NAME    [Toc]    [Back]

       dn_comp - Compress a domain name

SYNOPSIS    [Toc]    [Back]

       #include  <sys/types.h>  #include  <netinet/in.h> #include
       <arpa/nameser.h> #include <resolv.h>

       int dn_comp(
               const char *expanded_name,
               u_char *compressed_name,
               int length,
               u_char **name_ptrs,
               u_char **end_ptr );

LIBRARY    [Toc]    [Back]

       Standard C Library (libc)

PARAMETERS    [Toc]    [Back]

       Points to a domain name.  Points to  an  array  containing
       the  compressed  domain  name.   Specifies the size of the
       array pointed to by the compressed_name parameter.  Specifies
  a list of pointers to previously compressed names in
       the current message.  Points  to  the  end  of  the  array
       pointed to by the compressed_name parameter.

DESCRIPTION    [Toc]    [Back]

       The  dn_comp()  (domain  name  compression)  function compresses
 the domain name pointed to  by  the  expanded_name
       parameter and stores it in the area pointed to by the compressed_name
 parameter.

       The dn_comp() function inserts labels into the message  as
       the name is compressed.  The dn_comp() function also maintains
 a list of pointers to the message labels.

       If the value of  the  name_ptrs  parameter  is  null,  the
       dn_comp()  function  does  not  compress  any  names,  but
       instead translates a domain name from  ASCII  to  internal
       format  without  removing  suffixes (compressing).  Otherwise,
 the name_ptrs parameter is the address  of  pointers
       to  previously  compressed  suffixes.  The  list ends with
       NULL.

       If the end_ptr parameter is null, the  dn_comp()  function
       does not update the list of label pointers.

       The dn_comp() function is one of a set of subroutines that
       form the resolver, a set of functions that resolves domain
       names.   Global  information  that is used by the resolver
       functions  is  kept  in  the  _res  data  structure.   The
       /include/resolv.h  file  contains  the _res data structure
       definition.

RETURN VALUES    [Toc]    [Back]

       Upon successful completion, the dn_comp() function returns
       the size of the compressed domain name. Otherwise, a value
       of -1 is returned and the h_errno external variable is set
       with an error code, if any.  Error code values and reasons
       are defined in <netdb.h>.

FILES    [Toc]    [Back]

       Defines name server and domain name structures, constants,
       and values.

SEE ALSO    [Toc]    [Back]

       Functions:  dn_expand(3), dn_find(3), dn_skipname(3), putshort(3),   putlong(3),    res_init(3),    res_mkquery(3),
       res_query(3),  res_search(3),  res_send(3),  _getshort(3),
       _getlong(3).

       Commands: named(8).



                                                       dn_comp(3)