/*
 *  call-seq:
 *    register(uri, custom_handler_class)
 *
 *  Register a class that implements custom XLST transformation functions.
 */
static VALUE registr(VALUE self, VALUE uri, VALUE obj)
{
    VALUE modules = rb_iv_get(self, "@modules");
    if(NIL_P(modules)) rb_raise(rb_eRuntimeError, "wtf! @modules isn't set");

    rb_hash_aset(modules, uri, obj);
    xsltRegisterExtModule((unsigned char *)StringValuePtr(uri), initFunc, shutdownFunc);
    return self;
}