class Aws::S3::FileDownloader

def download_in_threads(pending, total_size)
  threads = []
  progress = MultipartProgress.new(pending, total_size, @progress_callback) if @progress_callback
  @thread_count.times do
    thread = Thread.new do
      begin
        while part = pending.shift
          if progress
            part.params[:on_chunk_received] =
              proc do |_chunk, bytes, total|
                progress.call(part.part_number, bytes, total)
              end
          end
          resp = @client.get_object(part.params)
          write(resp)
          if @on_checksum_validated && resp.checksum_validated
            @on_checksum_validated.call(resp.checksum_validated, resp)
          end
        end
        nil
      rescue => error
        # keep other threads from downloading other parts
        pending.clear!
        raise error
      end
    end
    threads << thread
  end
  threads.map(&:value).compact
end