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

   1 //! This crate provides the `AnyMap` type, a safe and convenient store for one value of each type.
   2
   3 #![crate_name = "anymap"]
   4 #![crate_type = "lib"]
   5 #![feature(default_type_params, tuple_indexing)]
   6 #![warn(unused_qualifications, non_upper_case_globals,
   7         variant_size_differences, unused_typecasts,
   8         missing_docs, unused_results)]
   9
  10 #[cfg(test)]
  11 extern crate test;
  12
  13 use std::any::Any;
  14 use std::intrinsics::{forget, TypeId};
  15 use std::collections::HashMap;
  16 use std::collections::hash_map;
  17 use std::hash::{Hash, Hasher, Writer};
  18 use std::mem::{transmute, transmute_copy};
  19 use std::raw::TraitObject;
  20
  21 pub use Entry::{Vacant, Occupied};
  22
  23 struct TypeIdHasher;
  24
  25 struct TypeIdState {
  26     value: u64,
  27 }
  28
  29 impl Writer for TypeIdState {
  30     #[inline(always)]
  31     fn write(&mut self, bytes: &[u8]) {
  32         // This expects to receive one and exactly one 64-bit value
  33         debug_assert!(bytes.len() == 8);
  34         unsafe {
  35             std::ptr::copy_nonoverlapping_memory(&mut self.value,
  36                                                  transmute(&bytes[0]),
  37                                                  1)
  38         }
  39     }
  40 }
  41
  42 impl Hasher<TypeIdState> for TypeIdHasher {
  43     fn hash<Sized? T: Hash<TypeIdState>>(&self, value: &T) -> u64 {
  44         let mut state = TypeIdState {
  45             value: 0,
  46         };
  47         value.hash(&mut state);
  48         state.value
  49     }
  50 }
  51
  52 /// An extension of `AnyRefExt` allowing unchecked downcasting of trait objects to `&T`.
  53 trait UncheckedAnyRefExt<'a> {
  54     /// Returns a reference to the boxed value, assuming that it is of type `T`. This should only be
  55     /// called if you are ABSOLUTELY CERTAIN of `T` as you will get really wacky output if it’s not.
  56     unsafe fn downcast_ref_unchecked<T: 'static>(self) -> &'a T;
  57 }
  58
  59 impl<'a> UncheckedAnyRefExt<'a> for &'a Any + 'a {
  60     #[inline]
  61     unsafe fn downcast_ref_unchecked<T: 'static>(self) -> &'a T {
  62         // Get the raw representation of the trait object
  63         let to: TraitObject = transmute_copy(&self);
  64
  65         // Extract the data pointer
  66         transmute(to.data)
  67     }
  68 }
  69
  70 /// An extension of `AnyMutRefExt` allowing unchecked downcasting of trait objects to `&mut T`.
  71 trait UncheckedAnyMutRefExt<'a> {
  72     /// Returns a reference to the boxed value, assuming that it is of type `T`. This should only be
  73     /// called if you are ABSOLUTELY CERTAIN of `T` as you will get really wacky output if it’s not.
  74     unsafe fn downcast_mut_unchecked<T: 'static>(self) -> &'a mut T;
  75 }
  76
  77 impl<'a> UncheckedAnyMutRefExt<'a> for &'a mut Any + 'a {
  78     #[inline]
  79     unsafe fn downcast_mut_unchecked<T: 'static>(self) -> &'a mut T {
  80         // Get the raw representation of the trait object
  81         let to: TraitObject = transmute_copy(&self);
  82
  83         // Extract the data pointer
  84         transmute(to.data)
  85     }
  86 }
  87
  88 /// An extension of `BoxAny` allowing unchecked downcasting of trait objects to `Box<T>`.
  89 trait UncheckedBoxAny {
  90     /// Returns the boxed value, assuming that it is of type `T`. This should only be called if you
  91     /// are ABSOLUTELY CERTAIN of `T` as you will get really wacky output if it’s not.
  92     unsafe fn downcast_unchecked<T: 'static>(self) -> Box<T>;
  93 }
  94
  95 impl UncheckedBoxAny for Box<Any + 'static> {
  96     #[inline]
  97     unsafe fn downcast_unchecked<T: 'static>(self) -> Box<T> {
  98         // Get the raw representation of the trait object
  99         let to: TraitObject = *transmute::<&Box<Any>, &TraitObject>(&self);
 100
 101         // Prevent destructor on self being run
 102         forget(self);
 103
 104         // Extract the data pointer
 105         transmute(to.data)
 106     }
 107 }
 108
 109 /// A map containing zero or one values for any given type and allowing convenient,
 110 /// type-safe access to those values.
