src/raw.rs - anymap blob - Chris Morgan’s Git repositories

   1 //! The raw form of a `Map`, allowing untyped access.
   2 //!
   3 //! All relevant details are in the `RawMap` struct.
   4
   5 use core::any::{Any, TypeId};
   6 use core::borrow::Borrow;
   7 use std::collections::hash_map::{self, HashMap};
   8 use core::convert::TryInto;
   9 use core::hash::Hash;
  10 use core::hash::{Hasher, BuildHasherDefault};
  11 use core::ops::{Index, IndexMut};
  12
  13 use crate::any::UncheckedAnyExt;
  14
  15 #[derive(Default)]
  16 struct TypeIdHasher {
  17     value: u64,
  18 }
  19
  20 impl Hasher for TypeIdHasher {
  21     #[inline]
  22     fn write(&mut self, bytes: &[u8]) {
  23         // This expects to receive exactly one 64-bit value, and there’s no realistic chance of
  24         // that changing, but I don’t want to depend on something that isn’t expressly part of the
  25         // contract for safety. But I’m OK with release builds putting everything in one bucket
  26         // if it *did* change (and debug builds panicking).
  27         debug_assert_eq!(bytes.len(), 8);
  28         let _ = bytes.try_into()
  29             .map(|array| self.value = u64::from_ne_bytes(array));
  30     }
  31
  32     #[inline]
  33     fn finish(&self) -> u64 { self.value }
  34 }
  35
  36 #[test]
  37 fn type_id_hasher() {
  38     fn verify_hashing_with(type_id: TypeId) {
  39         let mut hasher = TypeIdHasher::default();
  40         type_id.hash(&mut hasher);
  41         // SAFETY: u64 is valid for all bit patterns.
  42         assert_eq!(hasher.finish(), unsafe { core::mem::transmute::<TypeId, u64>(type_id) });
  43     }
  44     // Pick a variety of types, just to demonstrate it’s all sane. Normal, zero-sized, unsized, &c.
  45     verify_hashing_with(TypeId::of::<usize>());
  46     verify_hashing_with(TypeId::of::<()>());
  47     verify_hashing_with(TypeId::of::<str>());
  48     verify_hashing_with(TypeId::of::<&str>());
  49     verify_hashing_with(TypeId::of::<Vec<u8>>());
  50 }
  51
  52 /// The raw, underlying form of a `Map`.
  53 ///
  54 /// At its essence, this is a wrapper around `HashMap<TypeId, Box<Any>>`, with the portions that
  55 /// would be memory-unsafe removed or marked unsafe. Normal people are expected to use the safe
  56 /// `Map` interface instead, but there is the occasional use for this such as iteration over the
  57 /// contents of an `Map`. However, because you will then be dealing with `Any` trait objects, it
  58 /// doesn’t tend to be so very useful. Still, if you need it, it’s here.
  59 #[derive(Debug)]
  60 pub struct RawMap<A: ?Sized + UncheckedAnyExt = dyn Any> {
  61     inner: HashMap<TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
  62 }
  63
  64 // #[derive(Clone)] would want A to implement Clone, but in reality it’s only Box<A> that can.
  65 impl<A: ?Sized + UncheckedAnyExt> Clone for RawMap<A> where Box<A>: Clone {
  66     #[inline]
  67     fn clone(&self) -> RawMap<A> {
  68         RawMap {
  69             inner: self.inner.clone(),
  70         }
  71     }
  72 }
  73
  74 impl_common_methods! {
  75     field: RawMap.inner;
  76     new() => HashMap::with_hasher(Default::default());
  77     with_capacity(capacity) => HashMap::with_capacity_and_hasher(capacity, Default::default());
  78 }
  79
  80 /// `RawMap` iterator.
  81 #[derive(Clone)]
  82 pub struct Iter<'a, A: ?Sized + UncheckedAnyExt> {
  83     inner: hash_map::Iter<'a, TypeId, Box<A>>,
  84 }
  85 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Iter<'a, A> {
  86     type Item = &'a A;
  87     #[inline] fn next(&mut self) -> Option<&'a A> { self.inner.next().map(|x| &**x.1) }
  88     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
  89 }
  90 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Iter<'a, A> {
  91     #[inline] fn len(&self) -> usize { self.inner.len() }
  92 }
  93
  94 /// `RawMap` mutable iterator.
  95 pub struct IterMut<'a, A: ?Sized + UncheckedAnyExt> {
  96     inner: hash_map::IterMut<'a, TypeId, Box<A>>,
  97 }
  98 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for IterMut<'a, A> {
  99     type Item = &'a mut A;
 100     #[inline] fn next(&mut self) -> Option<&'a mut A> { self.inner.next().map(|x| &mut **x.1) }
 101     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 102 }
 103 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IterMut<'a, A> {
 104     #[inline] fn len(&self) -> usize { self.inner.len() }
 105 }
 106
 107 /// `RawMap` move iterator.
