A cell whose value can only be accessed by a owning thread. Much like a Mutex but without blocking locks. Access to ThreadCells is passed cooperatively between threads.

Semantics

ThreadCell

A ThreadCell and references therof can always be send to other threads

• A ThreadCell that is owned by a thread then only that thread can:
  • Access its value
  • Drop the cell.
  • Set the Cell into a disowned state.
• On a ThreadCell that is disowned any thread can:
  • Take ownership of it
  • Drop it

Threads that do not own a ThreadCell and access its value will panic. There are 'try_*' variants in the API that will not panic but return a bool or Option instead.

Guard

threadcell::Guard and threadcell::GuardMut are optional and handle proper acquire/release for thradcells. There can be only one guard active per threadcell.

Guards implement Deref and DerefMut making accessing threadcells more ergonomic.

A side effect of being optional is that becomes possible to explicitly release a ThreadCell while it still has a active guard. Dereferencing such a Guard will panic then. Thus care should be taken than threadcells are either managed by guards or manually managed.

Use Cases

• Single threaded applications that need a static mutable global variable can use ThreadCell<RefCell<T>>.
• A static mut ThreadCell<T> will needs unsafe code but is actually safe because ThreadCell guards against concurrent access.
• Sharing data between threads where synchronizaton is done out of band with other syncronization primitives.