Unnamed repository; edit this file 'description' to name the repository.
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diff --git a/crates/stdx/src/anymap.rs b/crates/stdx/src/anymap.rs new file mode 100644 index 0000000000..fd44e6c6d0 --- /dev/null +++ b/crates/stdx/src/anymap.rs @@ -0,0 +1,379 @@ +//! This file is a port of only the necessary features from https://github.com/chris-morgan/anymap version 1.0.0-beta.2 for use within rust-analyzer. +//! Copyright © 2014–2022 Chris Morgan. COPYING: https://github.com/chris-morgan/anymap/blob/master/COPYING" +//! Note that the license is changed from Blue Oak Model 1.0.0 or MIT or Apache-2.0 to MIT OR Apache-2.0 +//! +//! This implementation provides a safe and convenient store for one value of each type. +//! +//! Your starting point is [`Map`]. It has an example. +//! +//! # Cargo features +//! +//! This implementation has two independent features, each of which provides an implementation providing +//! types `Map`, `AnyMap`, `OccupiedEntry`, `VacantEntry`, `Entry` and `RawMap`: +//! +//! - **std** (default, *enabled* in this build): +//! an implementation using `std::collections::hash_map`, placed in the crate root +//! (e.g. `anymap::AnyMap`). + +#![warn(missing_docs, unused_results)] + +use core::convert::TryInto; +use core::hash::Hasher; + +/// A hasher designed to eke a little more speed out, given `TypeId`’s known characteristics. +/// +/// Specifically, this is a no-op hasher that expects to be fed a u64’s worth of +/// randomly-distributed bits. It works well for `TypeId` (eliminating start-up time, so that my +/// get_missing benchmark is ~30ns rather than ~900ns, and being a good deal faster after that, so +/// that my insert_and_get_on_260_types benchmark is ~12μs instead of ~21.5μs), but will +/// panic in debug mode and always emit zeros in release mode for any other sorts of inputs, so +/// yeah, don’t use it! 😀 +#[derive(Default)] +pub struct TypeIdHasher { + value: u64, +} + +impl Hasher for TypeIdHasher { + #[inline] + fn write(&mut self, bytes: &[u8]) { + // This expects to receive exactly one 64-bit value, and there’s no realistic chance of + // that changing, but I don’t want to depend on something that isn’t expressly part of the + // contract for safety. But I’m OK with release builds putting everything in one bucket + // if it *did* change (and debug builds panicking). + debug_assert_eq!(bytes.len(), 8); + let _ = bytes.try_into().map(|array| self.value = u64::from_ne_bytes(array)); + } + + #[inline] + fn finish(&self) -> u64 { + self.value + } +} + +use core::any::{Any, TypeId}; +use core::hash::BuildHasherDefault; +use core::marker::PhantomData; + +use ::std::collections::hash_map::{self, HashMap}; + +/// Raw access to the underlying `HashMap`. +/// +/// This alias is provided for convenience because of the ugly third generic parameter. +pub type RawMap<A> = HashMap<TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>; + +/// A collection containing zero or one values for any given type and allowing convenient, +/// type-safe access to those values. +/// +/// The type parameter `A` allows you to use a different value type; normally you will want +/// it to be `core::any::Any` (also known as `std::any::Any`), but there are other choices: +/// +/// - If you want the entire map to be cloneable, use `CloneAny` instead of `Any`; with +/// that, you can only add types that implement `Clone` to the map. +/// - You