def renderHTTP(self, ctx):
        request = IRequest(ctx)

        # FIXME: This is for testing with litmus; comment out when not in use
        litmus = request.headers.getRawHeaders("x-litmus")
        if litmus: log.msg("*** Litmus test: %s ***" % (litmus,))

        # FIXME: Ideally, this logging would be in Resource, not here
        protocol = "HTTP/%s.%s" % request.clientproto
        log.msg("%s %s %s"
                % (request.method, urllib.unquote(request.uri), protocol))

        #
        # Check the If-Match and If-None-Match headers
        #
        # FIXME: RFC 2068 (HTTP) section 14.25, and 14.26 say:
        #   If the request would, without the If-Match header field, result in
        #   anything other than a 2xx status, then the If-Match header MUST be
        #   ignored.
        # This implies that we have to attempt the request, check the status,
        # and act on the If-Match header only if the request resulted in an
        # error.  That seems rather expensive.  Furthermore, for many
        # operations, such as PUT, COPY, MOVE and DELETE, we'd have to back out
        # the successful operation first.  Ouch!
        #
        # FIXME: This probably belongs in Resource, but that would require
        # adding an etag property to its interface.
        match = request.headers.getHeader("if-match")
        if match:
            self.fp.restat(False)

            if match == ("*",):
                if not self.fp.exists(): return responsecode.PRECONDITION_FAILED
            else:
                my_etag = self.etag
                if my_etag is None: return responsecode.PRECONDITION_FAILED
                for etag in match:
                    if etag.match(my_etag, True): break
                else:
                    return responsecode.PRECONDITION_FAILED

        match = request.headers.getHeader("if-none-match")
        if match:
            # FIXME: For GET, we should respond with NOT_MODIFIED and set some
            # cache headers.  See RFC 2066 (HTTP) section 14.26.

            self.fp.restat(False)

            if match == ("*",):
                if self.fp.exists(): return responsecode.PRECONDITION_FAILED
            else:
                my_etag = self.etag
                if my_etag is not None:
                    for etag in match:
                        if etag.match(my_etag, True):
                            return responsecode.PRECONDITION_FAILED

        #
        # Call super and append DAV header
        #
        response = File.renderHTTP(self, ctx)
        response = setHeaderInResponse(response,
                                       "dav",
                                       self.davComplianceClasses)
        return response