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//! The `PClone` trait for types that cannot be 'implicitly copied' use crate::alloc::*; use crate::stm::*; use crate::PSafe; /// A common trait for the ability to explicitly duplicate an object. /// /// Differs from [`Copy`] in that [`Copy`] is implicit and extremely /// inexpensive, while `PClone` is always explicit and may or may not be /// expensive. Its difference with [`Clone`] is that it a `&`[`Journal`] to be /// used for logging in [`Prc`] and [`Parc`]. In order to enforce these /// characteristics, Rust does not allow you to reimplement [`Copy`], but you /// may reimplement [`Clone`] and `PClone` and run arbitrary code. /// /// Since `PClone` is more general than [`Copy`], you can automatically make /// anything [`Copy`] be `Clone` as well. /// /// ## Derivable /// /// This trait can be used with `#[derive]` if all fields are `PClone`. The /// `derive`d implementation of [`PClone`] calls [`pclone`] on each field. It /// uses [`default::BuddyAlloc`] by default. It is possible to change the pool /// type(s) by using `pools()` attribute. /// /// [`pclone`]: #method.pclone /// [`Prc`]: ../prc/struct.Prc.html /// [`Parc`]: ../sync/struct.Parc.html /// [`default::BuddyAlloc`]: ../default/struct.BuddyAlloc.html /// /// For a generic struct, `#[derive]` implements `PClone` conditionally by /// adding bound `Clone` on generic parameters. /// /// ``` /// # use corundum::*; /// // `derive` implements PClone<BuddyAlloc> for Reading<T> when T is /// // PClone<BuddyAlloc> /// #[derive(PClone)] /// struct Reading<T> { /// frequency: T, /// } /// ``` /// /// ``` /// # use corundum::*; /// # use corundum::alloc::heap::*; /// # pool!(p); type P = p::BuddyAlloc; /// # pool!(q); type Q = q::BuddyAlloc; /// // `derive` implements PClone<P> and PClone<Q> for Reading<T> when T is /// // PClone<P> and PClone<Q> specified by `pools`. /// #[derive(PClone)] /// #[pools(P,Q)] /// struct Reading<T> { /// frequency: T, /// } /// ``` /// /// ## How can I implement `PClone`? /// /// Types that are [`Copy`] should have a trivial implementation of `PClone`. /// More formally: if `T: Copy`, `x: T`, and `y: &T`, then `let x = y.pclone();` /// is equivalent to `let x = *y;`. Manual implementations should be careful to /// uphold this invariant; however, unsafe code must not rely on it to ensure /// memory safety. Note that, the implementation should be done for a specific /// (or generic) pool type. /// /// [`Copy`]: std::marker::Copy pub trait PClone<A: MemPool>: Sized { fn pclone(&self, journal: &Journal<A>) -> Self; /// Performs copy-assignment from `source`. /// /// `a.clone_from(&b)` is equivalent to `a = b.clone()` in functionality, /// but can be overridden to reuse the resources of `a` to avoid unnecessary /// allocations. fn pclone_from(&mut self, source: &Self, journal: &Journal<A>) { *self = source.pclone(journal) } } impl<T: PSafe + PClone<A>, A: MemPool> PClone<A> for Option<T> { fn pclone(&self, journal: &Journal<A>) -> Self { if let Some(x) = self { Some(x.pclone(journal)) } else { None } } } impl<T: PSafe + PClone<A> + ?Sized, A: MemPool> PClone<A> for &[T] { fn pclone(&self, j: &Journal<A>) -> Self { let res = unsafe { A::new_slice(self, j) }; for i in 0..res.len() { res[i] = self[i].pclone(j); } res } } impl<T: PSafe + PClone<A>, A: MemPool, const N: usize> PClone<A> for [T;N] { fn pclone(&self, j: &Journal<A>) -> Self { use std::mem::MaybeUninit; let mut res = unsafe { MaybeUninit::<Self>::uninit().assume_init() }; for i in 0..res.len() { std::mem::forget(std::mem::replace(&mut res[i],self[i].pclone(j))); } res } } use impl_trait_for_tuples::*; #[impl_for_tuples(32)] impl<A: MemPool> PClone<A> for Tuple { fn pclone(&self, j: &Journal<A>) -> Self { for_tuples!( ( #( Tuple.pclone(j) ),* ) ) } } /// Implementations of `PClone` for primitive types. mod impls { use super::PClone; use crate::alloc::MemPool; use crate::stm::Journal; macro_rules! impl_clone { ($($t:ty)*) => { $( impl<A: MemPool> PClone<A> for $t { #[inline] fn pclone(&self, _j: &Journal<A>) -> Self { *self } } )* } } impl_clone! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 bool char } }