LRUHash

This is a hash class that holds a maximum number of elements. If adding an element causes the hash to grow over this size, the least recently used element is removed. Elements in the hash are maintained in LRU order.

Useful for implementing in-process caches where memory growth control is desired.

Example:

myhash = LRUHash.new(max: 2)

myhash['a'] = 'apples'
myhash['b'] = 'banana'

myhash.length # => 2

myhash['c'] = 'cookie' # displaces 'a'

myhash.length # => 2

myhash['a'] # => nil

myhash
=> {"b"=>"banana", "c"=>"cookie"}

Installation

Add this line to your application's Gemfile:

gem 'lruhash'

And then execute:

$ bundle

Or install it yourself as:

$ gem install lruhash

Usage

require 'lruhash'

myhash = LRUHash.new(max: 100)

# Works like a regular Hash, except limited to 100 elements.
# When that size is exceeded, the Least Recently Used element will be ejected.
# Simply reading an element will move it to the front of the Most Recently Used list (back of LRU list).

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

Credit

This was forked from http://github.com/oldmoe/lruhash and modernized. Thanks to oldmoe for the first version.