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dn_comp(3)
NAME
  dn_comp - Compress a domain name

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 );

LIBRARY
  Standard C Library (libc)

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

SEE ALSO
  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).

Index for Section 3

Alphabetical listing for D

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