1 files changed, 146 insertions, 0 deletions

diff --git a/embassy-time-queue-driver/src/queue_generic.rs b/embassy-time-queue-driver/src/queue_generic.rs
new file mode 100644
index 000000000..232035bc6
--- /dev/null
+++ b/embassy-time-queue-driver/src/queue_generic.rs
@@ -0,0 +1,146 @@
+//! Generic timer queue implementations.
+//!
+//! Time queue drivers may use this to simplify their implementation.
+
+use core::cmp::{min, Ordering};
+use core::task::Waker;
+
+use heapless::Vec;
+
+#[derive(Debug)]
+struct Timer {
+    at: u64,
+    waker: Waker,
+}
+
+impl PartialEq for Timer {
+    fn eq(&self, other: &Self) -> bool {
+        self.at == other.at
+    }
+}
+
+impl Eq for Timer {}
+
+impl PartialOrd for Timer {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.at.partial_cmp(&other.at)
+    }
+}
+
+impl Ord for Timer {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.at.cmp(&other.at)
+    }
+}
+
+/// A timer queue with a pre-determined capacity.
+pub struct ConstGenericQueue<const QUEUE_SIZE: usize> {
+    queue: Vec<Timer, QUEUE_SIZE>,
+}
+
+impl<const QUEUE_SIZE: usize> ConstGenericQueue<QUEUE_SIZE> {
+    /// Creates a new timer queue.
+    pub const fn new() -> Self {
+        Self { queue: Vec::new() }
+    }
+
+    /// Schedules a task to run at a specific time, and returns whether any changes were made.
+    ///
+    /// If this function returns `true`, the called should find the next expiration time and set
+    /// a new alarm for that time.
+    pub fn schedule_wake(&mut self, at: u64, waker: &Waker) -> bool {
+        self.queue
+            .iter_mut()
+            .find(|timer| timer.waker.will_wake(waker))
+            .map(|timer| {
+                if timer.at > at {
+                    timer.at = at;
+                    true
+                } else {
+                    false
+                }
+            })
+            .unwrap_or_else(|| {
+                let mut timer = Timer {
+                    waker: waker.clone(),
+                    at,
+                };
+
+                loop {
+                    match self.queue.push(timer) {
+                        Ok(()) => break,
+                        Err(e) => timer = e,
+                    }
+
+                    self.queue.pop().unwrap().waker.wake();
+                }
+
+                true
+            })
+    }
+
+    /// Dequeues expired timers and returns the next alarm time.
+    pub fn next_expiration(&mut self, now: u64) -> u64 {
+        let mut next_alarm = u64::MAX;
+
+        let mut i = 0;
+        while i < self.queue.len() {
+            let timer = &self.queue[i];
+            if timer.at <= now {
+                let timer = self.queue.swap_remove(i);
+                timer.waker.wake();
+            } else {
+                next_alarm = min(next_alarm, timer.at);
+                i += 1;
+            }
+        }
+
+        next_alarm
+    }
+}
+
+#[cfg(feature = "generic-queue-8")]
+const QUEUE_SIZE: usize = 8;
+#[cfg(feature = "generic-queue-16")]
+const QUEUE_SIZE: usize = 16;
+#[cfg(feature = "generic-queue-32")]
+const QUEUE_SIZE: usize = 32;
+#[cfg(feature = "generic-queue-64")]
+const QUEUE_SIZE: usize = 64;
+#[cfg(feature = "generic-queue-128")]
+const QUEUE_SIZE: usize = 128;
+#[cfg(not(any(
+    feature = "generic-queue-8",
+    feature = "generic-queue-16",
+    feature = "generic-queue-32",
+    feature = "generic-queue-64",
+    feature = "generic-queue-128"
+)))]
+const QUEUE_SIZE: usize = 64;
+
+/// A timer queue with a pre-determined capacity.
+pub struct Queue {
+    queue: ConstGenericQueue<QUEUE_SIZE>,
+}
+
+impl Queue {
+    /// Creates a new timer queue.
+    pub const fn new() -> Self {
+        Self {
+            queue: ConstGenericQueue::new(),
+        }
+    }
+
+    /// Schedules a task to run at a specific time, and returns whether any changes were made.
+    ///
+    /// If this function returns `true`, the called should find the next expiration time and set
+    /// a new alarm for that time.
+    pub fn schedule_wake(&mut self, at: u64, waker: &Waker) -> bool {
+        self.queue.schedule_wake(at, waker)
+    }
+
+    /// Dequeues expired timers and returns the next alarm time.
+    pub fn next_expiration(&mut self, now: u64) -> u64 {
+        self.queue.next_expiration(now)
+    }
+}