For unofficial google reader api, we can use Atom feed api and also can use parameter &c= to continuous get old items.
Google Official Feed API has two kinds: Find and Load
for Load API with JSON, it seems it only allow you load up to 100 newest items from a feed. And there is no parameter like &c=
What if I want item 101 - 1000?
(I try to use this official feed api because I want JSON for higher efficiency than Atom.)
thanks
I don't know how to do that using the Google Feeds API, but you can get feed items as JSON from the unofficial Google Reader API. The endpoint is http:://www.google.com/reader/api/0/stream/contents/feed/{escaped URL}
. The result contains a "continuation" element, which you can use to request additional items. Authentication should not be neccessary as long as you don't request Google Reader per-user data (such as starred items).
You can find more documentation on the arguments to this endpoint (and some others) in Mihai Parparita's unofficial Google Reader API documentation.