Revert "perf(transport): remove Server::timers (#1784)" (#1800)

This reverts commit 61fcd28.

neqo-common/Cargo.toml

@@ -34,3 +34,7 @@ features = ["timeapi"]
 [lib]
 # See https://github.com/bheisler/criterion.rs/blob/master/book/src/faq.md#cargo-bench-gives-unrecognized-option-errors-for-valid-command-line-options
 bench = false
+
+[[bench]]
+name = "timer"
+harness = false

neqo-common/benches/timer.rs

@@ -0,0 +1,39 @@
+// 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.
+
+use std::time::{Duration, Instant};
+
+use criterion::{criterion_group, criterion_main, Criterion};
+use neqo_common::timer::Timer;
+use test_fixture::now;
+
+fn benchmark_timer(c: &mut Criterion) {
+    c.bench_function("drain a timer quickly", |b| {
+        b.iter_batched_ref(
+            make_timer,
+            |(_now, timer)| {
+                while let Some(t) = timer.next_time() {
+                    assert!(timer.take_next(t).is_some());
+                }
+            },
+            criterion::BatchSize::SmallInput,
+        );
+    });
+}
+
+fn make_timer() -> (Instant, Timer<()>) {
+    const TIMES: &[u64] = &[1, 2, 3, 5, 8, 13, 21, 34];
+
+    let now = now();
+    let mut timer = Timer::new(now, Duration::from_millis(777), 100);
+    for &t in TIMES {
+        timer.add(now + Duration::from_secs(t), ());
+    }
+    (now, timer)
+}
+
+criterion_group!(benches, benchmark_timer);
+criterion_main!(benches);

neqo-common/src/lib.rs

@@ -14,6 +14,7 @@ pub mod hrtime;
 mod incrdecoder;
 pub mod log;
 pub mod qlog;
+pub mod timer;
 pub mod tos;
 
 use std::fmt::Write;