zephyr: sys: Create queue type based on k_queue

A simple wrapper around Zephyr's k_queue.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

zephyr/src/sys.rs

@@ -11,6 +11,7 @@
 
 use zephyr_sys::k_timeout_t;
 
+pub mod queue;
 pub mod sync;
 pub mod thread;
 

zephyr/src/sys/queue.rs

@@ -0,0 +1,79 @@
+//! Lightweight wrapper around Zephyr's `k_queue`.
+//!
+//! The underlying operations on the `k_queue` are all unsafe, as the model does not match the
+//! borrowing model that Rust expects.  This module is mainly intended to be used by the
+//! implementation of `zephyr::sys::channel`, which can be used without needing unsafe.
+
+use core::ffi::c_void;
+
+use zephyr_sys::{
+    k_queue,
+    k_queue_init,
+    k_queue_append,
+    k_queue_get,
+};
+
+use crate::sys::K_FOREVER;
+use crate::object::{StaticKernelObject, Wrapped};
+
+/// A wrapper around a Zephyr `k_queue` object.
+#[derive(Clone, Debug)]
+pub struct Queue {
+    item: *mut k_queue,
+}
+
+unsafe impl Sync for StaticKernelObject<k_queue> { }
+
+unsafe impl Sync for Queue { }
+unsafe impl Send for Queue { }
+
+impl Queue {
+    /// Append an element to the end of a queue.
+    ///
+    /// This adds an element to the given [`Queue`].  Zephyr requires the
+    /// first word of this message to be available for the OS to enqueue
+    /// the message.  See [`Message`] for details on how this can be used
+    /// safely.
+    ///
+    /// [`Message`]: crate::sync::channel::Message
+    pub unsafe fn send(&self, data: *mut c_void) {
+        k_queue_append(self.item, data)
+    }
+
+    /// Get an element from a queue.
+    ///
+    /// This routine removes the first data item from the [`Queue`].
+    pub unsafe fn recv(&self) -> *mut c_void {
+        k_queue_get(self.item, K_FOREVER)
+    }
+}
+
+impl Wrapped for StaticKernelObject<k_queue> {
+    type T = Queue;
+
+    type I = ();
+
+    fn get_wrapped(&self, _arg: Self::I) -> Queue {
+        let ptr = self.value.get();
+        unsafe {
+            k_queue_init(ptr);
+        }
+        Queue {
+            item: ptr,
+        }
+    }
+}
+
+/// A statically defined Zephyr `k_queue`.
+///
+/// This should be declared as follows:
+/// ```
+/// kobj_define! {
+///     static MY_QUEUE: StaticQueue;
+/// }
+///
+/// let my_queue = MY_QUEUE.init_once(());
+///
+/// my_queue.send(...);
+/// ```
+pub type StaticQueue = StaticKernelObject<k_queue>;