RoLock

Read Only Lock.

This is a wrapper around Arc<RwLock<T>> that only implements RwLock::read() operations.

Usage

Create a normal Arc<RwLock<T>> in thread_1, send a RoLock to thread_2:

let rw = Arc::new(RwLock::new(0));     // Regular Arc<RwLock<T>>.
let ro = RoLock::new(&rw);             // Read Only Lock.

assert!(*rw.read().unwrap() == 0);     // This can read...
*rw.write().unwrap() = 1;              // and write.

std::thread::spawn(move|| {
	assert!(*ro.read().unwrap() == 1); // This one can only read.
});

• thread_1 still has full read/write control
• thread_2 can only RoLock::read()

This type guarantees at compile time that you cannot write because the function doesn't even exist:

let rw = Arc::new(RwLock::new(0));
let ro = RoLock::new(&rw);

ro.write(); // Compile error!

Since the inner field of RoLock (self.0) is private, you can't call RwLock::write directly either:

let rw = Arc::new(RwLock::new(0));
let ro = RoLock::new(&rw);

ro.0.write(); // Compile error!