485 lines
20 KiB
Python
485 lines
20 KiB
Python
# Copyright (C) 2004-2006 Python Software Foundation
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# Authors: Baxter, Wouters and Warsaw
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# Contact: email-sig@python.org
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"""FeedParser - An email feed parser.
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The feed parser implements an interface for incrementally parsing an email
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message, line by line. This has advantages for certain applications, such as
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those reading email messages off a socket.
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FeedParser.feed() is the primary interface for pushing new data into the
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parser. It returns when there's nothing more it can do with the available
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data. When you have no more data to push into the parser, call .close().
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This completes the parsing and returns the root message object.
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The other advantage of this parser is that it will never raise a parsing
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exception. Instead, when it finds something unexpected, it adds a 'defect' to
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the current message. Defects are just instances that live on the message
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object's .defects attribute.
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"""
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__all__ = ['FeedParser']
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import re
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from email import errors
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from email import message
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NLCRE = re.compile('\r\n|\r|\n')
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NLCRE_bol = re.compile('(\r\n|\r|\n)')
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NLCRE_eol = re.compile('(\r\n|\r|\n)\Z')
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NLCRE_crack = re.compile('(\r\n|\r|\n)')
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# RFC 2822 $3.6.8 Optional fields. ftext is %d33-57 / %d59-126, Any character
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# except controls, SP, and ":".
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headerRE = re.compile(r'^(From |[\041-\071\073-\176]{1,}:|[\t ])')
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EMPTYSTRING = ''
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NL = '\n'
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NeedMoreData = object()
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class BufferedSubFile(object):
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"""A file-ish object that can have new data loaded into it.
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You can also push and pop line-matching predicates onto a stack. When the
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current predicate matches the current line, a false EOF response
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(i.e. empty string) is returned instead. This lets the parser adhere to a
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simple abstraction -- it parses until EOF closes the current message.
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"""
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def __init__(self):
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# The last partial line pushed into this object.
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self._partial = ''
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# The list of full, pushed lines, in reverse order
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self._lines = []
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# The stack of false-EOF checking predicates.
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self._eofstack = []
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# A flag indicating whether the file has been closed or not.
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self._closed = False
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def push_eof_matcher(self, pred):
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self._eofstack.append(pred)
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def pop_eof_matcher(self):
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return self._eofstack.pop()
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def close(self):
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# Don't forget any trailing partial line.
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self._lines.append(self._partial)
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self._partial = ''
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self._closed = True
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def readline(self):
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if not self._lines:
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if self._closed:
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return ''
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return NeedMoreData
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# Pop the line off the stack and see if it matches the current
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# false-EOF predicate.
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line = self._lines.pop()
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# RFC 2046, section 5.1.2 requires us to recognize outer level
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# boundaries at any level of inner nesting. Do this, but be sure it's
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# in the order of most to least nested.
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for ateof in self._eofstack[::-1]:
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if ateof(line):
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# We're at the false EOF. But push the last line back first.
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self._lines.append(line)
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return ''
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return line
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def unreadline(self, line):
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# Let the consumer push a line back into the buffer.
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assert line is not NeedMoreData
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self._lines.append(line)
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def push(self, data):
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"""Push some new data into this object."""
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# Handle any previous leftovers
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data, self._partial = self._partial + data, ''
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# Crack into lines, but preserve the newlines on the end of each
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parts = NLCRE_crack.split(data)
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# The *ahem* interesting behaviour of re.split when supplied grouping
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# parentheses is that the last element of the resulting list is the
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# data after the final RE. In the case of a NL/CR terminated string,
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# this is the empty string.
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self._partial = parts.pop()
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#GAN 29Mar09 bugs 1555570, 1721862 Confusion at 8K boundary ending with \r:
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# is there a \n to follow later?
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if not self._partial and parts and parts[-1].endswith('\r'):
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self._partial = parts.pop(-2)+parts.pop()
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# parts is a list of strings, alternating between the line contents
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# and the eol character(s). Gather up a list of lines after
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# re-attaching the newlines.
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lines = []
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for i in range(len(parts) // 2):
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lines.append(parts[i*2] + parts[i*2+1])
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self.pushlines(lines)
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def pushlines(self, lines):
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# Reverse and insert at the front of the lines.
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self._lines[:0] = lines[::-1]
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def is_closed(self):
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return self._closed
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def __iter__(self):
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return self
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def next(self):
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line = self.readline()
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if line == '':
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raise StopIteration
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return line
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class FeedParser:
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"""A feed-style parser of email."""
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def __init__(self, _factory=message.Message):
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"""_factory is called with no arguments to create a new message obj"""
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self._factory = _factory
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self._input = BufferedSubFile()
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self._msgstack = []
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self._parse = self._parsegen().next
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self._cur = None
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self._last = None
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self._headersonly = False
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# Non-public interface for supporting Parser's headersonly flag
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def _set_headersonly(self):
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self._headersonly = True
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def feed(self, data):
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"""Push more data into the parser."""
