dn_comp(3)						     Library Functions Manual							dn_comp(3)

NAME

       dn_comp - Compresses a domain name

LIBRARY

       Standard C Library (libc.a, libc.so)

SYNOPSIS

       #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 );

PARAMETERS

       Points to a domain name.  Points to an array containing the compressed domain name.  Specifies the size of the array pointed to by the com-
       pressed_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

       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 infor-
       mation 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

       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

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

RELATED INFORMATION

       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).  delim off

																	dn_comp(3)