Crate tokenlock [−] [src]

Provides a Send-able cell type whose contents can be accessed only via an inforgeable token.

Examples

let mut token = Token::new();

let lock = TokenLock::new(&token, 1);
assert_eq!(*lock.read(&token).unwrap(), 1);

let mut guard = lock.write(&mut token).unwrap();
assert_eq!(*guard, 1);
*guard = 2;

TokenLock implements Send and Sync so it can be shared between threads, but only the thread holding the original Token can access its contents. Token cannot be cloned:

let lock = Arc::new(TokenLock::new(&token, 1));

let lock_1 = Arc::clone(&lock);
thread::Builder::new().spawn(move || {
    let lock_1 = lock_1;
    let mut token_1 = token;

    // I have `Token` so I can get a mutable reference to the contents
    lock_1.write(&mut token_1).unwrap();
}).unwrap();

// can't access the contents; I no longer have `Token`
// lock.write(&mut token).unwrap();

The lifetime of the returned reference is limited by both of the TokenLock and Token.

⚠This code doesn't compile so be extra careful!
let mut token = Token::new();
let lock = TokenLock::new(&token, 1);
let guard = lock.write(&mut token).unwrap();
drop(lock); // compile error: `guard` cannot outlive `TokenLock`
⚠This code doesn't compile so be extra careful!
drop(token); // compile error: `guard` cannot outlive `Token`

It also prevents from forming a reference to the contained value when there already is a mutable reference to it:

⚠This code doesn't compile so be extra careful!
let write_guard = lock.write(&mut token).unwrap();
let read_guard = lock.read(&token).unwrap(); // compile error

While allowing multiple immutable references:

let read_guard1 = lock.read(&token).unwrap();
let read_guard2 = lock.read(&token).unwrap();

Structs

Token

An inforgeable token used to access the contents of a TokenLock.
TokenLock

A mutual exclusive primitive that can be accessed using a Token with a very low over-head.
TokenRef

Token that cannot be used to access the contents of a TokenLock, but can be used to create a new TokenLock.