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# Copyright (C) 2021 Philipp Hörist <philipp AT hoerist.com>
#
# This file is part of nbxmpp.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 3
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; If not, see <http://www.gnu.org/licenses/>.
from __future__ import annotations
from copy import deepcopy
from typing import Any
from typing import Optional
from typing import Callable
from typing import Union
from typing import cast
import logging
from lxml import etree
from lxml.etree import ElementBase
from nbxmpp import types
from nbxmpp.elements import ElementLookup
from nbxmpp.util import Observable
from nbxmpp.util import LogAdapter
DispatchCallable = Callable[[ElementBase], None]
log = logging.getLogger('nbxmpp.parser')
PARSER_SETTINGS = {
'load_dtd': False,
'dtd_validation': False,
'no_network': True,
'recover': False,
'resolve_entities': False,
'remove_comments': True,
'remove_pis': True,
}
class BaseParser(Observable):
def __init__(self, log_context: str) -> None:
Observable.__init__(self, log)
self._log = LogAdapter(log, {'context': log_context})
self._destroyed = False
self._parser = self._create_parser()
def _create_parser(self) -> Any:
raise NotImplementedError
def feed(self, data: str) -> None:
raise NotImplementedError
def _cleanup(self) -> None:
raise NotImplementedError
def destroy(self) -> None:
self.remove_subscriptions()
self._destroyed = True
self._cleanup()
class TCPStreamParser(BaseParser):
_dispatch_depth = 1
def __init__(self, log_context: str):
BaseParser.__init__(self, log_context)
self._depth = 0
self._root = None
def get_root(self) -> ElementBase:
return self._root
def get_tree(self) -> Any:
return self._root.getroottree()
def _create_parser(self) -> etree.XMLPullParser:
parser = etree.XMLPullParser(events=['start', 'end'], **PARSER_SETTINGS)
parser.set_element_class_lookup(ElementLookup)
return parser
def feed(self, data: Union[str, bytes]):
if self._destroyed:
raise ValueError('Parser is destroyed')
self._parser.feed(data)
for action, element in list(self._parser.read_events()):
if action == 'start':
if self._depth == 0:
element = self._cleanup_stream_start(element)
self.notify('stream-start', element)
self._depth += 1
elif action == 'end':
self._depth -= 1
if self._depth == self._dispatch_depth:
self.notify('element', element)
self._free_elements(element)
if self._depth == 0:
self._stream_end = True
self.notify('stream-end', element)
self.destroy()
break
def _free_elements(self, element: ElementBase):
'''
XMLPullParser stores the whole tree in memory by default.
this deletes all previous siblings from the tree and frees the memory
'''
if element.getprevious() is not None:
del element.getparent()[0]
def _cleanup_stream_start(self, element: ElementBase):
'''
The first data contains often also the stream features. So the first
element lxml yields already has a features child. This removes it so it
creates no confusion.
'''
element = deepcopy(element)
for child in list(element):
element.remove(child)
return element
def _cleanup(self):
try:
self._root = self._parser.close()
except Exception:
pass
self._parser = cast(etree.XMLPullParser, None)
class WebsocketParser(BaseParser):
def __init__(self, log_context: str):
BaseParser.__init__(self, log_context)
def _create_parser(self) -> etree.XMLPullParser:
parser = etree.XMLParser(**PARSER_SETTINGS)
parser.set_element_class_lookup(ElementLookup)
return parser
def feed(self, data: str) -> None:
if self._destroyed:
raise ValueError('Parser is destroyed')
element = etree.fromstring(data, self._parser)
if isinstance(element, types.Open):
self.notify('stream-start', element)
elif isinstance(element, types.Close):
self.notify('stream-end', element)
else:
self.notify('element', element)
def _cleanup(self) -> None:
self._parser = cast(etree.XMLParser, None)
def get_stream_parser(websocket: bool, log_context: Optional[str] = None) -> BaseParser:
if websocket:
return WebsocketParser(log_context or '')
return TCPStreamParser(log_context or '')
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