-// Rust-101, Part 15: Mutex, Interior Mutability (cont.), Sync
-// ===========================================================
+// Rust-101, Part 15: Mutex, Interior Mutability (cont.), RwLock, Sync
+// ===================================================================
use std::sync::{Arc, Mutex};
use std::thread;
+use std::time::Duration;
// The derived `Clone` implementation will clone the `Arc`, so all clones will actually talk about the same counter.
unimplemented!()
}
+ // The core operation is, of course, `increment`.
pub fn increment(&self, by: usize) {
- // `lock` on a mutex returns a *guard*, giving access to the data contained in the mutex.
+ // `lock` on a mutex returns a guard, very much like `RefCell`. The guard gives access to the data contained in the mutex.
let mut counter = self.0.lock().unwrap();
*counter = *counter + by;
}
let counter1 = counter.clone();
let handle1 = thread::spawn(move || {
for _ in 0..10 {
- thread::sleep_ms(15);
+ thread::sleep(Duration::from_millis(15));
counter1.increment(2);
}
});
let counter2 = counter.clone();
let handle2 = thread::spawn(move || {
for _ in 0..10 {
- thread::sleep_ms(20);
+ thread::sleep(Duration::from_millis(20));
counter2.increment(3);
}
});
// Now we watch the threads working on the counter.
for _ in 0..50 {
- thread::sleep_ms(5);
+ thread::sleep(Duration::from_millis(5));
println!("Current value: {}", counter.get());
}
println!("Final value: {}", counter.get());
}
-// **Exercise 14.1**: Besides `Mutex`, there's also [`RwLock`](http://doc.rust-lang.org/stable/std/sync/struct.RwLock.html), which
-// provides two ways of locking: One that grants only read-only access, to any number of concurrent readers, and another one
-// for exclusive write access. (Notice that this is the same pattern we already saw with shared vs. mutable borrows.) Change
-// the code above to use `RwLock`, such that multiple calls to `get` can be executed at the same time.
-//
-// **Exercise 14.2**: Add an operation `compare_and_inc(&self, test: usize, by: usize)` that increments the counter by
+// **Exercise 15.1**: Add an operation `compare_and_inc(&self, test: usize, by: usize)` that increments the counter by
// `by` *only if* the current value is `test`.
+//
+// **Exercise 15.2**: Rather than panicking in case the lock is poisoned, we can use `into_inner` on the error to recover
+// the data inside the lock. Change the code above to do that. Try using `unwrap_or_else` for this job.
-// FIXME TODO some old outdated explanation FIXME TODO
-
+// **Exercise 15.3**: Change the code above to use `RwLock`, such that multiple calls to `get` can be executed at the same time.