Alloc-WG
========
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An attempt to collect several proposals of [rust-lang/wg-allocators](https://github.com/rust-lang/wg-allocators) into a
MVP.
Changes regarding the current `Alloc` trait
-------------------------------------------
- The first thing to notice is, that [`Alloc`] was renamed to [`AllocRef`] in order to show that they are typically
implemented for a reference or smart pointer or ZST, not directly for the type that actually holds the allocator’s
state.
Issue: [rust-lang/wg-allocators#8](https://github.com/rust-lang/wg-allocators/issues/8)
- [`AllocRef`] was split up into [`AllocRef`], [`DeallocRef`], and [`ReallocRef`] to make more flexible allocators
possible.
Issue: [rust-lang/wg-allocators#9](https://github.com/rust-lang/wg-allocators/issues/9)
- All three traits were associated with a Builder: [`BuildAlloc`], [`BuildDealloc`], and [`BuildRealloc`] such those
traits are related to their association similar how `BuildHasher` is related to `Hasher`. Although the signatures are
different, it makes an even more flexible allocator design possible.
Issue: [rust-lang/wg-allocators#12](https://github.com/rust-lang/wg-allocators/issues/12)
- Add an associative error type to [`AllocRef`]. Besides adding the possibility of returning additional information on
allocation failure, it's also possible to split the usage of the `AllocRef` into a fallible and an infallible case.
Personally I think this is a pretty big deal, as kernel programmer can rely on allocation, which will never fail. If
an allocation can fail, only a `try_*_in` method may be available. To maintain backwards compatibility, [`AbortAlloc`]
was introduced. [`AbortAlloc`] wraps another allocator, but aborts on OOM thus `AbortAlloc<Global>` may be used as
default allocator for `Box` or `Vec`. To realize this, [`AbortAlloc`] implements `AllocRef<Error=!>`.
Issue: [rust-lang/wg-allocators#23](https://github.com/rust-lang/wg-allocators/issues/23)
- The new layout type [`NonZeroLayout`] was introduced. Currently, implementors of [`Alloc`] can chose to allow
zero-sized allocation so in a generic context it's impossible to rely on this, so banning zero-sized allocation is a
possible step to prevent this. This also removes `unsafe` from [`AllocRef::alloc`] and [`AllocRef::alloc_zeroed`], and
unlocks the possibility to move the extension API like `alloc_array` into a separate trait.
Issue: [rust-lang/wg-allocators#16](https://github.com/rust-lang/wg-allocators/issues/16)
To Do
-----
- provide a minimal implementation for `Box<T, B: BuildDealloc>`. So far I'm basically done with this, but things has
to be cleaned up a bit before.
- provide a decent documentation for the new traits
[`Alloc`]: https://doc.rust-lang.org/1.38.0/alloc/alloc/trait.Alloc.html
[`AllocRef`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.AllocRef.html
[`AllocRef::alloc`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.AllocRef.html#tymethod.alloc
[`AllocRef::alloc_zeroed`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.AllocRef.html#method.alloc_zeroed
[`DeallocRef`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.DeallocRef.html
[`ReallocRef`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.ReallocRef.html
[`BuildAlloc`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.BuildAlloc.html
[`BuildDealloc`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.BuildDealloc.html
[`BuildRealloc`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/trait.BuildRealloc.html
[`BuildHasher`]: https://doc.rust-lang.org/1.38.0/core/hash/trait.BuildHasher.html
[`Hasher`]: https://doc.rust-lang.org/1.38.0/core/hash/trait.Hasher.html
[`NonZeroLayout`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/struct.NonZeroLayout.html
[`AbortAlloc`]: https://timdiekmann.github.io/alloc-wg/alloc_wg/alloc/struct.AbortAlloc.html
License
-------
Alloc-WG is distributed under the terms of both the MIT license and the Apache License (Version 2.0).
See [LICENSE-APACHE](https://github.com/TimDiekmann/alloc-wg/blob/master/LICENSE-APACHE) and [LICENSE-MIT](https://github.com/TimDiekmann/alloc-wg/blob/master/LICENSE-MIT) for details.