Class: LRUCache

Inherits:
Hash show all
Defined in:
lib/more/facets/lrucache.rb

Overview

LRUCache

A cache utilizing a simple LRU (Least Recently Used) policy. The items managed by this cache must respond to the #key method. Attempts to optimize reads rather than inserts!

LRU semantics are enforced by inserting the items in a queue. The lru item is always at the tail. Two special sentinels (head, tail) are used to simplify (?) the code.

Defined Under Namespace

Modules: Item Classes: Sentinel

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Hash

#&, #*, #+, #-, #<<, #alias!, #argumentize, autonew, #delete_unless, #delete_values, #delete_values_at, #diff, #each_with_key, #except, #except!, #has_keys?, #has_only_keys?, #insert, #inverse, #join, #mash!, #normalize_keys, #normalize_keys!, #pairs_at, #rand_key, #rand_key!, #rand_pair, #rand_pair!, #rand_value, #rand_value!, #rekey, #rekey!, #replace_each, #restore_snapshot, #reverse_merge, #reverse_merge!, #select!, #shuffle, #shuffle!, #slice, #slice!, #stringify_keys, #stringify_keys!, #swap!, #swapkey!, #symbolize_keys, #symbolize_keys!, #take_snapshot, #to_console, #to_h, #to_openobject, #to_ostruct, #to_ostruct_recurse, #to_proc, #to_proc_with_reponse, #to_struct, #traverse, #traverse!, #update_each, #update_keys, #update_values, #variablize_keys, #variablize_keys!, #weave, zipnew, #|

Constructor Details

#initialize(max_items) ⇒ LRUCache

Returns a new instance of LRUCache.



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# File 'lib/more/facets/lrucache.rb', line 58

def initialize(max_items)
  @max_items = max_items
  lru_clear()
end

Instance Attribute Details

#head ⇒ Object (readonly)

the head sentinel and the tail sentinel, tail.prev points to the lru item.



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# File 'lib/more/facets/lrucache.rb', line 56

def head
  @head
end

#max_items ⇒ Object

the maximum number of items in the cache.



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# File 'lib/more/facets/lrucache.rb', line 52

def max_items
  @max_items
end

#tail ⇒ Object (readonly)

the head sentinel and the tail sentinel, tail.prev points to the lru item.



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# File 'lib/more/facets/lrucache.rb', line 56

def tail
  @tail
end

Instance Method Details

#[](key) ⇒ Object

Lookup an item in the cache.



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# File 'lib/more/facets/lrucache.rb', line 65

def [](key)
  if item = super
    return lru_touch(item)
  end
end

#[]=(key, item) ⇒ Object

The inserted item is considered mru!



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# File 'lib/more/facets/lrucache.rb', line 73

def []=(key, item)
  item = super
  item.lru_key = key
  lru_insert(item)
end

#clear ⇒ Object

Clear the cache.



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# File 'lib/more/facets/lrucache.rb', line 89

def clear
  super
  lru_clear()
end

#delete(key) ⇒ Object

Delete an item from the cache.



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# File 'lib/more/facets/lrucache.rb', line 81

def delete(key)
  if item = super
    lru_delete(item)
  end
end

#first ⇒ Object

The first (mru) element in the cache.



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# File 'lib/more/facets/lrucache.rb', line 96

def first
  @head.lru_next
end

#last ⇒ Object Also known as: lru

The last (lru) element in the cache.



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# File 'lib/more/facets/lrucache.rb', line 102

def last
  @tail.lru_prev
end