How send to pagination length of source?

Hi guys! i get an issue - need to send number of all items in table to calculate correct pagination.
I managed to set up number items per page. For example l send request for 20 items and set show to me 10 items/per page. But i have array length on server from 100 items. It will show to me only 2 pagination buttons, but it should to add 5 pagination buttons for correct understanding how many items i can get.