xml/sax/saxutils.py

"""\
A library of useful helper classes to the SAX classes, for the
convenience of application and driver writers.
"""

import os, urlparse, urllib, types
import handler
import xmlreader

try:
    _StringTypes = [types.StringType, types.UnicodeType]
except AttributeError:
    _StringTypes = [types.StringType]

# See whether the xmlcharrefreplace error handler is

# supported

try:
    from codecs import xmlcharrefreplace_errors
    _error_handling = "xmlcharrefreplace"
    del xmlcharrefreplace_errors
except ImportError:
    _error_handling = "strict"

def __dict_replace(s, d):
    """Replace substrings of a string using a dictionary."""
    for key, value in d.items():
        s = s.replace(key, value)
    return s

def escape(data, entities={}):
    """Escape &, <, and > in a string of data.

    You can escape other strings of data by passing a dictionary as
    the optional entities parameter.  The keys and values must all be
    strings; each key will be replaced with its corresponding value.
    """

    # must do ampersand first

    data = data.replace("&", "&amp;")
    data = data.replace(">", "&gt;")
    data = data.replace("<", "&lt;")
    if entities:
        data = __dict_replace(data, entities)
    return data

def unescape(data, entities={}):
    """Unescape &amp;, &lt;, and &gt; in a string of data.

    You can unescape other strings of data by passing a dictionary as
    the optional entities parameter.  The keys and values must all be
    strings; each key will be replaced with its corresponding value.
    """
    data = data.replace("&lt;", "<")
    data = data.replace("&gt;", ">")
    if entities:
        data = __dict_replace(data, entities)
    # must do ampersand last

    return data.replace("&amp;", "&")

def quoteattr(data, entities={}):
    """Escape and quote an attribute value.

    Escape &, <, and > in a string of data, then quote it for use as
    an attribute value.  The \" character will be escaped as well, if
    necessary.

    You can escape other strings of data by passing a dictionary as
    the optional entities parameter.  The keys and values must all be
    strings; each key will be replaced with its corresponding value.
    """
    entities = entities.copy()
    entities.update({'\n': '&#10;', '\r': '&#13;', '\t':'&#9;'})
    data = escape(data, entities)
    if '"' in data:
        if "'" in data:
            data = '"%s"' % data.replace('"', "&quot;")
        else:
            data = "'%s'" % data
    else:
        data = '"%s"' % data
    return data


class XMLGenerator(handler.ContentHandler):

    def __init__(self, out=None, encoding="iso-8859-1"):
        if out is None:
            import sys
            out = sys.stdout
        handler.ContentHandler.__init__(self)
        self._out = out
        self._ns_contexts = [{}] # contains uri -> prefix dicts

        self._current_context = self._ns_contexts[-1]
        self._undeclared_ns_maps = []
        self._encoding = encoding

    def _write(self, text):
        if isinstance(text, str):
            self._out.write(text)
        else:
            self._out.write(text.encode(self._encoding, _error_handling))

    def _qname(self, name):
        """Builds a qualified name from a (ns_url, localname) pair"""
        if name[0]:
            # Per http://www.w3.org/XML/1998/namespace, The 'xml' prefix is

            # bound by definition to http://www.w3.org/XML/1998/namespace.  It

            # does not need to be declared and will not usually be found in

            # self._current_context.

            if 'http://www.w3.org/XML/1998/namespace' == name[0]:
                return 'xml:' + name[1]
            # The name is in a non-empty namespace

            prefix = self._current_context[name[0]]
            if prefix:
                # If it is not the default namespace, prepend the prefix

                return prefix + ":" + name[1]
        # Return the unqualified name

        return name[1]

    # ContentHandler methods


    def startDocument(self):
        self._write('<?xml version="1.0" encoding="%s"?>\n' %
                        self._encoding)

    def startPrefixMapping(self, prefix, uri):
        self._ns_contexts.append(self._current_context.copy())
        self._current_context[uri] = prefix
        self._undeclared_ns_maps.append((prefix, uri))

    def endPrefixMapping(self, prefix):
        self._current_context = self._ns_contexts[-1]
        del self._ns_contexts[-1]

    def startElement(self, name, attrs):
        self._write('<' + name)
        for (name, value) in attrs.items():
            self._write(' %s=%s' % (name, quoteattr(value)))
        self._write('>')

    def endElement(self, name):
        self._write('</%s>' % name)

    def startElementNS(self, name, qname, attrs):
        self._write('<' + self._qname(name))

