    # File lib/sqlite3/driver/dl/driver.rb, line 267
          def progress_handler( db, n, data=nil, &block )
            @progress_handler = block

            unless @progress_handler_callback
              @progress_handler_callback = ::DL.callback( "IP" ) do |cookie|
                @progress_handler.call( cookie )
              end
            end

            API.sqlite3_progress_handler( db, n, block&&@progress_handler_callback,
              data )
          end