Added interface for cancel/reschedule

Use wrapping add for marker

No need to store handle to queue

Remove unnecessary `SpawnHandle::new`

Fix test

Updated interface to follow proposal

6 files changed, 108 insertions, 249 deletions

diff --git a/examples/t-schedule.rs b/examples/t-schedule.rs
index bd0ab668..6b6245eb 100644
--- a/examples/t-schedule.rs
+++ b/examples/t-schedule.rs
@@ -26,18 +26,29 @@ mod app {
 
         let mono = DwtSystick::new(&mut dcb, dwt, systick, 8_000_000);
 
-        let _: Result<(), ()> = foo::spawn_after(Seconds(1_u32));
-        let _: Result<(), u32> = bar::spawn_after(Seconds(2_u32), 0);
-        let _: Result<(), (u32, u32)> = baz::spawn_after(Seconds(3_u32), 0, 1);
+        let a: Result<foo::MyMono::SpawnHandle, ()> = foo::spawn_after(Seconds(1_u32));
+        if let Ok(handle) = a {
+            let _: Result<foo::MyMono::SpawnHandle, ()> = handle.reschedule_after(Seconds(1_u32));
+        }
+
+        let b: Result<bar::MyMono::SpawnHandle, u32> = bar::spawn_after(Seconds(2_u32), 0);
+        if let Ok(handle) = b {
+            let _: Result<u32, ()> = handle.cancel();
+        }
+
+        let _: Result<baz::MyMono::SpawnHandle, (u32, u32)> =
+            baz::spawn_after(Seconds(3_u32), 0, 1);
 
         (init::LateResources {}, init::Monotonics(mono))
     }
 
     #[idle]
     fn idle(_: idle::Context) -> ! {
-        let _: Result<(), ()> = foo::spawn_at(MyMono::now() + Seconds(3_u32));
-        let _: Result<(), u32> = bar::spawn_at(MyMono::now() + Seconds(4_u32), 0);
-        let _: Result<(), (u32, u32)> = baz::spawn_at(MyMono::now() + Seconds(5_u32), 0, 1);
+        let _: Result<foo::MyMono::SpawnHandle, ()> = foo::spawn_at(MyMono::now() + Seconds(3_u32));
+        let _: Result<bar::MyMono::SpawnHandle, u32> =
+            bar::spawn_at(MyMono::now() + Seconds(4_u32), 0);
+        let _: Result<baz::MyMono::SpawnHandle, (u32, u32)> =
+            baz::spawn_at(MyMono::now() + Seconds(5_u32), 0, 1);
 
         loop {
             cortex_m::asm::nop();
diff --git a/macros/src/codegen/module.rs b/macros/src/codegen/module.rs
index 75435b54..fb028e01 100644
--- a/macros/src/codegen/module.rs
+++ b/macros/src/codegen/module.rs
@@ -264,15 +264,64 @@ pub fn codegen(
             };
 
             let user_imports = &app.user_imports;
+            let tq_marker = util::mark_internal_ident(&util::timer_queue_marker_ident());
 
             items.push(quote!(
             /// Holds methods related to this monotonic
             pub mod #m {
+                #[allow(unused_imports)]
+                use #app_path::#tq_marker;
+                #[allow(unused_imports)]
+                use #app_path::#t;
                 #(
                     #[allow(unused_imports)]
                     #user_imports
                 )*
 
