gistfile1.rb

require 'digest/sha1'
require 'csv'
require 'pp'

class ShaRand

  attr_reader :data

  def initialize
    @data = {}
  end

  # add a hash to the hash database
  def add( hash = nil )
    hash ||= Digest::SHA1.hexdigest( Time.now.to_f.to_s ).upcase
    @data[hash] = shorthand( hash )
  end

  # create a hash shorthand
  def shorthand( hash )
    shorthand = ''
    hash.split('').each_with_index do |char, index|
      shorthand += char
      next if shorthand.length < 2
      return shorthand unless @data.values.include?( shorthand )
    end
  end

  # populate the database
  def populate( limit )
    limit.times{ |i| add }
  end

  # save to a csv
  def to_csv( file )
    CSV.open(file, "wb") do |csv|
      @data.each_pair do |key, shorthand|
        csv << [ key, shorthand ]
      end
    end
  end

  # load from a csv
  def from_csv( file )
    CSV.foreach(file) do |row|
      add row.first
    end
  end

end

# simply populating a sharand database
def scenario1( limit = 100 )
  sharand = ShaRand.new
  sharand.populate( limit )
  sharand.data
end

# populating a sharand database and save it to csv
def scenario2( limit = 100 )
  sharand = ShaRand.new
  sharand.populate( limit )
  sharand.to_csv( 'sha1.csv' )
  sharand.data
end

# load a csv database, add some values and save as a different csv:
def scenario3( limit = 100 )
  sharand = ShaRand.new
  sharand.from_csv( 'sha1.csv' )
  sharand.populate( limit )
  sharand.to_csv( 'sha1_2.csv' )
  sharand.data
end

pp scenario1
pp scenario2
pp scenario3