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Diffstat (limited to 'compiler/rustc_data_structures/src/owning_ref/mod.rs')
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diff --git a/compiler/rustc_data_structures/src/owning_ref/mod.rs b/compiler/rustc_data_structures/src/owning_ref/mod.rs deleted file mode 100644 index d1d92b905b8..00000000000 --- a/compiler/rustc_data_structures/src/owning_ref/mod.rs +++ /dev/null @@ -1,1211 +0,0 @@ -#![warn(missing_docs)] - -/*! -# An owning reference. - -This crate provides the _owning reference_ types `OwningRef` and `OwningRefMut` -that enables it to bundle a reference together with the owner of the data it points to. -This allows moving and dropping of an `OwningRef` without needing to recreate the reference. - -This can sometimes be useful because Rust borrowing rules normally prevent -moving a type that has been moved from. For example, this kind of code gets rejected: - -```compile_fail,E0515 -fn return_owned_and_referenced<'a>() -> (Vec<u8>, &'a [u8]) { - let v = vec![1, 2, 3, 4]; - let s = &v[1..3]; - (v, s) -} -``` - -Even though, from a memory-layout point of view, this can be entirely safe -if the new location of the vector still lives longer than the lifetime `'a` -of the reference because the backing allocation of the vector does not change. - -This library enables this safe usage by keeping the owner and the reference -bundled together in a wrapper type that ensure that lifetime constraint: - -``` -# use rustc_data_structures::owning_ref::OwningRef; -# fn main() { -fn return_owned_and_referenced() -> OwningRef<Vec<u8>, [u8]> { - let v = vec![1, 2, 3, 4]; - let or = OwningRef::new(v); - let or = or.map(|v| &v[1..3]); - or -} -# } -``` - -It works by requiring owner types to dereference to stable memory locations -and preventing mutable access to root containers, which in practice requires heap allocation -as provided by `Box<T>`, `Rc<T>`, etc. - -Also provided are typedefs for common owner type combinations, -which allow for less verbose type signatures. -For example, `BoxRef<T>` instead of `OwningRef<Box<T>, T>`. - -The crate also provides the more advanced `OwningHandle` type, -which allows more freedom in bundling a dependent handle object -along with the data it depends on, at the cost of some unsafe needed in the API. -See the documentation around `OwningHandle` for more details. - -# Examples - -## Basics - -``` -use rustc_data_structures::owning_ref::BoxRef; - -fn main() { - // Create an array owned by a Box. - let arr = Box::new([1, 2, 3, 4]) as Box<[i32]>; - - // Transfer into a BoxRef. - let arr: BoxRef<[i32]> = BoxRef::new(arr); - assert_eq!(&*arr, &[1, 2, 3, 4]); - - // We can slice the array without losing ownership or changing type. - let arr: BoxRef<[i32]> = arr.map(|arr| &arr[1..3]); - assert_eq!(&*arr, &[2, 3]); - - // Also works for Arc, Rc, String and Vec! -} -``` - -## Caching a reference to a struct field - -``` -use rustc_data_structures::owning_ref::BoxRef; - -fn main() { - struct Foo { - tag: u32, - x: u16, - y: u16, - z: u16, - } - let foo = Foo { tag: 1, x: 100, y: 200, z: 300 }; - - let or = BoxRef::new(Box::new(foo)).map(|foo| { - match foo.tag { - 0 => &foo.x, - 1 => &foo.y, - 2 => &foo.z, - _ => panic!(), - } - }); - - assert_eq!(*or, 200); -} -``` - -## Caching a reference to an entry in a vector - -``` -use rustc_data_structures::owning_ref::VecRef; - -fn main() { - let v = VecRef::new(vec![1, 2, 3, 4, 5]).map(|v| &v[3]); - assert_eq!(*v, 4); -} -``` - -## Caching a subslice of a String - -``` -use rustc_data_structures::owning_ref::StringRef; - -fn main() { - let s = StringRef::new("hello world".to_owned()) - .map(|s| s.split(' ').nth(1).unwrap()); - - assert_eq!(&*s, "world"); -} -``` - -## Reference counted slices that share ownership of the backing storage - -``` -use rustc_data_structures::owning_ref::RcRef; -use std::rc::Rc; - -fn main() { - let rc: RcRef<[i32]> = RcRef::new(Rc::new([1, 2, 3, 4]) as Rc<[i32]>); - assert_eq!(&*rc, &[1, 2, 3, 4]); - - let rc_a: RcRef<[i32]> = rc.clone().map(|s| &s[0..2]); - let rc_b = rc.clone().map(|s| &s[1..3]); - let rc_c = rc.clone().map(|s| &s[2..4]); - assert_eq!(&*rc_a, &[1, 2]); - assert_eq!(&*rc_b, &[2, 3]); - assert_eq!(&*rc_c, &[3, 4]); - - let rc_c_a = rc_c.clone().map(|s| &s[1]); - assert_eq!