360 lines
12 KiB
Rust
360 lines
12 KiB
Rust
//! The raw form of a `Map`, allowing untyped access.
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//!
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//! All relevant details are in the `RawMap` struct.
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use std::any::TypeId;
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use std::borrow::Borrow;
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use std::collections::hash_map::{self, HashMap};
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use std::convert::TryInto;
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use std::hash::Hash;
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use std::hash::{Hasher, BuildHasherDefault};
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#[cfg(test)]
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use std::mem;
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use std::ops::{Index, IndexMut};
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use any::{Any, UncheckedAnyExt};
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#[derive(Default)]
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struct TypeIdHasher {
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value: u64,
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}
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impl Hasher for TypeIdHasher {
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#[inline]
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fn write(&mut self, bytes: &[u8]) {
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// This expects to receive exactly one 64-bit value, and there’s no realistic chance of
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// that changing, but I don’t want to depend on something that isn’t expressly part of the
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// contract for safety. But I’m OK with release builds putting everything in one bucket
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// if it *did* change (and debug builds panicking).
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debug_assert_eq!(bytes.len(), 8);
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let _ = bytes.try_into()
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.map(|array| self.value = u64::from_ne_bytes(array));
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}
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#[inline]
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fn finish(&self) -> u64 { self.value }
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}
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#[test]
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fn type_id_hasher() {
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fn verify_hashing_with(type_id: TypeId) {
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let mut hasher = TypeIdHasher::default();
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type_id.hash(&mut hasher);
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// SAFETY: u64 is valid for all bit patterns.
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assert_eq!(hasher.finish(), unsafe { mem::transmute::<TypeId, u64>(type_id) });
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}
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// Pick a variety of types, just to demonstrate it’s all sane. Normal, zero-sized, unsized, &c.
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verify_hashing_with(TypeId::of::<usize>());
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verify_hashing_with(TypeId::of::<()>());
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verify_hashing_with(TypeId::of::<str>());
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verify_hashing_with(TypeId::of::<&str>());
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verify_hashing_with(TypeId::of::<Vec<u8>>());
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}
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/// The raw, underlying form of a `Map`.
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///
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/// At its essence, this is a wrapper around `HashMap<TypeId, Box<Any>>`, with the portions that
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/// would be memory-unsafe removed or marked unsafe. Normal people are expected to use the safe
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/// `Map` interface instead, but there is the occasional use for this such as iteration over the
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/// contents of an `Map`. However, because you will then be dealing with `Any` trait objects, it
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/// doesn’t tend to be so very useful. Still, if you need it, it’s here.
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#[derive(Debug)]
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pub struct RawMap<A: ?Sized + UncheckedAnyExt = dyn Any> {
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inner: HashMap<TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
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}
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// #[derive(Clone)] would want A to implement Clone, but in reality it’s only Box<A> that can.
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impl<A: ?Sized + UncheckedAnyExt> Clone for RawMap<A> where Box<A>: Clone {
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#[inline]
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fn clone(&self) -> RawMap<A> {
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RawMap {
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inner: self.inner.clone(),
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}
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}
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}
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impl_common_methods! {
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field: RawMap.inner;
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new() => HashMap::with_hasher(Default::default());
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with_capacity(capacity) => HashMap::with_capacity_and_hasher(capacity, Default::default());
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}
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/// `RawMap` iterator.
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#[derive(Clone)]
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pub struct Iter<'a, A: ?Sized + UncheckedAnyExt> {
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inner: hash_map::Iter<'a, TypeId, Box<A>>,
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Iter<'a, A> {
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type Item = &'a A;
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#[inline] fn next(&mut self) -> Option<&'a A> { self.inner.next().map(|x| &**x.1) }
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#[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Iter<'a, A> {
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#[inline] fn len(&self) -> usize { self.inner.len() }
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}
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/// `RawMap` mutable iterator.
