380 lines
15 KiB
Python
380 lines
15 KiB
Python
# -*- coding: iso-8859-1 -*-
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""" A SAX2 driver for libxml2, on top of it's XmlReader API
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USAGE
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# put this file (drv_libxml2.py) in PYTHONPATH
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import xml.sax
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reader = xml.sax.make_parser(["drv_libxml2"])
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# ...and the rest is standard python sax.
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CAVEATS
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- Lexical handlers are supported, except for start/endEntity
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(waiting for XmlReader.ResolveEntity) and start/endDTD
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- Error callbacks are not exactly synchronous, they tend
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to be invoked before the corresponding content callback,
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because the underlying reader interface parses
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data by chunks of 512 bytes
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TODO
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- search for TODO
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- some ErrorHandler events (warning)
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- some ContentHandler events (setDocumentLocator, skippedEntity)
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- EntityResolver (using libxml2.?)
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- DTDHandler (if/when libxml2 exposes such node types)
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- DeclHandler (if/when libxml2 exposes such node types)
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- property_xml_string?
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- feature_string_interning?
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- Incremental parser
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- additional performance tuning:
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- one might cache callbacks to avoid some name lookups
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- one might implement a smarter way to pass attributes to startElement
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(some kind of lazy evaluation?)
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- there might be room for improvement in start/endPrefixMapping
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- other?
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"""
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__author__ = "Stéphane Bidoul <sbi@skynet.be>"
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__version__ = "0.3"
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import sys
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import codecs
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if sys.version_info[0] < 3:
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__author__ = codecs.unicode_escape_decode(__author__)[0]
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StringTypes = (str, unicode)
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# libxml2 returns strings as UTF8
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_decoder = codecs.lookup("utf8")[1]
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def _d(s):
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if s is None:
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return s
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else:
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return _decoder(s)[0]
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else:
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StringTypes = str
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# s is Unicode `str` already
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def _d(s):
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return s
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from xml.sax._exceptions import *
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from xml.sax import xmlreader, saxutils
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from xml.sax.handler import \
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feature_namespaces, \
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feature_namespace_prefixes, \
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feature_string_interning, \
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feature_validation, \
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feature_external_ges, \
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feature_external_pes, \
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property_lexical_handler, \
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property_declaration_handler, \
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property_dom_node, \
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property_xml_string
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try:
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import libxml2
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except ImportError:
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raise SAXReaderNotAvailable("libxml2 not available: " \
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"import error was: %s" % sys.exc_info()[1])
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class Locator(xmlreader.Locator):
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"""SAX Locator adapter for libxml2.xmlTextReaderLocator"""
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def __init__(self,locator):
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self.__locator = locator
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def getColumnNumber(self):
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"Return the column number where the current event ends."
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return -1
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def getLineNumber(self):
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"Return the line number where the current event ends."
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return self.__locator.LineNumber()
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def getPublicId(self):
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"Return the public identifier for the current event."
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return None
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def getSystemId(self):
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"Return the system identifier for the current event."
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return self.__locator.BaseURI()
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class LibXml2Reader(xmlreader.XMLReader):
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def __init__(self):
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xmlreader.XMLReader.__init__(self)
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# features
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self.__ns = 0
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self.__nspfx = 0
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self.__validate = 0
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self.__extparams = 1
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# parsing flag
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self.__parsing = 0
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# additional handlers
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self.__lex_handler = None
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self.__decl_handler = None
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# error messages accumulator
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self.__errors = None
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def _errorHandler(self,arg,msg,severity,locator):
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if self.__errors is None:
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self.__errors = []
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self.__errors.append((severity,
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SAXParseException(msg,None,
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Locator(locator))))
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def _reportErrors(self,fatal):
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for severity,exception in self.__errors:
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if severity in (libxml2.PARSER_SEVERITY_VALIDITY_WARNING,
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libxml2.PARSER_SEVERITY_WARNING):
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self._err_handler.warning(exception)
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else:
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# when fatal is set, the parse will stop;
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# we consider that the last error reported
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# is the fatal one.
