lru 1.0.1

LRU (Least recently used) cache with additional weak map layer.

LRU Cache

Cache based on Least Recently Used evict strategy.

Supports caching more than capacity via Week references (such values are cached until they garbage collected).

Supports additional eviction strategy for TypedData for limiting maximum capacity in bytes. Useful for caching buffers such as raw images.

Features

• Supports full Map interface.
• Store TypedData and evict entries by bytes capacity via LruTypedDataCache.
• Expando compatible objects can be optionally cached via LruWeakCache.

Usage

Create cache, add values, when space is exhausted;

// no weak cache, because String is not supported by Expando
final cache = new LruCache<int, String>(2);

cache[0] = '0';
cache[1] = '1';
cache[2] = '2'; // key 0 is evicted here

cache[0]; // try to touch

print(cache[0]); // null
print(cache[1]); // 1
print(cache[2]); // 2

Example with bytes capacity for TypedData.

// use capacityInBytes as additional eviction strategy
final cache = LruTypedDataCache<int, Uint8List>(capacity: 100, capacityInBytes: 2);
cache[0] = Uint8List(1)..[0] = 0;
cache[1] = Uint8List(1)..[0] = 1;
cache[2] = Uint8List(1)..[0] = 2;

print(cache[0]); // null
print(cache[1]); // [1]
print(cache[2]); // [2]

Example with Weak Cache support:

/// Helper class to demonstrate LruWeakCache
class Key {
  const Key(this.key);
  final String key;
  @override
  String toString() => key;
}

void main() {
  final cache = LruWeakCache<int, Key>(2);

  cache[0] = Key('0');
  cache[1] = Key('1');
  cache[2] = Key('2'); // key 0 is evicted from LRU and moved to weak cache

  // try to touch, if key 0 is not garbage collected yet
  // key 1 is moved to weak cache, and key 0 is restored
  cache[0];

  print(cache[0]); // likely 0
  print(cache[1]); // likely 1
  print(cache[2]); // 2
}