def rnp_preprocess(tmpl, dest, defines):
"""
Generic preprocessing
:param BinaryIO tmpl: open filehandle (read) input
:param BinaryIO dest: open filehandle (write) output
:param dict defines: result of get_defines()
:return boolean:
"""
pp = Preprocessor()
pp.setMarker("%")
pp.addDefines(defines)
pp.do_filter("substitution")
pp.out = dest
pp.do_include(tmpl, True)
return True
