drain_while.rs

let mut collection_buffer = Vec::with_capacity(input_buffer.len());
let mut input_iter = input_buffer.drain(..);
loop {
    if let Some(input) = input_iter.next() {
        let result = context.as_ref()
            .unwrap()
            .listener_tx
            .send(input);

        // if we fail to send, it implies the listener has stopped listening
        // we then buffer all of the input for the next activity
        if let Err(SendError(missed_input)) = result {
            collection_buffer.push(missed_input);
            while let Some(input) = input_iter.next() {
                collection_buffer.push(input);
            }
        }
    }
}