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if fatal and exception is self.__errors[-1][1]:
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self._err_handler.fatalError(exception)
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else:
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self._err_handler.error(exception)
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self.__errors = None
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def parse(self, source):
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self.__parsing = 1
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try:
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# prepare source and create reader
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if isinstance(source, StringTypes):
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reader = libxml2.newTextReaderFilename(source)
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else:
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source = saxutils.prepare_input_source(source)
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input = libxml2.inputBuffer(source.getByteStream())
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reader = input.newTextReader(source.getSystemId())
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reader.SetErrorHandler(self._errorHandler,None)
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# configure reader
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if self.__extparams:
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reader.SetParserProp(libxml2.PARSER_LOADDTD,1)
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reader.SetParserProp(libxml2.PARSER_DEFAULTATTRS,1)
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reader.SetParserProp(libxml2.PARSER_SUBST_ENTITIES,1)
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reader.SetParserProp(libxml2.PARSER_VALIDATE,self.__validate)
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else:
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reader.SetParserProp(libxml2.PARSER_LOADDTD, 0)
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# we reuse attribute maps (for a slight performance gain)
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if self.__ns:
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attributesNSImpl = xmlreader.AttributesNSImpl({},{})
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else:
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attributesImpl = xmlreader.AttributesImpl({})
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# prefixes to pop (for endPrefixMapping)
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prefixes = []
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# start loop
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self._cont_handler.startDocument()
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while 1:
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r = reader.Read()
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# check for errors
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if r == 1:
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if not self.__errors is None:
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self._reportErrors(0)
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elif r == 0:
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if not self.__errors is None:
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self._reportErrors(0)
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break # end of parse
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else:
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if not self.__errors is None:
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self._reportErrors(1)
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else:
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self._err_handler.fatalError(\
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SAXException("Read failed (no details available)"))
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break # fatal parse error
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# get node type
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nodeType = reader.NodeType()
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# Element
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if nodeType == 1:
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if self.__ns:
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eltName = (_d(reader.NamespaceUri()),\
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_d(reader.LocalName()))
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eltQName = _d(reader.Name())
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attributesNSImpl._attrs = attrs = {}
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attributesNSImpl._qnames = qnames = {}
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newPrefixes = []
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while reader.MoveToNextAttribute():
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qname = _d(reader.Name())
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value = _d(reader.Value())
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if qname.startswith("xmlns"):
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if len(qname) > 5:
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newPrefix = qname[6:]
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else:
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newPrefix = None
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newPrefixes.append(newPrefix)
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self._cont_handler.startPrefixMapping(\
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newPrefix,value)
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if not self.__nspfx:
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continue # don't report xmlns attribute
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attName = (_d(reader.NamespaceUri()),
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_d(reader.LocalName()))
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qnames[attName] = qname
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attrs[attName] = value
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reader.MoveToElement()
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self._cont_handler.startElementNS( \
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eltName,eltQName,attributesNSImpl)
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if reader.IsEmptyElement():
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self._cont_handler.endElementNS(eltName,eltQName)
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for newPrefix in newPrefixes:
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self._cont_handler.endPrefixMapping(newPrefix)
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else:
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prefixes.append(newPrefixes)
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else:
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eltName = _d(reader.Name())
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attributesImpl._attrs = attrs = {}
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while reader.MoveToNextAttribute():
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attName = _d(reader.Name())
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attrs[attName] = _d(reader.Value())
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reader.MoveToElement()
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self._cont_handler.startElement( \
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eltName,attributesImpl)
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if reader.IsEmptyElement():
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self._cont_handler.endElement(eltName)
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# EndElement
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elif nodeType == 15:
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if self.__ns:
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self._cont_handler.endElementNS( \
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(_d(reader.NamespaceUri()),_d(reader.LocalName())),
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_d(reader.Name()))
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for prefix in prefixes.pop():
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self._cont_handler.endPrefixMapping(prefix)
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else:
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self._cont_handler.endElement(_d(reader.Name()))
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# Text
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elif nodeType == 3:
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self._cont_handler.characters(_d(reader.Value()))
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# Whitespace
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elif nodeType == 13:
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self._cont_handler.ignorableWhitespace(_d(reader.Value()))
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# SignificantWhitespace
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elif nodeType == 14:
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self._cont_handler.characters(_d(reader.Value()))
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# CDATA
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elif nodeType == 4:
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if not self.__lex_handler is None:
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self.__lex_handler.startCDATA()
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self._cont_handler.characters(_d(reader.Value()))
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if not self.__lex_handler is None:
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self.__lex_handler.endCDATA()
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# EntityReference
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elif nodeType == 5:
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if not self.__lex_handler is None:
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self.startEntity(_d(reader.Name()))
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reader.ResolveEntity()
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# EndEntity
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elif nodeType == 16:
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if not self.__lex_handler is None:
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self.endEntity(_d(reader.Name()))
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# ProcessingInstruction
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elif nodeType == 7:
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self._cont_handler.processingInstruction( \
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_d(reader.Name()),_d(reader.Value()))
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# Comment
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elif nodeType == 8:
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if not self.__lex_handler is None:
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self.__lex_handler.comment(_d(reader.Value()))
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# DocumentType
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elif nodeType == 10:
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#if not self.__lex_handler is None:
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# self.__lex_handler.startDTD()
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pass # TODO (how to detect endDTD? on first non-dtd event?)