can add on `+ Send` or `+ Send + Sync` (e.g. `Map<dyn Any + Send>`) to add those +/// auto traits. +/// +/// Cumulatively, there are thus six forms of map: +/// +/// - <code>[Map]<dyn [core::any::Any]></code>, +/// also spelled [`AnyMap`] for convenience. +/// - <code>[Map]<dyn [core::any::Any] + Send></code> +/// - <code>[Map]<dyn [core::any::Any] + Send + Sync></code> +/// - <code>[Map]<dyn [CloneAny]></code> +/// - <code>[Map]<dyn [CloneAny] + Send></code> +/// - <code>[Map]<dyn [CloneAny] + Send + Sync></code> +/// +/// ## Example +/// +/// (Here using the [`AnyMap`] convenience alias; the first line could use +/// <code>[anymap::Map][Map]::<[core::any::Any]>::new()</code> instead if desired.) +/// +/// ```rust +#[doc = "let mut data = anymap::AnyMap::new();"] +/// assert_eq!(data.get(), None::<&i32>); +/// ``` +/// +/// Values containing non-static references are not permitted. +#[derive(Debug)] +pub struct Map<A: ?Sized + Downcast = dyn Any> { + raw: RawMap<A>, +} + +/// The most common type of `Map`: just using `Any`; <code>[Map]<dyn [Any]></code>. +/// +/// Why is this a separate type alias rather than a default value for `Map<A>`? +/// `Map::new()` doesn’t seem to be happy to infer that it should go with the default +/// value. It’s a bit sad, really. Ah well, I guess this approach will do. +pub type AnyMap = Map<dyn Any>; +impl<A: ?Sized + Downcast> Default for Map<A> { + #[inline] + fn default() -> Map<A> { + Map::new() + } +} + +impl<A: ?Sized + Downcast> Map<A> { + /// Create an empty collection. + #[inline] + pub fn new() -> Map<A> { + Map { raw: RawMap::with_hasher(Default::default()) } + } + + /// Returns a reference to the value stored in the collection for the type `T`, + /// if it exists. + #[inline] + pub fn get<T: IntoBox<A>>(&self) -> Option<&T> { + self.raw.get(&TypeId::of::<T>()).map(|any| unsafe { any.downcast_ref_unchecked::<T>() }) + } + + /// Gets the entry for the given type in the collection for in-place manipulation + #[inline] + pub fn entry<T: IntoBox<A>>(&mut self) -> Entry<'_, A, T> { + match self.raw.entry(TypeId::of::<T>()) { + hash_map::Entry::Occupied(e) => { + Entry::Occupied(OccupiedEntry { inner: e, type_: PhantomData }) + } + hash_map::Entry::Vacant(e) => { + Entry::Vacant(VacantEntry { inner: e, type_: PhantomData }) + } + } + } +} + +/// A view into a single occupied location in an `Map`. +pub struct OccupiedEntry<'a, A: ?Sized + Downcast, V: 'a> { + inner: hash_map::OccupiedEntry<'a, TypeId, Box<A>>, + type_: PhantomData<V>, +} + +/// A view into a single empty location in an `Map`. +pub struct VacantEntry<'a, A: ?Sized + Downcast, V: 'a> { + inner: hash_map::VacantEntry<'a, TypeId, Box<A>>, + type_: PhantomData<V>, +} + +/// A view into a single location in an `Map`, which may be vacant or occupied. +pub enum Entry<'a, A: ?Sized + Downcast, V> { + /// An occupied Entry + Occupied(OccupiedEntry<'a, A, V>), + /// A vacant Entry + Vacant(VacantEntry<'a, A, V>), +} + +impl<'a, A: ?Sized + Downcast, V: IntoBox<A>> Entry<'a, A, V> { + /// Ensures a value is in the entry by inserting the result of the default function if + /// empty, and returns a mutable reference to the value in the entry. + #[inline] + pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V { + match self { + Entry::Occupied(inner) => inner.into_mut(), + Entry::Vacant(inner) => inner.insert(default()), + } + } +} + +impl<'a, A: ?Sized + Downcast, V: IntoBox<A>> OccupiedEntry<'a, A, V> { + /// Converts