1 files changed, 98 insertions, 0 deletions
diff --git a/third_party/rust/neqo-transport/tests/sim/delay.rs b/third_party/rust/neqo-transport/tests/sim/delay.rs
new file mode 100644
index 0000000000..95188c0562
--- /dev/null
+++ b/third_party/rust/neqo-transport/tests/sim/delay.rs
@@ -0,0 +1,98 @@
+// 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 super::{Node, Rng};
+use neqo_common::Datagram;
+use neqo_transport::Output;
+use std::collections::BTreeMap;
+use std::convert::TryFrom;
+use std::fmt::{self, Debug};
+use std::ops::Range;
+use std::time::{Duration, Instant};
+
+/// An iterator that shares a `Random` instance and produces uniformly
+/// random `Duration`s within a specified range.
+pub struct RandomDelay {
+    start: Duration,
+    max: u64,
+    rng: Option<Rng>,
+}
+
+impl RandomDelay {
+    /// Make a new random `Duration` generator.  This panics if the range provided
+    /// is inverted (i.e., `bounds.start > bounds.end`), or spans 2^64
+    /// or more nanoseconds.
+    /// A zero-length range means that random values won't be taken from the Rng
+    pub fn new(bounds: Range<Duration>) -> Self {
+        let max = u64::try_from((bounds.end - bounds.start).as_nanos()).unwrap();
+        Self {
+            start: bounds.start,
+            max,
+            rng: None,
+        }
+    }
+
+    pub fn set_rng(&mut self, rng: Rng) {
+        self.rng = Some(rng);
+    }
+
+    pub fn next(&mut self) -> Duration {
+        let mut rng = self.rng.as_ref().unwrap().borrow_mut();
+        let r = rng.random_from(0..self.max);
+        self.start + Duration::from_nanos(r)
+    }
+}
+
+pub struct Delay {
+    random: RandomDelay,
+    queue: BTreeMap<Instant, Datagram>,
+}
+
+impl Delay {
+    pub fn new(bounds: Range<Duration>) -> Self {
+        Self {
+            random: RandomDelay::new(bounds),
+            queue: BTreeMap::default(),
+        }
+    }
+
+    fn insert(&mut self, d: Datagram, now: Instant) {
+        let mut t = now + self.random.next();
+        while self.queue.contains_key(&t) {
+            // This is a little inefficient, but it avoids drops on collisions,
+            // which are super-common for a fixed delay.
+            t += Duration::from_nanos(1);
+        }
+        self.queue.insert(t, d);
+    }
+}
+
+impl Node for Delay {
+    fn init(&mut self, rng: Rng, _now: Instant) {
+        self.random.set_rng(rng);
+    }
+
+    fn process(&mut self, d: Option<Datagram>, now: Instant) -> Output {
+        if let Some(dgram) = d {
+            self.insert(dgram, now);
+        }
+        if let Some((&k, _)) = self.queue.range(..=now).next() {
+            Output::Datagram(self.queue.remove(&k).unwrap())
+        } else if let Some(&t) = self.queue.keys().next() {
+            Output::Callback(t - now)
+        } else {
+            Output::None
+        }
+    }
+}
+
+impl Debug for Delay {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("delay")
+    }
+}