(&*rc_c_a, &4); -} -``` - -## Atomic reference counted slices that share ownership of the backing storage - -``` -use rustc_data_structures::owning_ref::ArcRef; -use std::sync::Arc; - -fn main() { - use std::thread; - - fn par_sum(rc: ArcRef<[i32]>) -> i32 { - if rc.len() == 0 { - return 0; - } else if rc.len() == 1 { - return rc[0]; - } - let mid = rc.len() / 2; - let left = rc.clone().map(|s| &s[..mid]); - let right = rc.map(|s| &s[mid..]); - - let left = thread::spawn(move || par_sum(left)); - let right = thread::spawn(move || par_sum(right)); - - left.join().unwrap() + right.join().unwrap() - } - - let rc: Arc<[i32]> = Arc::new([1, 2, 3, 4]); - let rc: ArcRef<[i32]> = rc.into(); - - assert_eq!(par_sum(rc), 10); -} -``` - -## References into RAII locks - -``` -use rustc_data_structures::owning_ref::RefRef; -use std::cell::{RefCell, Ref}; - -fn main() { - let refcell = RefCell::new((1, 2, 3, 4)); - // Also works with Mutex and RwLock - - let refref = { - let refref = RefRef::new(refcell.borrow()).map(|x| &x.3); - assert_eq!(*refref, 4); - - // We move the RAII lock and the reference to one of - // the subfields in the data it guards here: - refref - }; - - assert_eq!(*refref, 4); - - drop(refref); - - assert_eq!(*refcell.borrow(), (1, 2, 3, 4)); -} -``` - -## Mutable reference - -When the owned container implements `DerefMut`, it is also possible to make -a _mutable owning reference_. (e.g., with `Box`, `RefMut`, `MutexGuard`) - -``` -use rustc_data_structures::owning_ref::RefMutRefMut; -use std::cell::{RefCell, RefMut}; - -fn main() { - let refcell = RefCell::new((1, 2, 3, 4)); - - let mut refmut_refmut = { - let mut refmut_refmut = RefMutRefMut::new(refcell.borrow_mut()).map_mut(|x| &mut x.3); - assert_eq!(*refmut_refmut, 4); - *refmut_refmut *= 2; - - refmut_refmut - }; - - assert_eq!(*refmut_refmut, 8); - *refmut_refmut *= 2; - - drop(refmut_refmut); - - assert_eq!(*refcell.borrow(), (1, 2, 3, 16)); -} -``` -*/ - -pub use stable_deref_trait::{ - CloneStableDeref as CloneStableAddress, StableDeref as StableAddress, -}; -use std::mem; - -/// An owning reference. -/// -/// This wraps an owner `O` and a reference `&T` pointing -/// at something reachable from `O::Target` while keeping -/// the ability to move `self` around. -/// -/// The owner is usually a pointer that points at some base type. -/// -/// For more details and examples, see the module and method docs. -pub struct OwningRef<O, T: ?Sized> { - owner: O, - reference: *const T, -} - -/// An mutable owning reference. -/// -/// This wraps an owner `O` and a reference `&mut T` pointing -/// at something reachable from `O::Target` while keeping -/// the ability to move `self` around. -/// -/// The owner is usually a pointer that points at some base type. -/// -/// For more details and examples, see the module and method docs. -pub struct OwningRefMut<O, T: ?Sized> { - owner: O, - reference: *mut T, -} - -/// Helper trait for an erased concrete type an owner dereferences to. -/// This is used in form of a trait object for keeping -/// something around to (virtually) call the destructor. -pub trait Erased {} -impl<T> Erased for T {} - -/// Helper trait for erasing the concrete type of what an owner dereferences to, -/// for example `Box<T> -> Box<Erased>`. This would be unneeded with -/// higher kinded types support in the language. -#[allow(unused_lifetimes)] -pub unsafe trait IntoErased<'a> { - /// Owner with the dereference type substituted to `Erased`. - type Erased; - /// Performs the type erasure. - fn into_erased(self) -> Self::Erased; -} - -/// Helper trait for erasing the concrete type of what an owner dereferences to, -/// for example `Box<T> -> Box<Erased + Send>`. This would be unneeded with -/// higher kinded types support in the language. -#[allow(unused_lifetimes)] -pub unsafe trait IntoErasedSend<'a> { - /// Owner with the dereference type substituted to `Erased + Send`. - type Erased: Send; - /// Performs the type erasure. - fn into_erased_send(self) -> Self::Erased; -} - -/// Helper trait for erasing the concrete type of what an owner dereferences to, -/// for example `Box<T> -> Box<Erased + Send + Sync>`. This would be unneeded with -/// higher kinded types support in the language. -#[allow(unused_lifetimes)] -pub unsafe trait IntoErasedSendSync<'a> { - /// Owner with the dereference type substituted to `Erased + Send + Sync`. - type Erased: Send + Sync; - /// Performs the type erasure. - fn into_erased_send_sync(self) -> Self::Erased; -} - -///////////////////////////////////////////////////////////////////////////// -// OwningRef -///////////////////////////////////////////////////////////////////////////// - -impl<O, T: ?Sized> OwningRef<O, T> { - /// Creates a new owning reference from an owner - /// initialized to the direct dereference of it. