mirror of
https://github.com/python/cpython.git
synced 2025-10-31 05:31:20 +00:00
67f8f2fe2a
Ben. If s is a byte string, make sure it can be converted to unicode with the input codec, and from unicode with the output codec, or raise a UnicodeError exception early. Skip this test (and the unicode->byte string conversion) when the charset is our faux 8bit raw charset.
423 lines
18 KiB
Python
423 lines
18 KiB
Python
# 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=' '):
|
||
"""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.
|
||
"""
|
||
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)
|
||
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):
|
||
"""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.
|
||
"""
|
||
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)
|
||
# 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)
|
||
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)
|
||
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)
|