 111 ///
 112 /// ```rust
 113 /// # use anymap::AnyMap;
 114 /// let mut data = AnyMap::new();
 115 /// assert_eq!(data.get(), None::<&int>);
 116 /// data.insert(42i);
 117 /// assert_eq!(data.get(), Some(&42i));
 118 /// data.remove::<int>();
 119 /// assert_eq!(data.get::<int>(), None);
 120 ///
 121 /// #[deriving(PartialEq, Show)]
 122 /// struct Foo {
 123 ///     str: String,
 124 /// }
 125 ///
 126 /// assert_eq!(data.get::<Foo>(), None);
 127 /// data.insert(Foo { str: "foo".to_string() });
 128 /// assert_eq!(data.get(), Some(&Foo { str: "foo".to_string() }));
 129 /// data.get_mut::<Foo>().map(|foo| foo.str.push('t'));
 130 /// assert_eq!(data.get::<Foo>().unwrap().str.as_slice(), "foot");
 131 /// ```
 132 ///
 133 /// Values containing non-static references are not permitted.
 134 pub struct AnyMap {
 135     data: HashMap<TypeId, Box<Any + 'static>, TypeIdHasher>,
 136 }
 137
 138 impl AnyMap {
 139     /// Construct a new `AnyMap`.
 140     pub fn new() -> AnyMap {
 141         AnyMap {
 142             data: HashMap::with_hasher(TypeIdHasher),
 143         }
 144     }
 145 }
 146
 147 impl AnyMap {
 148     /// Deprecated: Renamed to `get`.
 149     #[deprecated = "Renamed to `get`"]
 150     pub fn find<T: Any + 'static>(&self) -> Option<&T> {
 151         self.get::<T>()
 152     }
 153
 154     /// Deprecated: Renamed to `get_mut`.
 155     #[deprecated = "Renamed to `get_mut`"]
 156     pub fn find_mut<T: Any + 'static>(&mut self) -> Option<&mut T> {
 157         self.get_mut::<T>()
 158     }
 159
 160     /// Retrieve the value stored in the map for the type `T`, if it exists.
 161     pub fn get<T: Any + 'static>(&self) -> Option<&T> {
 162         self.data.get(&TypeId::of::<T>())
 163             .map(|any| unsafe { any.downcast_ref_unchecked::<T>() })
 164     }
 165
 166     /// Retrieve a mutable reference to the value stored in the map for the type `T`, if it exists.
 167     pub fn get_mut<T: Any + 'static>(&mut self) -> Option<&mut T> {
 168         self.data.get_mut(&TypeId::of::<T>())
 169             .map(|any| unsafe { any.downcast_mut_unchecked::<T>() })
 170     }
 171
 172     /// Set the value contained in the map for the type `T`.
 173     /// If there is a previous value stored, it will be returned.
 174     pub fn insert<T: Any + 'static>(&mut self, value: T) -> Option<T> {
 175         self.data.insert(TypeId::of::<T>(), box value as Box<Any>)
 176             .map(|any| *unsafe { any.downcast_unchecked::<T>() })
 177     }
 178
 179     /// Remove and return the value for the type `T` if it existed.
 180     pub fn remove<T: Any + 'static>(&mut self) -> Option<T> {
 181         self.data.remove(&TypeId::of::<T>())
 182             .map(|any| *unsafe { any.downcast_unchecked::<T>() })
 183     }
 184
 185     /// Does a value of type `T` exist?
 186     pub fn contains<T: Any + 'static>(&self) -> bool {
 187         self.data.contains_key(&TypeId::of::<T>())
 188     }
 189
 190     /// Gets the given key's corresponding entry in the map for in-place manipulation
 191     pub fn entry<T: Any + 'static>(&mut self) -> Entry<T> {
 192         match self.data.entry(TypeId::of::<T>()) {
 193             hash_map::Occupied(e) => Occupied(OccupiedEntry { entry: e }),
 194             hash_map::Vacant(e) => Vacant(VacantEntry { entry: e }),
 195         }
 196     }
 197
 198     /// Returns the number of items in the collection.
 199     pub fn len(&self) -> uint {
 200         self.data.len()
 201     }
 202
 203     /// Returns true if there are no items in the collection.
 204     pub fn is_empty(&self) -> bool {
 205         self.data.is_empty()
 206     }
 207
 208     /// Removes all items from the collection.
