Class: LRUCache

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

Direct Known Subclasses

ThreadSafe

Defined Under Namespace

Classes: Node, ThreadSafe

Constant Summary collapse

Error = 
Class.new RuntimeError
InvalidLimitError = 
Class.new Error
NoLimitError = 
Class.new Error

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(limit = nil) ⇒ LRUCache

Sets up the new cache, optionally assigning given limit.



12
13
14
15
16
 
# File 'lib/lru_cache.rb', line 12

def initialize(limit=nil)
  @index = {}
  @count = 0
  self.limit = limit if limit
end

Instance Attribute Details

#count ⇒ Object (readonly)

Returns the value of attribute count.



9
10
11
 
# File 'lib/lru_cache.rb', line 9

def count
  @count
end

#limit ⇒ Object

Returns the value of attribute limit.



9
10
11
 
# File 'lib/lru_cache.rb', line 9

def limit
  @limit
end

Instance Method Details

#clear ⇒ Object

Empties the cache of all values.



19
20
21
 
# File 'lib/lru_cache.rb', line 19

def clear
  count.times.each { delete_lru }
end

#delete(key) ⇒ Object

Remove and return value from cache.



24
25
26
27
28
29
30
31
32
33
 
# File 'lib/lru_cache.rb', line 24

def delete(key)
  node = @index.delete(key)
  return unless node
  @count -= 1
  node.mru.lru = node.lru if node.mru
  node.lru.mru = node.mru if node.lru
  @mru = node.lru if @mru == node
  @lru = node.mru if @lru == node
  node.value
end

#get(key) ⇒ Object Also known as: []

Return value from cache and sets it as most-recently-used.



36
37
38
39
40
41
42
 
# File 'lib/lru_cache.rb', line 36

def get(key)
  node = @index[key]
  if node
    set_mru(node)
    node.value
  end
end

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

Stores a value in the cache.



54
55
56
57
58
59
60
61
62
63
64
 
# File 'lib/lru_cache.rb', line 54

def set(key, value)
  node = @index[key]
  unless node
    node = Node.new(key)
    @index[key] = node
    @count += 1
    delete_lru if count > ensure_limit
  end
  set_mru(node)
  node.value = value
end