queueing

.rustfmt.toml

@@ -0,0 +1,3 @@
+imports_granularity = "Crate"
+newline_style = "Unix"
+group_imports = "StdExternalCrate"

src/linked_list.rs

@@ -1,5 +1,4 @@
-use std::ptr;
-use std::sync::atomic::AtomicPtr;
+use std::{ptr, sync::atomic::AtomicPtr};
 
 pub struct LinkedList<T> {
     head: AtomicPtr<Node<T>>,

src/mutex.rs

@@ -1,6 +1,8 @@
-use std::cell::UnsafeCell;
-use std::ops::{Deref, DerefMut};
-use std::sync::atomic::{AtomicU8, Ordering};
+use std::{
+    cell::UnsafeCell,
+    ops::{Deref, DerefMut},
+    sync::atomic::{AtomicU8, Ordering},
+};
 
 const INIT: u8 = 0;
 const ACQUIRED: u8 = 1;

src/spsc.rs

@@ -1,35 +1,103 @@
-use std::cell::UnsafeCell;
-use std::mem::MaybeUninit;
-use std::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+use std::{
+    cell::UnsafeCell,
+    error::Error,
+    fmt::{Display, Formatter, Write},
+    mem::MaybeUninit,
+    sync::{
+        atomic::{AtomicPtr, AtomicUsize, Ordering},
+        Arc,
+    },
+};
 
-struct Spsc<const N: usize, T> {
+const BUF_SIZE: usize = 16;
+
+/// A fancy ring buffer
+struct Spsc<T> {
+    /// The first element in the buffer
     start: AtomicUsize,
+    /// A pointer *at* the last element in the buffer. usize::MAX when it's empty,
+    /// in which case the next element will be put directly at `start`
     end: AtomicUsize,
-    buffer: [UnsafeCell<MaybeUninit<T>>; N],
+    buffer: [UnsafeCell<MaybeUninit<T>>; BUF_SIZE],
 }
 
-impl<const N: usize, T> Spsc<N, T> {
-    pub fn new() -> Self {
+impl<T> Spsc<T> {
+    fn new() -> Self {
         Self {
             start: AtomicUsize::default(),
-            end: AtomicUsize::default(),
-            buffer: [UnsafeCell::new(MaybeUninit::uninit()); N],
+            end: AtomicUsize::new(usize::MAX),
+            buffer: [UnsafeCell::new(MaybeUninit::uninit()); BUF_SIZE],
         }
     }
 
-    pub fn push(&self, value: T) {
+    fn try_send(&self, value: T) -> Result<(), errors::QueueFullError> {
         let end = self.end.load(Ordering::Acquire);
         let start = self.start.load(Ordering::Acquire);
 
-        if end != 0 && end == start {}w
+        let idx = if end == usize::MAX { start } else { end };
 
-        if end < self.buffer.len() {
-            let end = unsafe { &self.buffer[end] };
-            unsafe { end.get().write(value) };
-            self.end.fetch_and(1, Ordering::Release);
+        if end != usize::MAX && end + 1 != start {
+            Err(errors::QueueFullError)
+        } else {
+            unsafe { self.write(value, idx) };
+            self.end.store(idx, Ordering::Release);
+            Ok(())
         }
     }
+
+    unsafe fn read(&self, index: usize) -> T {
+        self.buffer[index].get().read()
+    }
+
+    unsafe fn write(&self, value: T, index: usize) {
+        self.buffer[index].get().write(value)
+    }
 }
 
-unsafe impl<const N: usize, T> Sync for Spsc<N, T> {}
-unsafe impl<const N: usize, T> Send for Spsc<N, T> {}
+pub struct Producer<T> {
+    queue: Arc<Spsc<T>>,
+}
+
+impl<T> Producer<T> {
+    pub fn try_send(&self, value: T) -> Result<(), errors::QueueFullError> {
+        self.queue.try_send(value)
+    }
+}
+
+pub struct Consumer<T> {
+    queue: Arc<Spsc<T>>,
+}
+
+impl<T> Consumer<T> {}
+
+unsafe impl<T> Sync for Spsc<T> {}
+unsafe impl<T> Send for Spsc<T> {}
+
+mod errors {
+    use std::{
+        error::Error,
+        fmt::{Display, Formatter},
+    };
+
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash)]
+    pub struct QueueFullError;
+
+    impl Display for QueueFullError {
+        fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+            f.write_str("spsc queue is full")
+        }
+    }
+
+    impl Error for QueueFullError {}
+
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash)]
+    pub struct QueueEmptyError;
+
+    impl Display for QueueEmptyError {
+        fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+            f.write_str("spsc queue is empty")
+        }
+    }
+
+    impl Error for QueueEmptyError {}
+}