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRef; - /// - /// fn main() { - /// let owning_ref = OwningRef::new(Box::new(42)); - /// assert_eq!(*owning_ref, 42); - /// } - /// ``` - pub fn new(o: O) -> Self - where - O: StableAddress, - O: Deref<Target = T>, - { - OwningRef { reference: &*o, owner: o } - } - - /// Like `new`, but doesn’t require `O` to implement the `StableAddress` trait. - /// Instead, the caller is responsible to make the same promises as implementing the trait. - /// - /// This is useful for cases where coherence rules prevents implementing the trait - /// without adding a dependency to this crate in a third-party library. - pub unsafe fn new_assert_stable_address(o: O) -> Self - where - O: Deref<Target = T>, - { - OwningRef { reference: &*o, owner: o } - } - - /// Converts `self` into a new owning reference that points at something reachable - /// from the previous one. - /// - /// This can be a reference to a field of `U`, something reachable from a field of - /// `U`, or even something unrelated with a `'static` lifetime. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRef; - /// - /// fn main() { - /// let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4])); - /// - /// // create an owning reference that points at the - /// // third element of the array. - /// let owning_ref = owning_ref.map(|array| &array[2]); - /// assert_eq!(*owning_ref, 3); - /// } - /// ``` - pub fn map<F, U: ?Sized>(self, f: F) -> OwningRef<O, U> - where - O: StableAddress, - F: FnOnce(&T) -> &U, - { - OwningRef { reference: f(&self), owner: self.owner } - } - - /// Tries to convert `self` into a new owning reference that points - /// at something reachable from the previous one. - /// - /// This can be a reference to a field of `U`, something reachable from a field of - /// `U`, or even something unrelated with a `'static` lifetime. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRef; - /// - /// fn main() { - /// let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4])); - /// - /// // create an owning reference that points at the - /// // third element of the array. - /// let owning_ref = owning_ref.try_map(|array| { - /// if array[2] == 3 { Ok(&array[2]) } else { Err(()) } - /// }); - /// assert_eq!(*owning_ref.unwrap(), 3); - /// } - /// ``` - pub fn try_map<F, U: ?Sized, E>(self, f: F) -> Result<OwningRef<O, U>, E> - where - O: StableAddress, - F: FnOnce(&T) -> Result<&U, E>, - { - Ok(OwningRef { reference: f(&self)?, owner: self.owner }) - } - - /// Converts `self` into a new owning reference with a different owner type. - /// - /// The new owner type needs to still contain the original owner in some way - /// so that the reference into it remains valid. This function is marked unsafe - /// because the user needs to manually uphold this guarantee. - pub unsafe fn map_owner<F, P>(self, f: F) -> OwningRef<P, T> - where - O: StableAddress, - P: StableAddress, - F: FnOnce(O) -> P, - { - OwningRef { reference: self.reference, owner: f(self.owner) } - } - - /// Converts `self` into a new owning reference where the owner is wrapped - /// in an additional `Box<O>`. - /// - /// This can be used to safely erase the owner of any `OwningRef<O, T>` - /// to an `OwningRef<Box<Erased>, T>`. - pub fn map_owner_box(self) -> OwningRef<Box<O>, T> { - OwningRef { reference: self.reference, owner: Box::new(self.owner) } - } - - /// Erases the concrete base type of the owner with a trait object. - /// - /// This allows mixing of owned references with different owner base types. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::{OwningRef, Erased}; - /// - /// fn main() { - /// // N.B., using the concrete types here for explicitness. - /// // For less verbose code type aliases like `BoxRef` are provided. - /// - /// let owning_ref_a: OwningRef<Box<[i32; 4]>, [i32; 4]> - /// = OwningRef::new(Box::new([1, 2, 3, 4])); - /// - /// let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, Vec<(i32, bool)>> - /// = OwningRef::new(Box::new(vec![(0, false), (1, true)])); - /// - /// let owning_ref_a: OwningRef<Box<[i32; 4]>, i32> - /// = owning_ref_a.map(|a| &a[0]); - /// - /// let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, i32> - /// = owning_ref_b.map(|a| &a[1].0); - /// - /// let owning_refs: [OwningRef<Box<dyn Erased>, i32>; 2] - /// = [owning_ref_a.erase_owner(), owning_ref_b.erase_owner()]; - /// - /// assert_eq!