Change hash-ref -> zone-ref etc. prior to improving TTL processing

resolver.rkt

@@ -60,7 +60,7 @@
 ;; caller to decide what to do about that.
 (define (answer-from-zone q zone start-of-authority)
   (match-define (question name qtype qclass) q)
-  (define rrset (hash-ref zone name set))
+  (define rrset (or (zone-ref zone name) (set)))
   (define filtered-rrs (filter-rrs rrset qtype qclass))
   (define cnames (filter-by-type rrset 'cname)) ;; TODO: filter by class too??
   (define answer-set (set-union cnames filtered-rrs))
@@ -81,7 +81,7 @@
 (define (closest-nameservers name zone)
   (let search ((name name))
     (cond
-     ((hash-ref zone name #f) =>
+     ((zone-ref zone name) =>
       ;; There's an entry for this suffix of the original name. Check
       ;; to see if it has an NS record indicating a subzone.
       (lambda (rrset)
@@ -105,7 +105,7 @@
 (define (empty-answer q zone start-of-authority)
   (if (and start-of-authority ;; we are authoritative for something
 	   (in-bailiwick? (question-name q) (rr-name start-of-authority)) ;; for this in particular
-	   (not (hash-has-key? zone (question-name q)))) ;; and there are no RRs at all for this q
+	   (not (zone-includes-name? zone (question-name q)))) ;; there are no RRs at all for this q
       ;; NXDOMAIN/name-error: we definitely know there are no RRs at all for this q.
       #f
       ;; A normal no-answers packet otherwise.
@@ -122,7 +122,7 @@
 	   (set-union section
 		      (set-filter (lambda (rr) (and (memv (rr-type rr) '(a aaaa))
 						    (eqv? (rr-class rr) 'in)))
-				  (hash-ref zone name set))))
+				  (or (zone-ref zone name) (set)))))
 	 (set)
 	 names))
 

zonedb.rkt

@@ -7,7 +7,9 @@
 (require "api.rkt")
 (require "codec.rkt")
 
-(provide incorporate-rr
+(provide zone-ref
+	 zone-includes-name?
+	 incorporate-rr
 	 incorporate-complete-answer
 	 empty-zone-db
 	 compile-zone-db
@@ -25,6 +27,13 @@
 ;; and subzone checks into prefix rather than suffix checks. It makes
 ;; domain names into paths through the DNS DB tree.
 
+;; CompiledZone DomainName -> Maybe<Set<RR>>
+(define (zone-ref db name)
+  (hash-ref db name #f))
+
+(define (zone-includes-name? db name)
+  (hash-has-key? db name))
+
 ;; RR CompiledZone -> CompiledZone
 (define (incorporate-rr rr db)
   (hash-set db (rr-name rr) (set-add (hash-ref db (rr-name rr) set) rr)))