threading

src/buffer.rs

@@ -0,0 +1,132 @@
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread;
+use std::time::Duration;
+// Using MaybeUninit is the idiomatic way to handle a buffer
+// of potentially uninitialized items without requiring a Default trait.
+use std::mem::MaybeUninit;
+
+/// A fixed-capacity, overwriting ring buffer.
+pub struct RingBuffer<T, const N: usize> {
+    buffer: [MaybeUninit<T>; N],
+    head: usize,
+    tail: usize,
+    size: usize,
+}
+
+impl<T, const N: usize> RingBuffer<T, N> {
+    /// Creates a new, empty RingBuffer.
+    pub fn new() -> Self {
+        Self {
+            // This is a safe way to create an array of uninitialized data.
+            buffer: unsafe { MaybeUninit::uninit().assume_init() },
+            head: 0,
+            tail: 0,
+            size: 0,
+        }
+    }
+
+    /// Checks if the buffer is empty.
+    pub fn is_empty(&self) -> bool {
+        self.size == 0
+    }
+
+    /// Pushes an item into the buffer.
+    /// If the buffer is full, the oldest item is overwritten.
+    pub fn push(&mut self, item: T) {
+        // Write the item to the tail position.
+        // This is safe because we manage initialization with `size`.
+        self.buffer[self.tail].write(item);
+        self.tail = (self.tail + 1) % N;
+
+        if self.size < N {
+            // Buffer is not full, just increment size.
+            self.size += 1;
+        } else {
+            // Buffer was full. The push overwrote the oldest item.
+            // The head must also advance to the new oldest item.
+            self.head = (self.head + 1) % N;
+        }
+    }
+
+    /// Pops an item from the buffer.
+    /// Returns None if the buffer is empty.
+    pub fn pop(&mut self) -> Option<T> {
+        if self.is_empty() {
+            return None;
+        }
+
+        // Read the item from the head, leaving that slot uninitialized.
+        // This is safe because is_empty() check ensures `head` points to valid data.
+        let item = unsafe { self.buffer[self.head].assume_init_read() };
+        self.head = (self.head + 1) % N;
+        self.size -= 1;
+        Some(item)
+    }
+}
+
+fn main() {
+    const CAPACITY: usize = 5;
+    println!("Ring Buffer Capacity: {}", CAPACITY);
+    println!("Producer will produce 15 items, so overwrites are expected.");
+
+    // The state is shared between threads using an Arc (Atomic Reference Counter).
+    // The Mutex ensures exclusive access, and the Condvar allows threads to wait efficiently.
+    let pair = Arc::new((
+        Mutex::new(RingBuffer::<i32, CAPACITY>::new()),
+        Condvar::new(),
+    ));
+
+    // --- Producer Thread ---
+    let producer_pair = Arc::clone(&pair);
+    let producer_handle = thread::spawn(move || {
+        for i in 0..15 {
+            // Lock the mutex to get exclusive access to the buffer.
+            let (lock, cvar) = &*producer_pair;
+            let mut buffer = lock.lock().unwrap();
+
+            buffer.push(i);
+            println!("➡️ Produced: {}", i);
+
+            // This is crucial: after adding an item, we notify one waiting thread.
+            cvar.notify_one();
+            
+            // We don't need the lock anymore, so we can drop it explicitly
+            // before sleeping to allow the consumer to work.
+            drop(buffer);
+            thread::sleep(Duration::from_millis(100)); // Producer is fast
+        }
+        println!("✅ Producer finished.");
+    });
+
+    // --- Consumer Thread ---
+    let consumer_pair = Arc::clone(&pair);
+    let consumer_handle = thread::spawn(move || {
+        let mut items_processed = 0;
+        while items_processed < 15 {
+            let (lock, cvar) = &*consumer_pair;
+            let mut buffer = lock.lock().unwrap();
+
+            // Use a while loop to handle spurious wakeups.
+            // The thread will sleep until the buffer is no longer empty.
+            while buffer.is_empty() {
+                // `cvar.wait` atomically unlocks the mutex and waits.
+                // When woken, it re-locks the mutex before returning.
+                buffer = cvar.wait(buffer).unwrap();
+            }
+
+            // At this point, the buffer is not empty.
+            if let Some(item) = buffer.pop() {
+                println!("   Consumed: {}", item);
+                items_processed += 1;
+            }
+            
+            drop(buffer);
+            thread::sleep(Duration::from_millis(300)); // Consumer is slow
+        }
+        println!("✅ Consumer finished.");
+    });
+    
+    producer_handle.join().unwrap();
+    consumer_handle.join().unwrap();
+}
+

