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 #[cfg(all(feature = "std", not(feature = "hashbrown")))]
   8 use std::collections::hash_map::{self, HashMap};
   9 #[cfg(feature = "hashbrown")]
  10 use hashbrown::hash_map::{self, HashMap};
  11 #[cfg(not(feature = "std"))]
  12 use alloc::boxed::Box;
  13 use core::convert::TryInto;
  14 use core::hash::Hash;
  15 use core::hash::{Hasher, BuildHasherDefault};
  16 use core::ops::{Index, IndexMut};
  17
  18 use crate::any::UncheckedAnyExt;
  19
  20 #[derive(Default)]
  21 struct TypeIdHasher {
  22     value: u64,
  23 }
  24
  25 impl Hasher for TypeIdHasher {
  26     #[inline]
  27     fn write(&mut self, bytes: &[u8]) {
  28         // This expects to receive exactly one 64-bit value, and there’s no realistic chance of
  29         // that changing, but I don’t want to depend on something that isn’t expressly part of the
  30         // contract for safety. But I’m OK with release builds putting everything in one bucket
  31         // if it *did* change (and debug builds panicking).
  32         debug_assert_eq!(bytes.len(), 8);
  33         let _ = bytes.try_into()
  34             .map(|array| self.value = u64::from_ne_bytes(array));
  35     }
  36
  37     #[inline]
  38     fn finish(&self) -> u64 { self.value }
  39 }
  40
  41 #[test]
  42 fn type_id_hasher() {
  43     #[cfg(not(feature = "std"))]
  44     use alloc::vec::Vec;
  45     fn verify_hashing_with(type_id: TypeId) {
  46         let mut hasher = TypeIdHasher::default();
  47         type_id.hash(&mut hasher);
  48         // SAFETY: u64 is valid for all bit patterns.
  49         assert_eq!(hasher.finish(), unsafe { core::mem::transmute::<TypeId, u64>(type_id) });
  50     }
  51     // Pick a variety of types, just to demonstrate it’s all sane. Normal, zero-sized, unsized, &c.
  52     verify_hashing_with(TypeId::of::<usize>());
  53     verify_hashing_with(TypeId::of::<()>());
  54     verify_hashing_with(TypeId::of::<str>());
  55     verify_hashing_with(TypeId::of::<&str>());
  56     verify_hashing_with(TypeId::of::<Vec<u8>>());
  57 }
  58
  59 /// The raw, underlying form of a `Map`.
  60 ///
  61 /// At its essence, this is a wrapper around `HashMap<TypeId, Box<Any>>`, with the portions that
  62 /// would be memory-unsafe removed or marked unsafe. Normal people are expected to use the safe
  63 /// `Map` interface instead, but there is the occasional use for this such as iteration over the
  64 /// contents of an `Map`. However, because you will then be dealing with `Any` trait objects, it
  65 /// doesn’t tend to be so very useful. Still, if you need it, it’s here.
  66 #[derive(Debug)]
  67 pub struct RawMap<A: ?Sized + UncheckedAnyExt = dyn Any> {
  68     inner: HashMap<TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
  69 }
  70
  71 // #[derive(Clone)] would want A to implement Clone, but in reality it’s only Box<A> that can.
  72 impl<A: ?Sized + UncheckedAnyExt> Clone for RawMap<A> where Box<A>: Clone {
  73     #[inline]
  74     fn clone(&self) -> RawMap<A> {
  75         RawMap {
  76             inner: self.inner.clone(),
  77         }
  78     }
  79 }
  80
  81 impl_common_methods! {
  82     field: RawMap.inner;
  83     new() => HashMap::with_hasher(Default::default());
  84     with_capacity(capacity) => HashMap::with_capacity_and_hasher(capacity, Default::default());
  85 }
  86
  87 /// `RawMap` iterator.
  88 #[derive(Clone)]
  89 pub struct Iter<'a, A: ?Sized + UncheckedAnyExt> {
  90     inner: hash_map::Iter<'a, TypeId, Box<A>>,
  91 }
  92 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Iter<'a, A> {
  93     type Item = &'a A;
  94     #[inline] fn next(&mut self) -> Option<&'a A> { self.inner.next().map(|x| &**x.1) }
  95     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
  96 }
  97 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Iter<'a, A> {
  98     #[inline] fn len(&self) -> usize { self.inner.len() }
  99 }
 100
 101 /// `RawMap` mutable iterator.
 102 pub struct IterMut<'a, A: ?Sized + UncheckedAnyExt> {
 103     inner: hash_map::IterMut<'a, TypeId, Box<A>>,
 104 }
 105 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for IterMut<'a, A> {
 106     type Item = &'a mut A;
 107     #[inline] fn next(&mut self) -> Option<&'a mut A> { self.inner.next().map(|x| &mut **x.1) }
 108     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 109 }
 110 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IterMut<'a, A> {
 111     #[inline] fn len(&self) -> usize { self.inner.len() }
 112 }
 113
 114 /// `RawMap` move iterator.
