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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![allow(clippy::module_name_repetitions)]
use std::{
fmt::{self, Debug},
time::Instant,
};
use neqo_common::{qtrace, Datagram};
use neqo_transport::Output;
use super::{Node, Rng};
/// A random dropper.
pub struct Drop {
threshold: u64,
max: u64,
rng: Option<Rng>,
}
impl Drop {
/// Make a new random drop generator. Each `drop` is called, this generates a
/// random value between 0 and `max` (exclusive). If this value is less than
/// `threshold` a value of `true` is returned.
pub fn new(threshold: u64, max: u64) -> Self {
Self {
threshold,
max,
rng: None,
}
}
/// Generate random drops with the given percentage.
pub fn percentage(pct: u8) -> Self {
// Multiply by 10 so that the random number generator works more efficiently.
Self::new(u64::from(pct) * 10, 1000)
}
pub fn drop(&mut self) -> bool {
let mut rng = self.rng.as_ref().unwrap().borrow_mut();
let r = rng.random_from(0..self.max);
r < self.threshold
}
}
impl Node for Drop {
fn init(&mut self, rng: Rng, _now: Instant) {
self.rng = Some(rng);
}
// Pass any datagram provided directly out, but drop some of them.
fn process(&mut self, d: Option<Datagram>, _now: Instant) -> Output {
if let Some(dgram) = d {
if self.drop() {
qtrace!("drop {}", dgram.len());
Output::None
} else {
Output::Datagram(dgram)
}
} else {
Output::None
}
}
}
impl Debug for Drop {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str("drop")
}
}
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