the OccupiedEntry into a mutable reference to the value in the entry + /// with a lifetime bound to the collection itself + #[inline] + pub fn into_mut(self) -> &'a mut V { + unsafe { self.inner.into_mut().downcast_mut_unchecked() } + } +} + +impl<'a, A: ?Sized + Downcast, V: IntoBox<A>> VacantEntry<'a, A, V> { + /// Sets the value of the entry with the VacantEntry's key, + /// and returns a mutable reference to it + #[inline] + pub fn insert(self, value: V) -> &'a mut V { + unsafe { self.inner.insert(value.into_box()).downcast_mut_unchecked() } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[derive(Clone, Debug, PartialEq)] + struct A(i32); + #[derive(Clone, Debug, PartialEq)] + struct B(i32); + #[derive(Clone, Debug, PartialEq)] + struct C(i32); + #[derive(Clone, Debug, PartialEq)] + struct D(i32); + #[derive(Clone, Debug, PartialEq)] + struct E(i32); + #[derive(Clone, Debug, PartialEq)] + struct F(i32); + #[derive(Clone, Debug, PartialEq)] + struct J(i32); + + #[test] + fn test_varieties() { + fn assert_send<T: Send>() {} + fn assert_sync<T: Sync>() {} + fn assert_debug<T: ::core::fmt::Debug>() {} + assert_send::<Map<dyn Any + Send>>(); + assert_send::<Map<dyn Any + Send + Sync>>(); + assert_sync::<Map<dyn Any + Send + Sync>>(); + assert_debug::<Map<dyn Any>>(); + assert_debug::<Map<dyn Any + Send>>(); + assert_debug::<Map<dyn Any + Send + Sync>>(); + assert_send::<Map<dyn CloneAny + Send>>(); + assert_send::<Map<dyn CloneAny + Send + Sync>>(); + assert_sync::<Map<dyn CloneAny + Send + Sync>>(); + assert_debug::<Map<dyn CloneAny>>(); + assert_debug::<Map<dyn CloneAny + Send>>(); + assert_debug::<Map<dyn CloneAny + Send + Sync>>(); + } + + #[test] + fn type_id_hasher() { + use core::any::TypeId; + use core::hash::Hash; + fn verify_hashing_with(type_id: TypeId) { + let mut hasher = TypeIdHasher::default(); + type_id.hash(&mut hasher); + // SAFETY: u64 is valid for all bit patterns. + let _ = hasher.finish(); + } + // Pick a variety of types, just to demonstrate it’s all sane. Normal, zero-sized, unsized, &c. + verify_hashing_with(TypeId::of::<usize>()); + verify_hashing_with(TypeId::of::<()>()); + verify_hashing_with(TypeId::of::<str>()); + verify_hashing_with(TypeId::of::<&str>()); + verify_hashing_with(TypeId::of::<Vec<u8>>()); + } +} + +// impl some traits for dyn Any +use core::fmt; + +#[doc(hidden)] +pub trait CloneToAny { + /// Clone `self` into a new `Box<dyn CloneAny>` object. + fn clone_to_any(&self) -> Box<dyn CloneAny>; +} + +impl<T: Any + Clone> CloneToAny for T { + #[inline] + fn clone_to_any(&self) -> Box<dyn CloneAny> { + Box::new(self.clone()) + } +} + +macro_rules! impl_clone { + ($t:ty) => { + impl Clone for Box<$t> { + #[inline] + fn clone(&self) -> Box<$t> { + // SAFETY: this dance is to reapply any Send/Sync marker. I’m not happy about this + // approach, given that I used to do it in safe code, but then came a dodgy + // future-compatibility warning where_clauses_object_safety, which is spurious for + // auto traits but still super annoying (future-compatibility lints seem to mean + // your bin crate needs a corresponding allow!). Although I explained my plight¹ + // and it was all explained and agreed upon, no action has been taken. So I finally + // caved and worked around it by doing it this way, which matches what’s done for + // core::any², so it’s probably not *too* bad. + // + // ¹ https://github.com/rust-lang/rust/issues/51443#issuecomment-421988013 + // ² https://github.com/rust-lang/rust/blob/e7825f2b690c9a0d21b6f6d84c404bb53b151b38/library/alloc/src/boxed.rs#L1613-L1616 + let clone: Box<dyn CloneAny> = (**self).clone_to_any(); + let raw: *mut dyn CloneAny = Box::into_raw(clone); + unsafe { Box::from_raw(raw as *mut $t) } + } + } + + impl fmt::Debug for $t { + #[inline] + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.pad(stringify!