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pub struct IterMut<'a, A: ?Sized + UncheckedAnyExt> {
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inner: hash_map::IterMut<'a, TypeId, Box<A>>,
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for IterMut<'a, A> {
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type Item = &'a mut A;
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#[inline] fn next(&mut self) -> Option<&'a mut A> { self.inner.next().map(|x| &mut **x.1) }
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#[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IterMut<'a, A> {
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#[inline] fn len(&self) -> usize { self.inner.len() }
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}
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/// `RawMap` move iterator.
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pub struct IntoIter<A: ?Sized + UncheckedAnyExt> {
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inner: hash_map::IntoIter<TypeId, Box<A>>,
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}
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impl<A: ?Sized + UncheckedAnyExt> Iterator for IntoIter<A> {
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type Item = Box<A>;
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#[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
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#[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
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}
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impl<A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IntoIter<A> {
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#[inline] fn len(&self) -> usize { self.inner.len() }
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}
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/// `RawMap` drain iterator.
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pub struct Drain<'a, A: ?Sized + UncheckedAnyExt> {
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inner: hash_map::Drain<'a, TypeId, Box<A>>,
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Drain<'a, A> {
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type Item = Box<A>;
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#[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
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#[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Drain<'a, A> {
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#[inline] fn len(&self) -> usize { self.inner.len() }
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}
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impl<A: ?Sized + UncheckedAnyExt> RawMap<A> {
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/// An iterator visiting all entries in arbitrary order.
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///
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/// Iterator element type is `&Any`.
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#[inline]
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pub fn iter(&self) -> Iter<A> {
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Iter {
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inner: self.inner.iter(),
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}
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}
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/// An iterator visiting all entries in arbitrary order.
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///
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/// Iterator element type is `&mut Any`.
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#[inline]
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pub fn iter_mut(&mut self) -> IterMut<A> {
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IterMut {
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inner: self.inner.iter_mut(),
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}
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}
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/// Clears the map, returning all items as an iterator.
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///
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/// Iterator element type is `Box<Any>`.
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///
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/// Keeps the allocated memory for reuse.
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#[inline]
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pub fn drain(&mut self) -> Drain<A> {
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Drain {
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inner: self.inner.drain(),
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}
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}
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/// Gets the entry for the given type in the collection for in-place manipulation.
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#[inline]
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pub fn entry(&mut self, key: TypeId) -> Entry<A> {
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match self.inner.entry(key) {
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hash_map::Entry::Occupied(e) => Entry::Occupied(OccupiedEntry {
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inner: e,
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}),
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hash_map::Entry::Vacant(e) => Entry::Vacant(VacantEntry {
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inner: e,
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}),
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}
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}
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/// Returns a reference to the value corresponding to the key.
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///
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/// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
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/// form *must* match those for the key type.
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#[inline]
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pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&A>
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where TypeId: Borrow<Q>, Q: Hash + Eq {
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self.inner.get(k).map(|x| &**x)
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}
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/// Returns true if the map contains a value for the specified key.
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///
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/// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
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/// form *must* match those for the key type.
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#[inline]
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pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
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where TypeId: Borrow<Q>, Q: Hash + Eq {
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self.inner.contains_key(k)
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}
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/// Returns a mutable reference to the value corresponding to the key.
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///
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/// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
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/// form *must* match those for the key type.
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#[inline]
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pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut A>
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where TypeId: Borrow<Q>, Q: Hash + Eq {
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self.inner.get_mut(k).map(|x| &mut **x)
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}
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/// Inserts a key-value pair from the map. If the key already had a value present in the map,
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/// that value is returned. Otherwise, `None` is returned.
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///
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/// # Safety
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///
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/// `key` and the type ID of `value` must match, or *undefined behaviour* occurs.
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#[inline]
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pub unsafe fn insert(&mut self, key: TypeId, value: Box<A>) -> Option<Box<A>> {
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self.inner.insert(key, value)
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}
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/// Removes a key from the map, returning the value at the key if the key was previously in the
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/// map.
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///
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/// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
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/// form *must* match those for the key type.
