static VALUE parse_file(VALUE klass, VALUE filename, VALUE encoding)
{
  htmlParserCtxtPtr ctxt = htmlCreateFileParserCtxt(
      StringValueCStr(filename),
      StringValueCStr(encoding)
  );
  return Data_Wrap_Struct(klass, NULL, deallocate, ctxt);
}

static VALUE
parse_memory(VALUE klass, VALUE data, VALUE encoding)
{
    htmlParserCtxtPtr ctxt;

    if (NIL_P(data))
        rb_raise(rb_eArgError, "data cannot be nil");
    if (!(int)RSTRING_LEN(data))
        rb_raise(rb_eRuntimeError, "data cannot be empty");

    ctxt = htmlCreateMemoryParserCtxt(StringValuePtr(data),
                                      (int)RSTRING_LEN(data));
    if (ctxt->sax) {
        xmlFree(ctxt->sax);
        ctxt->sax = NULL;
    }

    if (RTEST(encoding)) {
        xmlCharEncodingHandlerPtr enc = xmlFindCharEncodingHandler(StringValueCStr(encoding));
        if (enc != NULL) {
            xmlSwitchToEncoding(ctxt, enc);
            if (ctxt->errNo == XML_ERR_UNSUPPORTED_ENCODING) {
                rb_raise(rb_eRuntimeError, "Unsupported encoding %s",
                         StringValueCStr(encoding));
            }
        }
    }

    return Data_Wrap_Struct(klass, NULL, deallocate, ctxt);
}

# File lib/nokogiri/html/sax/parser_context.rb, line 9
def self.new thing, encoding = 'UTF-8'
  [:read, :close].all? { |x| thing.respond_to?(x) } ?  super :
    memory(thing, encoding)
end

static VALUE
parse_with(VALUE self, VALUE sax_handler)
{
    htmlParserCtxtPtr ctxt;
    htmlSAXHandlerPtr sax;

    if (!rb_obj_is_kind_of(sax_handler, cNokogiriXmlSaxParser))
        rb_raise(rb_eArgError, "argument must be a Nokogiri::XML::SAX::Parser");

    Data_Get_Struct(self, htmlParserCtxt, ctxt);
    Data_Get_Struct(sax_handler, htmlSAXHandler, sax);

    /* Free the sax handler since we'll assign our own */
    if (ctxt->sax && ctxt->sax != (xmlSAXHandlerPtr)&xmlDefaultSAXHandler)
        xmlFree(ctxt->sax);

    ctxt->sax = sax;
    ctxt->userData = (void *)NOKOGIRI_SAX_TUPLE_NEW(ctxt, sax_handler);

    rb_ensure(parse_doc, (VALUE)ctxt, parse_doc_finalize, (VALUE)ctxt);

    return self;
}