Checks the retained window of a chain, recomputing every hash.
floor is the hash of the last entry dropped from the ring, which the first retained entry
must name as its prev (absent while the ring has never wrapped, so the first entry must be
sequence 1 chaining from the genesis hash). head is the pointer the object keeps beside the
ring; without it a chain cut short at the end would still verify. An edit to one entry shows
at that entry; an edit that also rewrites its hash shows at the next one.
Checks the retained window of a chain, recomputing every hash.
flooris the hash of the last entry dropped from the ring, which the first retained entry must name as itsprev(absent while the ring has never wrapped, so the first entry must be sequence 1 chaining from the genesis hash).headis the pointer the object keeps beside the ring; without it a chain cut short at the end would still verify. An edit to one entry shows at that entry; an edit that also rewrites its hash shows at the next one.