id_cache/lib.rs
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312
///! A crate providing a simple data structure for caching id values.
///!
///! See the documentation for the [`IdCache<I, T>`] type for more information.
use id_collections::{Count, Id, IdVec};
use std::{borrow::Borrow, collections::HashMap, fmt::Debug, hash::Hash, ops::Index};
/// A cache which generates sequentially-assigned ids for unique values.
///
/// # Example
///
/// ```
/// use id_collections::id_type;
/// use id_cache::IdCache;
///
/// #[id_type]
/// struct WordId(u32);
///
/// let mut word_cache: IdCache<WordId, &str> = IdCache::new();
///
/// let foo_id = word_cache.make_id("foo");
/// let bar_id = word_cache.make_id("bar");
///
/// assert_eq!(word_cache[foo_id], "foo");
/// assert_eq!(word_cache[bar_id], "bar");
///
/// // ids for repeated values are reused:
/// assert_eq!(word_cache.make_id("foo"), foo_id);
/// ```
///
/// # Serde Support
///
/// When the `serde` Cargo feature is enabled, the `IdCache<I, T>` type can be serialized and
/// deserialized using [Serde](https://serde.rs). An `IdCache<I, T>` is serialized as a sequence
/// consisting of the unique values in the cache, ordered by id:
///
/// ```
/// # #[cfg(feature = "serde")]
/// # {
/// use id_collections::id_type;
/// use id_cache::IdCache;
///
/// #[id_type]
/// struct WordId(u32);
///
/// let mut word_cache: IdCache<WordId, &str> = IdCache::new();
/// word_cache.make_id("foo");
/// word_cache.make_id("bar");
///
/// let serialized = serde_json::to_string(&word_cache).unwrap();
/// assert_eq!(&serialized, r#"["foo","bar"]"#);
/// # }
/// ```
#[derive(Clone)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "serde", serde(transparent))]
pub struct IdCache<I: Id, T> {
#[cfg_attr(feature = "serde", serde(bound(serialize = "T: serde::Serialize")))]
id_to_value: IdVec<I, T>,
#[cfg_attr(feature = "serde", serde(skip))]
value_to_id: HashMap<T, I>,
}
#[cfg(feature = "serde")]
impl<'de, I: Id, T: Eq + Hash + Clone + serde::Deserialize<'de>> serde::Deserialize<'de>
for IdCache<I, T>
{
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
let id_to_value = IdVec::<I, T>::deserialize(deserializer)?;
let mut value_to_id = HashMap::new();
for (id, value) in &id_to_value {
let existing = value_to_id.insert(value.clone(), id);
if existing.is_some() {
use serde::de::Error;
return Err(D::Error::custom("duplicate value in IdCache"));
}
}
Ok(IdCache {
id_to_value,
value_to_id,
})
}
}
#[cfg(feature = "serde")]
mod serde_test {
#[test]
fn test_round_trip() {
use crate::IdCache;
use id_collections::id_type;
#[id_type]
struct TestId(u32);
let mut cache: IdCache<u32, String> = IdCache::new();
cache.make_id("foo".to_owned());
cache.make_id("bar".to_owned());
let serialized = serde_json::to_string(&cache).unwrap();
assert_eq!(serialized, r#"["foo","bar"]"#);
let deserialized = serde_json::from_str::<IdCache<u32, String>>(&serialized).unwrap();
assert_eq!(&deserialized, &cache);
}
#[test]
fn test_duplicate_err() {
use crate::IdCache;
let result = serde_json::from_str::<IdCache<u32, String>>(r#"["foo","foo"]"#);
assert!(result.is_err());
}
}
impl<I: Id, T> Default for IdCache<I, T> {
fn default() -> Self {
Self::new()
}
}
impl<I: Id + Debug, T: Debug> Debug for IdCache<I, T> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.id_to_value.fmt(f)
}
}
impl<I: Id, T: PartialEq> PartialEq for IdCache<I, T> {
fn eq(&self, other: &Self) -> bool {
self.id_to_value == other.id_to_value
}
}
impl<I: Id, T: Eq> Eq for IdCache<I, T> {}
impl<I: Id, T> IdCache<I, T> {
/// Constructs a new, empty `IdCache<I, T>`.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let cache: IdCache<u32, &str> = IdCache::new();
/// assert!(cache.is_empty());
