charset = USASCII |
| if not isinstance(charset, Charset): |
| charset = Charset(charset) |
| self._charset = charset |
| self._continuation_ws = continuation_ws |
| cws_expanded_len = len(continuation_ws.replace('\t', SPACE8)) |
| # BAW: I believe `chunks' and `maxlinelen' should be non-public. |
| self._chunks = [] |
| if s is not None: |
| self.append(s, charset, errors) |
| if maxlinelen is None: |
| maxlinelen = MAXLINELEN |
| if header_name is None: |
| # We don't know anything about the field header so the first line |
| # is the same length as subsequent lines. |
| self._firstlinelen = maxlinelen |
| else: |
| # The first line should be shorter to take into account the field |
| # header. Also subtract off 2 extra for the colon and space. |
| self._firstlinelen = maxlinelen - len(header_name) - 2 |
| # Second and subsequent lines should subtract off the length in |
| # columns of the continuation whitespace prefix. |
| self._maxlinelen = maxlinelen - cws_expanded_len |
| |
| def __str__(self): |
| """A synonym for self.encode().""" |
| return self.encode() |
| |
| def __unicode__(self): |
| """Helper for the built-in unicode function.""" |
| # charset item is a Charset instance so we need to stringify it. |
| uchunks = [unicode(s, str(charset)) for s, charset in self._chunks] |
| return u''.join(uchunks) |
| |
| # Rich comparison operators for equality only. BAW: does it make sense to |
| # have or explicitly disable <, <=, >, >= operators? |
| def __eq__(self, other): |
| # other may be a Header or a string. Both are fine so coerce |
| # ourselves to a string, swap the args and do another comparison. |
| return other == self.encode() |
| |
| def __ne__(self, other): |
| return not self == other |
| |
| def append(self, s, charset=None, errors='strict'): |
| """Append a string to the MIME header. |
| |
| Optional charset, if given, should be a Charset instance or the name |
| of a character set (which will be converted to a Charset instance). A |
| value of None (the default) means that the charset given in the |
| constructor is used. |
| |
| s may be a byte string or a Unicode string. If it is a byte string |
| (i.e. isinstance(s, StringType) is true), then charset is the encoding |
| of that byte string, and a UnicodeError will be raised if the string |
| cannot be decoded with that charset. If s is a Unicode string, then |
| charset is a hint specifying the character set of the characters in |
| the string. In this case, when producing an RFC 2822 compliant header |
| using RFC 2047 rules, the Unicode string will be encoded using the |
| following charsets in order: us-ascii, the charset hint, utf-8. The |
| first character set not to provoke a UnicodeError is used. |
| |
| Optional `errors' is passed as the third argument to any unicode() or |
| ustr.encode() call. |
| """ |
| if charset is None: |
| charset = self._charset |
| elif not isinstance(charset, Charset): |
| charset = Charset(charset) |
| # If the charset is our faux 8bit charset, leave the string unchanged |
| if charset <> '8bit': |
| # We need to test that the string can be converted to unicode and |
| # back to a byte string, given the input and output codecs of the |
| # charset. |
| if isinstance(s, StringType): |
| # Possibly raise UnicodeError if the byte string can't be |
| # converted to a unicode with the input codec of the charset. |
| incodec = charset.input_codec or 'us-ascii' |
| ustr = unicode(s, incodec, errors) |
| # Now make sure that the unicode could be converted back to a |
| # byte string with the output codec, which may be different |
| # than the iput coded. Still, use the original byte string. |
| outcodec = charset.output_codec or 'us-ascii' |
| ustr.encode(outcodec, errors) |
| elif isinstance(s, UnicodeType): |
| # Now we have to be sure the unicode string can be converted |
| # to a byte string with a reasonable output codec. We want to |
| # use the byte string in the chunk. |
| for charset in USASCII, charset, UTF8: |
| try: |
| outcodec = charset.output_codec or 'us-ascii' |
| s = s.encode(outcodec, errors) |
| break |
| except UnicodeError: |
| pass |
| else: |
| assert False, 'utf-8 conversion failed' |
| self._chunks.append((s, charset)) |
| |
| def _split(self, s, charset, firstline=False): |
| # Split up a header safely for use with encode_chunks. |
| splittable = charset.to_splittable(s) |
| encoded = charset.from_splittable(splittable) |
| elen = charset.encoded_header_len(encoded) |
| |
| if elen <= self._maxlinelen: |
| return [(encoded, charset)] |
| # If we have undetermined raw 8bit characters sitting in a byte |
| # string, we really don't know what the right thing to do is. We |
| # can't really split it because it might be multibyte data which we |
