libxml2: xpath from xmlNode

I've looked through the docs and it seems that you can only execute an xpath search from a xmlDocPtr by creating an xpath context. Is there anyway in libxml2 to xpath search fr开发者_JAVA百科om a xmlNodePtr?

Call xmlXPathNewContext(), specifying the real top-level xmlDocPtr for the document, then set the xmlXPathContext::node field to the desired xmlNodePtr pointer that is a child of the xmlDocPtr document.

It turns out you can cast xmlNodePtr to xmlDocPtr and visa-versa.