Class: Wee::LRUCache

Inherits:
Object show all
Defined in:
lib/wee/lru_cache.rb

Overview

Implementation of a Least Recently Used (LRU) Cache

Direct Known Subclasses

Application::SessionCache

Defined Under Namespace

Classes: Item

Instance Method Summary collapse

Constructor Details

#initialize(capacity = 20, &replace_callback) ⇒ LRUCache

Returns a new instance of LRUCache.



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# File 'lib/wee/lru_cache.rb', line 13

def initialize(capacity=20, &replace_callback)
  @capacity = capacity
  @replace_callback = replace_callback
  @store = Hash.new
  @time = 0
end

Instance Method Details

#delete(key) ⇒ Object 



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# File 'lib/wee/lru_cache.rb', line 24

def delete(key)
  @store.delete(key)
end

#delete_if ⇒ Object 



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# File 'lib/wee/lru_cache.rb', line 28

def delete_if
  @store.delete_if {|id, item|
    yield id, item.value
  }
end

#each(&block) ⇒ Object 



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# File 'lib/wee/lru_cache.rb', line 65

def each(&block)
  @store.each(&block)
end

#fetch(key, default_value = nil) ⇒ Object Also known as: [] 



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# File 'lib/wee/lru_cache.rb', line 34

def fetch(key, default_value=nil)
  if item = @store[key]
    item.time = (@time += 1)
    item.value
  else
    default_value
  end
end

#garbage_collect ⇒ Object 



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# File 'lib/wee/lru_cache.rb', line 62

def garbage_collect
end

#has_key?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/wee/lru_cache.rb', line 20

def has_key?(key)
  @store.has_key?(key)
end

#store(key, value) ⇒ Object Also known as: []= 



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# File 'lib/wee/lru_cache.rb', line 43

def store(key, value)
  if item = @store[key]
    # update item only
    item.time = (@time += 1)
    item.value = value
  else
    # insert new item
    item = Item.new
    item.time = (@time += 1)
    item.value = value
    garbage_collect() if @store.size >= @capacity
    while @store.size >= @capacity 
      old_item = @store.delete(min_key()) || raise
      @replace_callback.call(old_item) if @replace_callback
    end
    @store[key] = item
  end
end