2c8595098c
git-svn-id: http://google-refine.googlecode.com/svn/trunk@883 7d457c2a-affb-35e4-300a-418c747d4874
349 lines
13 KiB
Python
349 lines
13 KiB
Python
# Copyright (C) 2001-2006 Python Software Foundation
|
||
# Author: Barry Warsaw
|
||
# Contact: email-sig@python.org
|
||
|
||
"""Classes to generate plain text from a message object tree."""
|
||
|
||
__all__ = ['Generator', 'DecodedGenerator']
|
||
|
||
import re
|
||
import sys
|
||
import time
|
||
import random
|
||
import warnings
|
||
|
||
from cStringIO import StringIO
|
||
from email.header import Header
|
||
|
||
UNDERSCORE = '_'
|
||
NL = '\n'
|
||
|
||
fcre = re.compile(r'^From ', re.MULTILINE)
|
||
|
||
def _is8bitstring(s):
|
||
if isinstance(s, str):
|
||
try:
|
||
unicode(s, 'us-ascii')
|
||
except UnicodeError:
|
||
return True
|
||
return False
|
||
|
||
|
||
|
||
class Generator:
|
||
"""Generates output from a Message object tree.
|
||
|
||
This basic generator writes the message to the given file object as plain
|
||
text.
|
||
"""
|
||
#
|
||
# Public interface
|
||
#
|
||
|
||
def __init__(self, outfp, mangle_from_=True, maxheaderlen=78):
|
||
"""Create the generator for message flattening.
|
||
|
||
outfp is the output file-like object for writing the message to. It
|
||
must have a write() method.
|
||
|
||
Optional mangle_from_ is a flag that, when True (the default), escapes
|
||
From_ lines in the body of the message by putting a `>' in front of
|
||
them.
|
||
|
||
Optional maxheaderlen specifies the longest length for a non-continued
|
||
header. When a header line is longer (in characters, with tabs
|
||
expanded to 8 spaces) than maxheaderlen, the header will split as
|
||
defined in the Header class. Set maxheaderlen to zero to disable
|
||
header wrapping. The default is 78, as recommended (but not required)
|
||
by RFC 2822.
|
||
"""
|
||
self._fp = outfp
|
||
self._mangle_from_ = mangle_from_
|
||
self._maxheaderlen = maxheaderlen
|
||
|
||
def write(self, s):
|
||
# Just delegate to the file object
|
||
self._fp.write(s)
|
||
|
||
def flatten(self, msg, unixfrom=False):
|
||
"""Print the message object tree rooted at msg to the output file
|
||
specified when the Generator instance was created.
|
||
|
||
unixfrom is a flag that forces the printing of a Unix From_ delimiter
|
||
before the first object in the message tree. If the original message
|
||
has no From_ delimiter, a `standard' one is crafted. By default, this
|
||
is False to inhibit the printing of any From_ delimiter.
|
||
|
||
Note that for subobjects, no From_ line is printed.
|
||
"""
|
||
if unixfrom:
|
||
ufrom = msg.get_unixfrom()
|
||
if not ufrom:
|
||
ufrom = 'From nobody ' + time.ctime(time.time())
|
||
print >> self._fp, ufrom
|
||
self._write(msg)
|
||
|
||
def clone(self, fp):
|
||
"""Clone this generator with the exact same options."""
|
||
return self.__class__(fp, self._mangle_from_, self._maxheaderlen)
|
||
|
||
#
|
||
# Protected interface - undocumented ;/
|
||
#
|
||
|
||
def _write(self, msg):
|
||
# We can't write the headers yet because of the following scenario:
|
||
# say a multipart message includes the boundary string somewhere in
|
||
# its body. We'd have to calculate the new boundary /before/ we write
|
||
# the headers so that we can write the correct Content-Type:
|
||
# parameter.
|
||
#
|
||
# The way we do this, so as to make the _handle_*() methods simpler,
|
||
# is to cache any subpart writes into a StringIO. The we write the
|
||
# headers and the StringIO contents. That way, subpart handlers can
|
||
# Do The Right Thing, and can still modify the Content-Type: header if
|
||
# necessary.
|
||
oldfp = self._fp
|
||
try:
|
||
self._fp = sfp = StringIO()
|
||
self._dispatch(msg)
|
||
finally:
|
||
self._fp = oldfp
|
||
# Write the headers. First we see if the message object wants to
|
||
# handle that itself. If not, we'll do it generically.
|
||
meth = getattr(msg, '_write_headers', None)
|
||
if meth is None:
|
||
self._write_headers(msg)
|
||
else:
|
||
meth(self)
|
||
self._fp.write(sfp.getvalue())
|
||
|
||
def _dispatch(self, msg):
