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use std::sync::mpsc::{RecvError, TryRecvError};
pub trait EventStream {
type Item;
fn next_ev(&mut self) -> Result<Self::Item, RecvError>;
fn try_next_ev(&mut self) -> Result<Self::Item, TryRecvError>;
fn poll(&mut self) -> bool;
}
pub trait EventStepper {
type Item;
fn produce_events(&mut self) -> Result<(), RecvError>;
fn try_produce_events(&mut self) -> Result<(), TryRecvError>;
fn pop_item(&mut self) -> Option<Self::Item>;
}
impl<S> EventStream for S
where S: EventStepper
{
type Item = <S as EventStepper>::Item;
fn next_ev(&mut self) -> Result<Self::Item, RecvError> {
loop {
if let Some(cached_ev) = self.pop_item() {
return Ok(cached_ev);
}
match self.produce_events() {
Ok(()) => {}
Err(RecvError) => return Err(RecvError),
}
}
}
fn try_next_ev(&mut self) -> Result<Self::Item, TryRecvError> {
if let Some(cached_ev) = self.pop_item() {
return Ok(cached_ev);
}
match self.try_produce_events() {
Ok(()) => {
self.pop_item().ok_or(TryRecvError::Empty)
}
Err(err) => Err(err),
}
}
fn poll(&mut self) -> bool {
let mut result = false;
while Ok(()) == self.try_produce_events() {
result = true;
}
result
}
}