Questions about the internal of fastpath function call

Hi,

I am reading the source code of fastpath to understand the internal of
fastpath. I can not understand how does it send result to the client, I hope
somebody can help me on this.

I see it call it invoke the function in

HandleFunctionRequest()
-> retval = FunctionCallInvoke(&fcinfo);
-> SendFunctionResult(retval, fcinfo.isnull, fip->rettype, rformat);
->OidOutputFunctionCall()
-> OutputFunctionCall()
-> result =
DatumGetCString(FunctionCall1(flinfo, val));
-> result =
FunctionCallInvoke(&fcinfo);

but I can not see in where it send the tuples to the client, instead it
invoke FunctionCallInvoke again. Can anyone tell me how it copy the tuples
and send it to the client.

Thanks a lot.

Clipper