Garant

Gem helps to prevent the collisions when generating a large number of hashes. For example: you decided to try Ruby module SecureRandom:

require 'set'
require 'securerandom'

NUMBER_OF_HASHES = 1_000_000
STORAGE = Set.new

NUMBER_OF_HASHES.times do |num|
  STORAGE << SecureRandom.urlsafe_base64(4, false)
end

puts NUMBER_OF_HASHES - STORAGE.size # => 123

that is, out of 1 million approximately 123 hashes will be duplicated. It's OK if uniqueness is not the goal but sometimes it's necessary to get unique hashes from a specific hash-function (see hash function quality and speed tests).

The Garant will make sure that there are no duplicates.

Working pre-alpha, not for production.

Add this line to your application's Gemfile:

gem 'garant'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install garant

require 'garant'
require 'securerandom'

Garant.setup do |s|
  # Bloom filter params
  s.storage_type      = :bloom  # To store unique values will be used Bloom filter.
  s.expected_size     = 10_000  # Expected (or more) number of the hashes.
  s.error_probability = 0.01    # The probability of false positives.

  # Set params
  s.storage_type      = :set    # To store unique values will be used Set structure.

  # Common params
  s.max_retries       = 15      # The number of attempts to regenerate the not unique hash.
end

1000.times do
  puts Garant.safe{ SecureRandom.urlsafe_base64(4, false) }
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/creadone/garant.

The gem is available as open source under the terms of the MIT License.