From 1e26a536cd6aeec4c6e1f27266c9ba044f158118 Mon Sep 17 00:00:00 2001
From: Per Lindgren <per.lindgren@ltu.se>
Date: Mon, 26 Oct 2020 20:13:20 +0100
Subject: [PATCH] now uses the async_await syntax

---
 examples/async_systick3.rs | 215 +++++++++++++++++++++++++++++++++++++
 1 file changed, 215 insertions(+)
 create mode 100644 examples/async_systick3.rs

diff --git a/examples/async_systick3.rs b/examples/async_systick3.rs
new file mode 100644
index 0000000000..eaaa325708
--- /dev/null
+++ b/examples/async_systick3.rs
@@ -0,0 +1,215 @@
+//! examples/async_task2
+#![no_main]
+#![no_std]
+#![feature(const_fn)]
+#![feature(type_alias_impl_trait)]
+
+// use core::cell::Cell;
+// use core::cell::UnsafeCell;
+use core::future::Future;
+use core::mem;
+// use core::mem::MaybeUninit;
+use core::pin::Pin;
+// use core::ptr;
+// use core::ptr::NonNull;
+// use core::sync::atomic::{AtomicPtr, AtomicU32, Ordering};
+use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+use rtic::async_util::Task;
+
+use cortex_m_semihosting::{debug, hprintln};
+
+use panic_semihosting as _;
+use rtic::Mutex;
+
+#[rtic::app(device = lm3s6965, dispatchers = [SSI0])]
+mod app {
+    use crate::*;
+
+    #[resources]
+    struct Resources {
+        systick: Systick,
+    }
+
+    #[init]
+    fn init(cx: init::Context) -> init::LateResources {
+        hprintln!("init").ok();
+        foo::spawn().unwrap();
+        init::LateResources {
+            systick: Systick {
+                syst: cx.core.SYST,
+                state: State::Done,
+                queue: BinaryHeap::new(),
+                // waker: None,
+            },
+        }
+    }
+
+    #[idle]
+    fn idle(_: idle::Context) -> ! {
+        // debug::exit(debug::EXIT_SUCCESS);
+        loop {
+            hprintln!("idle").ok();
+            cortex_m::asm::wfi(); // put the MCU in sleep mode until interrupt occurs
+        }
+    }
+
+    #[task(resources = [systick])]
+    async fn foo(mut cx: foo::Context) {
+        // BEGIN BOILERPLATE
+        type F = impl Future + 'static;
+        fn create(cx: foo::Context<'static>) -> F {
+            task(cx)
+        }
+
+        static mut TASK: Task<F> = Task::new();
+
+        hprintln!("foo trampoline").ok();
+        unsafe {
+            match TASK {
+                Task::Idle | Task::Done(_) => {
+                    hprintln!("foo spawn task").ok();
+                    TASK.spawn(|| create(mem::transmute(cx)));
+                }
+                _ => {}
+            };
+
+            hprintln!("foo trampoline poll").ok();
+            TASK.poll(|| {
+                let _ = foo::spawn();
+            });
+
+            match TASK {
+                Task::Done(ref r) => {
+                    hprintln!("foo trampoline done").ok();
+                    // hprintln!("r = {:?}", mem::transmute::<_, &u32>(r)).ok();
+                }
+                _ => {
+                    hprintln!("foo trampoline running").ok();
+                }
+            }
+        }
+        // END BOILERPLATE
+
+        async fn task(mut cx: foo::Context<'static>) {
+            hprintln!("foo task").ok();
+
+            hprintln!("prepare two futures").ok();
+            let d1 = timer_delay(&mut cx.resources.systick, 5000000);
+            let d2 = timer_delay(&mut cx.resources.systick, 1000000);
+
+            //let pair = futures::future::join(d1, d2);
+            hprintln!("foo task resumed").ok();
+
+            hprintln!("delay short time").ok();
+            timer_delay(&mut cx.resources.systick, 1000000).await;
+            hprintln!("foo task resumed").ok();
+        }
+    }
+
+    // RTIC task bound to the HW SysTick interrupt
+    #[task(binds = SysTick, resources = [systick], priority = 2)]
+    fn systic(mut cx: systic::Context) {
+        hprintln!("systic interrupt").ok();
+        cx.resources.systick.lock(|s| {
+            s.syst.disable_interrupt();
+            s.state = State::Done;
+            s.queue.pop().map(|w| w.waker.wake());
+            if let Some(w) = s.queue.peek() {
+                s.syst.set_reload(w.time);
+            } else {
+                s.syst.disable_interrupt();
+            }
+        });
+    }
+}
+
+//=============
+// Timer
+// Later we want a proper queue
+
+//use core::cmp::{Ord, Ordering, PartialOrd};
+use core::cmp::Ordering;
+use heapless::binary_heap::{BinaryHeap, Max};
+use heapless::consts::U8;
+use heapless::Vec;
+
+pub enum State {
+    Started,
+    Done,
+}
+
+struct Timeout {
+    time: u32,
+    waker: Waker,
+}
+
+impl Ord for Timeout {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.time.cmp(&other.time)
+    }
+}
+
+impl PartialOrd for Timeout {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(&other))
+    }
+}
+
+impl PartialEq for Timeout {
+    fn eq(&self, other: &Self) -> bool {
+        self.time == other.time
+    }
+}
+
+impl Eq for Timeout {}
+
+pub struct Systick {
+    syst: cortex_m::peripheral::SYST,
+    state: State,
+    queue: BinaryHeap<Timeout, U8, Max>,
+}
+
+//=============
+// Timer
+// Later we want a proper queue
+
+pub struct Timer<'a, T: Mutex<T = Systick>> {
+    request: Option<u32>,
+    systick: &'a mut T,
+}
+
+impl<'a, T: Mutex<T = Systick>> Future for Timer<'a, T> {
+    type Output = ();
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let Self { request, systick } = &mut *self;
+        systick.lock(|s| {
+            // enqueue a new request
+            request.take().map(|t| {
+                s.syst.set_reload(t);
+                s.syst.enable_counter();
+                s.syst.enable_interrupt();
+                s.state = State::Started;
+                s.queue.push(Timeout {
+                    time: t,
+                    waker: cx.waker().clone(),
+                });
+            });
+
+            match s.state {
+                State::Done => Poll::Ready(()),
+                State::Started => {
+                    // s.waker = Some(cx.waker().clone());
+                    Poll::Pending
+                }
+            }
+        })
+    }
+}
+
+fn timer_delay<'a, T: Mutex<T = Systick>>(systick: &'a mut T, t: u32) -> Timer<'a, T> {
+    hprintln!("timer_delay {}", t);
+    Timer {
+        request: Some(t),
+        systick,
+    }
+}