#![warn(missing_docs, unused_results)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
use core::any::{Any, TypeId};
+use core::convert::TryInto;
+use core::hash::{Hasher, BuildHasherDefault};
use core::marker::PhantomData;
-use raw::RawMap;
+#[cfg(not(any(feature = "std", feature = "hashbrown")))]
+compile_error!("anymap: you must enable the 'std' feature or the 'hashbrown' feature");
+
+#[cfg(not(feature = "std"))]
+extern crate alloc;
+
+#[cfg(not(feature = "std"))]
+use alloc::boxed::Box;
+
use any::{UncheckedAnyExt, IntoBox};
pub use any::CloneAny;
+#[cfg(all(feature = "std", not(feature = "hashbrown")))]
+/// A re-export of [`std::collections::hash_map`] for raw access.
+///
+/// If the `hashbrown` feature gets enabled, this will become an export of `hashbrown::hash_map`.
+///
+/// As with [`RawMap`][crate::RawMap], this is exposed for compatibility reasons, since features
+/// are supposed to be additive. This *is* imperfect, since the two modules are incompatible in a
+/// few places (e.g. hashbrown’s entry types have an extra generic parameter), but it’s close, and
+/// much too useful to give up the whole concept.
+pub use std::collections::hash_map as raw_hash_map;
+
+#[cfg(feature = "hashbrown")]
+/// A re-export of [`hashbrown::hash_map`] for raw access.
+///
+/// If the `hashbrown` feature was disabled, this would become an export of
+/// `std::collections::hash_map`.
+///
+/// As with [`RawMap`][crate::RawMap], this is exposed for compatibility reasons, since features
+/// are supposed to be additive. This *is* imperfect, since the two modules are incompatible in a
+/// few places (e.g. hashbrown’s entry types have an extra generic parameter), but it’s close, and
+/// much too useful to give up the whole concept.
+pub use hashbrown::hash_map as raw_hash_map;
+
+use self::raw_hash_map::HashMap;
+
macro_rules! impl_common_methods {
(
field: $t:ident.$field:ident;
self.$field.shrink_to_fit()
}
+ // Additional stable methods (as of 1.60.0-nightly) that could be added:
+ // try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> (1.57.0)
+ // shrink_to(&mut self, min_capacity: usize) (1.56.0)
+
/// Returns the number of items in the collection.
#[inline]
pub fn len(&self) -> usize {
}
mod any;
-pub mod raw;
+
+/// Raw access to the underlying `HashMap`.
+///
+/// This is a public type alias because the underlying `HashMap` could be
+/// `std::collections::HashMap` or `hashbrown::HashMap`, depending on the crate features enabled.
+/// For that reason, you should refer to this type as `anymap::RawMap` rather than
+/// `std::collections::HashMap` to avoid breakage if something else in your crate tree enables
+/// hashbrown.
+///
+/// See also [`raw_hash_map`], an export of the corresponding `hash_map` module.
+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.
impl_common_methods! {
field: Map.raw;
- new() => RawMap::new();
- with_capacity(capacity) => RawMap::with_capacity(capacity);
+ new() => RawMap::with_hasher(Default::default());
+ with_capacity(capacity) => RawMap::with_capacity_and_hasher(capacity, Default::default());
}
impl<A: ?Sized + UncheckedAnyExt> Map<A> {
}
}
+ // rustc 1.60.0-nightly has another method try_insert that would be nice to add when stable.
+
/// Removes the `T` value from the collection,
/// returning it if there was one or `None` if there was not.
#[inline]
#[inline]
pub fn entry<T: IntoBox<A>>(&mut self) -> Entry<A, T> {
match self.raw.entry(TypeId::of::<T>()) {
- raw::Entry::Occupied(e) => Entry::Occupied(OccupiedEntry {
+ raw_hash_map::Entry::Occupied(e) => Entry::Occupied(OccupiedEntry {
inner: e,
type_: PhantomData,
}),
- raw::Entry::Vacant(e) => Entry::Vacant(VacantEntry {
+ raw_hash_map::Entry::Vacant(e) => Entry::Vacant(VacantEntry {
inner: e,
type_: PhantomData,
}),
}
}
-}
-impl<A: ?Sized + UncheckedAnyExt> AsRef<RawMap<A>> for Map<A> {
+ /// Get access to the raw hash map that backs this.
+ ///
+ /// This will seldom be useful, but it’s conceivable that you could wish to iterate over all
+ /// the items in the collection, and this lets you do that.
+ ///
+ /// To improve compatibility with Cargo features, interact with this map through the names
+ /// [`anymap::RawMap`][RawMap] and [`anymap::raw_hash_map`][raw_hash_map], rather than through
+ /// `std::collections::{HashMap, hash_map}` or `hashbrown::{HashMap, hash_map}`, for anything
+ /// beyond self methods. Otherwise, if you use std and another crate in the tree enables
+ /// hashbrown, your code will break.
#[inline]
-
fn as_ref(&self) -> &RawMap<A> {
+
pub fn as_raw(&self) -> &RawMap<A> {
&self.raw
}
-}
-impl<A: ?Sized + UncheckedAnyExt> AsMut<RawMap<A>> for Map<A> {
+ /// Get mutable access to the raw hash map that backs this.
+ ///
+ /// This will seldom be useful, but it’s conceivable that you could wish to iterate over all
+ /// the items in the collection mutably, or drain or something, or *possibly* even batch
+ /// insert, and this lets you do that.