 108 pub struct IntoIter<A: ?Sized + UncheckedAnyExt> {
 109     inner: hash_map::IntoIter<TypeId, Box<A>>,
 110 }
 111 impl<A: ?Sized + UncheckedAnyExt> Iterator for IntoIter<A> {
 112     type Item = Box<A>;
 113     #[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
 114     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 115 }
 116 impl<A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IntoIter<A> {
 117     #[inline] fn len(&self) -> usize { self.inner.len() }
 118 }
 119
 120 /// `RawMap` drain iterator.
 121 pub struct Drain<'a, A: ?Sized + UncheckedAnyExt> {
 122     inner: hash_map::Drain<'a, TypeId, Box<A>>,
 123 }
 124 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Drain<'a, A> {
 125     type Item = Box<A>;
 126     #[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
 127     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 128 }
 129 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Drain<'a, A> {
 130     #[inline] fn len(&self) -> usize { self.inner.len() }
 131 }
 132
 133 impl<A: ?Sized + UncheckedAnyExt> RawMap<A> {
 134     /// An iterator visiting all entries in arbitrary order.
 135     ///
 136     /// Iterator element type is `&Any`.
 137     #[inline]
 138     pub fn iter(&self) -> Iter<A> {
 139         Iter {
 140             inner: self.inner.iter(),
 141         }
 142     }
 143
 144     /// An iterator visiting all entries in arbitrary order.
 145     ///
 146     /// Iterator element type is `&mut Any`.
 147     #[inline]
 148     pub fn iter_mut(&mut self) -> IterMut<A> {
 149         IterMut {
 150             inner: self.inner.iter_mut(),
 151         }
 152     }
 153
 154     /// Clears the map, returning all items as an iterator.
 155     ///
 156     /// Iterator element type is `Box<Any>`.
 157     ///
 158     /// Keeps the allocated memory for reuse.
 159     #[inline]
 160     pub fn drain(&mut self) -> Drain<A> {
 161         Drain {
 162             inner: self.inner.drain(),
 163         }
 164     }
 165
 166     /// Gets the entry for the given type in the collection for in-place manipulation.
 167     #[inline]
 168     pub fn entry(&mut self, key: TypeId) -> Entry<A> {
 169         match self.inner.entry(key) {
 170             hash_map::Entry::Occupied(e) => Entry::Occupied(OccupiedEntry {
 171                 inner: e,
 172             }),
 173             hash_map::Entry::Vacant(e) => Entry::Vacant(VacantEntry {
 174                 inner: e,
 175             }),
 176         }
 177     }
 178
 179     /// Returns a reference to the value corresponding to the key.
 180     ///
 181     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 182     /// form *must* match those for the key type.
 183     #[inline]
 184     pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&A>
 185     where TypeId: Borrow<Q>, Q: Hash + Eq {
 186         self.inner.get(k).map(|x| &**x)
 187     }
 188
 189     /// Returns true if the map contains a value for the specified key.
 190     ///
 191     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 192     /// form *must* match those for the key type.
 193     #[inline]
 194     pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
 195     where TypeId: Borrow<Q>, Q: Hash + Eq {
 196         self.inner.contains_key(k)
 197     }
 198
 199     /// Returns a mutable reference to the value corresponding to the key.
 200     ///
 201     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 202     /// form *must* match those for the key type.
 203     #[inline]
 204     pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut A>
 205     where TypeId: Borrow<Q>, Q: Hash + Eq {
 206         self.inner.get_mut(k).map(|x| &mut **x)
 207     }
 208
 209     /// Inserts a key-value pair from the map. If the key already had a value present in the map,
 210     /// that value is returned. Otherwise, `None` is returned.
 211     ///
 212     /// # Safety
 213     ///
 214     /// `key` and the type ID of `value` must match, or *undefined behaviour* occurs.
 215     #[inline]
 216     pub unsafe fn insert(&mut self, key: TypeId, value: Box<A>) -> Option<Box<A>> {
 217         self.inner.insert(key, value)
 218     }
 219
 220     /// Removes a key from the map, returning the value at the key if the key was previously in the
 221     /// map.
 222     ///
 223     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 224     /// form *must* match those for the key type.