src/main.rs

@@ -1,7 +1,11 @@
+mod buffer;
+use crate::buffer::{RingBuffer};
 use std::fs::File;
 use std::io::BufReader;
 use std::net::{ToSocketAddrs, UdpSocket};
 use std::time::Duration;
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread;
 
 // Constants from the C code
 const QUEUE_LEN: usize = 1000;
@@ -96,6 +100,7 @@ impl BouncingImage {
 struct Display {
     socket: UdpSocket,
     bufs: Vec<[u8; MSGSIZE]>,
+    pair: Arc<(Mutex<RingBuffer::<i32, QUEUE_LEN>>,Condvar)>,
     next_buf: usize,
     pos_in_buf: usize,
 }
@@ -117,10 +122,14 @@ impl Display {
             buf[0] = 0x00;
             buf[1] = 0x01;
         }
-
+    let pair = Arc::new((
+        Mutex::new(RingBuffer::<i32, QUEUE_LEN>::new()),
+        Condvar::new(),
+    ));
         Display {
             socket,
             bufs,
+            pair,
             next_buf: 0,
             pos_in_buf: 0,
         }
@@ -167,32 +176,45 @@ impl Display {
             }
         }
     }
+    fn send_thread(&mut self) {
+        let consumer_pair = Arc::clone(&self.pair);
+        let consumer_handle = thread::spawn(move || {
+        let mut items_processed = 0;
+        loop {
+            let (lock, cvar) = &*consumer_pair;
+            let mut buffer = lock.lock().unwrap();
 
-    /// Clears the entire screen to black.
-    #[allow(dead_code)]
-    fn blank_screen(&mut self) {
-        for x in 0..DISPLAY_WIDTH {
-            for y in 0..DISPLAY_HEIGHT {
-                self.set_pixel(x as u16, y as u16, 0, 0, 0);
+            // Use a while loop to handle spurious wakeups.
+            // The thread will sleep until the buffer is no longer empty.
+            while buffer.is_empty() {
+                // `cvar.wait` atomically unlocks the mutex and waits.
+                // When woken, it re-locks the mutex before returning.
+                buffer = cvar.wait(buffer).unwrap();
             }
+
+            // At this point, the buffer is not empty.
+            if let Some(item) = buffer.pop() {
+                println!("   Consumed: {}", item);
+                items_processed += 1;
+            }
+
+            drop(buffer);
+            thread::sleep(Duration::from_millis(300)); // Consumer is slow
         }
-        self.flush_frame();
+    });
+        
     }
 }
 
 fn main() {
     let mut images = vec![
         BouncingImage::new("images/unicorn_cc.png", 13, -10, 1, -1, -1),
-        BouncingImage::new("images/windows_logo.png", -8, 3, 2, -1, -1),
-        BouncingImage::new("images/spade.png", 32, -12, 1, 0, 0),
-        BouncingImage::new("images/dvdvideo.png", 20, 6, 5, 1000, 800),
-        BouncingImage::new("images/hackaday.png", 40, 18, 3, 500, 800),
     ];
 
     let mut display = Display::new(DISPLAY_HOST, DISPLAY_PORT);
     let mut frame_counter: u32 = 0;
 
-    // display.blank_screen();
+    display.send_thread();
 
     loop {
         for (i, bb) in images.iter_mut().enumerate() {
@@ -203,7 +225,7 @@ fn main() {
         }
         display.flush_frame();
         frame_counter += 1;
-        
+        println!("test");
         // A small delay to control the frame rate
         std::thread::sleep(Duration::from_millis(16));
     }