(*owning_refs[0], 1); - /// assert_eq!(*owning_refs[1], 1); - /// } - /// ``` - pub fn erase_owner<'a>(self) -> OwningRef<O::Erased, T> - where - O: IntoErased<'a>, - { - OwningRef { reference: self.reference, owner: self.owner.into_erased() } - } - - /// Erases the concrete base type of the owner with a trait object which implements `Send`. - /// - /// This allows mixing of owned references with different owner base types. - pub fn erase_send_owner<'a>(self) -> OwningRef<O::Erased, T> - where - O: IntoErasedSend<'a>, - { - OwningRef { reference: self.reference, owner: self.owner.into_erased_send() } - } - - /// Erases the concrete base type of the owner with a trait object - /// which implements `Send` and `Sync`. - /// - /// This allows mixing of owned references with different owner base types. - pub fn erase_send_sync_owner<'a>(self) -> OwningRef<O::Erased, T> - where - O: IntoErasedSendSync<'a>, - { - OwningRef { reference: self.reference, owner: self.owner.into_erased_send_sync() } - } - - // UNIMPLEMENTED: wrap_owner - - // FIXME: Naming convention? - /// A getter for the underlying owner. - pub fn owner(&self) -> &O { - &self.owner - } - - // FIXME: Naming convention? - /// Discards the reference and retrieves the owner. - pub fn into_inner(self) -> O { - self.owner - } -} - -impl<O, T: ?Sized> OwningRefMut<O, T> { - /// Creates a new owning reference from an owner - /// initialized to the direct dereference of it. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRefMut; - /// - /// fn main() { - /// let owning_ref_mut = OwningRefMut::new(Box::new(42)); - /// assert_eq!(*owning_ref_mut, 42); - /// } - /// ``` - pub fn new(mut o: O) -> Self - where - O: StableAddress, - O: DerefMut<Target = T>, - { - OwningRefMut { reference: &mut *o, owner: o } - } - - /// Like `new`, but doesn’t require `O` to implement the `StableAddress` trait. - /// Instead, the caller is responsible to make the same promises as implementing the trait. - /// - /// This is useful for cases where coherence rules prevents implementing the trait - /// without adding a dependency to this crate in a third-party library. - pub unsafe fn new_assert_stable_address(mut o: O) -> Self - where - O: DerefMut<Target = T>, - { - OwningRefMut { reference: &mut *o, owner: o } - } - - /// Converts `self` into a new _shared_ owning reference that points at - /// something reachable from the previous one. - /// - /// This can be a reference to a field of `U`, something reachable from a field of - /// `U`, or even something unrelated with a `'static` lifetime. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRefMut; - /// - /// fn main() { - /// let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4])); - /// - /// // create an owning reference that points at the - /// // third element of the array. - /// let owning_ref = owning_ref_mut.map(|array| &array[2]); - /// assert_eq!(*owning_ref, 3); - /// } - /// ``` - pub fn map<F, U: ?Sized>(mut self, f: F) -> OwningRef<O, U> - where - O: StableAddress, - F: FnOnce(&mut T) -> &U, - { - OwningRef { reference: f(&mut self), owner: self.owner } - } - - /// Converts `self` into a new _mutable_ owning reference that points at - /// something reachable from the previous one. - /// - /// This can be a reference to a field of `U`, something reachable from a field of - /// `U`, or even something unrelated with a `'static` lifetime. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRefMut; - /// - /// fn main() { - /// let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4])); - /// - /// // create an owning reference that points at the - /// // third element of the array. - /// let owning_ref_mut = owning_ref_mut.map_mut(|array| &mut array[2]); - /// assert_eq!(*owning_ref_mut, 3); - /// } - /// ``` - pub fn map_mut<F, U: ?Sized>(mut self, f: F) -> OwningRefMut<O, U> - where - O: StableAddress, - F: FnOnce(&mut T) -> &mut U, - { - OwningRefMut { reference: f(&mut self), owner: self.owner } - } - - /// Tries to convert `self` into a new _shared_ owning reference that points - /// at something reachable from the previous one. - /// - /// This can be a reference to a field of `U`, something reachable from a field of - /// `U`, or even something unrelated with a `'static` lifetime. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRefMut; - /// - /// fn main() { - /// let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4])); - /// - /// // create an owning reference that points at the - /// // third element of the array. - /// let owning_ref = owning_ref_mut.try_map(|array| { - /// if array[2] == 3 { Ok(&array[2]) } else { Err(()) } - /// }); - /// assert_eq!(*owning_ref.unwrap(), 3); - /// } - /// ``` - pub fn try_map<F, U: ?Sized, E>(mut self, f: F) -> Result<OwningRef<O, U>, E> - where - O: StableAddress, - F: FnOnce(&mut T) -> Result<&U, E>, - { - Ok(OwningRef { reference: f(&mut self)?, owner: self.owner }) - } - - /// Tries to convert `self` into a new _mutable_ owning reference that points - /// at something reachable from the previous one. - /// - /// This can be a reference to a field of `U`, something reachable from a field of - /// `U`, or even something unrelated with a `'static` lifetime. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::OwningRefMut; - /// - /// fn main() { - /// let owning_ref_mut = OwningRefMut::new(Box::new([1, 2, 3, 4])); - /// - /// // create an owning reference that points at the - /// // third element of the array. - /// let owning_ref_mut = owning_ref_mut.try_map_mut(|array| { - /// if array[2] == 3 { Ok(&mut array[2]) } else { Err(()) } - /// }); - /// assert_eq!(*owning_ref_mut.unwrap(), 3); - /// } - /// ``` - pub fn try_map_mut<F, U: ?Sized, E>(mut self, f: F) -> Result<OwningRefMut<O, U>, E> - where - O: StableAddress, - F: FnOnce(&mut T) -> Result<&mut U, E>, - { - Ok(OwningRefMut { reference: f(&mut self)?, owner: self.owner }) - } - - /// Converts `self` into a new owning reference with a different owner type. - /// - /// The new owner type needs to still contain the original owner in some way - /// so that the reference into it remains valid. This function is marked unsafe - /// because the user needs to manually uphold this guarantee. - pub unsafe fn map_owner<F, P>(self, f: F) -> OwningRefMut<P, T> - where - O: StableAddress, - P: StableAddress, - F: FnOnce(O) -> P, - { - OwningRefMut { reference: self.reference, owner: f(self.owner) } - } - - /// Converts `self` into a new owning reference where the owner is wrapped - /// in an additional `Box<O>`. - /// - /// This can be used to safely erase the owner of any `OwningRefMut<O, T>` - /// to an `OwningRefMut<Box<Erased>, T>`. - pub fn map_owner_box(self) -> OwningRefMut<Box<O>, T> { - OwningRefMut { reference: self.reference, owner: Box::new(self.owner) } - } - - /// Erases the concrete base type of the owner with a trait object. - /// - /// This allows mixing of owned references with different owner base types. - /// - /// # Example - /// ``` - /// use rustc_data_structures::owning_ref::{OwningRefMut, Erased}; - /// - /// fn main() { - /// // N.B., using the concrete types here for explicitness. - /// // For less verbose code type aliases like `BoxRef` are provided. - /// - /// let owning_ref_mut_a: OwningRefMut<Box<[i32; 4]>, [i32; 4]> - /// = OwningRefMut::new(Box::new([1, 2, 3, 4])); - /// - /// let owning_ref_mut_b: OwningRefMut<Box<Vec<(i32, bool)>>, Vec<(i32, bool)>> - /// = OwningRefMut::new(Box::new(vec![(0, false), (1, true)])); - /// - /// let owning_ref_mut_a: OwningRefMut<Box<[i32; 4]>, i32> - /// = owning_ref_mut_a.map_mut(|a| &mut a[0]); - /// - /// let owning_ref_mut_b: OwningRefMut<Box<Vec<(i32, bool)>>, i32> - /// = owning_ref_mut_b.map_mut(|a| &mut a[1].0); - /// - /// let owning_refs_mut: [OwningRefMut<Box<dyn Erased>, i32>; 2] - /// = [owning_ref_mut_a.erase_owner(), owning_ref_mut_b.erase_owner()]; - /// - /// assert_eq!(*owning_refs_mut[0], 1); - /// assert_eq!(*owning_refs_mut[1], 1); - /// } - /// ``` - pub fn erase_owner<'a>(self) -> OwningRefMut<O::Erased, T> - where - O: IntoErased<'a>, - { - OwningRefMut { reference: self.reference, owner: self.owner.into_erased() } - } - - // UNIMPLEMENTED: wrap_owner - - // FIXME: Naming convention? - /// A getter for the underlying owner. - pub fn owner(&self) -> &O { - &self.owner - } - - // FIXME: Naming convention? - /// Discards the reference and retrieves the owner. - pub fn into_inner(self) -> O { - self.owner - } -} - -///////////////////////////////////////////////////////////////////////////// -// OwningHandle -///////////////////////////////////////////////////////////////////////////// - -use std::ops::{Deref, DerefMut}; - -/// `OwningHandle` is a complement to `OwningRef`. Where `OwningRef` allows -/// consumers to pass around an owned object and a dependent reference, -/// `OwningHandle` contains an owned object