+                pub struct SpawnHandle {
+                    #[doc(hidden)]
+                    marker: u32,
+                }
+
+                // TODO: remove
+                impl core::fmt::Debug for SpawnHandle
+                {
+                    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+                        let handle = unsafe { &#app_path::#tq as *const _ as u32 };
+                        f.debug_struct("SpawnHandle")
+                            .field("marker", &self.marker)
+                            .field("handle", &handle)
+                            .finish()
+                    }
+                }
+
+                impl SpawnHandle {
+                    pub fn cancel(self) -> Result<#ty, ()> {
+                        // TODO: Actually cancel...
+                        // &mut #app_path::#tq;
+
+                        Err(())
+                    }
+
+                    #[inline]
+                    pub fn reschedule_after<D>(self, duration: D) -> Result<Self, ()>
+                        where D: rtic::time::duration::Duration + rtic::time::fixed_point::FixedPoint,
+                                 D::T: Into<<#app_path::#mono_type as rtic::time::Clock>::T>,
+                    {
+                        self.reschedule_at(#app_path::#m::now() + duration)
+                    }
+
+                    pub fn reschedule_at(self, instant: rtic::time::Instant<#app_path::#mono_type>) -> Result<Self, ()>
+                    {
+                        let _ = instant;
+
+                        // TODO: Actually reschedule...
+                        // &mut #app_path::#tq;
+
+                        Err(())
+                    }
+                }
+
                 #(#cfgs)*
                 /// Spawns the task after a set duration relative to the current time
                 ///
@@ -281,7 +330,7 @@ pub fn codegen(
                 pub fn spawn_after<D>(
                     duration: D
                     #(,#args)*
-                ) -> Result<(), #ty>
+                ) -> Result<SpawnHandle, #ty>
                     where D: rtic::time::duration::Duration + rtic::time::fixed_point::FixedPoint,
                         D::T: Into<<#app_path::#mono_type as rtic::time::Clock>::T>,
                 {
@@ -300,7 +349,7 @@ pub fn codegen(
                 pub fn spawn_at(
                     instant: rtic::time::Instant<#app_path::#mono_type>
                     #(,#args)*
-                ) -> Result<(), #ty> {
+                ) -> Result<SpawnHandle, #ty> {
                     unsafe {
                         let input = #tupled;
                         if let Some(index) = rtic::export::interrupt::free(|_| #app_path::#fq.dequeue()) {
@@ -314,13 +363,17 @@ pub fn codegen(
                                 .as_mut_ptr()
                                 .write(instant);
 
-                            let nr = rtic::export::NotReady {
-                                instant,
-                                index,
-                                task: #app_path::#t::#name,
-                            };
+                            rtic::export::interrupt::free(|_| {
+                                let marker = #tq_marker;
+                                let nr = rtic::export::NotReady {
+                                    instant,
+                                    index,
+                                    task: #app_path::#t::#name,
+                                    marker,
+                                };
+
+                                #tq_marker = #tq_marker.wrapping_add(1);
 
-                            rtic::export::interrupt::free(|_|
                                 if let Some(mono) = #app_path::#m_ident.as_mut() {
                                     #app_path::#tq.enqueue_unchecked(
                                         nr,
@@ -331,9 +384,10 @@ pub fn codegen(
                                     // We can only use the timer queue if `init` has returned, and it
                                     // writes the `Some(monotonic)` we are accessing here.
                                     core::hint::unreachable_unchecked()
-                                });
+                                }
 
-                            Ok(())
+                                Ok(SpawnHandle { marker })
+                            })
                         } else {
                             Err(input)
                         }
diff --git a/macros/src/codegen/timer_queue.rs b/macros/src/codegen/timer_queue.rs
index 82d0ac98..33905516 100644
--- a/macros/src/codegen/timer_queue.rs
+++ b/macros/src/codegen/timer_queue.rs
@@ -9,6 +9,15 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
     let mut items = vec![];
 
     if !app.monotonics.is_empty() {
+        // Generate the marker counter used to track for `cancel` and `reschedule`
+        let tq_marker = util::mark_internal_ident(&util::timer_queue_marker_ident());
+        items.push(quote!(
+            // #[doc = #doc]
+            #[doc(hidden)]
+            #[allow(non_camel_case_types)]
+            static mut #tq_marker: u32 = 0;
+        ));
+
         let t = util::schedule_t_ident();
 
         // Enumeration of `schedule`-able tasks
@@ -32,7 +41,7 @@ pub fn codegen(app: &App, analysis: &Analysis, _extra: &Extra) -> Vec<TokenStrea
                 #[doc(hidden)]
                 #[allow(non_camel_case_types)]
                 #[derive(Clone, Copy)]
-                enum #t {
+                pub enum #t {
                     #(#variants,)*
                 }
             ));
diff --git a/macros/src/codegen/util.rs b/macros/src/codegen/util.rs
index 6589f62d..9ccdbf78 100644
--- a/macros/src/codegen/util.rs
+++ b/macros/src/codegen/util.rs
@@ -89,6 +89,11 @@ pub fn interrupt_ident() -> Ident {
     Ident::new("interrupt", span)
 }
 
