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350 lines (302 loc) · 12 KB
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"""Support for building partial DOM trees from SAX events."""
import xml.sax
import xml.sax.handler
START_ELEMENT = "START_ELEMENT"
END_ELEMENT = "END_ELEMENT"
COMMENT = "COMMENT"
START_DOCUMENT = "START_DOCUMENT"
END_DOCUMENT = "END_DOCUMENT"
PROCESSING_INSTRUCTION = "PROCESSING_INSTRUCTION"
IGNORABLE_WHITESPACE = "IGNORABLE_WHITESPACE"
CHARACTERS = "CHARACTERS"
class PullDOM(xml.sax.ContentHandler):
"""Content handler which turns SAX events into pull parser events.
The nodes are created, but they are not added to the tree."""
_locator = None
document = None
def __init__(self, documentFactory=None):
from xml.dom import XML_NAMESPACE
self.documentFactory = documentFactory
self.firstEvent = [None, None]
self.lastEvent = self.firstEvent
self.elementStack = []
self.push = self.elementStack.append
try:
self.pop = self.elementStack.pop
except AttributeError:
# use class' pop instead
pass
self._ns_contexts = [{XML_NAMESPACE:'xml'}] # contains uri -> prefix dicts
self._current_context = self._ns_contexts[-1]
self.pending_events = []
def pop(self):
result = self.elementStack[-1]
del self.elementStack[-1]
return result
def setDocumentLocator(self, locator):
self._locator = locator
def startPrefixMapping(self, prefix, uri):
if not hasattr(self, '_xmlns_attrs'):
self._xmlns_attrs = []
self._xmlns_attrs.append((prefix or 'xmlns', uri))
self._ns_contexts.append(self._current_context.copy())
self._current_context[uri] = prefix or None
def endPrefixMapping(self, prefix):
self._current_context = self._ns_contexts.pop()
def startElementNS(self, name, tagName , attrs):
# Retrieve xml namespace declaration attributes.
xmlns_uri = 'http://www.w3.org/2000/xmlns/'
xmlns_attrs = getattr(self, '_xmlns_attrs', None)
if xmlns_attrs is not None:
for aname, value in xmlns_attrs:
attrs._attrs[(xmlns_uri, aname)] = value
self._xmlns_attrs = []
uri, localname = name
if uri:
# When using namespaces, the reader may or may not
# provide us with the original name. If not, create
# *a* valid tagName from the current context.
if tagName is None:
prefix = self._current_context[uri]
if prefix:
tagName = prefix + ":" + localname
else:
tagName = localname
if self.document:
node = self.document.createElementNS(uri, tagName)
else:
node = self.buildDocument(uri, tagName)
else:
# When the tagname is not prefixed, it just appears as
# localname
if self.document:
node = self.document.createElement(localname)
else:
node = self.buildDocument(None, localname)
for aname,value in attrs.items():
a_uri, a_localname = aname
if a_uri == xmlns_uri:
if a_localname == 'xmlns':
qname = a_localname
else:
qname = 'xmlns:' + a_localname
attr = self.document.createAttributeNS(a_uri, qname)
node.setAttributeNodeNS(attr)
elif a_uri:
prefix = self._current_context[a_uri]
if prefix:
qname = prefix + ":" + a_localname
else:
qname = a_localname
attr = self.document.createAttributeNS(a_uri, qname)
node.setAttributeNodeNS(attr)
else:
attr = self.document.createAttribute(a_localname)
node.setAttributeNode(attr)
attr.value = value
self.lastEvent[1] = [(START_ELEMENT, node), None]
self.lastEvent = self.lastEvent[1]
self.push(node)
def endElementNS(self, name, tagName):
self.lastEvent[1] = [(END_ELEMENT, self.pop()), None]
self.lastEvent = self.lastEvent[1]
def startElement(self, name, attrs):
if self.document:
node = self.document.createElement(name)
else:
node = self.buildDocument(None, name)
for aname,value in attrs.items():
attr = self.document.createAttribute(aname)
attr.value = value
node.setAttributeNode(attr)
self.lastEvent[1] = [(START_ELEMENT, node), None]
self.lastEvent = self.lastEvent[1]
self.push(node)
def endElement(self, name):
self.lastEvent[1] = [(END_ELEMENT, self.pop()), None]
self.lastEvent = self.lastEvent[1]
def comment(self, s):
if self.document:
node = self.document.createComment(s)
self.lastEvent[1] = [(COMMENT, node), None]
self.lastEvent = self.lastEvent[1]
else:
event = [(COMMENT, s), None]
self.pending_events.append(event)
def processingInstruction(self, target, data):
if self.document:
node = self.document.createProcessingInstruction(target, data)
self.lastEvent[1] = [(PROCESSING_INSTRUCTION, node), None]
self.lastEvent = self.lastEvent[1]
else:
event = [(PROCESSING_INSTRUCTION, target, data), None]
self.pending_events.append(event)
def ignorableWhitespace(self, chars):
node = self.document.createTextNode(chars)
self.lastEvent[1] = [(IGNORABLE_WHITESPACE, node), None]
self.lastEvent = self.lastEvent[1]
def characters(self, chars):
node = self.document.createTextNode(chars)
self.lastEvent[1] = [(CHARACTERS, node), None]
self.lastEvent = self.lastEvent[1]
def startDocument(self):
if self.documentFactory is None:
import xml.dom.minidom
self.documentFactory = xml.dom.minidom.Document.implementation
def buildDocument(self, uri, tagname):
# Can't do that in startDocument, since we need the tagname
# XXX: obtain DocumentType
node = self.documentFactory.createDocument(uri, tagname, None)
self.document = node
self.lastEvent[1] = [(START_DOCUMENT, node), None]
self.lastEvent = self.lastEvent[1]
self.push(node)
# Put everything we have seen so far into the document
for e in self.pending_events:
if e[0][0] == PROCESSING_INSTRUCTION:
_,target,data = e[0]
n = self.document.createProcessingInstruction(target, data)
e[0] = (PROCESSING_INSTRUCTION, n)
elif e[0][0] == COMMENT:
n = self.document.createComment(e[0][1])
e[0] = (COMMENT, n)
else:
raise AssertionError("Unknown pending event ",e[0][0])
self.lastEvent[1] = e
self.lastEvent = e
self.pending_events = None
return node.firstChild
def endDocument(self):
self.lastEvent[1] = [(END_DOCUMENT, self.document), None]
self.pop()
def clear(self):
"clear(): Explicitly release parsing structures"
self.document = None
class ErrorHandler:
def warning(self, exception):
print(exception)
def error(self, exception):
raise exception
def fatalError(self, exception):
raise exception
class DOMEventStream:
"""Stream of the pull parser events."""
