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// This file is part of Substrate.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
use futures::{future::FutureExt, ready, stream::Stream};
use futures_timer::Delay;
use std::{
pin::Pin,
task::{Context, Poll},
time::Duration,
};
/// Exponentially increasing interval
///
/// Doubles interval duration on each tick until the configured maximum is reached.
pub struct ExpIncInterval {
start: Duration,
max: Duration,
next: Duration,
delay: Delay,
}
impl ExpIncInterval {
/// Create a new [`ExpIncInterval`].
pub fn new(start: Duration, max: Duration) -> Self {
let delay = Delay::new(start);
Self { start, max, next: start * 2, delay }
}
/// Fast forward the exponentially increasing interval to the configured maximum, if not already
/// set.
pub fn set_to_max(&mut self) {
if self.next == self.max {
return;
}
self.next = self.max;
self.delay = Delay::new(self.next);
}
/// Rewind the exponentially increasing interval to the configured start, if not already set.
pub fn set_to_start(&mut self) {
if self.next == self.start * 2 {
return;
}
self.next = self.start * 2;
self.delay = Delay::new(self.start);
}
}
impl Stream for ExpIncInterval {
type Item = ();
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
ready!(self.delay.poll_unpin(cx));
self.delay = Delay::new(self.next);
self.next = std::cmp::min(self.max, self.next * 2);
Poll::Ready(Some(()))
}
}