I got to know that Rackspace Cloud Files is based on OpenStack Object Storage service (Swift).
As OpenStack allows configuring/manipulating object storage using S3 APIs through swift3 http://docs.openstack.org/trunk/openstack-object-storage/admin/content/configuring-openstack-object-storage-with-s3_api.html I am thinking whether Rackspace Cloud Files provides S3 API support as well. I have a client written for Amazon Web Services using S3 RESTful APIs so was thinking to reuse it for Rackspace Cloud Files as well.