Builds the QName @prefix:@ncname in @memory if there is
      enough space and prefix is not None nor empty, otherwise
      allocate a new string. If prefix is None or empty it
       returns ncname.

def buildQName(ncname, prefix, memory, len):
    """Builds the QName @prefix:@ncname in @memory if there is
      enough space and prefix is not None nor empty, otherwise
      allocate a new string. If prefix is None or empty it
       returns ncname. """
    ret = libxml2mod.xmlBuildQName(ncname, prefix, memory, len)
    return ret