Extending the drupal 7 feed-aggregator module to modify the URL programmatically and add feed options

I'd like to use the Drupal feed aggregator to fetch events from a web service (providing Atom, JSON, etc. access to those events). However, it allows to retrieve protected events by providing not only an API key but also signing the request.开发者_StackOverflow中文版

So I'd like to know if it's easily possible to extend the aggregator module (preferably through a separate module without having to modify the aggregator module's code) in a way to process the used URL with a custom function (to add timestamp, signature etc.). Being able to add custom option fields ("API key", "Secret key" etc) would be important, too.

Right now I'm using a completely custom module which does not use a cronjob to retrieve the events, relies on the block cache, etc - the main issue of it is that it's just a block without e.g. a "view more" option.

You may have more success implementing the various aggregator module hooks.

For example hook_aggregator_fetch

and the other related hooks listed on that page.