+pub fn timer_queue_marker_ident() -> Ident {
+    let span = Span::call_site();
+    Ident::new("TIMER_QUEUE_MARKER", span)
+}
+
 /// Whether `name` is an exception with configurable priority
 pub fn is_exception(name: &Ident) -> bool {
     let s = name.to_string();
diff --git a/src/cyccnt.rs b/src/cyccnt.rs
deleted file mode 100644
index 8e07b001..00000000
--- a/src/cyccnt.rs
+++ /dev/null
@@ -1,221 +0,0 @@
-//! Data Watchpoint Trace (DWT) unit's CYCle CouNTer (CYCCNT)
-
-use core::{
-    cmp::Ordering,
-    convert::{Infallible, TryInto},
-    fmt, ops,
-};
-
-use cortex_m::peripheral::DWT;
-
-use crate::Fraction;
-
-/// A measurement of the CYCCNT. Opaque and useful only with `Duration`
-///
-/// This data type is only available on ARMv7-M
-///
-/// # Correctness
-///
-/// Adding or subtracting a `Duration` of more than `(1 << 31)` cycles to an `Instant` effectively
-/// makes it "wrap around" and creates an incorrect value. This is also true if the operation is
-/// done in steps, e.g. `(instant + dur) + dur` where `dur` is `(1 << 30)` ticks.
-#[derive(Clone, Copy, Eq, PartialEq)]
-pub struct Instant {
-    inner: i32,
-}
-
-impl Instant {
-    /// Returns an instant corresponding to "now"
-    ///
-    /// *HEADS UP* this function can, and will, return nonsensical values if called within `init`.
-    /// Only use it in `idle` and tasks. In `init`, use the `init::Context.start` field, or the
-    /// `CYCCNT::zero` function, instead of this function
-    pub fn now() -> Self {
-        Instant {
-            inner: DWT::get_cycle_count() as i32,
-        }
-    }
-
-    /// Returns the amount of time elapsed since this instant was created.
-    pub fn elapsed(&self) -> Duration {
-        let diff = Instant::now().inner.wrapping_sub(self.inner);
-        assert!(diff >= 0, "instant now is earlier than self");
-        Duration { inner: diff as u32 }
-    }
-
-    /// Returns the amount of time elapsed from another instant to this one.
-    pub fn duration_since(&self, earlier: Instant) -> Duration {
-        let diff = self.inner.wrapping_sub(earlier.inner);
-        assert!(diff >= 0, "second instant is later than self");
-        Duration { inner: diff as u32 }
-    }
-}
-
-impl fmt::Debug for Instant {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_tuple("Instant")
-            .field(&(self.inner as u32))
-            .finish()
-    }
-}
-
-impl ops::AddAssign<Duration> for Instant {
-    fn add_assign(&mut self, dur: Duration) {
-        // NOTE this is a debug assertion because there's no foolproof way to detect a wrap around;
-        // the user may write `(instant + dur) + dur` where `dur` is `(1<<31)-1` ticks.
-        debug_assert!(dur.inner < (1 << 31));
-        self.inner = self.inner.wrapping_add(dur.inner as i32);
-    }
-}
-
-impl ops::Add<Duration> for Instant {
-    type Output = Self;
-
-    fn add(mut self, dur: Duration) -> Self {
-        self += dur;
-        self
-    }
-}
-
-impl ops::SubAssign<Duration> for Instant {
-    fn sub_assign(&mut self, dur: Duration) {
-        // NOTE see the NOTE in `<Instant as AddAssign<Duration>>::add_assign`
-        debug_assert!(dur.inner < (1 << 31));
-        self.inner = self.inner.wrapping_sub(dur.inner as i32);
-    }
-}
-
-impl ops::Sub<Duration> for Instant {
-    type Output = Self;
-
-    fn sub(mut self, dur: Duration) -> Self {
-        self -= dur;
-        self
-    }
-}
-
-impl ops::Sub<Instant> for Instant {
-    type Output = Duration;
-
-    fn sub(self, other: Instant) -> Duration {
-        self.duration_since(other)
-    }
-}
-
-impl Ord for Instant {
-    fn cmp(&self, rhs: &Self) -> Ordering {
-        self.inner.wrapping_sub(rhs.inner).cmp(&0)
-    }
-}
-
-impl PartialOrd for Instant {
-    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
-        Some(self.cmp(rhs))
-    }
-}
-
-/// A `Duration` type to represent a span of time.
-///
-/// This data type is only available on ARMv7-M
-///
-/// # Correctness
-///
-/// This type is *not* appropriate for representing time spans in the order of, or larger than,
-/// seconds because it can hold a maximum of `(1 << 31)` "ticks" where each tick is the inverse of
-/// the CPU frequency, which usually is dozens of MHz.
-#[derive(Clone, Copy, Default, Eq, Ord, PartialEq, PartialOrd)]
-pub struct Duration {
-    inner: u32,
-}
-
-impl Duration {
-    /// Creates a new `Duration` from the specified number of clock cycles
-    pub fn from_cycles(cycles: u32) -> Self {
-        Duration { inner: cycles }
-    }
-
-    /// Returns the total number of clock cycles contained by this `Duration`
-    pub fn as_cycles(&self) -> u32 {
-        self.inner
-    }
-}
-
-impl TryInto<u32> for Duration {
-    type Error = Infallible;
-
-    fn try_into(self) -> Result<u32, Infallible> {
-        Ok(self.as_cycles())
-    }
-}
-
-impl ops::AddAssign for Duration {
-    fn add_assign(&mut self, dur: Duration) {
-        self.inner += dur.inner;
-    }
-}
-
-impl ops::Add<Duration> for Duration {
-    type Output = Self;
-
-    fn add(self, other: Self) -> Self {
-        Duration {
-            inner: self.inner + other.inner,
-        }
-    }
-}
-
-impl ops::SubAssign for Duration {
-    fn sub_assign(&mut self, rhs: Duration) {
-        self.inner -= rhs.inner;
-    }
-}
-
-impl ops::Sub<Duration> for Duration {
-    type Output = Self;
-
-    fn sub(self, rhs: Self) -> Self {
-        Duration {
-            inner: self.inner - rhs.inner,
-        }
-    }
-}
-
-/// Adds the `cycles` method to the `u32` type
-///
-/// This trait is only available on ARMv7-M
-pub trait U32Ext {
-    /// Converts the `u32` value into clock cycles
-    fn cycles(self) -> Duration;
-}
-
-impl U32Ext for u32 {
-    fn cycles(self) -> Duration {
-        Duration { inner: self }
-    }
-}
-
-/// Implementation of the `Monotonic` trait based on CYCle CouNTer
-pub struct CYCCNT;
-
-impl crate::Monotonic for CYCCNT {
-    type Instant = Instant;
-
-    fn ratio() -> Fraction {
-        Fraction {
-            numerator: 1,
-            denominator: 1,
-        }
-    }
-
-    unsafe fn reset() {
-        (0xE0001004 as *mut u32).write_volatile(0)
-    }
-
-    fn now() -> Instant {
-        Instant::now()
-    }
-
-    fn zero() -> Instant {
-        Instant { inner: 0 }
-    }
-}
diff --git a/src/tq.rs b/src/tq.rs
index 063bbd8e..f341d8cc 100644
--- a/src/tq.rs
+++ b/src/tq.rs
@@ -5,6 +5,15 @@ use crate::{
 use core::cmp::Ordering;
 use heapless::{binary_heap::Min, ArrayLength, BinaryHeap};
 
