task: use a faster enum instead of fancy heap allocations for task states

src/task.rs

@@ -9,81 +9,16 @@ pub trait Task: core::fmt::Debug {
     }
 }
 
-trait ScheduledState: std::fmt::Debug {
+#[derive(Debug, Copy, Clone)]
-    fn start(self: Box<Self>) -> Box<dyn ScheduledState>;
+enum ScheduledState {
-    fn stop(self: Box<Self>) -> Box<dyn ScheduledState>;
+    Stopped,
-    fn tick(self: Box<Self>, task: &mut dyn Task) -> Box<dyn ScheduledState>;
+    Start,
-}
+    Running,
-
+    Stop
-#[derive(Debug)]
-struct Starting {}
-impl ScheduledState for Starting {
-    fn start(self: Box<Self>) -> Box<dyn ScheduledState> {
-        self
-    }
-
-    fn stop(self: Box<Self>) -> Box<dyn ScheduledState> {
-        Box::new(Stopped {})
-    }
-
-    fn tick(self: Box<Self>, task: &mut dyn Task) -> Box<dyn ScheduledState> {
-        task.start();
-        Box::new(Running{})
-    }
-}
-
-#[derive(Debug)]
-struct Running {}
-impl ScheduledState for Running {
-    fn start(self: Box<Self>) -> Box<dyn ScheduledState> {
-        self
-    }
-
-    fn stop(self: Box<Self>) -> Box<dyn ScheduledState> {
-        Box::new(Stopping {})
-    }
-
-    fn tick(self: Box<Self>, task: &mut dyn Task) -> Box<dyn ScheduledState> {
-        task.tick();
-        self
-    }
-}
-
-#[derive(Debug)]
-struct Stopping {}
-impl ScheduledState for Stopping  {
-    fn start(self: Box<Self>) -> Box<dyn ScheduledState> {
-        Box::new(Running {})
-    }
-
-    fn stop(self: Box<Self>) -> Box<dyn ScheduledState> {
-        self
-    }
-
-    fn tick(self: Box<Self>, task: &mut dyn Task) -> Box<dyn ScheduledState> {
-        task.stop();
-        Box::new(Stopped {})
-    }
-}
-
-#[derive(Debug)]
-struct Stopped {}
-impl ScheduledState for Stopped  {
-    fn start(self: Box<Self>) -> Box<dyn ScheduledState> {
-        Box::new(Starting {})
-    }
-
-    fn stop(self: Box<Self>) -> Box<dyn ScheduledState> {
-        self
-    }
-
-    fn tick(self: Box<Self>, _task: &mut dyn Task) -> Box<dyn ScheduledState> {
-        self
-    }
 }
 
 struct ScheduledTask {
-    state: Option<Box<dyn ScheduledState>>,
+    state: ScheduledState,
     task: Box<dyn Task>,
 }
 
@@ -99,26 +34,44 @@ impl std::fmt::Debug for ScheduledTask {
 impl ScheduledTask {
     fn new(task: Box<dyn Task>) -> Self {
         ScheduledTask {
-            state: Some(Box::new(Starting{})),
+            state: ScheduledState::Start,
             task: task,
         }
     }
 
     fn start(&mut self) {
-        if let Some(s) = self.state.take() {
+        self.state = match self.state {
-            self.state = Some(s.start());
+            ScheduledState::Stopped => ScheduledState::Start,
+            ScheduledState::Stop => ScheduledState::Running,
+            _ => self.state
         }
     }
 
     fn stop(&mut self) {
-        if let Some(s) = self.state.take() {
+        self.state = match self.state {
-            self.state = Some(s.stop());
+            ScheduledState::Running => ScheduledState::Stop,
+            ScheduledState::Start => ScheduledState::Stopped,
+            _ => self.state
         }
     }
 
     fn tick(&mut self) {
-        if let Some(s) = self.state.take() {
+        self.state = match self.state {
-            self.state = Some(s.tick(self.task.as_mut()));
+            ScheduledState::Start => {
+                log::info!("Starting task {}", self.task.name());
+                self.task.start();
+                ScheduledState::Running
+            },
+            ScheduledState::Running => {
+                self.task.tick();
+                ScheduledState::Running
+            },
+            ScheduledState::Stop => {
+                log::info!("Stopping task {}", self.task.name());
+                self.task.stop();
+                ScheduledState::Stopped
+            },
+            ScheduledState::Stopped => ScheduledState::Stopped
         }
     }
 }