RustyLRU

gem 'rusty_lru'

# Creates a cache with a cap of 1,000 entries.
cache = RustyLRU::Cache.new(1000)

# Returns true iff the cache is empty.
cache.empty? #=> true

# Returns the number of pairs in the cache (not the cap).
cache.size #=> 0

# Adds a key-value pair to the cache.
cache['x'] = :y
cache['y'] = proc { 'anything can go here' }
cache['z'] = {"x" => 1}
cache.size #=> 3

# Overwriting a key returns the old value.
cache['x'] = :q #=> :y

# Retrieves the least recently used key-value pair without updating the LRU
# list.
cache.lru_pair #=> ['x', :q]

# Returns true iff the key exists. Does not affect the LRU list.
cache.key?('x') #=> true
cache.key?(:test) #=> false

# Retrieves a value by key, updating the LRU list.
cache['x'] #=> :q
cache.lru_pair #=> ['y', #<Proc:...>]

# Retrieves and deletes the least recently used key-value pair.
cache.pop #=> ['y', #<Proc:...>]
cache.size #=> 2
cache.lru_pair #=> ['z', {"x" => 1}]

# Retrieves a value by key without updating LRU list.
cache.peek('z') #=> {"x" => 1}
cache.lru_pair #=> ['z', {"x" => 1}]

# Deletes a key-value pair, returning the deleted value.
cache.delete('x') #=> :q
cache.size #=> 1

# Deletes all pairs from the cache
cache.clear #=> nil

# Changes the cache's cap.  If necessary, elements will be deleted (in LRU
# order) to accommodate this.
cache.resize(1)
cache[:test1] = 'test1'
cache[:test2] = 'test2'
cache.size #=> 1

# includes Enumerable, so things like conversion to Array and Hash are simple:
cache.to_a
cache.to_h
cache.each_key { |k| cache[k] = 'replaced' }