Provides an interface to unify single-threaded code and RwLocks-based code.

A nice side effect of this trait is manifested in the activation of the borrow-checker to check the absence of deadlocks introduced in the current scope. This is because Self::write can now only be called on a mutable, but not constant, reference.

Example

```rust use parkinglot::RwLock; use readwrite_api::{RwApi, RwApiWrapper, RwApiWrapperOwned};

fn do_something(mut x: impl RwApi) -> u64 { if *x.read() == 1 { *x.write() = 2; *x.read() } else { *x.read() } }

asserteq!(dosomething(RwApiWrapperOwned(1)), 2); asserteq!(dosomething(RwApiWrapperOwned(3)), 3); asserteq!(dosomething(&mut RwApiWrapperOwned(1)), 2); asserteq!(dosomething(&mut RwApiWrapperOwned(3)), 3);

asserteq!(dosomething(RwLock::new(1)), 2); asserteq!(dosomething(RwLock::new(3)), 3); asserteq!(dosomething(&RwLock::new(1)), 2); asserteq!(dosomething(&RwLock::new(3)), 3); asserteq!(dosomething(&mut RwLock::new(1)), 2); asserteq!(dosomething(&mut RwLock::new(3)), 3);

fn dosomethingref<'a>(mut x: impl RwApi) -> u64 { if *x.read() == 1 { *x.write() = 2; *x.read() } else { *x.read() } }

asserteq!(dosomethingref(RwApiWrapper(&mut 1)), 2); asserteq!(dosomethingref(RwApiWrapper(&mut 3)), 3); asserteq!(dosomethingref(&mut RwApiWrapper(&mut 1)), 2); asserteq!(dosomethingref(&mut RwApiWrapper(&mut 3)), 3);

asserteq!(dosomethingref(RwLock::new(&mut 1)), 2); asserteq!(dosomethingref(RwLock::new(&mut 3)), 3); asserteq!(dosomethingref(&RwLock::new(&mut 1)), 2); asserteq!(dosomethingref(&RwLock::new(&mut 3)), 3); asserteq!(dosomethingref(&mut RwLock::new(&mut 1)), 2); asserteq!(dosomethingref(&mut RwLock::new(&mut 3)), 3); ```