| //! Limitations and common pitfalls. |
| //! |
| //! # Sized types |
| //! |
| //! This currently works only for `Sized` types. Unsized types have „fat pointers“, which are twice |
| //! as large as the normal ones. The [`AtomicPtr`] doesn't support them. One could use something |
| //! like `AtomicU128` for them. The catch is this doesn't exist and the difference would make it |
| //! really hard to implement the debt storage/stripped down hazard pointers. |
| //! |
| //! A workaround is to use double indirection: |
| //! |
| //! ```rust |
| //! # use arc_swap::ArcSwap; |
| //! // This doesn't work: |
| //! // let data: ArcSwap<[u8]> = ArcSwap::new(Arc::from([1, 2, 3])); |
| //! |
| //! // But this does: |
| //! let data: ArcSwap<Box<[u8]>> = ArcSwap::from_pointee(Box::new([1, 2, 3])); |
| //! # drop(data); |
| //! ``` |
| //! |
| //! It also may be possible to use `ArcSwap` with the [`triomphe::ThinArc`] (that crate needs |
| //! enabling a feature flag to cooperate with `ArcSwap`). |
| //! |
| //! # Too many [`Guard`]s |
| //! |
| //! There's only limited number of "fast" slots for borrowing from [`ArcSwap`] for each single |
| //! thread (currently 8, but this might change in future versions). If these run out, the algorithm |
| //! falls back to slower path. |
| //! |
| //! If too many [`Guard`]s are kept around, the performance might be poor. These are not intended |
| //! to be stored in data structures or used across async yield points. |
| //! |
| //! [`ArcSwap`]: crate::ArcSwap |
| //! [`Guard`]: crate::Guard |
| //! [`AtomicPtr`]: std::sync::atomic::AtomicPtr |
| //! |
| //! # No `Clone` implementation |
| //! |
| //! Previous version implemented [`Clone`], but it turned out to be very confusing to people, since |
| //! it created fully independent [`ArcSwap`]. Users expected the instances to be tied to each |
| //! other, that store in one would change the result of future load of the other. |
| //! |
| //! To emulate the original behaviour, one can do something like this: |
| //! |
| //! ```rust |
| //! # use arc_swap::ArcSwap; |
| //! # let old = ArcSwap::from_pointee(42); |
| //! let new = ArcSwap::new(old.load_full()); |
| //! # let _ = new; |
| //! ``` |
| //! |
| //! [`triomphe::ThinArc`]: https://docs.rs/triomphe/latest/triomphe/struct.ThinArc.html |