 209     pub fn clear(&mut self) {
 210         self.data.clear();
 211     }
 212 }
 213
 214 /// A view into a single occupied location in a HashMap
 215 pub struct OccupiedEntry<'a, V: 'a> {
 216     entry: hash_map::OccupiedEntry<'a, TypeId, Box<Any + 'static>>,
 217 }
 218
 219 /// A view into a single empty location in a HashMap
 220 pub struct VacantEntry<'a, V: 'a> {
 221     entry: hash_map::VacantEntry<'a, TypeId, Box<Any + 'static>>,
 222 }
 223
 224 /// A view into a single location in a map, which may be vacant or occupied
 225 pub enum Entry<'a, V: 'a> {
 226     /// An occupied Entry
 227     Occupied(OccupiedEntry<'a, V>),
 228     /// A vacant Entry
 229     Vacant(VacantEntry<'a, V>),
 230 }
 231
 232 impl<'a, V: 'static> OccupiedEntry<'a, V> {
 233     /// Gets a reference to the value in the entry
 234     pub fn get(&self) -> &V {
 235         unsafe { self.entry.get().downcast_ref_unchecked() }
 236     }
 237
 238     /// Gets a mutable reference to the value in the entry
 239     pub fn get_mut(&mut self) -> &mut V {
 240         unsafe { self.entry.get_mut().downcast_mut_unchecked() }
 241     }
 242
 243     /// Converts the OccupiedEntry into a mutable reference to the value in the entry
 244     /// with a lifetime bound to the map itself
 245     pub fn into_mut(self) -> &'a mut V {
 246         unsafe { self.entry.into_mut().downcast_mut_unchecked() }
 247     }
 248
 249     /// Sets the value of the entry, and returns the entry's old value
 250     pub fn set(&mut self, value: V) -> V {
 251         unsafe { *self.entry.set(box value as Box<Any + 'static>).downcast_unchecked() }
 252     }
 253
 254     /// Takes the value out of the entry, and returns it
 255     pub fn take(self) -> V {
 256         unsafe { *self.entry.take().downcast_unchecked() }
 257     }
 258 }
 259
 260 impl<'a, V: 'static> VacantEntry<'a, V> {
 261     /// Sets the value of the entry with the VacantEntry's key,
 262     /// and returns a mutable reference to it
 263     pub fn set(self, value: V) -> &'a mut V {
 264         unsafe { self.entry.set(box value as Box<Any + 'static>).downcast_mut_unchecked() }
 265     }
 266 }
 267
 268 #[bench]
 269 fn bench_insertion(b: &mut ::test::Bencher) {
 270     b.iter(|| {
 271         let mut data = AnyMap::new();
 272         for _ in range(0u, 100) {
 273             let _ = data.insert(42i);
 274         }
 275     })
 276 }
 277
 278 #[bench]
 279 fn bench_get_missing(b: &mut ::test::Bencher) {
 280     b.iter(|| {
 281         let data = AnyMap::new();
 282         for _ in range(0u, 100) {
 283             assert_eq!(data.get(), None::<&int>);
 284         }
 285     })
 286 }
 287
 288 #[bench]
 289 fn bench_get_present(b: &mut ::test::Bencher) {
 290     b.iter(|| {
 291         let mut data = AnyMap::new();
 292         let _ = data.insert(42i);
 293         // These inner loops are a feeble attempt to drown the other factors.
 294         for _ in range(0u, 100) {
 295             assert_eq!(data.get(), Some(&42i));
 296         }
 297     })
 298 }
 299
 300 #[test]
 301 fn test_entry() {
 302     #[deriving(Show, PartialEq)] struct A(int);
 303     #[deriving(Show, PartialEq)] struct B(int);
 304     #[deriving(Show, PartialEq)] struct C(int);
 305     #[deriving(Show, PartialEq)] struct D(int);
 306     #[deriving(Show, PartialEq)] struct E(int);
 307     #[deriving(Show, PartialEq)] struct F(int);
 308     #[deriving(Show, PartialEq)] struct J(int);
 309
 310     let mut map: AnyMap = AnyMap::new();
 311     assert_eq!(map.insert(A(10)), None);
 312     assert_eq!(map.insert(B(20)), None);
 313     assert_eq!(map.insert(C(30)), None);
 314     assert_eq!(map.insert(D(40)), None);
 315     assert_eq!(map.insert(E(50)), None);
 316     assert_eq!(map.insert(F(60)), None);
 317
 318     // Existing key (insert)
 319     match map.entry::<A>() {
 320         Vacant(_) => unreachable!(),
 321         Occupied(mut view) => {
 322             assert_eq!(view.get(), &A(10));
 323             assert_eq!(view.set(A(100)), A(10));
 324         }
 325     }
 326     assert_eq!(map.get::<A>().unwrap(), &A(100));
 327     assert_eq!(map.len(), 6);
 328
 329
 330     // Existing key (update)
 331     match map.entry::<B>() {
 332         Vacant(_) => unreachable!(),
 333         Occupied(mut view) => {
 334             let v = view.get_mut();
 335             let new_v = B(v.0 * 10);
 336             *v = new_v;
 337         }
 338     }
 339     assert_eq!(map.get().unwrap(), &B(200));
 340     assert_eq!(map.len(), 6);
 341
 342
 343     // Existing key (take)
 344     match map.entry::<C>() {
 345         Vacant(_) => unreachable!(),
 346         Occupied(view) => {
 347             assert_eq!(view.take(), C(30));
 348         }
 349     }
 350     assert_eq!(map.get::<C>(), None);
 351     assert_eq!(map.len(), 5);
 352
 353
 354     // Inexistent key (insert)
 355     match map.entry::<J>() {
 356         Occupied(_) => unreachable!(),
 357         Vacant(view) => {
 358             assert_eq!(*view.set(J(1000)), J(1000));
 359         }
 360     }
 361     assert_eq!(map.get::<J>().unwrap(), &J(1000));
 362     assert_eq!(map.len(), 6);
 363 }