#![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;
#[cfg(not(any(feature = "std", feature = "hashbrown")))]
#[cfg(not(feature = "std"))]
use alloc::boxed::Box;
-use raw::RawMap;
-use any::{UncheckedAnyExt, IntoBox};
+use any::{Downcast, IntoBox};
pub use any::CloneAny;
-macro_rules! impl_common_methods {
- (
- field: $t:ident.$field:ident;
- new() => $new:expr;
- with_capacity($with_capacity_arg:ident) => $with_capacity:expr;
- ) => {
- impl<A: ?Sized + UncheckedAnyExt> $t<A> {
- /// Create an empty collection.
- #[inline]
- pub fn new() -> $t<A> {
- $t {
- $field: $new,
- }
- }
-
- /// Creates an empty collection with the given initial capacity.
- #[inline]
- pub fn with_capacity($with_capacity_arg: usize) -> $t<A> {
- $t {
- $field: $with_capacity,
- }
- }
-
- /// Returns the number of elements the collection can hold without reallocating.
- #[inline]
- pub fn capacity(&self) -> usize {
- self.$field.capacity()
- }
-
- /// Reserves capacity for at least `additional` more elements to be inserted
- /// in the collection. The collection may reserve more space to avoid
- /// frequent reallocations.
- ///
- /// # Panics
- ///
- /// Panics if the new allocation size overflows `usize`.
- #[inline]
- pub fn reserve(&mut self, additional: usize) {
- self.$field.reserve(additional)
- }
-
- /// Shrinks the capacity of the collection as much as possible. It will drop
- /// down as much as possible while maintaining the internal rules
- /// and possibly leaving some space in accordance with the resize policy.
- #[inline]
- pub fn shrink_to_fit(&mut self) {
- self.$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 {
- self.$field.len()
- }
-
- /// Returns true if there are no items in the collection.
- #[inline]
- pub fn is_empty(&self) -> bool {
- self.$field.is_empty()
- }
-
- /// Removes all items from the collection. Keeps the allocated memory for reuse.
- #[inline]
- pub fn clear(&mut self) {
- self.$field.clear()
- }
- }
+#[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;
- impl<A: ?Sized + UncheckedAnyExt> Default for $t<A> {
- #[inline]
- fn default() -> $t<A> {
- $t::new()
- }
- }
- }
-}
+use self::raw_hash_map::HashMap;
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.
///
/// Values containing non-static references are not permitted.
#[derive(Debug)]
-pub struct Map<A: ?Sized + UncheckedAnyExt = dyn Any> {
+pub struct Map<A: ?Sized + Downcast = dyn Any> {
raw: RawMap<A>,
}
// #[derive(Clone)] would want A to implement Clone, but in reality it’s only Box<A> that can.
-impl<A: ?Sized +
UncheckedAnyExt> Clone for Map<A> where Box<A>: Clone {
+impl<A: ?Sized +
Downcast> Clone for Map<A> where Box<A>: Clone {
#[inline]
fn clone(&self) -> Map<A> {
Map {
/// It’s a bit sad, really. Ah well, I guess this approach will do.
pub type AnyMap = Map<dyn Any>;
-impl_common_methods! {
- field: Map.raw;
- new() => RawMap::new();
- with_capacity(capacity) => RawMap::with_capacity(capacity);
+impl<A: ?Sized + Downcast> Default for Map<A> {
+ #[inline]
+ fn default() -> Map<A> {
+ Map::new()
+ }
}
-impl<A: ?Sized + UncheckedAnyExt> Map<A> {
+impl<A: ?Sized + Downcast> Map<A> {
+ /// Create an empty collection.
+ #[inline]
+ pub fn new() -> Map<A> {
+ Map {
+ raw: RawMap::with_hasher(Default::default()),
+ }
+ }
+
+ /// Creates an empty collection with the given initial capacity.
+ #[inline]
+ pub fn with_capacity(capacity: usize) -> Map<A> {
+ Map {
+ raw: RawMap::with_capacity_and_hasher(capacity, Default::default()),
+ }
+ }
+
+ /// Returns the number of elements the collection can hold without reallocating.
+ #[inline]
+ pub fn capacity(&self) -> usize {
+ self.raw.capacity()
+ }
+
+ /// Reserves capacity for at least `additional` more elements to be inserted
+ /// in the collection. The collection may reserve more space to avoid
+ /// frequent reallocations.
+ ///
+ /// # Panics
+ ///
+ /// Panics if the new allocation size overflows `usize`.
+ #[inline]
+ pub fn reserve(&mut self, additional: usize) {
+ self.raw.reserve(additional)
+ }
+
+ /// Shrinks the capacity of the collection as much as possible. It will drop
+ /// down as much as possible while maintaining the internal rules
+ /// and possibly leaving some space in accordance with the resize policy.
