A rough mock up of a Hash storage/retrieval container

hashdb.rb

require 'sqlite3'
require 'digest'

class Hasher
  def self.md5(file_name)
    ::Digest::MD5.file(file_name).hexdigest
  end
end

class HashDB
  def initialize(database_name)
    if File.exists?(database_name)
      @db = ::SQLite3::Database.open(database_name)
    else
      @db = ::SQLite3::Database.new(database_name)
      @db.create_schema
    end
  end

  def create_schema
    @db.execute <<-SQL
      create table hashes (
        hash varchar(30),
        name varchar(30)
      );
    SQL
  end

  def add_hash(hash, name)
    # Prevent the adding of duplicate hashes
    unless get_name(hash).nil?
      existing_name = get_name(hash)
      raise "The hash #{hash} already exists and is mapped to #{existing_name}"
    end

    @db.execute "insert into hashes values ( ?, ? )", [hash, name]
  end

  def get_name(hash)
    names = []

    @db.execute( "select * from hashes where hash like ( ? )", [hash] ) do |row|
      names << row[1]
    end
    
    return names.first
  end
end

hash_db = HashDB.new("hash_database.sql3")
hash_db.create_schema

name = "pony"
file = "test.out"
hash = Hasher.md5(file)

hash_db.add_hash(hash, name)
hash_db.get_name(hash)