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self._input.push(data)
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self._call_parse()
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def _call_parse(self):
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try:
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self._parse()
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except StopIteration:
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pass
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def close(self):
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"""Parse all remaining data and return the root message object."""
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self._input.close()
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self._call_parse()
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root = self._pop_message()
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assert not self._msgstack
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# Look for final set of defects
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if root.get_content_maintype() == 'multipart' \
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and not root.is_multipart():
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root.defects.append(errors.MultipartInvariantViolationDefect())
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return root
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def _new_message(self):
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msg = self._factory()
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if self._cur and self._cur.get_content_type() == 'multipart/digest':
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msg.set_default_type('message/rfc822')
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if self._msgstack:
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self._msgstack[-1].attach(msg)
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self._msgstack.append(msg)
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self._cur = msg
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self._last = msg
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def _pop_message(self):
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retval = self._msgstack.pop()
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if self._msgstack:
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self._cur = self._msgstack[-1]
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else:
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self._cur = None
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return retval
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def _parsegen(self):
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# Create a new message and start by parsing headers.
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self._new_message()
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headers = []
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# Collect the headers, searching for a line that doesn't match the RFC
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# 2822 header or continuation pattern (including an empty line).
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for line in self._input:
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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if not headerRE.match(line):
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# If we saw the RFC defined header/body separator
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# (i.e. newline), just throw it away. Otherwise the line is
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# part of the body so push it back.
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if not NLCRE.match(line):
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self._input.unreadline(line)
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break
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headers.append(line)
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# Done with the headers, so parse them and figure out what we're
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# supposed to see in the body of the message.
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self._parse_headers(headers)
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# Headers-only parsing is a backwards compatibility hack, which was
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# necessary in the older parser, which could raise errors. All
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# remaining lines in the input are thrown into the message body.
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if self._headersonly:
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lines = []
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while True:
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line = self._input.readline()
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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if line == '':
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break
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lines.append(line)
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self._cur.set_payload(EMPTYSTRING.join(lines))
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return
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if self._cur.get_content_type() == 'message/delivery-status':
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# message/delivery-status contains blocks of headers separated by
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# a blank line. We'll represent each header block as a separate
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# nested message object, but the processing is a bit different
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# than standard message/* types because there is no body for the
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# nested messages. A blank line separates the subparts.
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while True:
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self._input.push_eof_matcher(NLCRE.match)
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for retval in self._parsegen():
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if retval is NeedMoreData:
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yield NeedMoreData
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continue
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break
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msg = self._pop_message()
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# We need to pop the EOF matcher in order to tell if we're at
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# the end of the current file, not the end of the last block
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# of message headers.
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self._input.pop_eof_matcher()
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# The input stream must be sitting at the newline or at the
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# EOF. We want to see if we're at the end of this subpart, so
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# first consume the blank line, then test the next line to see
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# if we're at this subpart's EOF.
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while True:
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line = self._input.readline()
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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break
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while True:
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line = self._input.readline()
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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break
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if line == '':
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break
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# Not at EOF so this is a line we're going to need.
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self._input.unreadline(line)
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return
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if self._cur.get_content_maintype() == 'message':
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# The message claims to be a message/* type, then what follows is
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# another RFC 2822 message.
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for retval in self._parsegen():
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if retval is NeedMoreData:
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yield NeedMoreData
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continue
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break
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self._pop_message()
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return
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if self._cur.get_content_maintype() == 'multipart':
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boundary = self._cur.get_boundary()
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if boundary is None:
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# The message /claims/ to be a multipart but it has not
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# defined a boundary. That's a problem which we'll handle by
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# reading everything until the EOF and marking the message as
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# defective.
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self._cur.defects.append(errors.NoBoundaryInMultipartDefect())
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lines = []
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for line in self._input:
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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lines.append(line)
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self._cur.set_payload(EMPTYSTRING.join(lines))
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return
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# Create a line match predicate which matches the inter-part
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# boundary as well as the end-of-multipart boundary. Don't push
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# this onto the input stream until we've scanned past the
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# preamble.
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separator = '--' + boundary
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boundaryre = re.compile(
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'(?P<sep>' + re.escape(separator) +
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r')(?P<end>--)?(?P<ws>[ \t]*)(?P<linesep>\r\n|\r|\n)?$')
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capturing_preamble = True
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preamble = []
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linesep = False
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while True:
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line = self._input.readline()
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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if line == '':
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break
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mo = boundaryre.match(line)
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if mo:
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# If we're looking at the end boundary, we're done with
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# this multipart. If there was a newline at the end of
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# the closing boundary, then we need to initialize the
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# epilogue with the empty string (see below).
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if mo.group('end'):
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linesep = mo.group('linesep')
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break
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# We saw an inter-part boundary. Were we in the preamble?
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if capturing_preamble:
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if preamble:
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# According to RFC 2046, the last newline belongs
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# to the boundary.
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lastline = preamble[-1]
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eolmo = NLCRE_eol.search(lastline)
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if eolmo:
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preamble[-1] = lastline[:-len(eolmo.group(0))]
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self._cur.preamble = EMPTYSTRING.join(preamble)
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capturing_preamble = False
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self._input.unreadline(line)
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continue
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# We saw a boundary separating two parts. Consume any
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# multiple boundary lines that may be following. Our
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# interpretation of RFC 2046 BNF grammar does not produce
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# body parts within such double boundaries.
