feat: bring back driver in fastimer-driver (#19)

Signed-off-by: tison <[email protected]>

Cargo.toml

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 [workspace]
-members = ["fastimer", "fastimer-tokio", "xtask"]
+members = ["fastimer", "fastimer-driver", "fastimer-tokio", "xtask"]
 resolver = "2"
 
 [workspace.package]

fastimer-driver/Cargo.toml

@@ -0,0 +1,42 @@
+# Copyright 2024 FastLabs Developers
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+[package]
+name = "fastimer-driver"
+
+description = "This crate implements a timer driver that can work with any async runtime scheduler."
+
+edition.workspace = true
+homepage.workspace = true
+license.workspace = true
+readme.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+version.workspace = true
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[dependencies]
+atomic-waker = { version = "1.1.2" }
+crossbeam-queue = { version = "0.3.12" }
+fastimer = { workspace = true }
+parking = { version = "2.2.1" }
+
+[dev-dependencies]
+tokio = { workspace = true, features = ["full"] }
+
+[lints]
+workspace = true

fastimer-driver/src/lib.rs

@@ -0,0 +1,233 @@
+// Copyright 2024 FastLabs Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+#![deny(missing_docs)]
+
+//! Runtime-agnostic time driver for creating delay futures.
+
+use std::cmp;
+use std::collections::BinaryHeap;
+use std::future::Future;
+use std::pin::Pin;
+use std::sync::atomic;
+use std::sync::atomic::AtomicBool;
+use std::sync::Arc;
+use std::task::Context;
+use std::task::Poll;
+use std::time::Duration;
+use std::time::Instant;
+
+use atomic_waker::AtomicWaker;
+use crossbeam_queue::SegQueue;
+use fastimer::make_instant_from_now;
+use fastimer::MakeDelay;
+use parking::Parker;
+use parking::Unparker;
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Debug)]
+struct TimeEntry {
+    when: Instant,
+    waker: Arc<AtomicWaker>,
+}
+
+impl PartialEq for TimeEntry {
+    fn eq(&self, other: &Self) -> bool {
+        self.when == other.when
+    }
+}
+
+impl Eq for TimeEntry {}
+
+impl PartialOrd for TimeEntry {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        Some(self.when.cmp(&other.when))
+    }
+}
+
+impl Ord for TimeEntry {
+    fn cmp(&self, other: &Self) -> cmp::Ordering {
+        self.when.cmp(&other.when)
+    }
+}
+
+/// Future returned by [`delay`] and [`delay_until`].
+///
+/// [`delay`]: TimeContext::delay
+/// [`delay_until`]: TimeContext::delay_until
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+#[derive(Debug)]
+pub struct Delay {
+    when: Instant,
+    waker: Arc<AtomicWaker>,
+}
+
+impl Future for Delay {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        if Instant::now() >= self.when {
+            self.waker.take();
+            Poll::Ready(())
+        } else {
+            self.waker.register(cx.waker());
+            Poll::Pending
+        }
+    }
+}
+
+impl Drop for Delay {
+    fn drop(&mut self) {
+        self.waker.take();
+    }
+}
+
+/// Returns a new time driver, its time context and the shutdown handle.
+pub fn driver() -> (TimeDriver, TimeContext, TimeDriverShutdown) {
+    let (parker, unparker) = parking::pair();
+    let timers = BinaryHeap::new();
+    let inbounds = Arc::new(SegQueue::new());
+    let shutdown = Arc::new(AtomicBool::new(false));
+
+    let driver = TimeDriver {
+        parker,
+        unparker,
+        timers,
+        inbounds,
+        shutdown,
+    };
+
+    let context = TimeContext {
+        unparker: driver.unparker.clone(),
+        inbounds: driver.inbounds.clone(),
+    };
+
+    let shutdown = TimeDriverShutdown {
+        unparker: driver.unparker.clone(),
+        shutdown: driver.shutdown.clone(),
+    };
+
+    (driver, context, shutdown)
+}
+
+/// A time context for creating [`Delay`]s.
+#[derive(Debug, Clone)]
+pub struct TimeContext {
+    unparker: Unparker,
+    inbounds: Arc<SegQueue<TimeEntry>>,
+}
+
+impl TimeContext {
+    /// Returns a future that completes after the specified duration.
+    pub fn delay(&self, dur: Duration) -> Delay {
+        self.delay_until(make_instant_from_now(dur))
+    }
+
+    /// Returns a future that completes at the specified instant.
+    pub fn delay_until(&self, when: Instant) -> Delay {
+        let waker = Arc::new(AtomicWaker::new());
+        let delay = Delay {
+            when,
+            waker: waker.clone(),
+        };
+        self.inbounds.push(TimeEntry { when, waker });
+        self.unparker.unpark();
+        delay
+    }
+}
+
+/// A handle to shut down the time driver.
+#[derive(Debug, Clone)]
+pub struct TimeDriverShutdown {
+    unparker: Unparker,
+    shutdown: Arc<AtomicBool>,
+}
+
+impl TimeDriverShutdown {
+    /// Shuts down the time driver.
+    pub fn shutdown(&self) {
+        self.shutdown.store(true, atomic::Ordering::Release);
+        self.unparker.unpark();
+    }
+}
+
+/// A time driver that drives registered timers.
+#[derive(Debug)]
+pub struct TimeDriver {
+    parker: Parker,
+    unparker: Unparker,
+    timers: BinaryHeap<TimeEntry>,
+    inbounds: Arc<SegQueue<TimeEntry>>,
+    shutdown: Arc<AtomicBool>,
+}
+
+impl TimeDriver {
+    /// Drives the timers and returns `true` if the driver has been shut down.
+    pub fn turn(&mut self) -> bool {
+        if self.shutdown.load(atomic::Ordering::Acquire) {
+            return true;
+        }
+
+        match self.timers.peek() {
+            None => self.parker.park(),
+            Some(entry) => {
+                let delta = entry.when.saturating_duration_since(Instant::now());
+                if delta > Duration::ZERO {
+                    self.parker.park_timeout(delta);
+                }
+            }
+        }
+
+        while let Some(entry) = self.inbounds.pop() {
+            self.timers.push(entry);
+        }
+
+        while let Some(entry) = self.timers.peek() {
+            if entry.when <= Instant::now() {
+                entry.waker.wake();
+                let _ = self.timers.pop();
+            } else {
+                break;
+            }
+        }
+
+        self.shutdown.load(atomic::Ordering::Acquire)
+    }
+}
+
+/// A delay implementation that uses the given time context.
+#[derive(Debug, Clone)]
+pub struct MakeFastimerDelay(TimeContext);
+
+impl MakeFastimerDelay {
+    /// Create a new [`MakeFastimerDelay`] with the given [`TimeContext`].
+    pub fn new(context: TimeContext) -> Self {
+        MakeFastimerDelay(context)
+    }
+}
+
+impl MakeDelay for MakeFastimerDelay {
+    type Delay = Delay;
+
+    fn delay_util(&self, at: Instant) -> Self::Delay {
+        self.0.delay_until(at)
+    }
+
+    fn delay(&self, duration: Duration) -> Self::Delay {
+        self.0.delay(duration)
+    }
+}