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dn_comp(3)
NAME
  dn_comp - Compresses a domain name

LIBRARY
  Standard C Library (libc.a)

SYNOPSIS

  #include <sys/types.h>

  #include <netinet/in.h>

  #include <arpa/nameser.h>

  #include <resolv.h>

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

PARAMETERS
  expanded_name
	    Points to a domain name.

  compressed_name
	    Points to an array containing the compressed domain name.

  length    Specifies the size of the array pointed to by the compressed_name
	    parameter.

  name_ptrs Specifies a list of pointers to previously compressed names in
	    the current message.

  end_ptr   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.

  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
  Upon successful completion, the dn_comp() function returns the size of the
  compressed domain name.  Otherwise, a value of -1 is returned.

FILES
  /etc/resolv.conf
	    Defines name server and domain name structures, constants, and
	    values.

RELATED INFORMATION
  Functions: res_init(3), res_mkquery(3), res_send(3), dn_expand(3),
  dn_find(3), _getshort(3), _getlong(3), putshort(3), putlong(3),
  dn_skipname(3)

  Commands: named(8)