/// ```
pub fn new() -> Self {
IdCache {
id_to_value: IdVec::new(),
value_to_id: HashMap::new(),
}
}
/// Constructs a new, empty `IdCache<I, T>` with space to hold at least `capacity` unique
/// values.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::with_capacity(100);
/// assert!(cache.is_empty());
/// ```
pub fn with_capacity(capacity: usize) -> Self {
IdCache {
id_to_value: IdVec::with_capacity(capacity),
value_to_id: HashMap::with_capacity(capacity),
}
}
/// Returns the total number of ids that have been assigned to unique values in the
/// `IdCache<I, T>`.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// assert!(cache.count().is_empty());
/// cache.make_id("foo");
/// cache.make_id("bar");
/// assert_eq!(cache.count().to_value(), 2);
/// cache.make_id("foo"); // value already present, so does not assign a new id
/// assert_eq!(cache.count().to_value(), 2);
/// ```
pub fn count(&self) -> Count<I> {
self.id_to_value.count()
}
/// Returns the total number of unique values in the `IdCache<I, T>`.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// assert_eq!(cache.len(), 0);
/// cache.make_id("foo");
/// cache.make_id("bar");
/// assert_eq!(cache.len(), 2);
/// cache.make_id("foo"); // value already present, so does not increase the len
/// assert_eq!(cache.len(), 2);
/// ```
pub fn len(&self) -> usize {
self.id_to_value.len()
}
/// Returns `true` if the `IdCache<I, T>` contains no values.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// assert!(cache.is_empty());
/// cache.make_id("foo");
/// assert!(!cache.is_empty());
/// ```
pub fn is_empty(&self) -> bool {
self.id_to_value.is_empty()
}
/// Ensures `value` has an id in the `IdCache<I, T>`, and returns that id.
///
/// If `value` is already present in the `IdCache<I, T>`, then `make_id` returns its existing
/// id. Otherwise, `make_id` returns a new sequentally-assigned id.
///
/// # Panics
///
/// Panics if the number of ids in the `IdCache<I, T>` overflows `I`.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// assert_eq!(cache.make_id("foo"), 0);
/// assert_eq!(cache.make_id("bar"), 1);
/// assert_eq!(cache.make_id("foo"), 0);
/// ```
pub fn make_id(&mut self, value: T) -> I
where
T: Eq + Hash + Clone,
{
*self
.value_to_id
.entry(value)
.or_insert_with_key(|value| self.id_to_value.push(value.clone()))
}
/// Returns the id of a value in the `IdCache<I, T>`, or `None` if the value is not present.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// let foo_id = cache.make_id("foo");
/// assert_eq!(cache.get_id(&"foo"), Some(foo_id));
/// assert_eq!(cache.get_id(&"bar"), None);
/// ```
pub fn get_id<U>(&self, value: &U) -> Option<I>
where
T: Borrow<U> + Eq + Hash,
U: Eq + Hash,
{
self.value_to_id.get(value).cloned()
}
/// Returns a reference to the value in the `IdCache<I, T>` associated with a given `id`, or
/// `None` if the id has not been assigned.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// let foo_id = cache.make_id("foo");
/// assert_eq!(foo_id, 0);
/// assert_eq!(cache.get_value(foo_id), Some(&"foo"));
/// assert_eq!(cache.get_value(1), None);
/// ```
pub fn get_value(&self, id: I) -> Option<&T> {
self.id_to_value.get(id)
}
}
impl<I: Id, T, J: Borrow<I>> Index<J> for IdCache<I, T> {
type Output = T;
/// Returns a reference to the value in the `IdCache<I, T>` associated with a given `id`.
///
/// # Panics
///
/// Panics if `id` has not been assigned.
///
/// # Examples
///
/// ```
/// # use id_cache::IdCache;
/// let mut cache: IdCache<u32, &str> = IdCache::new();
/// let foo_id = cache.make_id("foo");
/// assert_eq!(cache[foo_id], "foo");
/// ```
#[inline]
fn index(&self, id: J) -> &Self::Output {
let id = *id.borrow();
&self.id_to_value[id]
}
}