enum.scm

(define-module (dns enum)
  :export (rr-types
           int->rr rr->int
           class-types
           int->class class->int
           rcode-types
           int->rcode rcode->int
           opcode-types
           int->opcode opcode->int))

(define (flip-cons c)
  (cons (cdr c) (car c)))

(define (make-mappings name table)
  (values
   (lambda (i)
     (cond ((assv i (map flip-cons table)) => cdr)
           ((integer? i) (inexact->exact i))
           (else (scm-error 'wrong-type-arg (format #f "int->~a" name)
                            "Unknown value ~s, expected known integer or one of ~a"
                            (list i (map car table)) (list (map car table))))))

   (lambda (value)
     (cond ((integer? value) (inexact->exact value))
           ((assv value table) => cdr)
           (else (scm-error 'wrong-type-arg (format #f "~a->int" name)
                            "Unknown value ~s"
                            (list value) #f)))  )))

(define rr-types
  '((A     . 1)
    (NS    . 2)
    (MD    . 3)
    (MF    . 4)
    (CNAME . 5)
    (SOA   . 6)
    (MB    . 7)
    (MG    . 8)
    (MR    . 9)
    (NULL  . 10)
    (WKS   . 11)
    (PTR   . 12)
    (HINFO . 13)
    (MINFO . 14)
    (MX    . 15)
    (TXT   . 16)
    ;; I don't know where this is specified
    (AAAA  . 28)))

(define-values (int->rr rr->int)
  (make-mappings "rr" rr-types))

(define class-types
  '((IN . 1)
    (CS . 2)
    (CH . 3)
    (HS . 4)))

(define-values (int->class class->int)
  (make-mappings "class" class-types))

(define rcode-types
  '((NOERROR . 0)  ; no error condition
    (NXDOMAIN . 1) ; format error - name server can't interpret
    (SERVFAIL . 2) ; server failure
    ;; 3 ; name error
    ))

(define-values (int->rcode rcode->int)
               (make-mappings "rcode" rcode-types))


(define opcode-types
  '((QUERY  . 0)
    (IQUERY . 1)
    (STATUS . 2)))

(define-values (int->opcode opcode->int)
               (make-mappings "opcode" opcode-types))