Split embassy-time from embassy-executor.

embassy-executor/src/arch/std.rs

@@ -0,0 +1,84 @@
+use std::marker::PhantomData;
+use std::sync::{Condvar, Mutex};
+
+use super::{raw, Spawner};
+
+/// Single-threaded std-based executor.
+pub struct Executor {
+    inner: raw::Executor,
+    not_send: PhantomData<*mut ()>,
+    signaler: &'static Signaler,
+}
+
+impl Executor {
+    /// Create a new Executor.
+    pub fn new() -> Self {
+        let signaler = &*Box::leak(Box::new(Signaler::new()));
+        Self {
+            inner: raw::Executor::new(
+                |p| unsafe {
+                    let s = &*(p as *const () as *const Signaler);
+                    s.signal()
+                },
+                signaler as *const _ as _,
+            ),
+            not_send: PhantomData,
+            signaler,
+        }
+    }
+
+    /// Run the executor.
+    ///
+    /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+    /// this executor. Use it to spawn the initial task(s). After `init` returns,
+    /// the executor starts running the tasks.
+    ///
+    /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+    /// for example by passing it as an argument to the initial tasks.
+    ///
+    /// This function requires `&'static mut self`. This means you have to store the
+    /// Executor instance in a place where it'll live forever and grants you mutable
+    /// access. There's a few ways to do this:
+    ///
+    /// - a [Forever](crate::util::Forever) (safe)
+    /// - a `static mut` (unsafe)
+    /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+    ///
+    /// This function never returns.
+    pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+        init(self.inner.spawner());
+
+        loop {
+            unsafe { self.inner.poll() };
+            self.signaler.wait()
+        }
+    }
+}
+
+struct Signaler {
+    mutex: Mutex<bool>,
+    condvar: Condvar,
+}
+
+impl Signaler {
+    fn new() -> Self {
+        Self {
+            mutex: Mutex::new(false),
+            condvar: Condvar::new(),
+        }
+    }
+
+    fn wait(&self) {
+        let mut signaled = self.mutex.lock().unwrap();
+        while !*signaled {
+            signaled = self.condvar.wait(signaled).unwrap();
+        }
+        *signaled = false;
+    }
+
+    fn signal(&self) {
+        let mut signaled = self.mutex.lock().unwrap();
+        *signaled = true;
+        self.condvar.notify_one();
+    }
+}