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# XmlDeclaration
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elif nodeType == 17:
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pass # TODO
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# Entity
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elif nodeType == 6:
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pass # TODO (entity decl)
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# Notation (decl)
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elif nodeType == 12:
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pass # TODO
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# Attribute (never in this loop)
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#elif nodeType == 2:
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# pass
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# Document (not exposed)
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#elif nodeType == 9:
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# pass
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# DocumentFragment (never returned by XmlReader)
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#elif nodeType == 11:
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# pass
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# None
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#elif nodeType == 0:
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# pass
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# -
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else:
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raise SAXException("Unexpected node type %d" % nodeType)
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if r == 0:
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self._cont_handler.endDocument()
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reader.Close()
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finally:
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self.__parsing = 0
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def setDTDHandler(self, handler):
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# TODO (when supported, the inherited method works just fine)
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raise SAXNotSupportedException("DTDHandler not supported")
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def setEntityResolver(self, resolver):
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# TODO (when supported, the inherited method works just fine)
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raise SAXNotSupportedException("EntityResolver not supported")
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def getFeature(self, name):
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if name == feature_namespaces:
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return self.__ns
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elif name == feature_namespace_prefixes:
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return self.__nspfx
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elif name == feature_validation:
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return self.__validate
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elif name == feature_external_ges:
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return 1 # TODO (does that relate to PARSER_LOADDTD)?
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elif name == feature_external_pes:
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return self.__extparams
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else:
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raise SAXNotRecognizedException("Feature '%s' not recognized" % \
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name)
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def setFeature(self, name, state):
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if self.__parsing:
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raise SAXNotSupportedException("Cannot set feature %s " \
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"while parsing" % name)
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if name == feature_namespaces:
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self.__ns = state
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elif name == feature_namespace_prefixes:
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self.__nspfx = state
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elif name == feature_validation:
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self.__validate = state
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elif name == feature_external_ges:
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if state == 0:
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# TODO (does that relate to PARSER_LOADDTD)?
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raise SAXNotSupportedException("Feature '%s' not supported" % \
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name)
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elif name == feature_external_pes:
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self.__extparams = state
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else:
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raise SAXNotRecognizedException("Feature '%s' not recognized" % \
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name)
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def getProperty(self, name):
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if name == property_lexical_handler:
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return self.__lex_handler
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elif name == property_declaration_handler:
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return self.__decl_handler
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else:
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raise SAXNotRecognizedException("Property '%s' not recognized" % \
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name)
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def setProperty(self, name, value):
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if name == property_lexical_handler:
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self.__lex_handler = value
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elif name == property_declaration_handler:
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# TODO: remove if/when libxml2 supports dtd events
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raise SAXNotSupportedException("Property '%s' not supported" % \
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name)
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self.__decl_handler = value
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else:
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raise SAXNotRecognizedException("Property '%s' not recognized" % \
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name)
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def create_parser():
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return LibXml2Reader()
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