and a dependent _object_. -/// -/// `OwningHandle` can encapsulate a `RefMut` along with its associated -/// `RefCell`, or an `RwLockReadGuard` along with its associated `RwLock`. -/// However, the API is completely generic and there are no restrictions on -/// what types of owning and dependent objects may be used. -/// -/// `OwningHandle` is created by passing an owner object (which dereferences -/// to a stable address) along with a callback which receives a pointer to -/// that stable location. The callback may then dereference the pointer and -/// mint a dependent object, with the guarantee that the returned object will -/// not outlive the referent of the pointer. -/// -/// Since the callback needs to dereference a raw pointer, it requires `unsafe` -/// code. To avoid forcing this unsafety on most callers, the `ToHandle` trait is -/// implemented for common data structures. Types that implement `ToHandle` can -/// be wrapped into an `OwningHandle` without passing a callback. -pub struct OwningHandle<O, H> -where - O: StableAddress, - H: Deref, -{ - handle: H, - _owner: O, -} - -impl<O, H> Deref for OwningHandle<O, H> -where - O: StableAddress, - H: Deref, -{ - type Target = H::Target; - fn deref(&self) -> &H::Target { - self.handle.deref() - } -} - -unsafe impl<O, H> StableAddress for OwningHandle<O, H> -where - O: StableAddress, - H: StableAddress, -{ -} - -impl<O, H> DerefMut for OwningHandle<O, H> -where - O: StableAddress, - H: DerefMut, -{ - fn deref_mut(&mut self) -> &mut H::Target { - self.handle.deref_mut() - } -} - -/// Trait to implement the conversion of owner to handle for common types. -pub trait ToHandle { - /// The type of handle to be encapsulated by the OwningHandle. - type Handle: Deref; - - /// Given an appropriately-long-lived pointer to ourselves, create a - /// handle to be encapsulated by the `OwningHandle`. - unsafe fn to_handle(x: *const Self) -> Self::Handle; -} - -/// Trait to implement the conversion of owner to mutable handle for common types. -pub trait ToHandleMut { - /// The type of handle to be encapsulated by the OwningHandle. - type HandleMut: DerefMut; - - /// Given an appropriately-long-lived pointer to ourselves, create a - /// mutable handle to be encapsulated by the `OwningHandle`. - unsafe fn to_handle_mut(x: *const Self) -> Self::HandleMut; -} - -impl<O, H> OwningHandle<O, H> -where - O: StableAddress<Target: ToHandle<Handle = H>>, - H: Deref, -{ - /// Creates a new `OwningHandle` for a type that implements `ToHandle`. For types - /// that don't implement `ToHandle`, callers may invoke `new_with_fn`, which accepts - /// a callback to perform the conversion. - pub fn new(o: O) -> Self { - OwningHandle::new_with_fn(o, |x| unsafe { O::Target::to_handle(x) }) - } -} - -impl<O, H> OwningHandle<O, H> -where - O: StableAddress<Target: ToHandleMut<HandleMut = H>>, - H: DerefMut, -{ - /// Creates a new mutable `OwningHandle` for a type that implements `ToHandleMut`. - pub fn new_mut(o: O) -> Self { - OwningHandle::new_with_fn(o, |x| unsafe { O::Target::to_handle_mut(x) }) - } -} - -impl<O, H> OwningHandle<O, H> -where - O: StableAddress, - H: Deref, -{ - /// Creates a new OwningHandle. The provided callback will be invoked with - /// a pointer to the object owned by `o`, and the returned value is stored - /// as the object to which this `OwningHandle` will forward `Deref` and - /// `DerefMut`. - pub fn new_with_fn<F>(o: O, f: F) -> Self - where - F: FnOnce(*const O::Target) -> H, - { - let h: H; - { - h = f(o.deref() as *const O::Target); - } - - OwningHandle { handle: h, _owner: o } - } - - /// Creates a new OwningHandle. The provided callback will be invoked with - /// a pointer to the object owned by `o`, and the returned value is stored - /// as the object to which this `OwningHandle` will forward `Deref` and - /// `DerefMut`. - pub fn try_new<F, E>(o: O, f: F) -> Result<Self, E> - where - F: FnOnce(*const O::Target) -> Result<H, E>, - { - let h: H; - { - h = f(o.deref() as *const O::Target)?; - } - - Ok(OwningHandle { handle: h, _owner: o }) - } -} - -///////////////////////////////////////////////////////////////////////////// -// std traits -///////////////////////////////////////////////////////////////////////////// - -use std::borrow::Borrow; -use std::cmp::Ordering; -use std::fmt::{self, Debug}; -use std::hash::{Hash, Hasher}; - -impl<O, T: ?Sized> Deref for OwningRef<O, T> { - type Target = T; - - fn deref(&self) -> &T { - unsafe { &*self.reference } - } -} - -impl<O, T: ?Sized> Deref for OwningRefMut<O, T> { - type Target = T; - - fn deref(&self) -> &T { - unsafe { &*self.reference } - } -} - -impl<O, T: ?Sized> DerefMut for OwningRefMut<O, T> { - fn deref_mut(&mut self) -> &mut T { - unsafe { &mut *self.reference } - } -} - -unsafe impl<O, T: ?Sized> StableAddress for OwningRef<O, T> {} - -impl<O, T: ?Sized> AsRef<T> for OwningRef<O, T> { - fn as_ref(&self) -> &T { - self - } -} - -impl<O, T: ?Sized> AsRef<T> for OwningRefMut<O, T> { - fn as_ref(&self) -> &T { - self - } -} - -impl<O, T: ?Sized> AsMut<T> for OwningRefMut<O, T> { - fn as_mut(&mut self) -> &mut T { - self - } -} - -impl<O, T: ?Sized> Borrow<T> for OwningRef<O, T> { - fn borrow(&self) -> &T { - self - } -} - -impl<O, T: ?Sized> From<O> for OwningRef<O, T> -where - O: StableAddress, - O: Deref<Target = T>, -{ - fn from(owner: O) -> Self { - OwningRef::new(owner) - } -} - -impl<O, T: ?Sized> From<O> for OwningRefMut<O, T> -where - O: StableAddress, - O: DerefMut<Target = T>, -{ - fn from(owner: O) -> Self { - OwningRefMut::new(owner) - } -} - -impl<O, T: ?Sized> From<OwningRefMut<O, T>> for OwningRef<O, T> -where - O: StableAddress, - O: DerefMut<Target = T>, -{ - fn from(other: OwningRefMut<O, T>) -> Self { - OwningRef { owner: other.owner, reference: other.reference } - } -} - -// ^ FIXME: Is an Into impl for calling into_inner() possible as well? - -impl<O, T: ?Sized> Debug for OwningRef<O, T> -where - O: Debug, - T: Debug, -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - write!(f, "OwningRef {{ owner: {:?}, reference: {:?} }}", self.owner(), &**self) - } -} - -impl<O, T: ?Sized> Debug for OwningRefMut<O, T> -where - O: Debug, - T: Debug, -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - write!(f, "OwningRefMut {{ owner: {:?}, reference: {:?} }}", self.owner(), &**self) - } -} - -impl<O, T: ?Sized> Clone for OwningRef<O, T> -where - O: CloneStableAddress, -{ - fn clone(&self) -> Self { - OwningRef { owner: self.owner.clone(), reference: self.reference } - } -} - -unsafe impl<O, T: ?Sized> CloneStableAddress for OwningRef<O, T> where O: CloneStableAddress {} - -unsafe impl<O, T: ?Sized> Send for OwningRef<O, T> -where - O: Send, - for<'a> &'a T: Send, -{ -} -unsafe impl<O, T: ?Sized> Sync for OwningRef<O, T> -where - O: Sync, - for<'a> &'a T: Sync, -{ -} - -unsafe impl<O, T: ?Sized> Send for OwningRefMut<O, T> -where - O: Send, - for<'a> &'a mut T: Send, -{ -} -unsafe impl<O, T: ?Sized> Sync for OwningRefMut<O, T> -where - O: Sync, - for<'a> &'a mut T: Sync, -{ -} - -impl Debug for dyn Erased { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - write!(f, "<Erased>",) - } -} - -impl<O, T: ?Sized> PartialEq for OwningRef<O, T> -where - T: PartialEq, -{ - fn eq(&self, other: &Self) -> bool { - self.deref().eq(other.deref()) - } -} - -impl<O, T: ?Sized> Eq for OwningRef<O, T> where T: Eq {} - -impl<O, T: ?Sized> PartialOrd for OwningRef<O, T> -where - T: PartialOrd, -{ - fn partial_cmp(&self, other: &Self) -> Option<Ordering> { - self.deref().partial_cmp(other.deref()) - } -} - -impl<O, T: ?Sized> Ord for OwningRef<O, T> -where - T: Ord, -{ - fn cmp(&self, other: &Self) -> Ordering { - self.deref().cmp(other.deref()) - } -} - -impl<O, T: ?Sized> Hash for OwningRef<O, T> -where - T: Hash, -{ - fn hash<H: Hasher>(&self, state: &mut H) { - self.deref().hash(state); - } -} - -impl<O, T: ?Sized> PartialEq for OwningRefMut<O, T> -where - T: PartialEq, -{ - fn eq(&self, other: &Self) -> bool { - self.deref().eq(other.deref()) - } -} - -impl<O, T: ?Sized> Eq for OwningRefMut<O, T> where T: Eq {} - -impl<O, T: ?Sized> PartialOrd for OwningRefMut<O, T> -where - T: PartialOrd, -{ - fn partial_cmp(&self, other: &Self) -> Option<Ordering> { - self.deref().partial_cmp(other.deref()) - } -} - -impl<O, T: ?Sized> Ord for OwningRefMut<O, T> -where - T: Ord, -{ - fn cmp(&self, other: &Self) -> Ordering { - self.deref().cmp(other.deref()) - } -} - -impl<O, T: ?Sized> Hash for OwningRefMut<O, T> -where - T: Hash, -{ - fn hash<H: Hasher>(&self, state: &mut H) { - self.deref().hash(state); - } -} - -///////////////////////////////////////////////////////////////////////////// -// std types integration and convenience type defs -///////////////////////////////////////////////////////////////////////////// - -use std::cell::{Ref, RefCell, RefMut}; -use std::rc::Rc; -use std::sync::Arc; -use std::sync::{MutexGuard, RwLockReadGuard, RwLockWriteGuard}; - -impl<T: 'static> ToHandle for