c-api set optional record field

[Alan Miller]

Since I can't seem to use the custom fields in my schema from C.

I though I could just add an optional record field and only write the field
in the first record and leave the rest as null.

How would I write the "optional" record field to only the very first record.


[alan@localhost]$ avro cat --print-schema test.avro
{
    "namespace": "org.me",
    "type": "record",
    "name": "MyRecord",
    "fields": [
        {
            "type": {
                "type": "string"
            },
            "name": "myname"
        }, { "name": "optional",
               "type": [ "null", { "type": "record",
                                        "name": "info",
                                        "fields": [ { "name": "host",
 "type": "string" },
                                                      { "name":
"port",   "type": "string" } ]
                                    } ]
        }
    ]
}