blah

embassy-hal-common/src/atomic_ring_buffer.rs

@@ -0,0 +1,154 @@
+use core::slice;
+use core::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+
+pub struct RingBuffer {
+    buf: AtomicPtr<u8>,
+    len: AtomicUsize,
+    start: AtomicUsize,
+    end: AtomicUsize,
+}
+
+pub struct Reader<'a>(&'a RingBuffer);
+pub struct Writer<'a>(&'a RingBuffer);
+
+impl RingBuffer {
+    pub const fn new() -> Self {
+        Self {
+            buf: AtomicPtr::new(core::ptr::null_mut()),
+            len: AtomicUsize::new(0),
+            start: AtomicUsize::new(0),
+            end: AtomicUsize::new(0),
+        }
+    }
+
+    /// # Safety
+    /// - The buffer (`buf .. buf+len`) must be valid memory until `deinit` is called.
+    /// - Must not be called concurrently with any other methods.
+    pub unsafe fn init(&self, buf: *mut u8, len: usize) {
+        self.buf.store(buf, Ordering::Relaxed);
+        self.len.store(len, Ordering::Relaxed);
+        self.start.store(0, Ordering::Relaxed);
+        self.end.store(0, Ordering::Relaxed);
+    }
+
+    pub unsafe fn deinit(&self) {
+        self.len.store(0, Ordering::Relaxed);
+    }
+
+    pub unsafe fn reader(&self) -> Reader<'_> {
+        Reader(self)
+    }
+
+    pub unsafe fn writer(&self) -> Writer<'_> {
+        Writer(self)
+    }
+
+    pub fn is_full(&self) -> bool {
+        let start = self.start.load(Ordering::Relaxed);
+        let end = self.end.load(Ordering::Relaxed);
+
+        self.wrap(end + 1) == start
+    }
+
+    pub fn is_empty(&self) -> bool {
+        let start = self.start.load(Ordering::Relaxed);
+        let end = self.end.load(Ordering::Relaxed);
+
+        start == end
+    }
+
+    pub fn wrap(&self, n: usize) -> usize {
+        let len = self.len.load(Ordering::Relaxed);
+
+        assert!(n <= len);
+        if n == len {
+            0
+        } else {
+            n
+        }
+    }
+}
+
+impl<'a> Writer<'a> {
+    pub fn push(&self, f: impl FnOnce(&mut [u8]) -> usize) -> usize {
+        let (p, n) = self.push_buf();
+        let buf = unsafe { slice::from_raw_parts_mut(p, n) };
+        let n = f(buf);
+        self.push_done(n);
+        n
+    }
+
+    pub fn push_one(&self, val: u8) -> bool {
+        let n = self.push(|f| match f {
+            [] => 0,
+            [x, ..] => {
+                *x = val;
+                1
+            }
+        });
+        n != 0
+    }
+
+    pub fn push_buf(&self) -> (*mut u8, usize) {
+        let start = self.0.start.load(Ordering::Acquire);
+        let buf = self.0.buf.load(Ordering::Relaxed);
+        let len = self.0.len.load(Ordering::Relaxed);
+        let end = self.0.end.load(Ordering::Relaxed);
+
+        let n = if start <= end {
+            len - end - (start == 0) as usize
+        } else {
+            start - end - 1
+        };
+
+        trace!("  ringbuf: push_buf {:?}..{:?}", end, end + n);
+        (unsafe { buf.add(end) }, n)
+    }
+
+    pub fn push_done(&self, n: usize) {
+        trace!("  ringbuf: push {:?}", n);
+        let end = self.0.end.load(Ordering::Relaxed);
+        self.0.end.store(self.0.wrap(end + n), Ordering::Release);
+    }
+}
+
+impl<'a> Reader<'a> {
+    pub fn pop(&self, f: impl FnOnce(&[u8]) -> usize) -> usize {
+        let (p, n) = self.pop_buf();
+        let buf = unsafe { slice::from_raw_parts(p, n) };
+        let n = f(buf);
+        self.pop_done(n);
+        n
+    }
+
+    pub fn pop_one(&self) -> Option<u8> {
+        let mut res = None;
+        self.pop(|f| match f {
+            &[] => 0,
+            &[x, ..] => {
+                res = Some(x);
+                1
+            }
+        });
+        res
+    }
+
+    pub fn pop_buf(&self) -> (*mut u8, usize) {
+        let end = self.0.end.load(Ordering::Acquire);
+        let buf = self.0.buf.load(Ordering::Relaxed);
+        let len = self.0.len.load(Ordering::Relaxed);
+        let start = self.0.start.load(Ordering::Relaxed);
+
+        let n = if end < start { len - start } else { end - start };
+
+        trace!("  ringbuf: pop_buf {:?}..{:?}", start, start + n);
+        (unsafe { buf.add(start) }, n)
+    }
+
+    pub fn pop_done(&self, n: usize) {
+        trace!("  ringbuf: pop {:?}", n);
+
+        let start = self.0.start.load(Ordering::Relaxed);
+        self.0.start.store(self.0.wrap(start + n), Ordering::Release);
+    }
+}

embassy-hal-common/src/lib.rs

@@ -4,6 +4,7 @@
 // This mod MUST go first, so that the others see its macros.
 pub(crate) mod fmt;
 
+pub mod atomic_ring_buffer;
 pub mod drop;
 mod macros;
 mod peripheral;