|
||
# Get the Content-Type: for the message, then try to dispatch to
|
||
# self._handle_<maintype>_<subtype>(). If there's no handler for the
|
||
# full MIME type, then dispatch to self._handle_<maintype>(). If
|
||
# that's missing too, then dispatch to self._writeBody().
|
||
main = msg.get_content_maintype()
|
||
sub = msg.get_content_subtype()
|
||
specific = UNDERSCORE.join((main, sub)).replace('-', '_')
|
||
meth = getattr(self, '_handle_' + specific, None)
|
||
if meth is None:
|
||
generic = main.replace('-', '_')
|
||
meth = getattr(self, '_handle_' + generic, None)
|
||
if meth is None:
|
||
meth = self._writeBody
|
||
meth(msg)
|
||
|
||
#
|
||
# Default handlers
|
||
#
|
||
|
||
def _write_headers(self, msg):
|
||
for h, v in msg.items():
|
||
print >> self._fp, '%s:' % h,
|
||
if self._maxheaderlen == 0:
|
||
# Explicit no-wrapping
|
||
print >> self._fp, v
|
||
elif isinstance(v, Header):
|
||
# Header instances know what to do
|
||
print >> self._fp, v.encode()
|
||
elif _is8bitstring(v):
|
||
# If we have raw 8bit data in a byte string, we have no idea
|
||
# what the encoding is. There is no safe way to split this
|
||
# string. If it's ascii-subset, then we could do a normal
|
||
# ascii split, but if it's multibyte then we could break the
|
||
# string. There's no way to know so the least harm seems to
|
||
# be to not split the string and risk it being too long.
|
||
print >> self._fp, v
|
||
else:
|
||
# Header's got lots of smarts, so use it.
|
||
print >> self._fp, Header(
|
||
v, maxlinelen=self._maxheaderlen,
|
||
header_name=h, continuation_ws='\t').encode()
|
||
# A blank line always separates headers from body
|
||
print >> self._fp
|
||
|
||
#
|
||
# Handlers for writing types and subtypes
|
||
#
|
||
|
||
def _handle_text(self, msg):
|
||
payload = msg.get_payload()
|
||
if payload is None:
|
||
return
|
||
if not isinstance(payload, basestring):
|
||
raise TypeError('string payload expected: %s' % type(payload))
|
||
if self._mangle_from_:
|
||
payload = fcre.sub('>From ', payload)
|
||
self._fp.write(payload)
|
||
|
||
# Default body handler
|
||
_writeBody = _handle_text
|
||
|
||
def _handle_multipart(self, msg):
|
||
# The trick here is to write out each part separately, merge them all
|
||
# together, and then make sure that the boundary we've chosen isn't
|
||
# present in the payload.
|
||
msgtexts = []
|
||
subparts = msg.get_payload()
|
||
if subparts is None:
|
||
subparts = []
|
||
elif isinstance(subparts, basestring):
|
||
# e.g. a non-strict parse of a message with no starting boundary.
|
||
self._fp.write(subparts)
|
||
return
|
||
elif not isinstance(subparts, list):
|
||
# Scalar payload
|
||
subparts = [subparts]
|
||
for part in subparts:
|
||
s = StringIO()
|
||
g = self.clone(s)
|
||
g.flatten(part, unixfrom=False)
|
||
msgtexts.append(s.getvalue())
|
||
# Now make sure the boundary we've selected doesn't appear in any of
|
||
# the message texts.
|
||
alltext = NL.join(msgtexts)
|
||
# BAW: What about boundaries that are wrapped in double-quotes?
|
||
boundary = msg.get_boundary(failobj=_make_boundary(alltext))
|
||
# If we had to calculate a new boundary because the body text
|
||
# contained that string, set the new boundary. We don't do it
|
||
# unconditionally because, while set_boundary() preserves order, it
|
||
# doesn't preserve newlines/continuations in headers. This is no big
|
||
# deal in practice, but turns out to be inconvenient for the unittest
|
||
# suite.
|
||
if msg.get_boundary() <> boundary:
|
||
msg.set_boundary(boundary)
|
||
# If there's a preamble, write it out, with a trailing CRLF
|
||
if msg.preamble is not None:
|
||
print >> self._fp, msg.preamble
|
||
# dash-boundary transport-padding CRLF
|
||
print >> self._fp, '--' + boundary
|
||
# body-part
|
||
if msgtexts:
|
||
self._fp.write(msgtexts.pop(0))
|
||
# *encapsulation
|
||
# --> delimiter transport-padding
|
||
# --> CRLF body-part
|
||
for body_part in msgtexts:
|
||
# delimiter transport-padding CRLF
|
||
print >> self._fp, '\n--' + boundary
|
||
# body-part
|
||
self._fp.write(body_part)
|
||
# close-delimiter transport-padding
|
||
self._fp.write('\n--' + boundary + '--')
|
||
if msg.epilogue is not None:
|
||
print >> self._fp
|
||
self._fp.write(msg.epilogue)
|
||
|
||
def _handle_message_delivery_status(self, msg):
