Create archiver and offline code handlers

Somewhat messy. Will clean up gradually in future commits.

lib/mime-types.rkt

@@ -0,0 +1,34 @@
+#lang racket/base
+(require racket/contract
+         racket/match
+         racket/path
+         racket/runtime-path
+         racket/string)
+
+(provide
+ (contract-out
+  [ext->mime-type (-> bytes? bytes?)]
+  [mime-type->ext (-> bytes? bytes?)]))
+
+(define-runtime-path mime.types-path "mime.types")
+
+(define ls
+  (call-with-input-file mime.types-path
+    (λ (in) (for/list ([line (in-lines in)]
+                       #:when (not (regexp-match? #rx"^ *($|#)" line)))
+              (match line
+                [(regexp #rx"^([^ ]+) +(.+)$" (list _ mime ext))
+                 (cons (string->bytes/utf-8 ext) (string->bytes/utf-8 mime))]
+                [(regexp #rx"^ *#") (void)]
+                [_ (log-warning "mime-types: failed to parse line ~s" line)])))))
+
+(define forward-hash (make-immutable-hash ls))
+(define reverse-hash (make-immutable-hash (map (λ (x) (cons (cdr x) (car x))) ls)))
+
+(define (ext->mime-type ext-in)
+  (define ext (regexp-replace #rx"^\\." ext-in #""))
+  (hash-ref forward-hash ext))
+
+(define (mime-type->ext m-in)
+  (define m (regexp-replace #rx";.*" m-in #""))
+  (hash-ref reverse-hash m))