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6c2bc46355
8-bit data, we cannot split it safely, so return the original string unchanged. _is8bitstring(): Helper function which returns True when we have a byte string that contains non-ascii characters (i.e. mysterious 8-bit data).
378 lines
14 KiB
Python
378 lines
14 KiB
Python
# Copyright (C) 2001,2002 Python Software Foundation
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# Author: barry@zope.com (Barry Warsaw)
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"""Classes to generate plain text from a message object tree.
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"""
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import time
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import re
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import random
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from types import ListType, StringType
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from cStringIO import StringIO
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from email.Header import Header
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try:
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from email._compat22 import _isstring
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except SyntaxError:
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from email._compat21 import _isstring
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try:
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True, False
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except NameError:
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True = 1
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False = 0
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EMPTYSTRING = ''
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SEMISPACE = '; '
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BAR = '|'
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UNDERSCORE = '_'
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NL = '\n'
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NLTAB = '\n\t'
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SEMINLTAB = ';\n\t'
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SPACE8 = ' ' * 8
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fcre = re.compile(r'^From ', re.MULTILINE)
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def _is8bitstring(s):
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if isinstance(s, StringType):
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try:
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unicode(s, 'us-ascii')
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except UnicodeError:
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return True
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return False
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class Generator:
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"""Generates output from a Message object tree.
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This basic generator writes the message to the given file object as plain
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text.
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"""
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#
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# Public interface
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#
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def __init__(self, outfp, mangle_from_=True, maxheaderlen=78):
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"""Create the generator for message flattening.
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outfp is the output file-like object for writing the message to. It
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must have a write() method.
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Optional mangle_from_ is a flag that, when True (the default), escapes
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From_ lines in the body of the message by putting a `>' in front of
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them.
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Optional maxheaderlen specifies the longest length for a non-continued
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header. When a header line is longer (in characters, with tabs
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expanded to 8 spaces), than maxheaderlen, the header will be broken on
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semicolons and continued as per RFC 2822. If no semicolon is found,
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then the header is left alone. Set to zero to disable wrapping
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headers. Default is 78, as recommended (but not required by RFC
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2822.
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"""
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self._fp = outfp
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self._mangle_from_ = mangle_from_
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self.__maxheaderlen = maxheaderlen
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def write(self, s):
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# Just delegate to the file object
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self._fp.write(s)
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def flatten(self, msg, unixfrom=False):
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"""Print the message object tree rooted at msg to the output file
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specified when the Generator instance was created.
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unixfrom is a flag that forces the printing of a Unix From_ delimiter
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before the first object in the message tree. If the original message
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has no From_ delimiter, a `standard' one is crafted. By default, this
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is False to inhibit the printing of any From_ delimiter.
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Note that for subobjects, no From_ line is printed.
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"""
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if unixfrom:
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ufrom = msg.get_unixfrom()
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if not ufrom:
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ufrom = 'From nobody ' + time.ctime(time.time())
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print >> self._fp, ufrom
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self._write(msg)
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# For backwards compatibility, but this is slower
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__call__ = flatten
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def clone(self, fp):
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"""Clone this generator with the exact same options."""
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return self.__class__(fp, self._mangle_from_, self.__maxheaderlen)
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#
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# Protected interface - undocumented ;/
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#
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def _write(self, msg):
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# We can't write the headers yet because of the following scenario:
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# say a multipart message includes the boundary string somewhere in
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# its body. We'd have to calculate the new boundary /before/ we write
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# the headers so that we can write the correct Content-Type:
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# parameter.
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#
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# The way we do this, so as to make the _handle_*() methods simpler,
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# is to cache any subpart writes into a StringIO. The we write the
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# headers and the StringIO contents. That way, subpart handlers can
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# Do The Right Thing, and can still modify the Content-Type: header if
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# necessary.
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oldfp = self._fp
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try:
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self._fp = sfp = StringIO()
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self._dispatch(msg)
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finally:
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self._fp = oldfp
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# Write the headers. First we see if the message object wants to
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# handle that itself. If not, we'll do it generically.
