--- /dev/null
+
+USING: kernel sequences assocs sets locals combinators
+ accessors system math math.functions unicode prettyprint
+ combinators.smart dns ;
+
+IN: dns.cache.rr
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+TUPLE: <entry> time data ;
+
+: now ( -- seconds ) millis 1000.0 / round >integer ;
+
+: expired? ( <entry> -- ? ) time>> now <= ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: make-cache-key ( obj -- key )
+ [ [ name>> >lower ] [ type>> ] [ class>> ] tri ] output>array ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+: cache ( -- table ) H{ } ;
+
+: cache-at ( obj -- ent ) make-cache-key cache at ;
+: cache-delete ( obj -- ) make-cache-key cache delete-at ;
+: cache-set-at ( ent obj -- ) make-cache-key cache set-at ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: cache-get ( OBJ -- rrs/f )
+ [let | ENT [ OBJ cache-at ] |
+ {
+ { [ ENT f = ] [ f ] }
+ { [ ENT expired? ] [ OBJ cache-delete f ] }
+ {
+ [ t ]
+ [
+ [let | NAME [ OBJ name>> ]
+ TYPE [ OBJ type>> ]
+ CLASS [ OBJ class>> ]
+ TTL [ ENT time>> now - ] |
+ ENT data>>
+ [| RDATA | T{ rr f NAME TYPE CLASS TTL RDATA } ]
+ map
+ ]
+ ]
+ }
+ }
+ cond
+ ] ;
+
+! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+:: cache-add ( RR -- )
+ [let | ENT [ RR cache-at ]
+ TIME [ RR ttl>> now + ]
+ RDATA [ RR rdata>> ] |
+ {
+ { [ ENT f = ] [ T{ <entry> f TIME V{ RDATA } } RR cache-set-at ] }
+ { [ ENT expired? ] [ RR cache-delete RR cache-add ] }
+ { [ t ] [ TIME ENT time<< RDATA ENT data>> adjoin ] }
+ }
+ cond
+ ] ;