Class: N::LRUCache

Inherits:
Hash show all
Defined in:
lib/glue/cache.rb

Overview

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

Constructor Details

#initialize(max_items) ⇒ LRUCache

Returns a new instance of LRUCache.



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# File 'lib/glue/cache.rb', line 40

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

Instance Attribute Details

#head ⇒ Object (readonly)

the head sentinel



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# File 'lib/glue/cache.rb', line 34

def head
  @head
end

#max_items ⇒ Object

the maximum number of items in the cache.



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# File 'lib/glue/cache.rb', line 30

def max_items
  @max_items
end

#tail ⇒ Object (readonly)

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



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# File 'lib/glue/cache.rb', line 38

def tail
  @tail
end

Instance Method Details

#[](key) ⇒ Object

Lookup an item in the cache.



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# File 'lib/glue/cache.rb', line 47

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/glue/cache.rb', line 55

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

#clear ⇒ Object

Clear the cache.



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# File 'lib/glue/cache.rb', line 71

def clear
	super
	lru_clear()
end

#delete(key) ⇒ Object

Delete an item from the cache.



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# File 'lib/glue/cache.rb', line 63

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/glue/cache.rb', line 78

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/glue/cache.rb', line 84

def last
	@tail.lru_prev
end