Manuelles Polling-Muster für Asynchrone Streams

use std::task::{Context, Poll};
 
pub struct RingStream<T> {
    buffer: Vec<T>,
    cursor: usize,
}
 
impl<T: Clone> RingStream<T> {
    pub fn new(items: Vec<T>) -> Self {
        Self { buffer: items, cursor: 0 }
    }
 
    pub fn poll_next_item(&mut self, _cx: &mut Context<'_>) -> Poll<Result<T, &'static str>> {
        if self.buffer.is_empty() {
            Poll::Ready(Err("Stream source buffer is empty"))
        } else {
            let item = self.buffer[self.cursor].clone();
            self.cursor = (self.cursor + 1) % self.buffer.len();
            Poll::Ready(Ok(item))
        }
    }
}