+#[inline]
+fn unwrapper<T, E>(val: Result<T, E>) -> T {
+    if let Ok(v) = val {
+        v
+    } else {
+        unreachable!("Your monotonic is not infallible")
+    }
+}
+
 pub struct TimerQueue<Mono, Task, N>(pub BinaryHeap<NotReady<Mono, Task>, N, Min>)
 where
     Mono: Monotonic,
@@ -66,15 +75,6 @@ where
         self.0.is_empty()
     }
 
-    #[inline]
-    fn unwrapper<T, E>(val: Result<T, E>) -> T {
-        if let Ok(v) = val {
-            v
-        } else {
-            unreachable!("Your monotonic is not infallible")
-        }
-    }
-
     /// Dequeue a task from the TimerQueue
     #[inline]
     pub fn dequeue<F>(&mut self, disable_interrupt: F, mono: &mut Mono) -> Option<(Task, u8)>
@@ -84,7 +84,7 @@ where
         mono.clear_compare_flag();
 
         if let Some(instant) = self.0.peek().map(|p| p.instant) {
-            if instant <= Self::unwrapper(Clock::try_now(mono)) {
+            if instant <= unwrapper(Clock::try_now(mono)) {
                 // task became ready
                 let nr = unsafe { self.0.pop_unchecked() };
 
@@ -97,7 +97,7 @@ where
                 // dequeue. If the monotonic is fast enough it can happen that from the
                 // read of now to the set of the compare, the time can overflow. This is to
                 // guard against this.
-                if instant <= Self::unwrapper(Clock::try_now(mono)) {
+                if instant <= unwrapper(Clock::try_now(mono)) {
                     let nr = unsafe { self.0.pop_unchecked() };
 
                     Some((nr.task, nr.index))
@@ -125,6 +125,7 @@ where
     pub index: u8,
     pub instant: Instant<Mono>,
     pub task: Task,
+    pub marker: u32,
 }
 
 impl<Mono, Task> Eq for NotReady<Mono, Task>