feat(kernel): WatchDeath + SetTimer events as notification signals; adapter wakes at earliest deadline

crates/domain/src/timer.rs

@@ -0,0 +1,67 @@
+//! Events the kernel reports by signalling a notification: a process's
+//! death, a deadline passing. One timer per process.
+
+use types::{badge::Badge, generation::Generation, id::NotificationId, id::ProcessId, time::Ticks};
+
+use crate::process::MAX_PROCESSES;
+
+#[cfg(test)]
+#[path = "timer_tests.rs"]
+mod tests;
+
+/// A notification as a capability named it; once the notification is
+/// destroyed (its generation moves on) the target is dead.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct Target {
+    pub notification: NotificationId,
+    pub generation: Generation,
+    pub badge: Badge,
+}
+
+pub struct Timers {
+    deadlines: [Option<(Ticks, Target)>; MAX_PROCESSES],
+}
+
+impl Timers {
+    pub const fn new() -> Self {
+        Self {
+            deadlines: [None; MAX_PROCESSES],
+        }
+    }
+
+    /// Replaces `owner`'s timer.
+    pub fn set(&mut self, owner: ProcessId, deadline: Ticks, target: Target) -> bool {
+        match self.deadlines.get_mut(owner.raw() as usize) {
+            Some(slot) => {
+                *slot = Some((deadline, target));
+                true
+            }
+            None => false,
+        }
+    }
+
+    pub fn clear(&mut self, owner: ProcessId) {
+        if let Some(slot) = self.deadlines.get_mut(owner.raw() as usize) {
+            *slot = None;
+        }
+    }
+
+    /// Removes and returns one timer whose deadline is at or before `now`.
+    pub fn take_expired(&mut self, now: Ticks) -> Option<Target> {
+        let slot = self
+            .deadlines
+            .iter_mut()
+            .find(|s| s.is_some_and(|(d, _)| d <= now))?;
+        slot.take().map(|(_, t)| t)
+    }
+
+    pub fn earliest(&self) -> Option<Ticks> {
+        self.deadlines.iter().flatten().map(|(d, _)| *d).min()
+    }
+}
+
+impl Default for Timers {
+    fn default() -> Self {
+        Self::new()
+    }
+}