Merge #920

920: Remove Forever, switch to static_cell. r=Dirbaio a=Dirbaio



Co-authored-by: Dario Nieuwenhuis <[email protected]>

4 files changed, 8 insertions, 105 deletions

diff --git a/embassy-util/src/channel/mpmc.rs b/embassy-util/src/channel/mpmc.rs
index 535f77e6f..263f29bfc 100644
--- a/embassy-util/src/channel/mpmc.rs
+++ b/embassy-util/src/channel/mpmc.rs
@@ -471,10 +471,10 @@ mod tests {
     use futures_executor::ThreadPool;
     use futures_timer::Delay;
     use futures_util::task::SpawnExt;
+    use static_cell::StaticCell;
 
     use super::*;
     use crate::blocking_mutex::raw::{CriticalSectionRawMutex, NoopRawMutex};
-    use crate::Forever;
 
     fn capacity<T, const N: usize>(c: &ChannelState<T, N>) -> usize {
         c.queue.capacity() - c.queue.len()
@@ -549,8 +549,8 @@ mod tests {
     async fn receiver_receives_given_try_send_async() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 3>> = Forever::new();
-        let c = &*CHANNEL.put(Channel::new());
+        static CHANNEL: StaticCell<Channel<CriticalSectionRawMutex, u32, 3>> = StaticCell::new();
+        let c = &*CHANNEL.init(Channel::new());
         let c2 = c;
         assert!(executor
             .spawn(async move {
@@ -571,8 +571,8 @@ mod tests {
     async fn senders_sends_wait_until_capacity() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
-        let c = &*CHANNEL.put(Channel::new());
+        static CHANNEL: StaticCell<Channel<CriticalSectionRawMutex, u32, 1>> = StaticCell::new();
+        let c = &*CHANNEL.init(Channel::new());
         assert!(c.try_send(1).is_ok());
 
         let c2 = c;
diff --git a/embassy-util/src/forever.rs b/embassy-util/src/forever.rs
deleted file mode 100644
index 4f3698211..000000000
--- a/embassy-util/src/forever.rs
+++ /dev/null
@@ -1,95 +0,0 @@
-use core::cell::UnsafeCell;
-use core::mem::MaybeUninit;
-
-use atomic_polyfill::{AtomicBool, Ordering};
-
-/// Type with static lifetime that may be written to once at runtime.
-///
-/// This may be used to initialize static objects at runtime, typically in the init routine.
-/// This is useful for objects such as Embassy's RTC, which cannot be initialized in a const
-/// context.
-///
-/// Note: IF a global mutable variable is desired, use a CriticalSectionMutex or ThreadModeMutex instead.
-///
-/// ```
-/// use embassy_util::Forever;
-/// // Using an integer for the sake of keeping this example self-contained,
-/// // see https://github.com/embassy-rs/embassy/wiki/Getting-Started for a more "proper" example.
-/// static SOME_INT: Forever<u32> =Forever::new();
-///
-/// // put returns a mutable pointer to the object stored in the forever, which may then be passed
-/// // around.
-/// let mut x = SOME_INT.put(42);
-/// assert_eq!(*x, 42);
-/// ```
-pub struct Forever<T> {
-    used: AtomicBool,
-    t: UnsafeCell<MaybeUninit<T>>,
-}
-
-unsafe impl<T> Send for Forever<T> {}
-unsafe impl<T> Sync for Forever<T> {}
-
-impl<T> Forever<T> {
-    /// Create a new `Forever`.
-    #[inline(always)]
-    pub const fn new() -> Self {
-        Self {
-            used: AtomicBool::new(false),
-            t: UnsafeCell::new(MaybeUninit::uninit()),
-        }
-    }
-
-    /// Store a value in this `Forever`, returning a mutable reference to it.
-    ///
-    /// Using this method, the compiler usually constructs `val` in the stack and then moves
-    /// it into the `Forever`. If `T` is big, this is likely to cause stack overflows.
-    /// Considering using [`Signal::put_with`] instead, which will construct it in-place inside the `Forever`.
-    ///
-    /// # Panics
-    ///
-    /// Panics if this `Forever` already has a value stored in it.
-    #[inline(always)]
-    #[allow(clippy::mut_from_ref)]
-    pub fn put(&'static self, val: T) -> &'static mut T {
-        self.put_with(|| val)
-    }
-
-    /// Store the closure return value in this `Forever`, returning a mutable reference to it.
-    ///
-    /// The advantage over [`Forever::put`] is that this method allows the closure to construct
-    /// the `T` value in-place directly inside the `Forever`, saving stack space.
-    ///
-    /// # Panics
-    ///
-    /// Panics if this `Forever` already has a value stored in it.
-    #[inline(always)]
-    #[allow(clippy::mut_from_ref)]
-    pub fn put_with(&'static self, val: impl FnOnce() -> T) -> &'static mut T {
-        if self
-            .used
-            .compare_exchange(false, true, Ordering::Relaxed, Ordering::Relaxed)
-            .is_err()
-        {
-            panic!("Forever.put() called multiple times");
-        }
-
-        let p: &'static mut MaybeUninit<T> = unsafe { &mut *self.t.get() };
-        p.write(val())
-    }
-
-    /// Unsafely get a mutable reference to the contents of this Forever.
-    ///
-    /// # Safety
-    ///
-    /// This is undefined behavior if:
-    ///
-    /// - The `Forever` has not been initialized yet (with `put' or `put_with`), or
-    /// - A reference to the contents (mutable or not) already exists.
-    #[inline(always)]
-    #[allow(clippy::mut_from_ref)]
-    pub unsafe fn steal(&self) -> &mut T {
-        let p: &mut MaybeUninit<T> = &mut *self.t.get();
-        p.assume_init_mut()
-    }
-}
diff --git a/embassy-util/src/lib.rs b/embassy-util/src/lib.rs
index 110c72811..8ec3300d9 100644
--- a/embassy-util/src/lib.rs
+++ b/embassy-util/src/lib.rs
@@ -16,10 +16,8 @@ pub mod mutex;
 pub mod pipe;
 pub mod waitqueue;
 
-mod forever;
 mod select;
 mod yield_now;
 
-pub use forever::*;
 pub use select::*;
 pub use yield_now::*;
diff --git a/embassy-util/src/pipe.rs b/embassy-util/src/pipe.rs
index 9c20aeeff..d85b843e4 100644
--- a/embassy-util/src/pipe.rs
+++ b/embassy-util/src/pipe.rs
@@ -461,10 +461,10 @@ mod io_impls {
 mod tests {
     use futures_executor::ThreadPool;
     use futures_util::task::SpawnExt;
+    use static_cell::StaticCell;
 
     use super::*;
     use crate::blocking_mutex::raw::{CriticalSectionRawMutex, NoopRawMutex};
-    use crate::Forever;
 
     fn capacity<const N: usize>(c: &PipeState<N>) -> usize {
         N - c.buffer.len()
@@ -528,8 +528,8 @@ mod tests {
     async fn receiver_receives_given_try_write_async() {
         let executor = ThreadPool::new().unwrap();
 
-        static CHANNEL: Forever<Pipe<CriticalSectionRawMutex, 3>> = Forever::new();
-        let c = &*CHANNEL.put(Pipe::new());
+        static CHANNEL: StaticCell<Pipe<CriticalSectionRawMutex, 3>> = StaticCell::new();
+        let c = &*CHANNEL.init(Pipe::new());
         let c2 = c;
         let f = async move {
             assert_eq!(c2.try_write(&[42]), Ok(1));