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Jul 27, 2014
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Documentation examples for LruCache. #15941

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3c45fe9
Documentation examples for LruCache.
treeman Jul 24, 2014
6bbe92e
Cleanup LruCache doc.
treeman Jul 24, 2014
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86 changes: 86 additions & 0 deletions src/libstd/collections/lru_cache.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,13 @@ impl<K, V> LruEntry<K, V> {

impl<K: Hash + Eq, V> LruCache<K, V> {
/// Create an LRU Cache that holds at most `capacity` items.
///
/// # Example
///
/// ```
/// use std::collections::LruCache;
/// let mut cache: LruCache<int, &str> = LruCache::new(10u);
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Is the u suffix required?

/// ```
pub fn new(capacity: uint) -> LruCache<K, V> {
let cache = LruCache {
map: HashMap::new(),
Expand All @@ -106,6 +113,18 @@ impl<K: Hash + Eq, V> LruCache<K, V> {
}

/// Put a key-value pair into cache.
///
/// # Example
///
/// ```
/// use std::collections::LruCache;
/// let mut cache = LruCache::new(2u);
///
/// cache.put(1i, "a");
/// cache.put(2, "b");
/// assert_eq!(cache.get(&1), Some(&"a"));
/// assert_eq!(cache.get(&2), Some(&"b"));
/// ```
pub fn put(&mut self, k: K, v: V) {
let (node_ptr, node_opt) = match self.map.find_mut(&KeyRef{k: &k}) {
Some(node) => {
Expand Down Expand Up @@ -137,6 +156,21 @@ impl<K: Hash + Eq, V> LruCache<K, V> {
}

/// Return a value corresponding to the key in the cache.
///
/// # Example
///
/// ```
/// use std::collections::LruCache;
/// let mut cache = LruCache::new(2u);
///
/// cache.put(1i, "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"));
/// ```
pub fn get<'a>(&'a mut self, k: &K) -> Option<&'a V> {
let (value, node_ptr_opt) = match self.map.find_mut(&KeyRef{k: k}) {
None => (None, None),
Expand All @@ -156,6 +190,20 @@ impl<K: Hash + Eq, V> LruCache<K, V> {
}

/// Remove and return a value corresponding to the key from the cache.
///
/// # Example
///
/// ```
/// use std::collections::LruCache;
/// let mut cache = LruCache::new(2u);
///
/// cache.put(2i, "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);
/// ```
pub fn pop(&mut self, k: &K) -> Option<V> {
match self.map.pop(&KeyRef{k: k}) {
None => None,
Expand All @@ -164,12 +212,50 @@ impl<K: Hash + Eq, V> LruCache<K, V> {
}

/// Return the maximum number of key-value pairs the cache can hold.
///
/// # Example
///
/// ```
/// use std::collections::LruCache;
/// let mut cache: LruCache<int, &str> = LruCache::new(2u);
/// assert_eq!(cache.capacity(), 2);
/// ```
pub fn capacity(&self) -> uint {
self.max_size
}

/// Change the number of key-value pairs the cache can hold. Remove
/// least-recently-used key-value pairs if necessary.
///
/// # Example
///
/// ```
/// use std::collections::LruCache;
/// let mut cache = LruCache::new(2u);
///
/// cache.put(1i, "a");
/// cache.put(2, "b");
/// cache.put(3, "c");
///
/// assert_eq!(cache.get(&1), None);
/// assert_eq!(cache.get(&2), Some(&"b"));
/// assert_eq!(cache.get(&3), Some(&"c"));
///
/// cache.change_capacity(3u);
/// cache.put(1i, "a");
/// cache.put(2, "b");
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Maybe this section could just be

cache.put(1, "a");
cache.put(2, "d");

leaving 3 unchanged, to demonstrate inserting a new key, overwriting an old one, and also that old ones are preserved, if there's enough room.

/// cache.put(3, "c");
///
/// assert_eq!(cache.get(&1), Some(&"a"));
/// assert_eq!(cache.get(&2), Some(&"b"));
/// assert_eq!(cache.get(&3), Some(&"c"));
///
/// cache.change_capacity(1u);
///
/// assert_eq!(cache.get(&1), None);
/// assert_eq!(cache.get(&2), None);
/// assert_eq!(cache.get(&3), Some(&"c"));
/// ```
pub fn change_capacity(&mut self, capacity: uint) {
for _ in range(capacity, self.len()) {
self.remove_lru();
Expand Down