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