RefCell<T> { - type Handle = Ref<'static, T>; - unsafe fn to_handle(x: *const Self) -> Self::Handle { - (*x).borrow() - } -} - -impl<T: 'static> ToHandleMut for RefCell<T> { - type HandleMut = RefMut<'static, T>; - unsafe fn to_handle_mut(x: *const Self) -> Self::HandleMut { - (*x).borrow_mut() - } -} - -// N.B., implementing ToHandle{,Mut} for Mutex and RwLock requires a decision -// about which handle creation to use (i.e., read() vs try_read()) as well as -// what to do with error results. - -/// Typedef of an owning reference that uses a `Box` as the owner. -pub type BoxRef<T, U = T> = OwningRef<Box<T>, U>; -/// Typedef of an owning reference that uses a `Vec` as the owner. -pub type VecRef<T, U = T> = OwningRef<Vec<T>, U>; -/// Typedef of an owning reference that uses a `String` as the owner. -pub type StringRef = OwningRef<String, str>; - -/// Typedef of an owning reference that uses an `Rc` as the owner. -pub type RcRef<T, U = T> = OwningRef<Rc<T>, U>; -/// Typedef of an owning reference that uses an `Arc` as the owner. -pub type ArcRef<T, U = T> = OwningRef<Arc<T>, U>; - -/// Typedef of an owning reference that uses a `Ref` as the owner. -pub type RefRef<'a, T, U = T> = OwningRef<Ref<'a, T>, U>; -/// Typedef of an owning reference that uses a `RefMut` as the owner. -pub type RefMutRef<'a, T, U = T> = OwningRef<RefMut<'a, T>, U>; -/// Typedef of an owning reference that uses a `MutexGuard` as the owner. -pub type MutexGuardRef<'a, T, U = T> = OwningRef<MutexGuard<'a, T>, U>; -/// Typedef of an owning reference that uses an `RwLockReadGuard` as the owner. -pub type RwLockReadGuardRef<'a, T, U = T> = OwningRef<RwLockReadGuard<'a, T>, U>; -/// Typedef of an owning reference that uses an `RwLockWriteGuard` as the owner. -pub type RwLockWriteGuardRef<'a, T, U = T> = OwningRef<RwLockWriteGuard<'a, T>, U>; - -/// Typedef of a mutable owning reference that uses a `Box` as the owner. -pub type BoxRefMut<T, U = T> = OwningRefMut<Box<T>, U>; -/// Typedef of a mutable owning reference that uses a `Vec` as the owner. -pub type VecRefMut<T, U = T> = OwningRefMut<Vec<T>, U>; -/// Typedef of a mutable owning reference that uses a `String` as the owner. -pub type StringRefMut = OwningRefMut<String, str>; - -/// Typedef of a mutable owning reference that uses a `RefMut` as the owner. -pub type RefMutRefMut<'a, T, U = T> = OwningRefMut<RefMut<'a, T>, U>; -/// Typedef of a mutable owning reference that uses a `MutexGuard` as the owner. -pub type MutexGuardRefMut<'a, T, U = T> = OwningRefMut<MutexGuard<'a, T>, U>; -/// Typedef of a mutable owning reference that uses an `RwLockWriteGuard` as the owner. -pub type RwLockWriteGuardRefMut<'a, T, U = T> = OwningRef<RwLockWriteGuard<'a, T>, U>; - -unsafe impl<'a, T: 'a> IntoErased<'a> for Box<T> { - type Erased = Box<dyn Erased + 'a>; - fn into_erased(self) -> Self::Erased { - self - } -} -unsafe impl<'a, T: 'a> IntoErased<'a> for Rc<T> { - type Erased = Rc<dyn Erased + 'a>; - fn into_erased(self) -> Self::Erased { - self - } -} -unsafe impl<'a, T: 'a> IntoErased<'a> for Arc<T> { - type Erased = Arc<dyn Erased + 'a>; - fn into_erased(self) -> Self::Erased { - self - } -} - -unsafe impl<'a, T: Send + 'a> IntoErasedSend<'a> for Box<T> { - type Erased = Box<dyn Erased + Send + 'a>; - fn into_erased_send(self) -> Self::Erased { - self - } -} - -unsafe impl<'a, T: Send + 'a> IntoErasedSendSync<'a> for Box<T> { - type Erased = Box<dyn Erased + Sync + Send + 'a>; - fn into_erased_send_sync(self) -> Self::Erased { - let result: Box<dyn Erased + Send + 'a> = self; - // This is safe since Erased can always implement Sync - // Only the destructor is available and it takes &mut self - unsafe { mem::transmute(result) } - } -} - -unsafe impl<'a, T: Send + Sync + 'a> IntoErasedSendSync<'a> for Arc<T> { - type Erased = Arc<dyn Erased + Send + Sync + 'a>; - fn into_erased_send_sync(self) -> Self::Erased { - self - } -} - -/// Typedef of an owning reference that uses an erased `Box` as the owner. -pub type ErasedBoxRef<U> = OwningRef<Box<dyn Erased>, U>; -/// Typedef of an owning reference that uses an erased `Rc` as the owner. -pub type ErasedRcRef<U> = OwningRef<Rc<dyn Erased>, U>; -/// Typedef of an owning reference that uses an erased `Arc` as the owner. -pub type ErasedArcRef<U> = OwningRef<Arc<dyn Erased>, U>; - -/// Typedef of a mutable owning reference that uses an erased `Box` as the owner. -pub type ErasedBoxRefMut<U> = OwningRefMut<Box<dyn Erased>, U>; - -#[cfg(test)] -mod tests; |