pub struct UniqueArc<T: ?Sized>(_);
Arc that is known to be uniquely owned
Arcs are constructed, they are known to be
uniquely owned. In such a case it is safe to mutate
the contents of the
Arc. Normally, one would just handle
this by mutating the data on the stack before allocating the
Arc, however it’s possible the data is large or unsized
and you need to heap-allocate it earlier in such a way
that it can be freely converted into a regular
Arc once you’re
UniqueArc exists for this purpose, when constructed it performs
the same allocations necessary for an
Arc, however it allows mutable access.
Once the mutation is finished, you can call
.shareable() and get a regular
out of it.
Ignore the doctest below there’s no way to skip building with refcount logging during doc tests (see rust-lang/rust#45599).
let data = [1, 2, 3, 4, 5]; let mut x = UniqueArc::new(data); x = 7; // mutate! let y = x.shareable(); // y is an Arc<T>