61 lines
2.1 KiB
Rust
61 lines
2.1 KiB
Rust
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/// Unsafely unborrow an owned singleton out of a `&mut`.
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///
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/// It is intended to be implemented for owned peripheral singletons, such as `USART3` or `AnyPin`.
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/// Unborrowing an owned `T` yields the same `T`. Unborrowing a `&mut T` yields a copy of the T.
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///
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/// This allows writing HAL drivers that either own or borrow their peripherals, but that don't have
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/// to store pointers in the borrowed case.
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///
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/// Safety: this trait can be used to copy non-Copy types. Implementors must not cause
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/// immediate UB when copied, and must not cause UB when copies are later used, provided they
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/// are only used according the [`Self::unborrow`] safety contract.
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///
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pub unsafe trait Unborrow {
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/// Unborrow result type
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type Target;
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/// Unborrow a value.
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///
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/// Safety: This returns a copy of a singleton that's normally not
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/// copiable. The returned copy must ONLY be used while the lifetime of `self` is
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/// valid, as if it were accessed through `self` every time.
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unsafe fn unborrow(self) -> Self::Target;
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}
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unsafe impl<'a, T: Unborrow> Unborrow for &'a mut T {
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type Target = T::Target;
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unsafe fn unborrow(self) -> Self::Target {
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T::unborrow(core::ptr::read(self))
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}
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}
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macro_rules! unsafe_impl_unborrow_tuples {
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($($t:ident),+) => {
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unsafe impl<$($t),+> Unborrow for ($($t),+)
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where
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$(
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$t: Unborrow<Target = $t>
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),+
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{
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type Target = ($($t),+);
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unsafe fn unborrow(self) -> Self::Target {
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self
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}
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}
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};
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}
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unsafe_impl_unborrow_tuples!(A, B);
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unsafe_impl_unborrow_tuples!(A, B, C);
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unsafe_impl_unborrow_tuples!(A, B, C, D);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F, G);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F, G, H);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F, G, H, I);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F, G, H, I, J);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F, G, H, I, J, K);
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unsafe_impl_unborrow_tuples!(A, B, C, D, E, F, G, H, I, J, K, L);
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