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while True:
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line = self._input.readline()
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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mo = boundaryre.match(line)
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if not mo:
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self._input.unreadline(line)
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break
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# Recurse to parse this subpart; the input stream points
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# at the subpart's first line.
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self._input.push_eof_matcher(boundaryre.match)
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for retval in self._parsegen():
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if retval is NeedMoreData:
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yield NeedMoreData
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continue
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break
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# Because of RFC 2046, the newline preceding the boundary
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# separator actually belongs to the boundary, not the
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# previous subpart's payload (or epilogue if the previous
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# part is a multipart).
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if self._last.get_content_maintype() == 'multipart':
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epilogue = self._last.epilogue
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if epilogue == '':
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self._last.epilogue = None
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elif epilogue is not None:
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mo = NLCRE_eol.search(epilogue)
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if mo:
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end = len(mo.group(0))
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self._last.epilogue = epilogue[:-end]
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else:
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payload = self._last.get_payload()
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if isinstance(payload, basestring):
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mo = NLCRE_eol.search(payload)
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if mo:
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payload = payload[:-len(mo.group(0))]
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self._last.set_payload(payload)
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self._input.pop_eof_matcher()
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self._pop_message()
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# Set the multipart up for newline cleansing, which will
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# happen if we're in a nested multipart.
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self._last = self._cur
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else:
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# I think we must be in the preamble
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assert capturing_preamble
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preamble.append(line)
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# We've seen either the EOF or the end boundary. If we're still
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# capturing the preamble, we never saw the start boundary. Note
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# that as a defect and store the captured text as the payload.
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# Everything from here to the EOF is epilogue.
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if capturing_preamble:
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self._cur.defects.append(errors.StartBoundaryNotFoundDefect())
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self._cur.set_payload(EMPTYSTRING.join(preamble))
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epilogue = []
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for line in self._input:
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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self._cur.epilogue = EMPTYSTRING.join(epilogue)
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return
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# If the end boundary ended in a newline, we'll need to make sure
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# the epilogue isn't None
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if linesep:
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epilogue = ['']
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else:
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epilogue = []
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for line in self._input:
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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epilogue.append(line)
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# Any CRLF at the front of the epilogue is not technically part of
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# the epilogue. Also, watch out for an empty string epilogue,
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# which means a single newline.
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if epilogue:
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firstline = epilogue[0]
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bolmo = NLCRE_bol.match(firstline)
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if bolmo:
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epilogue[0] = firstline[len(bolmo.group(0)):]
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self._cur.epilogue = EMPTYSTRING.join(epilogue)
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return
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# Otherwise, it's some non-multipart type, so the entire rest of the
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# file contents becomes the payload.
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lines = []
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for line in self._input:
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if line is NeedMoreData:
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yield NeedMoreData
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continue
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lines.append(line)
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self._cur.set_payload(EMPTYSTRING.join(lines))
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def _parse_headers(self, lines):
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# Passed a list of lines that make up the headers for the current msg
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lastheader = ''
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lastvalue = []
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for lineno, line in enumerate(lines):
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# Check for continuation
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if line[0] in ' \t':
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if not lastheader:
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# The first line of the headers was a continuation. This
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# is illegal, so let's note the defect, store the illegal
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# line, and ignore it for purposes of headers.
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defect = errors.FirstHeaderLineIsContinuationDefect(line)
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self._cur.defects.append(defect)
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continue
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lastvalue.append(line)
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continue
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if lastheader:
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# XXX reconsider the joining of folded lines
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lhdr = EMPTYSTRING.join(lastvalue)[:-1].rstrip('\r\n')
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self._cur[lastheader] = lhdr
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lastheader, lastvalue = '', []
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# Check for envelope header, i.e. unix-from
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if line.startswith('From '):
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if lineno == 0:
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# Strip off the trailing newline
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mo = NLCRE_eol.search(line)
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if mo:
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line = line[:-len(mo.group(0))]
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self._cur.set_unixfrom(line)
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continue
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elif lineno == len(lines) - 1:
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# Something looking like a unix-from at the end - it's
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# probably the first line of the body, so push back the
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# line and stop.
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self._input.unreadline(line)
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return
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else:
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# Weirdly placed unix-from line. Note this as a defect
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# and ignore it.
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defect = errors.MisplacedEnvelopeHeaderDefect(line)
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self._cur.defects.append(defect)
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continue
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# Split the line on the colon separating field name from value.
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i = line.find(':')
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if i < 0:
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defect = errors.MalformedHeaderDefect(line)
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self._cur.defects.append(defect)
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continue
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lastheader = line[:i]
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lastvalue = [line[i+1:].lstrip()]
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# Done with all the lines, so handle the last header.
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if lastheader:
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# XXX reconsider the joining of folded lines
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self._cur[lastheader] = EMPTYSTRING.join(lastvalue).rstrip('\r\n')
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