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meth = getattr(msg, '_write_headers', None)
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if meth is None:
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self._write_headers(msg)
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else:
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meth(self)
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self._fp.write(sfp.getvalue())
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def _dispatch(self, msg):
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# Get the Content-Type: for the message, then try to dispatch to
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# self._handle_<maintype>_<subtype>(). If there's no handler for the
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# full MIME type, then dispatch to self._handle_<maintype>(). If
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# that's missing too, then dispatch to self._writeBody().
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main = msg.get_content_maintype()
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sub = msg.get_content_subtype()
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specific = UNDERSCORE.join((main, sub)).replace('-', '_')
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meth = getattr(self, '_handle_' + specific, None)
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if meth is None:
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generic = main.replace('-', '_')
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meth = getattr(self, '_handle_' + generic, None)
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if meth is None:
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meth = self._writeBody
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meth(msg)
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#
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# Default handlers
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#
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def _write_headers(self, msg):
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for h, v in msg.items():
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# RFC 2822 says that lines SHOULD be no more than maxheaderlen
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# characters wide, so we're well within our rights to split long
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# headers.
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text = '%s: %s' % (h, v)
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if self.__maxheaderlen > 0 and len(text) > self.__maxheaderlen:
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text = self._split_header(text)
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print >> self._fp, text
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# A blank line always separates headers from body
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print >> self._fp
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def _split_header(self, text):
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maxheaderlen = self.__maxheaderlen
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# Find out whether any lines in the header are really longer than
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# maxheaderlen characters wide. There could be continuation lines
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# that actually shorten it. Also, replace hard tabs with 8 spaces.
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lines = [s.replace('\t', SPACE8) for s in text.splitlines()]
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for line in lines:
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if len(line) > maxheaderlen:
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break
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else:
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# No line was actually longer than maxheaderlen characters, so
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# just return the original unchanged.
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return text
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# If we have raw 8bit data in a byte string, we have no idea what the
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# encoding is. I think there is no safe way to split this string. If
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# it's ascii-subset, then we could do a normal ascii split, but if
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# it's multibyte then we could break the string. There's no way to
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# know so the least harm seems to be to not split the string and risk
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# it being too long.
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if _is8bitstring(text):
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return text
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# The `text' argument already has the field name prepended, so don't
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# provide it here or the first line will get folded too short.
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h = Header(text, maxlinelen=maxheaderlen,
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# For backwards compatibility, we use a hard tab here
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continuation_ws='\t')
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return h.encode()
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#
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# Handlers for writing types and subtypes
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#
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def _handle_text(self, msg):
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payload = msg.get_payload()
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if payload is None:
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return
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cset = msg.get_charset()
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if cset is not None:
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payload = cset.body_encode(payload)
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if not _isstring(payload):
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raise TypeError, 'string payload expected: %s' % type(payload)
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if self._mangle_from_:
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payload = fcre.sub('>From ', payload)
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self._fp.write(payload)
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# Default body handler
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_writeBody = _handle_text
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def _handle_multipart(self, msg):
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# The trick here is to write out each part separately, merge them all
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# together, and then make sure that the boundary we've chosen isn't
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# present in the payload.
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msgtexts = []
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subparts = msg.get_payload()
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if subparts is None:
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# Nothing has ever been attached
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boundary = msg.get_boundary(failobj=_make_boundary())
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print >> self._fp, '--' + boundary
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print >> self._fp, '\n'
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print >> self._fp, '--' + boundary + '--'
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return
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elif _isstring(subparts):
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# e.g. a non-strict parse of a message with no starting boundary.
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self._fp.write(subparts)
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return
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elif not isinstance(subparts, ListType):
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# Scalar payload
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subparts = [subparts]
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for part in subparts:
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s = StringIO()
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g = self.clone(s)
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g.flatten(part, unixfrom=False)
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msgtexts.append(s.getvalue())
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# Now make sure the boundary we've selected doesn't appear in any of
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# the message texts.
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alltext = NL.join(msgtexts)
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# BAW: What about boundaries that are wrapped in double-quotes?
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boundary = msg.get_boundary(failobj=_make_boundary(alltext))
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# If we had to calculate a new boundary because the body text
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# contained that string, set the new boundary. We don't do it
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# unconditionally because, while set_boundary() preserves order, it
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# doesn't preserve newlines/continuations in headers. This is no big
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# deal in practice, but turns out to be inconvenient for the unittest
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# suite.