 225     #[inline]
 226     pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<Box<A>>
 227     where TypeId: Borrow<Q>, Q: Hash + Eq {
 228         self.inner.remove(k)
 229     }
 230
 231 }
 232
 233 impl<A: ?Sized + UncheckedAnyExt, Q> Index<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
 234     type Output = A;
 235
 236     #[inline]
 237     fn index(&self, index: Q) -> &A {
 238         self.get(&index).expect("no entry found for key")
 239     }
 240 }
 241
 242 impl<A: ?Sized + UncheckedAnyExt, Q> IndexMut<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
 243     #[inline]
 244     fn index_mut(&mut self, index: Q) -> &mut A {
 245         self.get_mut(&index).expect("no entry found for key")
 246     }
 247 }
 248
 249 impl<A: ?Sized + UncheckedAnyExt> IntoIterator for RawMap<A> {
 250     type Item = Box<A>;
 251     type IntoIter = IntoIter<A>;
 252
 253     #[inline]
 254     fn into_iter(self) -> IntoIter<A> {
 255         IntoIter {
 256             inner: self.inner.into_iter(),
 257         }
 258     }
 259 }
 260
 261 /// A view into a single occupied location in a `RawMap`.
 262 pub struct OccupiedEntry<'a, A: ?Sized + UncheckedAnyExt> {
 263     inner: hash_map::OccupiedEntry<'a, TypeId, Box<A>>,
 264 }
 265
 266 /// A view into a single empty location in a `RawMap`.
 267 pub struct VacantEntry<'a, A: ?Sized + UncheckedAnyExt> {
 268     inner: hash_map::VacantEntry<'a, TypeId, Box<A>>,
 269 }
 270
 271 /// A view into a single location in a `RawMap`, which may be vacant or occupied.
 272 pub enum Entry<'a, A: ?Sized + UncheckedAnyExt> {
 273     /// An occupied Entry
 274     Occupied(OccupiedEntry<'a, A>),
 275     /// A vacant Entry
 276     Vacant(VacantEntry<'a, A>),
 277 }
 278
 279 impl<'a, A: ?Sized + UncheckedAnyExt> Entry<'a, A> {
 280     /// Ensures a value is in the entry by inserting the default if empty, and returns
 281     /// a mutable reference to the value in the entry.
 282     ///
 283     /// # Safety
 284     ///
 285     /// The type ID of `default` must match the entry’s key, or *undefined behaviour* occurs.
 286     #[inline]
 287     pub unsafe fn or_insert(self, default: Box<A>) -> &'a mut A {
 288         match self {
 289             Entry::Occupied(inner) => inner.into_mut(),
 290             Entry::Vacant(inner) => inner.insert(default),
 291         }
 292     }
 293
 294     /// Ensures a value is in the entry by inserting the result of the default function if empty,
 295     /// and returns a mutable reference to the value in the entry.
 296     ///
 297     /// # Safety
 298     ///
 299     /// The type ID of the value returned by `default` must match the entry’s key,
 300     /// or *undefined behaviour* occurs.
 301     #[inline]
 302     pub unsafe fn or_insert_with<F: FnOnce() -> Box<A>>(self, default: F) -> &'a mut A {
 303         match self {
 304             Entry::Occupied(inner) => inner.into_mut(),
 305             Entry::Vacant(inner) => inner.insert(default()),
 306         }
 307     }
 308 }
 309
 310 impl<'a, A: ?Sized + UncheckedAnyExt> OccupiedEntry<'a, A> {
 311     /// Gets a reference to the value in the entry.
 312     #[inline]
 313     pub fn get(&self) -> &A {
 314         &**self.inner.get()
 315     }
 316
 317     /// Gets a mutable reference to the value in the entry.
 318     #[inline]
 319     pub fn get_mut(&mut self) -> &mut A {
 320         &mut **self.inner.get_mut()
 321     }
 322
 323     /// Converts the OccupiedEntry into a mutable reference to the value in the entry
 324     /// with a lifetime bound to the collection itself.
 325     #[inline]
 326     pub fn into_mut(self) -> &'a mut A {
 327         &mut **self.inner.into_mut()
 328     }
 329
 330     /// Sets the value of the entry, and returns the entry's old value.
 331     ///
 332     /// # Safety
 333     ///
 334     /// The type ID of `value` must match the entry’s key, or *undefined behaviour* occurs.
 335     #[inline]
 336     pub unsafe fn insert(&mut self, value: Box<A>) -> Box<A> {
 337         self.inner.insert(value)
 338     }
 339
 340     /// Takes the value out of the entry, and returns it.
 341     #[inline]
 342     pub fn remove(self) -> Box<A> {
 343         self.inner.remove()
 344     }
 345 }
 346
 347 impl<'a, A: ?Sized + UncheckedAnyExt> VacantEntry<'a, A> {
 348     /// Sets the value of the entry with the VacantEntry's key,
 349     /// and returns a mutable reference to it.
 350     ///
 351     /// # Safety
 352     ///
 353     /// The type ID of `value` must match the entry’s key, or *undefined behaviour* occurs.
 354     #[inline]
 355     pub unsafe fn insert(self, value: Box<A>) -> &'a mut A {
 356         &mut **self.inner.insert(value)
 357     }
 358 }