| # could break if we split it between pairs. The least harm seems to |
| # be to not split the header at all, but that means they could go out |
| # longer than maxlinelen. |
| elif charset == '8bit': |
| return [(s, charset)] |
| # BAW: I'm not sure what the right test here is. What we're trying to |
| # do is be faithful to RFC 2822's recommendation that ($2.2.3): |
| # |
| # "Note: Though structured field bodies are defined in such a way that |
| # folding can take place between many of the lexical tokens (and even |
| # within some of the lexical tokens), folding SHOULD be limited to |
| # placing the CRLF at higher-level syntactic breaks." |
| # |
| # For now, I can only imagine doing this when the charset is us-ascii, |
| # although it's possible that other charsets may also benefit from the |
| # higher-level syntactic breaks. |
| # |
| elif charset == 'us-ascii': |
| return self._ascii_split(s, charset, firstline) |
| # BAW: should we use encoded? |
| elif elen == len(s): |
| # We can split on _maxlinelen boundaries because we know that the |
| # encoding won't change the size of the string |
| splitpnt = self._maxlinelen |
| first = charset.from_splittable(splittable[:splitpnt], False) |
| last = charset.from_splittable(splittable[splitpnt:], False) |
| else: |
| # Divide and conquer. |
| halfway = _floordiv(len(splittable), 2) |
| first = charset.from_splittable(splittable[:halfway], False) |
| last = charset.from_splittable(splittable[halfway:], False) |
| # Do the split |
| return self._split(first, charset, firstline) + \ |
| self._split(last, charset) |
| |
| def _ascii_split(self, s, charset, firstline): |
| # Attempt to split the line at the highest-level syntactic break |
| # possible. Note that we don't have a lot of smarts about field |
| # syntax; we just try to break on semi-colons, then whitespace. |
| rtn = [] |
| lines = s.splitlines() |
| while lines: |
| line = lines.pop(0) |
| if firstline: |
| maxlinelen = self._firstlinelen |
| firstline = False |
| else: |
| #line = line.lstrip() |
| maxlinelen = self._maxlinelen |
| # Short lines can remain unchanged |
| if len(line.replace('\t', SPACE8)) <= maxlinelen: |
| rtn.append(line) |
| else: |
| oldlen = len(line) |
| # Try to break the line on semicolons, but if that doesn't |
| # work, try to split on folding whitespace. |
| while len(line) > maxlinelen: |
| i = line.rfind(';', 0, maxlinelen) |
| if i < 0: |
| break |
| rtn.append(line[:i] + ';') |
| line = line[i+1:] |
| # Is the remaining stuff still longer than maxlinelen? |
| if len(line) <= maxlinelen: |
| # Splitting on semis worked |
| rtn.append(line) |
| continue |
| # Splitting on semis didn't finish the job. If it did any |
| # work at all, stick the remaining junk on the front of the |
| # `lines' sequence and let the next pass do its thing. |
| if len(line) <> oldlen: |
| lines.insert(0, line) |
| continue |
| # Otherwise, splitting on semis didn't help at all. |
| parts = re.split(r'(\s+)', line) |
| if len(parts) == 1 or (len(parts) == 3 and |
| parts[0].endswith(':')): |
| # This line can't be split on whitespace. There's now |
| # little we can do to get this into maxlinelen. BAW: |
| # We're still potentially breaking the RFC by possibly |
| # allowing lines longer than the absolute maximum of 998 |
| # characters. For now, let it slide. |
| # |
| # len(parts) will be 1 if this line has no `Field: ' |
| # prefix, otherwise it will be len(3). |
| rtn.append(line) |
| continue |
| # There is whitespace we can split on. |
| first = parts.pop(0) |
| sublines = [first] |
| acc = len(first) |
| while parts: |
| len0 = len(parts[0]) |
| len1 = len(parts[1]) |
| if acc + len0 + len1 <= maxlinelen: |
| sublines.append(parts.pop(0)) |
| sublines.append(parts.pop(0)) |
| acc += len0 + len1 |
| else: |
| # Split it here, but don't forget to ignore the |
| # next whitespace-only part |
| if first <> '': |
| rtn.append(EMPTYSTRING.join(sublines)) |
| del parts[0] |
| first = parts.pop(0) |
| sublines = [first] |
| acc = len(first) |
| rtn.append(EMPTYSTRING.join(sublines)) |
| return [(chunk, charset) for chunk in rtn] |
| |
| def _encode_chunks(self, newchunks): |
| # 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 newchunks: |
| if charset is None or charset.header_encoding is None: |
| # There's no encoding for this chunk's charsets |
| _max_append(chunks, header, self._maxlinelen) |
| else: |
| _max_append(chunks, charset.header_encode(header), |
| self._maxlinelen, ' ') |
| joiner = NL + self._continuation_ws |
| return joiner.join(chunks) |
| |
| def encode(self): |
| """Encode a message header into an RFC-compliant format. |
| |
| 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, True) |
| return self._encode_chunks(newchunks) |