ip-netmask

iputil.rkt

@@ -1,14 +1,18 @@
 #lang racket
 
-(require racket/struct)
-
 (provide (struct-out peer) (struct-out subnet)
          string->ip
          ip->string
+         ip-netmask
          string->subnet
          subnet->string
          string->peer)
 
+(require racket/struct)
+
+(module+ test
+  (require rackunit))
+
 (struct peer [ip type]
   #:methods gen:custom-write
   [(define write-proc
@@ -37,6 +41,11 @@
                                             255)))))
   (string-join parts "."))
 
+(define (ip-netmask ip)
+  (for/sum ([i (in-range 32)])
+    #:break (positive? (bitwise-and ip (arithmetic-shift 1 i)))
+    1))
+
 (define (string->subnet str)
   (match-define (list ipstr maskstr) (string-split str "/"))
   (subnet (string->ip ipstr)
@@ -44,9 +53,18 @@
 
 (define (subnet->string sub)
   (format "~a/~a"
-          (subnet-ip sub)
+          (ip->string (subnet-ip sub))
           (subnet-mask sub)))
 
 (define (string->peer str)
   (match-define (list ip type) (string-split str "-"))
   (peer (string->ip ip) (string->symbol type)))
+
+;; ================================================================================
+
+(module+ test
+  (check-equal? (ip->string (string->ip "123.84.0.67")) "123.84.0.67")
+  (check-equal? (ip->string (string->ip "0.0.0.0")) "0.0.0.0")
+
+  (check-equal? (ip-netmask (string->ip "255.255.254.0")) 9)
+  (check-equal? (ip-netmask (string->ip "255.0.0.0")) 24))