Struct lru::LruCache [−][src]
pub struct LruCache<K, V, S = DefaultHasher> { /* fields omitted */ }Expand description
An LRU Cache
Implementations
Creates a new LRU Cache that holds at most cap items.
Example
use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(10);Creates a new LRU Cache that holds at most cap items and
uses the provided hash builder to hash keys.
Example
use lru::{LruCache, DefaultHasher};
let s = DefaultHasher::default();
let mut cache: LruCache<isize, &str> = LruCache::with_hasher(10, s);Creates a new LRU Cache that never automatically evicts items and uses the provided hash builder to hash keys.
Example
use lru::{LruCache, DefaultHasher};
let s = DefaultHasher::default();
let mut cache: LruCache<isize, &str> = LruCache::unbounded_with_hasher(s);Puts a key-value pair into cache. If the key already exists in the cache, then it updates
the key’s value and returns the old value. Otherwise, None is returned.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
assert_eq!(None, cache.put(1, "a"));
assert_eq!(None, cache.put(2, "b"));
assert_eq!(Some("b"), cache.put(2, "beta"));
assert_eq!(cache.get(&1), Some(&"a"));
assert_eq!(cache.get(&2), Some(&"beta"));Returns a reference to the value of the key in the cache or None if it is not
present in the cache. Moves the key to the head of the LRU list if it exists.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(1, "a");
cache.put(2, "b");
cache.put(2, "c");
cache.put(3, "d");
assert_eq!(cache.get(&1), None);
assert_eq!(cache.get(&2), Some(&"c"));
assert_eq!(cache.get(&3), Some(&"d"));Returns a mutable reference to the value of the key in the cache or None if it
is not present in the cache. Moves the key to the head of the LRU list if it exists.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put("apple", 8);
cache.put("banana", 4);
cache.put("banana", 6);
cache.put("pear", 2);
assert_eq!(cache.get_mut(&"apple"), None);
assert_eq!(cache.get_mut(&"banana"), Some(&mut 6));
assert_eq!(cache.get_mut(&"pear"), Some(&mut 2));Returns a reference to the value corresponding to the key in the cache or None if it is
not present in the cache. Unlike get, peek does not update the LRU list so the key’s
position will be unchanged.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(1, "a");
cache.put(2, "b");
assert_eq!(cache.peek(&1), Some(&"a"));
assert_eq!(cache.peek(&2), Some(&"b"));Returns a mutable reference to the value corresponding to the key in the cache or None
if it is not present in the cache. Unlike get_mut, peek_mut does not update the LRU
list so the key’s position will be unchanged.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(1, "a");
cache.put(2, "b");
assert_eq!(cache.peek_mut(&1), Some(&mut "a"));
assert_eq!(cache.peek_mut(&2), Some(&mut "b"));Returns the value corresponding to the least recently used item or None if the
cache is empty. Like peek, peek_lru does not update the LRU list so the item’s
position will be unchanged.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(1, "a");
cache.put(2, "b");
assert_eq!(cache.peek_lru(), Some((&1, &"a")));Returns a bool indicating whether the given key is in the cache. Does not update the LRU list.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(1, "a");
cache.put(2, "b");
cache.put(3, "c");
assert!(!cache.contains(&1));
assert!(cache.contains(&2));
assert!(cache.contains(&3));Removes and returns the value corresponding to the key from the cache or
None if it does not exist.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(2, "a");
assert_eq!(cache.pop(&1), None);
assert_eq!(cache.pop(&2), Some("a"));
assert_eq!(cache.pop(&2), None);
assert_eq!(cache.len(), 0);Removes and returns the key and value corresponding to the least recently
used item or None if the cache is empty.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
cache.put(2, "a");
cache.put(3, "b");
cache.put(4, "c");
cache.get(&3);
assert_eq!(cache.pop_lru(), Some((4, "c")));
assert_eq!(cache.pop_lru(), Some((3, "b")));
assert_eq!(cache.pop_lru(), None);
assert_eq!(cache.len(), 0);Returns the number of key-value pairs that are currently in the the cache.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
assert_eq!(cache.len(), 0);
cache.put(1, "a");
assert_eq!(cache.len(), 1);
cache.put(2, "b");
assert_eq!(cache.len(), 2);
cache.put(3, "c");
assert_eq!(cache.len(), 2);Returns a bool indicating whether the cache is empty or not.
Example
use lru::LruCache;
let mut cache = LruCache::new(2);
assert!(cache.is_empty());
cache.put(1, "a");
assert!(!cache.is_empty());Returns the maximum number of key-value pairs the cache can hold.
Example
use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(2);
assert_eq!(cache.cap(), 2);Resizes the cache. If the new capacity is smaller than the size of the current cache any entries past the new capacity are discarded.
Example
use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(2);
cache.put(1, "a");
cache.put(2, "b");
cache.resize(4);
cache.put(3, "c");
cache.put(4, "d");
assert_eq!(cache.len(), 4);
assert_eq!(cache.get(&1), Some(&"a"));
assert_eq!(cache.get(&2), Some(&"b"));
assert_eq!(cache.get(&3), Some(&"c"));
assert_eq!(cache.get(&4), Some(&"d"));Clears the contents of the cache.
Example
use lru::LruCache;
let mut cache: LruCache<isize, &str> = LruCache::new(2);
assert_eq!(cache.len(), 0);
cache.put(1, "a");
assert_eq!(cache.len(), 1);
cache.put(2, "b");
assert_eq!(cache.len(), 2);
cache.clear();
assert_eq!(cache.len(), 0);An iterator visiting all entries in most-recently used order. The iterator element type is
(&'a K, &'a V).
Examples
use lru::LruCache;
let mut cache = LruCache::new(3);
cache.put("a", 1);
cache.put("b", 2);
cache.put("c", 3);
for (key, val) in cache.iter() {
println!("key: {} val: {}", key, val);
}An iterator visiting all entries in most-recently-used order, giving a mutable reference on
V. The iterator element type is (&'a K, &'a mut V).
Examples
use lru::LruCache;
struct HddBlock {
dirty: bool,
data: [u8; 512]
}
let mut cache = LruCache::new(3);
cache.put(0, HddBlock { dirty: false, data: [0x00; 512]});
cache.put(1, HddBlock { dirty: true, data: [0x55; 512]});
cache.put(2, HddBlock { dirty: true, data: [0x77; 512]});
// write dirty blocks to disk.
for (block_id, block) in cache.iter_mut() {
if block.dirty {
// write block to disk
block.dirty = false
}
}