 115 pub struct IntoIter<A: ?Sized + UncheckedAnyExt> {
 116     inner: hash_map::IntoIter<TypeId, Box<A>>,
 117 }
 118 impl<A: ?Sized + UncheckedAnyExt> Iterator for IntoIter<A> {
 119     type Item = Box<A>;
 120     #[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
 121     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 122 }
 123 impl<A: ?Sized + UncheckedAnyExt> ExactSizeIterator for IntoIter<A> {
 124     #[inline] fn len(&self) -> usize { self.inner.len() }
 125 }
 126
 127 /// `RawMap` drain iterator.
 128 pub struct Drain<'a, A: ?Sized + UncheckedAnyExt> {
 129     inner: hash_map::Drain<'a, TypeId, Box<A>>,
 130 }
 131 impl<'a, A: ?Sized + UncheckedAnyExt> Iterator for Drain<'a, A> {
 132     type Item = Box<A>;
 133     #[inline] fn next(&mut self) -> Option<Box<A>> { self.inner.next().map(|x| x.1) }
 134     #[inline] fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
 135 }
 136 impl<'a, A: ?Sized + UncheckedAnyExt> ExactSizeIterator for Drain<'a, A> {
 137     #[inline] fn len(&self) -> usize { self.inner.len() }
 138 }
 139
 140 impl<A: ?Sized + UncheckedAnyExt> RawMap<A> {
 141     /// An iterator visiting all entries in arbitrary order.
 142     ///
 143     /// Iterator element type is `&Any`.
 144     #[inline]
 145     pub fn iter(&self) -> Iter<A> {
 146         Iter {
 147             inner: self.inner.iter(),
 148         }
 149     }
 150
 151     /// An iterator visiting all entries in arbitrary order.
 152     ///
 153     /// Iterator element type is `&mut Any`.
 154     #[inline]
 155     pub fn iter_mut(&mut self) -> IterMut<A> {
 156         IterMut {
 157             inner: self.inner.iter_mut(),
 158         }
 159     }
 160
 161     /// Clears the map, returning all items as an iterator.
 162     ///
 163     /// Iterator element type is `Box<Any>`.
 164     ///
 165     /// Keeps the allocated memory for reuse.
 166     #[inline]
 167     pub fn drain(&mut self) -> Drain<A> {
 168         Drain {
 169             inner: self.inner.drain(),
 170         }
 171     }
 172
 173     /// Gets the entry for the given type in the collection for in-place manipulation.
 174     #[inline]
 175     pub fn entry(&mut self, key: TypeId) -> Entry<A> {
 176         match self.inner.entry(key) {
 177             hash_map::Entry::Occupied(e) => Entry::Occupied(OccupiedEntry {
 178                 inner: e,
 179             }),
 180             hash_map::Entry::Vacant(e) => Entry::Vacant(VacantEntry {
 181                 inner: e,
 182             }),
 183         }
 184     }
 185
 186     /// Returns a reference to the value corresponding to the key.
 187     ///
 188     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 189     /// form *must* match those for the key type.
 190     #[inline]
 191     pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&A>
 192     where TypeId: Borrow<Q>, Q: Hash + Eq {
 193         self.inner.get(k).map(|x| &**x)
 194     }
 195
 196     /// Returns true if the map contains a value for the specified key.
 197     ///
 198     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 199     /// form *must* match those for the key type.
 200     #[inline]
 201     pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
 202     where TypeId: Borrow<Q>, Q: Hash + Eq {
 203         self.inner.contains_key(k)
 204     }
 205
 206     /// Returns a mutable reference to the value corresponding to the key.
 207     ///
 208     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 209     /// form *must* match those for the key type.
 210     #[inline]
 211     pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut A>
 212     where TypeId: Borrow<Q>, Q: Hash + Eq {
 213         self.inner.get_mut(k).map(|x| &mut **x)
 214     }
 215
 216     /// Inserts a key-value pair from the map. If the key already had a value present in the map,
 217     /// that value is returned. Otherwise, `None` is returned.
 218     ///
 219     /// # Safety
 220     ///
 221     /// `key` and the type ID of `value` must match, or *undefined behaviour* occurs.
 222     #[inline]
 223     pub unsafe fn insert(&mut self, key: TypeId, value: Box<A>) -> Option<Box<A>> {
 224         self.inner.insert(key, value)
 225     }
 226
 227     /// Removes a key from the map, returning the value at the key if the key was previously in the
 228     /// map.
 229     ///
 230     /// The key may be any borrowed form of the map's key type, but `Hash` and `Eq` on the borrowed
 231     /// form *must* match those for the key type.
 232     #[inline]
 233     pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<Box<A>>
 234     where TypeId: Borrow<Q>, Q: Hash + Eq {
 235         self.inner.remove(k)
 236     }
 237
 238 }
 239
 240 impl<A: ?Sized + UncheckedAnyExt, Q> Index<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
 241     type Output = A;
 242
 243     #[inline]
 244     fn index(&self, index: Q) -> &A {
 245         self.get(&index).expect("no entry found for key")
 246     }
 247 }
 248
 249 impl<A: ?Sized + UncheckedAnyExt, Q> IndexMut<Q> for RawMap<A> where TypeId: Borrow<Q>, Q: Eq + Hash {
 250     #[inline]
 251     fn index_mut(&mut self, index: Q) -> &mut A {
 252         self.get_mut(&index).expect("no entry found for key")
 253     }
 254 }
 255
 256 impl<A: ?Sized + UncheckedAnyExt> IntoIterator for RawMap<A> {
 257     type Item = Box<A>;
 258     type IntoIter = IntoIter<A>;
 259
 260     #[inline]
 261     fn into_iter(self) -> IntoIter<A> {
 262         IntoIter {
 263             inner: self.inner.into_iter(),
 264         }
 265     }
 266 }
 267
 268 /// A view into a single occupied location in a `RawMap`.
