stopped = false

function main()   
   ds, err = CreateDataSource('QJSIM', 'GAZP', INTERVAL_M1, 'bid')
   while (err == "" or err == nil) and ds:Size() == 0 do
      sleep(5)
   end

   if err ~= "" and err ~= nil then
      message("Error: " .. err)
      return
   end

   message("size:" .. tostring(ds:Size()))
   
   ds:SetUpdateCallback(myFunc)

   while stopped ~= true do
      sleep(50)
   end
end

function myFunc(index)
   message(tostring(index))
end