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if msg.get_boundary() <> boundary:
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msg.set_boundary(boundary)
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# Write out any preamble
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if msg.preamble is not None:
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self._fp.write(msg.preamble)
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# First boundary is a bit different; it doesn't have a leading extra
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# newline.
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print >> self._fp, '--' + boundary
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# Join and write the individual parts
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joiner = '\n--' + boundary + '\n'
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self._fp.write(joiner.join(msgtexts))
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print >> self._fp, '\n--' + boundary + '--',
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# Write out any epilogue
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if msg.epilogue is not None:
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if not msg.epilogue.startswith('\n'):
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print >> self._fp
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self._fp.write(msg.epilogue)
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def _handle_message_delivery_status(self, msg):
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# We can't just write the headers directly to self's file object
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# because this will leave an extra newline between the last header
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# block and the boundary. Sigh.
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blocks = []
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for part in msg.get_payload():
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s = StringIO()
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g = self.clone(s)
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g.flatten(part, unixfrom=False)
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text = s.getvalue()
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lines = text.split('\n')
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# Strip off the unnecessary trailing empty line
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if lines and lines[-1] == '':
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blocks.append(NL.join(lines[:-1]))
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else:
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blocks.append(text)
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# Now join all the blocks with an empty line. This has the lovely
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# effect of separating each block with an empty line, but not adding
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# an extra one after the last one.
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self._fp.write(NL.join(blocks))
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def _handle_message(self, msg):
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s = StringIO()
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g = self.clone(s)
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# The payload of a message/rfc822 part should be a multipart sequence
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# of length 1. The zeroth element of the list should be the Message
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# object for the subpart. Extract that object, stringify it, and
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# write it out.
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g.flatten(msg.get_payload(0), unixfrom=False)
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self._fp.write(s.getvalue())
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class DecodedGenerator(Generator):
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"""Generator a text representation of a message.
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Like the Generator base class, except that non-text parts are substituted
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with a format string representing the part.
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"""
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def __init__(self, outfp, mangle_from_=True, maxheaderlen=78, fmt=None):
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"""Like Generator.__init__() except that an additional optional
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argument is allowed.
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Walks through all subparts of a message. If the subpart is of main
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type `text', then it prints the decoded payload of the subpart.
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Otherwise, fmt is a format string that is used instead of the message
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payload. fmt is expanded with the following keywords (in
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%(keyword)s format):
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type : Full MIME type of the non-text part
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maintype : Main MIME type of the non-text part
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subtype : Sub-MIME type of the non-text part
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filename : Filename of the non-text part
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description: Description associated with the non-text part
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encoding : Content transfer encoding of the non-text part
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The default value for fmt is None, meaning
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[Non-text (%(type)s) part of message omitted, filename %(filename)s]
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"""
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Generator.__init__(self, outfp, mangle_from_, maxheaderlen)
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if fmt is None:
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fmt = ('[Non-text (%(type)s) part of message omitted, '
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'filename %(filename)s]')
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self._fmt = fmt
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def _dispatch(self, msg):
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for part in msg.walk():
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maintype = part.get_main_type('text')
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if maintype == 'text':
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print >> self, part.get_payload(decode=True)
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elif maintype == 'multipart':
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# Just skip this
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pass
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else:
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print >> self, self._fmt % {
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'type' : part.get_type('[no MIME type]'),
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'maintype' : part.get_main_type('[no main MIME type]'),
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'subtype' : part.get_subtype('[no sub-MIME type]'),
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'filename' : part.get_filename('[no filename]'),
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'description': part.get('Content-Description',
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'[no description]'),
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'encoding' : part.get('Content-Transfer-Encoding',
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'[no encoding]'),
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}
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# Helper
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def _make_boundary(text=None):
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# Craft a random boundary. If text is given, ensure that the chosen
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# boundary doesn't appear in the text.
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boundary = ('=' * 15) + repr(random.random()).split('.')[1] + '=='
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if text is None:
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return boundary
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b = boundary
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counter = 0
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while True:
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cre = re.compile('^--' + re.escape(b) + '(--)?$', re.MULTILINE)
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if not cre.search(text):
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break
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b = boundary + '.' + str(counter)
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counter += 1
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return b
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