+ #[inline]
+ pub fn shrink_to_fit(&mut self) {
+ self.raw.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 {
+ self.raw.len()
+ }
+
+ /// Returns true if there are no items in the collection.
+ #[inline]
+ pub fn is_empty(&self) -> bool {
+ self.raw.is_empty()
+ }
+
+ /// Removes all items from the collection. Keeps the allocated memory for reuse.
+ #[inline]
+ pub fn clear(&mut self) {
+ self.raw.clear()
+ }
+
/// 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> {
/// Otherwise, `None` is returned.
#[inline]
pub fn insert<T: IntoBox<A>>(&mut self, value: T) -> Option<T> {
- unsafe {
- self.raw.insert(TypeId::of::<T>(), value.into_box())
- .map(|any| *any.downcast_unchecked::<T>())
- }
+ self.raw.insert(TypeId::of::<T>(), value.into_box())
+ .map(|any| unsafe { *any.downcast_unchecked::<T>() })
}
// rustc 1.60.0-nightly has another method try_insert that would be nice to add when stable.
#[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> Extend<Box<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 extend<T: IntoIterator<Item = Box<A>>>(&mut self, iter: T) {
- for item in iter {
- let _ = unsafe { self.raw.insert(item.type_id(), item) };
- }
+ pub fn as_raw(&self) -> &RawMap<A> {
+ &self.raw
}
-}
-impl<A: ?Sized + UncheckedAnyExt> AsRef<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_ref(&self) -> &RawMap<A> {
- &self.raw
+
pub unsafe fn as_raw_mut(&mut self) -> &mut RawMap<A> {
+ &mut self.raw
}
-}
-impl<A: ?Sized + UncheckedAnyExt> AsMut<RawMap<A>> for Map<A> {
+ /// 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]
- fn as_mut(&mut self) -> &mut RawMap<A> {
- &mut self.raw
+ 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 +
Downcast> 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(Downcast::type_id(&*item), 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>,
+pub struct OccupiedEntry<'a, A: ?Sized + Downcast, V: '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>,
+pub struct VacantEntry<'a, A: ?Sized + Downcast, V: '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 view into a single location in an `Map`, which may be vacant or occupied.
-pub enum Entry<'a, A: ?Sized + UncheckedAnyExt, V: 'a> {
+pub enum Entry<'a, A: ?Sized + Downcast, V: 'a> {
/// An occupied Entry
Occupied(OccupiedEntry<'a, A, V>),
/// A vacant Entry
Vacant(VacantEntry<'a, A, V>),
}
-impl<'a, A: ?Sized +
UncheckedAnyExt, V: IntoBox<A>> Entry<'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 default if empty, and returns
/// a mutable reference to the value in the entry.
#[inline]
Entry::Vacant(inner) => inner.insert(default()),
}
}
+
+ /// Ensures a value is in the entry by inserting the default value if empty,
+ /// and returns a mutable reference to the value in the entry.
+ #[inline]
+ pub fn or_default(self) -> &'a mut V where V: Default {
+ match self {
+ Entry::Occupied(inner) => inner.into_mut(),
+ Entry::Vacant(inner) => inner.insert(Default::default()),
+ }
+ }
+
+ /// Provides in-place mutable access to an occupied entry before any potential inserts into the
+ /// map.
+ #[inline]
+ pub fn and_modify<F: FnOnce(&mut V)>(self, f: F) -> Self {
+ match self {
+ Entry::Occupied(mut inner) => {
+ f(inner.get_mut());
+ Entry::Occupied(inner)
+ },
+ Entry::Vacant(inner) => Entry::Vacant(inner),
+ }
+ }
+
+ // Additional stable methods (as of 1.60.0-nightly) that could be added:
+ // insert_entry(self, value: V) -> OccupiedEntry<'a, K, V> (1.59.0)
}
-impl<'a, A: ?Sized +
UncheckedAnyExt, V: IntoBox<A>> OccupiedEntry<'a, A, V> {
+impl<'a, A: ?Sized +
Downcast, V: IntoBox<A>> OccupiedEntry<'a, A, V> {
/// Gets a reference to the value in the entry
#[inline]
pub fn get(&self) -> &V {
}
}
-impl<'a, A: ?Sized +
UncheckedAnyExt, V: IntoBox<A>> VacantEntry<'a, A, V> {
+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]
}
}
+/// 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>>());
+ }
+
+ #[test]
+ fn test_extend() {
+ let mut map = AnyMap::new();
+ map.extend([Box::new(123) as Box<dyn Any>, Box::new(456), Box::new(true)]);
+ assert_eq!(map.get(), Some(&456));
+ assert_eq!(map.get::<bool>(), Some(&true));
+ assert!(map.get::<Box<dyn Any>>().is_none());
+ }
}