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#[inline]
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pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<Box<A>>
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where TypeId: Borrow<Q>, Q: Hash + Eq {
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self.inner.remove(k)
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}
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}
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impl<A: ?Sized + UncheckedAnyExt, Q> Index<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
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type Output = A;
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#[inline]
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fn index(&self, index: Q) -> &A {
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self.get(&index).expect("no entry found for key")
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}
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}
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impl<A: ?Sized + UncheckedAnyExt, Q> IndexMut<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
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#[inline]
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fn index_mut(&mut self, index: Q) -> &mut A {
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self.get_mut(&index).expect("no entry found for key")
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}
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}
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impl<A: ?Sized + UncheckedAnyExt> IntoIterator for RawMap<A> {
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type Item = Box<A>;
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type IntoIter = IntoIter<A>;
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#[inline]
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fn into_iter(self) -> IntoIter<A> {
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IntoIter {
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inner: self.inner.into_iter(),
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}
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}
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}
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/// A view into a single occupied location in a `RawMap`.
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pub struct OccupiedEntry<'a, A: ?Sized + UncheckedAnyExt> {
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inner: hash_map::OccupiedEntry<'a, TypeId, Box<A>>,
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}
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/// A view into a single empty location in a `RawMap`.
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pub struct VacantEntry<'a, A: ?Sized + UncheckedAnyExt> {
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inner: hash_map::VacantEntry<'a, TypeId, Box<A>>,
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}
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/// A view into a single location in a `RawMap`, which may be vacant or occupied.
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pub enum Entry<'a, A: ?Sized + UncheckedAnyExt> {
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/// An occupied Entry
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Occupied(OccupiedEntry<'a, A>),
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/// A vacant Entry
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Vacant(VacantEntry<'a, A>),
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> Entry<'a, A> {
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/// Ensures a value is in the entry by inserting the default if empty, and returns
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/// a mutable reference to the value in the entry.
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///
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/// # Safety
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///
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/// The type ID of `default` must match the entry’s key, or *undefined behaviour* occurs.
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#[inline]
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pub unsafe fn or_insert(self, default: Box<A>) -> &'a mut A {
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match self {
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Entry::Occupied(inner) => inner.into_mut(),
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Entry::Vacant(inner) => inner.insert(default),
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}
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}
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/// Ensures a value is in the entry by inserting the result of the default function if empty,
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/// and returns a mutable reference to the value in the entry.
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///
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/// # Safety
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///
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/// The type ID of the value returned by `default` must match the entry’s key,
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/// or *undefined behaviour* occurs.
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#[inline]
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pub unsafe fn or_insert_with<F: FnOnce() -> Box<A>>(self, default: F) -> &'a mut A {
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match self {
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Entry::Occupied(inner) => inner.into_mut(),
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Entry::Vacant(inner) => inner.insert(default()),
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}
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}
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> OccupiedEntry<'a, A> {
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/// Gets a reference to the value in the entry.
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#[inline]
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pub fn get(&self) -> &A {
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&**self.inner.get()
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}
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/// Gets a mutable reference to the value in the entry.
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#[inline]
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pub fn get_mut(&mut self) -> &mut A {
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&mut **self.inner.get_mut()
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}
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/// Converts the OccupiedEntry into a mutable reference to the value in the entry
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/// with a lifetime bound to the collection itself.
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#[inline]
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pub fn into_mut(self) -> &'a mut A {
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&mut **self.inner.into_mut()
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}
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/// Sets the value of the entry, and returns the entry's old value.
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///
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/// # Safety
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///
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/// The type ID of `value` must match the entry’s key, or *undefined behaviour* occurs.
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#[inline]
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pub unsafe fn insert(&mut self, value: Box<A>) -> Box<A> {
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self.inner.insert(value)
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}
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/// Takes the value out of the entry, and returns it.
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#[inline]
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pub fn remove(self) -> Box<A> {
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self.inner.remove()
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}
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}
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impl<'a, A: ?Sized + UncheckedAnyExt> VacantEntry<'a, A> {
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/// Sets the value of the entry with the VacantEntry's key,
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/// and returns a mutable reference to it.
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///
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/// # Safety
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///
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/// The type ID of `value` must match the entry’s key, or *undefined behaviour* occurs.
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#[inline]
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pub unsafe fn insert(self, value: Box<A>) -> &'a mut A {
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&mut **self.inner.insert(value)
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}
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}
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