        for prefix, uri in self._undeclared_ns_maps:
            if prefix:
                self._out.write(' xmlns:%s="%s"' % (prefix, uri))
            else:
                self._out.write(' xmlns="%s"' % uri)
        self._undeclared_ns_maps = []

        for (name, value) in attrs.items():
            self._write(' %s=%s' % (self._qname(name), quoteattr(value)))
        self._write('>')

    def endElementNS(self, name, qname):
        self._write('</%s>' % self._qname(name))

    def characters(self, content):
        self._write(escape(content))

    def ignorableWhitespace(self, content):
        self._write(content)

    def processingInstruction(self, target, data):
        self._write('<?%s %s?>' % (target, data))


class XMLFilterBase(xmlreader.XMLReader):
    """This class is designed to sit between an XMLReader and the
    client application's event handlers.  By default, it does nothing
    but pass requests up to the reader and events on to the handlers
    unmodified, but subclasses can override specific methods to modify
    the event stream or the configuration requests as they pass
    through."""

    def __init__(self, parent = None):
        xmlreader.XMLReader.__init__(self)
        self._parent = parent

    # ErrorHandler methods


    def error(self, exception):
        self._err_handler.error(exception)

    def fatalError(self, exception):
        self._err_handler.fatalError(exception)

    def warning(self, exception):
        self._err_handler.warning(exception)

    # ContentHandler methods


    def setDocumentLocator(self, locator):
        self._cont_handler.setDocumentLocator(locator)

    def startDocument(self):
        self._cont_handler.startDocument()

    def endDocument(self):
        self._cont_handler.endDocument()

    def startPrefixMapping(self, prefix, uri):
        self._cont_handler.startPrefixMapping(prefix, uri)

    def endPrefixMapping(self, prefix):
        self._cont_handler.endPrefixMapping(prefix)

    def startElement(self, name, attrs):
        self._cont_handler.startElement(name, attrs)

    def endElement(self, name):
        self._cont_handler.endElement(name)

    def startElementNS(self, name, qname, attrs):
        self._cont_handler.startElementNS(name, qname, attrs)

    def endElementNS(self, name, qname):
        self._cont_handler.endElementNS(name, qname)

    def characters(self, content):
        self._cont_handler.characters(content)

    def ignorableWhitespace(self, chars):
        self._cont_handler.ignorableWhitespace(chars)

    def processingInstruction(self, target, data):
        self._cont_handler.processingInstruction(target, data)

    def skippedEntity(self, name):
        self._cont_handler.skippedEntity(name)

    # DTDHandler methods


    def notationDecl(self, name, publicId, systemId):
        self._dtd_handler.notationDecl(name, publicId, systemId)

    def unparsedEntityDecl(self, name, publicId, systemId, ndata):
        self._dtd_handler.unparsedEntityDecl(name, publicId, systemId, ndata)

    # EntityResolver methods


    def resolveEntity(self, publicId, systemId):
        return self._ent_handler.resolveEntity(publicId, systemId)

    # XMLReader methods


    def parse(self, source):
        self._parent.setContentHandler(self)
        self._parent.setErrorHandler(self)
        self._parent.setEntityResolver(self)
        self._parent.setDTDHandler(self)
        self._parent.parse(source)

    def setLocale(self, locale):
        self._parent.setLocale(locale)

    def getFeature(self, name):
        return self._parent.getFeature(name)

    def setFeature(self, name, state):
        self._parent.setFeature(name, state)

    def getProperty(self, name):
        return self._parent.getProperty(name)

    def setProperty(self, name, value):
        self._parent.setProperty(name, value)

    # XMLFilter methods


    def getParent(self):
        return self._parent

    def setParent(self, parent):
        self._parent = parent

# --- Utility functions


def prepare_input_source(source, base = ""):
    """This function takes an InputSource and an optional base URL and
    returns a fully resolved InputSource object ready for reading."""

    if type(source) in _StringTypes:
        source = xmlreader.InputSource(source)
    elif hasattr(source, "read"):
        f = source
        source = xmlreader.InputSource()
        source.setByteStream(f)
        if hasattr(f, "name"):
            source.setSystemId(f.name)

    if source.getByteStream() is None:
        sysid = source.getSystemId()
        basehead = os.path.dirname(os.path.normpath(base))
        sysidfilename = os.path.join(basehead, sysid)
        if os.path.isfile(sysidfilename):
            source.setSystemId(sysidfilename)
            f = open(sysidfilename, "rb")
        else:
            source.setSystemId(urlparse.urljoin(base, sysid))
            f = urllib.urlopen(source.getSystemId())

        source.setByteStream(f)

    return source