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       dns_domain_* - The dns_domain library interface


       #include <dns.h>

       len = dns_domain_length(dn);
         char *dn;
         unsigned int len;

       dns_domain_equal(dn, dn2);
         char *dn;
         char *dn2;

       dns_domain_copy(&dn, in);
         char *dn = 0;
         char *in;

       dns_domain_fromdot(&dn, buf, len);
         char *dn = 0;
         char *buf;
         unsigned int len;


       A  DNS  domain  name  is a sequence of components.  Each component is a
       string of bytes, of length between  1  and  63  inclusive.   The  total
       length of all the components, plus the number of components, is between
       0 and 254 inclusive.

       A component is packet-encoded as a self-delimiting sequence  of  bytes,
       the  first  byte being the length of the component, the remaining bytes
       being the bytes in the component.  A DNS domain name is  packet-encoded
       as  a  sequence of bytes obtained by concatenating the encodings of the
       components and a terminating \0.  Beware  that  \0  can  appear  inside
       components.   The  total  length of a packet-encoded DNS domain name is
       between 1 and 255 inclusive.

       dns_domain_length returns the number of bytes in the packet-encoded DNS
       name that dn points to.

       dns_domain_equal  compares the packet-encoded DNS names that dn and dn2
       point to.  It returns 1 if the names are the same, 0 if not.  Lowercase
       ASCII and uppercase ASCII are considered the same.

       dns_domain_copy  reads  the  packet-encoded DNS name that in points to,
       copies the name into dynamically allocated space,  points  dn  to  that
       space,   and   returns   1.    If   not  enough  memory  is  available,
       dns_domain_copy returns 0, setting errno appropriately, and  leaves  dn

       You   can   call   dns_domain_copy   repeatedly.   If  dn  is  nonzero,
       dns_domain_copy frees it before replacing  it  with  the  new  pointer.
       Initially dn must be 0.

       dns_domain_fromdot reads a dot-encoded DNS name of length len from buf,
       copies the name in packet-encoded  format  into  dynamically  allocated
       space, points dn to that space, and returns 1.

       If  buf  violates DNS name length restrictions, or if not enough memory
       is available, dns_domain_fromdot leaves dn alone and returns 0, setting
       errno appropriately.

       Like  dns_domain_copy,  dns_domain_fromdot frees dn before changing it,
       if dn is nonzero.


       dns_ip4(3), dns_ip4_qualify(3), dns_mx(3), dns_name4(3), dns_packet(3),
       dns_random(3), dns_transmit(3), dns_txt(3)