X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/18e6fec08956d95a3fd1b4b1ef2a7bb9620c5fcf..ccf679adb3790903849f7d85b970b67582220952:/solutions/src/counter.rs

diff --git a/solutions/src/counter.rs b/solutions/src/counter.rs
new file mode 100644
index 0000000..265fb99
--- /dev/null
+++ b/solutions/src/counter.rs
@@ -0,0 +1,56 @@
+use std::sync::{Arc, RwLock};
+use std::thread;
+
+#[derive(Clone)]
+struct ConcurrentCounter(Arc<RwLock<usize>>);
+
+impl ConcurrentCounter {
+    // The constructor should not be surprising.
+    pub fn new(val: usize) -> Self {
+        ConcurrentCounter(Arc::new(RwLock::new(val)))
+    }
+
+    pub fn increment(&self, by: usize) {
+        let mut counter = self.0.write().unwrap();
+        *counter = *counter + by;
+    }
+
+    pub fn get(&self) -> usize {
+        let counter = self.0.read().unwrap();
+        *counter
+    }
+}
+
+// Now our counter is ready for action.
+pub fn main() {
+    let counter = ConcurrentCounter::new(0);
+
+    // We clone the counter for the first thread, which increments it by 2 every 15ms.
+    let counter1 = counter.clone();
+    let handle1 = thread::spawn(move || {
+        for _ in 0..10 {
+            thread::sleep_ms(15);
+            counter1.increment(2);
+        }
+    });
+
+    // The second thread increments the counter by 3 every 20ms.
+    let counter2 = counter.clone();
+    let handle2 = thread::spawn(move || {
+        for _ in 0..10 {
+            thread::sleep_ms(20);
+            counter2.increment(3);
+        }
+    });
+
+    // Now we want to watch the threads working on the counter.
+    for _ in 0..50 {
+        thread::sleep_ms(5);
+        println!("Current value: {}", counter.get());
+    }
+
+    // Finally, wait for all the threads to finish to be sure we can catch the counter's final value.
+    handle1.join().unwrap();
+    handle2.join().unwrap();
+    println!("Final value: {}", counter.get());
+}