+ ///
+ /// To improve compatibility with Cargo features, interact with this map through the names
+ /// [`anymap::RawMap`][RawMap] and [`anymap::raw_hash_map`][raw_hash_map], rather than through
+ /// `std::collections::{HashMap, hash_map}` or `hashbrown::{HashMap, hash_map}`, for anything
+ /// beyond self methods. Otherwise, if you use std and another crate in the tree enables
+ /// hashbrown, your code will break.
+ ///
+ /// # Safety
+ ///
+ /// If you insert any values to the raw map, the key (a `TypeId`) must match the value’s type,
+ /// or *undefined behaviour* will occur when you access those values.
+ ///
+ /// (*Removing* entries is perfectly safe.)
#[inline]
-
fn as_mut(&mut self) -> &mut RawMap<A> {
+
pub unsafe fn as_raw_mut(&mut self) -> &mut RawMap<A> {
&mut self.raw
}
+
+ /// Convert this into the raw hash map that backs this.
+ ///
+ /// This will seldom be useful, but it’s conceivable that you could wish to consume all the
+ /// items in the collection and do *something* with some or all of them, and this lets you do
+ /// that, without the `unsafe` that `.as_raw_mut().drain()` would require.
+ ///
+ /// To improve compatibility with Cargo features, interact with this map through the names
+ /// [`anymap::RawMap`][RawMap] and [`anymap::raw_hash_map`][raw_hash_map], rather than through
+ /// `std::collections::{HashMap, hash_map}` or `hashbrown::{HashMap, hash_map}`, for anything
+ /// beyond self methods. Otherwise, if you use std and another crate in the tree enables
+ /// hashbrown, your code will break.
+ #[inline]
+ pub fn into_raw(self) -> RawMap<A> {
+ self.raw
+ }
+
+ /// Construct a map from a collection of raw values.
+ ///
+ /// You know what? I can’t immediately think of any legitimate use for this, especially because
+ /// of the requirement of the `BuildHasherDefault<TypeIdHasher>` generic in the map.
+ ///
+ /// Perhaps this will be most practical as `unsafe { Map::from_raw(iter.collect()) }`, iter
+ /// being an iterator over `(TypeId, Box<A>)` pairs. Eh, this method provides symmetry with
+ /// `into_raw`, so I don’t care if literally no one ever uses it. I’m not even going to write a
+ /// test for it, it’s so trivial.
+ ///
+ /// To improve compatibility with Cargo features, interact with this map through the names
+ /// [`anymap::RawMap`][RawMap] and [`anymap::raw_hash_map`][raw_hash_map], rather than through
+ /// `std::collections::{HashMap, hash_map}` or `hashbrown::{HashMap, hash_map}`, for anything
+ /// beyond self methods. Otherwise, if you use std and another crate in the tree enables
+ /// hashbrown, your code will break.
+ ///
+ /// # Safety
+ ///
+ /// For all entries in the raw map, the key (a `TypeId`) must match the value’s type,
+ /// or *undefined behaviour* will occur when you access that entry.
+ #[inline]
+ pub unsafe fn from_raw(raw: RawMap<A>) -> Map<A> {
+ Self { raw }
+ }
}
-impl<A: ?Sized + UncheckedAnyExt>
From<Map<A>> for RawMap<A> {
+impl<A: ?Sized + UncheckedAnyExt>
Extend<Box<A>> for Map<A> {
#[inline]
- fn from(map: Map<A>) -> RawMap<A> {
- map.raw
+ fn extend<T: IntoIterator<Item = Box<A>>>(&mut self, iter: T) {
+ for item in iter {
+ let _ = self.raw.insert(item.type_id(), item);
+ }
}
}
/// A view into a single occupied location in an `Map`.
pub struct OccupiedEntry<'a, A: ?Sized + UncheckedAnyExt, V: 'a> {
- inner: raw::OccupiedEntry<'a, A>,
+ #[cfg(all(feature = "std", not(feature = "hashbrown")))]
+ inner: raw_hash_map::OccupiedEntry<'a, TypeId, Box<A>>,
+ #[cfg(feature = "hashbrown")]
+ inner: raw_hash_map::OccupiedEntry<'a, TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
type_: PhantomData<V>,
}
/// A view into a single empty location in an `Map`.
pub struct VacantEntry<'a, A: ?Sized + UncheckedAnyExt, V: 'a> {
- inner: raw::VacantEntry<'a, A>,
+ #[cfg(all(feature = "std", not(feature = "hashbrown")))]
+ inner: raw_hash_map::VacantEntry<'a, TypeId, Box<A>>,
+ #[cfg(feature = "hashbrown")]
+ inner: raw_hash_map::VacantEntry<'a, TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
type_: PhantomData<V>,
}
}
}
+/// 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 }
+}
+
#[cfg(test)]
mod tests {
use super::*;
assert_debug::<Map<dyn CloneAny + Send>>();
assert_debug::<Map<dyn CloneAny + Send + Sync>>();
}
+
+ #[test]
+ fn type_id_hasher() {
+ #[cfg(not(feature = "std"))]
+ use alloc::vec::Vec;
+ 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.
+ assert_eq!(hasher.finish(), unsafe { core::mem::transmute::<TypeId, u64>(type_id) });
+ }
+ // 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>>());
+ }
}