|
||
# We can't just write the headers directly to self's file object
|
||
# because this will leave an extra newline between the last header
|
||
# block and the boundary. Sigh.
|
||
blocks = []
|
||
for part in msg.get_payload():
|
||
s = StringIO()
|
||
g = self.clone(s)
|
||
g.flatten(part, unixfrom=False)
|
||
text = s.getvalue()
|
||
lines = text.split('\n')
|
||
# Strip off the unnecessary trailing empty line
|
||
if lines and lines[-1] == '':
|
||
blocks.append(NL.join(lines[:-1]))
|
||
else:
|
||
blocks.append(text)
|
||
# Now join all the blocks with an empty line. This has the lovely
|
||
# effect of separating each block with an empty line, but not adding
|
||
# an extra one after the last one.
|
||
self._fp.write(NL.join(blocks))
|
||
|
||
def _handle_message(self, msg):
|
||
s = StringIO()
|
||
g = self.clone(s)
|
||
# The payload of a message/rfc822 part should be a multipart sequence
|
||
# of length 1. The zeroth element of the list should be the Message
|
||
# object for the subpart. Extract that object, stringify it, and
|
||
# write it out.
|
||
g.flatten(msg.get_payload(0), unixfrom=False)
|
||
self._fp.write(s.getvalue())
|
||
|
||
|
||
|
||
_FMT = '[Non-text (%(type)s) part of message omitted, filename %(filename)s]'
|
||
|
||
class DecodedGenerator(Generator):
|
||
"""Generator a text representation of a message.
|
||
|
||
Like the Generator base class, except that non-text parts are substituted
|
||
with a format string representing the part.
|
||
"""
|
||
def __init__(self, outfp, mangle_from_=True, maxheaderlen=78, fmt=None):
|
||
"""Like Generator.__init__() except that an additional optional
|
||
argument is allowed.
|
||
|
||
Walks through all subparts of a message. If the subpart is of main
|
||
type `text', then it prints the decoded payload of the subpart.
|
||
|
||
Otherwise, fmt is a format string that is used instead of the message
|
||
payload. fmt is expanded with the following keywords (in
|
||
%(keyword)s format):
|
||
|
||
type : Full MIME type of the non-text part
|
||
maintype : Main MIME type of the non-text part
|
||
subtype : Sub-MIME type of the non-text part
|
||
filename : Filename of the non-text part
|
||
description: Description associated with the non-text part
|
||
encoding : Content transfer encoding of the non-text part
|
||
|
||
The default value for fmt is None, meaning
|
||
|
||
[Non-text (%(type)s) part of message omitted, filename %(filename)s]
|
||
"""
|
||
Generator.__init__(self, outfp, mangle_from_, maxheaderlen)
|
||
if fmt is None:
|
||
self._fmt = _FMT
|
||
else:
|
||
self._fmt = fmt
|
||
|
||
def _dispatch(self, msg):
|
||
for part in msg.walk():
|
||
maintype = part.get_content_maintype()
|
||
if maintype == 'text':
|
||
print >> self, part.get_payload(decode=True)
|
||
elif maintype == 'multipart':
|
||
# Just skip this
|
||
pass
|
||
else:
|
||
print >> self, self._fmt % {
|
||
'type' : part.get_content_type(),
|
||
'maintype' : part.get_content_maintype(),
|
||
'subtype' : part.get_content_subtype(),
|
||
'filename' : part.get_filename('[no filename]'),
|
||
'description': part.get('Content-Description',
|
||
'[no description]'),
|
||
'encoding' : part.get('Content-Transfer-Encoding',
|
||
'[no encoding]'),
|
||
}
|
||
|
||
|
||
|
||
# Helper
|
||
_width = len(repr(sys.maxint-1))
|
||
_fmt = '%%0%dd' % _width
|
||
|
||
def _make_boundary(text=None):
|
||
# Craft a random boundary. If text is given, ensure that the chosen
|
||
# boundary doesn't appear in the text.
|
||
token = random.randrange(sys.maxint)
|
||
boundary = ('=' * 15) + (_fmt % token) + '=='
|
||
if text is None:
|
||
return boundary
|
||
b = boundary
|
||
counter = 0
|
||
while True:
|
||
cre = re.compile('^--' + re.escape(b) + '(--)?$', re.MULTILINE)
|
||
if not cre.search(text):
|
||
break
|
||
b = boundary + '.' + str(counter)
|
||
counter += 1
|
||
return b
|