def __init__(self, stream, parser, bufsize):
self.stream = stream
self.parser = parser
self.bufsize = bufsize
if not hasattr(self.parser, 'feed'):
self.getEvent = self._slurp
self.reset()
def reset(self):
"""Discard unread events and prepare for parsing a new document."""
self.pulldom = PullDOM()
# This content handler relies on namespace support
self.parser.setFeature(xml.sax.handler.feature_namespaces, 1)
self.parser.setContentHandler(self.pulldom)
def __next__(self):
rc = self.getEvent()
if rc:
return rc
raise StopIteration
def __iter__(self):
return self
def expandNode(self, node):
"""Expand all children of the node into the node."""
event = self.getEvent()
parents = [node]
while event:
token, cur_node = event
if cur_node is node:
return
if token != END_ELEMENT:
parents[-1].appendChild(cur_node)
if token == START_ELEMENT:
parents.append(cur_node)
elif token == END_ELEMENT:
del parents[-1]
event = self.getEvent()
def getEvent(self):
"""Return the next (event, node) tuple, or None at the end."""
# use IncrementalParser interface, so we get the desired
# pull effect
if not self.pulldom.firstEvent[1]:
self.pulldom.lastEvent = self.pulldom.firstEvent
while not self.pulldom.firstEvent[1]:
buf = self.stream.read(self.bufsize)
if not buf:
self.parser.close()
return None
self.parser.feed(buf)
rc = self.pulldom.firstEvent[1][0]
self.pulldom.firstEvent[1] = self.pulldom.firstEvent[1][1]
return rc
def _slurp(self):
""" Fallback replacement for getEvent() using the
standard SAX2 interface, which means we slurp the
SAX events into memory (no performance gain, but
we are compatible to all SAX parsers).
"""
self.parser.parse(self.stream)
self.getEvent = self._emit
return self._emit()
def _emit(self):
""" Fallback replacement for getEvent() that emits
the events that _slurp() read previously.
"""
rc = self.pulldom.firstEvent[1][0]
self.pulldom.firstEvent[1] = self.pulldom.firstEvent[1][1]
return rc
def clear(self):
"""Release the parser and the document."""
self.pulldom.clear()
del self.pulldom
self.parser = None
self.stream = None
class SAX2DOM(PullDOM):
"""PullDOM which also adds every created node to the tree."""
def startElementNS(self, name, tagName , attrs):
PullDOM.startElementNS(self, name, tagName, attrs)
curNode = self.elementStack[-1]
parentNode = self.elementStack[-2]
parentNode.appendChild(curNode)
def startElement(self, name, attrs):
PullDOM.startElement(self, name, attrs)
curNode = self.elementStack[-1]
parentNode = self.elementStack[-2]
parentNode.appendChild(curNode)
def processingInstruction(self, target, data):
PullDOM.processingInstruction(self, target, data)
node = self.lastEvent[0][1]
parentNode = self.elementStack[-1]
parentNode.appendChild(node)
def ignorableWhitespace(self, chars):
PullDOM.ignorableWhitespace(self, chars)
node = self.lastEvent[0][1]
parentNode = self.elementStack[-1]
parentNode.appendChild(node)
def characters(self, chars):
PullDOM.characters(self, chars)
node = self.lastEvent[0][1]
parentNode = self.elementStack[-1]
parentNode.appendChild(node)
default_bufsize = (2 ** 14) - 20
def parse(stream_or_string, parser=None, bufsize=None):
"""Return a DOMEventStream for the given file name or file object."""
if bufsize is None:
bufsize = default_bufsize
if isinstance(stream_or_string, str):
stream = open(stream_or_string, 'rb')
else:
stream = stream_or_string
if not parser:
parser = xml.sax.make_parser()
return DOMEventStream(stream, parser, bufsize)
def parseString(string, parser=None):
"""Return a DOMEventStream for the given string."""
from io import StringIO
bufsize = len(string)
buf = StringIO(string)
if not parser:
parser = xml.sax.make_parser()
return DOMEventStream(buf, parser, bufsize)
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