hash64.rb

hash64.rb

module Hash64
  # Turn a string into a well distributed 64 bit integer
  # This matches the hash_64() PGSQL function used to partition streams.
  #
  # @param value [String] the string to hash
  # @return [Integer] a 64 bit integer
  def self.call(value)
    binary_string = ('0' + Digest::MD5.hexdigest(value)[0...16]).hex.to_s(2)
    # Convert the binary string to a signed BigInt
    bigint_value = binary_string.to_i(2)

    # Check if the most significant bit is set (indicating a negative value in 2's complement)
    if binary_string[0] == '1'
      # Handle negative value by applying 2's complement
      bigint_value -= 2**64
    end

    bigint_value.abs
  end
end