($t)) + } + } + }; +} + +/// Methods for downcasting from an `Any`-like trait object. +/// +/// This should only be implemented on trait objects for subtraits of `Any`, though you can +/// implement it for other types and it’ll work fine, so long as your implementation is correct. +pub trait Downcast { + /// Gets the `TypeId` of `self`. + fn type_id(&self) -> TypeId; + + // Note the bound through these downcast methods is 'static, rather than the inexpressible + // concept of Self-but-as-a-trait (where Self is `dyn Trait`). This is sufficient, exceeding + // TypeId’s requirements. Sure, you *can* do CloneAny.downcast_unchecked::<NotClone>() and the + // type system won’t protect you, but that doesn’t introduce any unsafety: the method is + // already unsafe because you can specify the wrong type, and if this were exposing safe + // downcasting, CloneAny.downcast::<NotClone>() would just return an error, which is just as + // correct. + // + // Now in theory we could also add T: ?Sized, but that doesn’t play nicely with the common + // implementation, so I’m doing without it. + + /// Downcast from `&Any` to `&T`, without checking the type matches. + /// + /// # Safety + /// + /// The caller must ensure that `T` matches the trait object, on pain of *undefined behaviour*. + unsafe fn downcast_ref_unchecked<T: 'static>(&self) -> &T; + + /// Downcast from `&mut Any` to `&mut T`, without checking the type matches. + /// + /// # Safety + /// + /// The caller must ensure that `T` matches the trait object, on pain of *undefined behaviour*. + unsafe fn downcast_mut_unchecked<T: 'static>(&mut self) -> &mut T; +} + +/// A trait for the conversion of an object into a boxed trait object. +pub trait IntoBox<A: ?Sized + Downcast>: Any { + /// Convert self into the appropriate boxed form. + fn into_box(self) -> Box<A>; +} + +macro_rules! implement { + ($any_trait:ident $(+ $auto_traits:ident)*) => { + impl Downcast for dyn $any_trait $(+ $auto_traits)* { + #[inline] + fn type_id(&self) -> TypeId { + self.type_id() + } + + #[inline] + unsafe fn downcast_ref_unchecked<T: 'static>(&self) -> &T { + &*(self as *const Self as *const T) + } + + #[inline] + unsafe fn downcast_mut_unchecked<T: 'static>(&mut self) -> &mut T { + &mut *(self as *mut Self as *mut T) + } + } + + impl<T: $any_trait $(+ $auto_traits)*> IntoBox<dyn $any_trait $(+ $auto_traits)*> for T { + #[inline] + fn into_box(self) -> Box<dyn $any_trait $(+ $auto_traits)*> { + Box::new(self) + } + } + } +} + +implement!(Any); +implement!(Any + Send); +implement!(Any + Send + Sync); + +/// [`Any`], but with cloning. +/// +/// Every type with no non-`'static` references that implements `Clone` implements `CloneAny`. +/// See [`core::any`] for more details on `Any` in general. +pub trait CloneAny: Any + CloneToAny {} +impl<T: Any + Clone> CloneAny for T {} +implement!(CloneAny); +implement!(CloneAny + Send); +implement!(CloneAny + Send + Sync); +impl_clone!(dyn CloneAny); +impl_clone!(dyn CloneAny + Send); +impl_clone!(dyn CloneAny + Send + Sync); |