JSON interface page count?

[rossjones]

It appears that because of the limits that are in place for the number of datasets downloaded per request, paging is in place. The only way to tell how many requests are to be made, is to keep incrementing the page number until an empty list is returned.

There's obviously no place in the json currently for total count and number pages etc. Is there another way (short of package_list) of determining how many results are to be expected and therefore how many pages to retrieve?