Class: Tins::LRUCache

Inherits:
Object show all
Includes:
Enumerable
Defined in:
lib/tins/lru_cache.rb

Overview

An LRU (Least Recently Used) cache implementation.

This cache maintains a fixed-size collection of key-value pairs, automatically removing the least recently accessed item when the capacity is exceeded.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(capacity) ⇒ LRUCache

Initializes a new LRU cache with the specified capacity.



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# File 'lib/tins/lru_cache.rb', line 18

def initialize(capacity)
  @capacity = Integer(capacity)
  @capacity >= 1 or
    raise ArgumentError, "capacity should be >= 1, was #@capacity"
  @data     = {}
end

Instance Attribute Details

#capacity ⇒ Integer (readonly)

Returns the maximum capacity of the cache.



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

def capacity
  @capacity
end

Instance Method Details

#[](key) ⇒ Object?

Retrieves the value associated with the given key.

If the key exists, it is moved to the most recently used position. Returns nil if the key does not exist.



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# File 'lib/tins/lru_cache.rb', line 37

def [](key)
  case value = @data.delete(key) { NOT_EXIST }
  when NOT_EXIST
    nil
  else
    @data[key] = value
  end
end

#[]=(key, value) ⇒ Object

Associates a value with a key in the cache.

If the key already exists, its position is updated to most recently used. If adding this item exceeds the capacity, the least recently used item is removed.



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# File 'lib/tins/lru_cache.rb', line 55

def []=(key, value)
  @data.delete(key)
  @data[key] = value
  if @data.size > @capacity
    @data.delete(@data.keys.first)
  end
  value
end

#clear ⇒ Tins::LRUCache

Removes all items from the cache.



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# File 'lib/tins/lru_cache.rb', line 87

def clear
  @data.clear
  self
end

#delete(key) ⇒ Object?

Removes and returns the value associated with the given key.



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# File 'lib/tins/lru_cache.rb', line 80

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

#each {|key, value| ... } ⇒ Enumerator

Iterates over all key-value pairs in the cache.

Items are yielded in order from most recently used to least recently used.

Yields:

  • (key, value) —

    yields each key-value pair

Yield Parameters:



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# File 'lib/tins/lru_cache.rb', line 72

def each(&block)
  @data.reverse_each(&block)
end

#size ⇒ Integer

Returns the number of items currently in the cache.



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# File 'lib/tins/lru_cache.rb', line 95

def size
  @data.size
end