gDataInputStreamReadLineAsync.gDataInputStreamReadLineFinish(object, result, .errwarn = TRUE)objectGDataInputStream.resultGAsyncResult that was provided to the callback.length to a numeric to get the length of the read line.
On an error, it will return NULL and error will be set. If there's no
content to read, it will still return NULL, but error won't be set.lengthnumeric to get the length of the data read in.errorGError for error reporting.