 269 pub struct OccupiedEntry<'a, A: ?Sized + UncheckedAnyExt> {
 270     #[cfg(all(feature = "std", not(feature = "hashbrown")))]
 271     inner: hash_map::OccupiedEntry<'a, TypeId, Box<A>>,
 272     #[cfg(feature = "hashbrown")]
 273     inner: hash_map::OccupiedEntry<'a, TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
 274 }
 275
 276 /// A view into a single empty location in a `RawMap`.
 277 pub struct VacantEntry<'a, A: ?Sized + UncheckedAnyExt> {
 278     #[cfg(all(feature = "std", not(feature = "hashbrown")))]
 279     inner: hash_map::VacantEntry<'a, TypeId, Box<A>>,
 280     #[cfg(feature = "hashbrown")]
 281     inner: hash_map::VacantEntry<'a, TypeId, Box<A>, BuildHasherDefault<TypeIdHasher>>,
 282 }
 283
 284 /// A view into a single location in a `RawMap`, which may be vacant or occupied.
 285 pub enum Entry<'a, A: ?Sized + UncheckedAnyExt> {
 286     /// An occupied Entry
 287     Occupied(OccupiedEntry<'a, A>),
 288     /// A vacant Entry
 289     Vacant(VacantEntry<'a, A>),
 290 }
 291
 292 impl<'a, A: ?Sized + UncheckedAnyExt> Entry<'a, A> {
 293     /// Ensures a value is in the entry by inserting the default if empty, and returns
 294     /// a mutable reference to the value in the entry.
 295     ///
 296     /// # Safety
 297     ///
 298     /// The type ID of `default` must match the entry’s key, or *undefined behaviour* occurs.
 299     #[inline]
 300     pub unsafe fn or_insert(self, default: Box<A>) -> &'a mut A {
 301         match self {
 302             Entry::Occupied(inner) => inner.into_mut(),
 303             Entry::Vacant(inner) => inner.insert(default),
 304         }
 305     }
 306
 307     /// Ensures a value is in the entry by inserting the result of the default function if empty,
 308     /// and returns a mutable reference to the value in the entry.
 309     ///
 310     /// # Safety
 311     ///
 312     /// The type ID of the value returned by `default` must match the entry’s key,
 313     /// or *undefined behaviour* occurs.
 314     #[inline]
 315     pub unsafe fn or_insert_with<F: FnOnce() -> Box<A>>(self, default: F) -> &'a mut A {
 316         match self {
 317             Entry::Occupied(inner) => inner.into_mut(),
 318             Entry::Vacant(inner) => inner.insert(default()),
 319         }
 320     }
 321 }
 322
 323 impl<'a, A: ?Sized + UncheckedAnyExt> OccupiedEntry<'a, A> {
 324     /// Gets a reference to the value in the entry.
 325     #[inline]
 326     pub fn get(&self) -> &A {
 327         &**self.inner.get()
 328     }
 329
 330     /// Gets a mutable reference to the value in the entry.
 331     #[inline]
 332     pub fn get_mut(&mut self) -> &mut A {
 333         &mut **self.inner.get_mut()
 334     }
 335
 336     /// Converts the OccupiedEntry into a mutable reference to the value in the entry
 337     /// with a lifetime bound to the collection itself.
 338     #[inline]
 339     pub fn into_mut(self) -> &'a mut A {
 340         &mut **self.inner.into_mut()
 341     }
 342
 343     /// Sets the value of the entry, and returns the entry's old value.
 344     ///
 345     /// # Safety
 346     ///
 347     /// The type ID of `value` must match the entry’s key, or *undefined behaviour* occurs.
 348     #[inline]
 349     pub unsafe fn insert(&mut self, value: Box<A>) -> Box<A> {
 350         self.inner.insert(value)
 351     }
 352
 353     /// Takes the value out of the entry, and returns it.
 354     #[inline]
 355     pub fn remove(self) -> Box<A> {
 356         self.inner.remove()
 357     }
 358 }
 359
 360 impl<'a, A: ?Sized + UncheckedAnyExt> VacantEntry<'a, A> {
 361     /// Sets the value of the entry with the VacantEntry's key,
 362     /// and returns a mutable reference to it.
 363     ///
 364     /// # Safety
 365     ///
 366     /// The type ID of `value` must match the entry’s key, or *undefined behaviour* occurs.
 367     #[inline]
 368     pub unsafe fn insert(self, value: Box<A>) -> &'a mut A {
 369         &mut **self.inner.insert(value)
 370     }
 371 }