use strict;
use warnings;

use Carp               qw( croak );
use Win32::API         qw( );
use Win32::API::Struct qw( );

use constant DS_IS_DNS_NAME => 0x00020000;

typedef Win32::API::Struct GUID => qw {
   DWORD Data1;
   WORD  Data2;
   WORD  Data3;
   BYTE  Data4[8];
};

sub _link {
   my $o = Win32::API->new( @_ );
   die "Can't link to DsGetDcName in dll Netapi32: $^E\n" if !$o;
   return $o;
}

{
   my $DsGetDcName = _link(
      'Netapi32', 'DsGetDcName', 'PPSPNP', 'N' );

   my $NetApiBufferFree = _link(
      'Netapi32', 'NetApiBufferFree', 'N', 'N' );

   my $GUID_FORMAT = 'L S S a8';
   my $SIZE_OF_GUID = 4+2+2+ 8;

   my $DCI_FORMAT = "p p L a$SIZE_OF_GUID p p L p p";
   my $SIZE_OF_DCI = 4+4+4+ $SIZE_OF_GUID+4+4+4+4+4;

   sub DsGetDcName {
      my $pk_ptr_to_pk_dci = pack('L', 0);

      if (!(my $rv = $DsGetDcName->Call( @_, $pk_ptr_to_pk_dci ))) {
         # It uses the same codes as GetLastError
         $^E = $rv;
         croak("$^E");
      }

      my $ptr_to_pk_dci = unpack('L', $pk_ptr_to_pk_dci);

      my $pk_dci = unpack("P$SIZE_OF_DCI", $pk_ptr_to_pk_dci);

      # If only Win32::API::Struct provided a public
      # interface that takes a packed struct.
      my ($dcn, $dca, $dcat, $pk_guid, $dn, $dfn, $flags, $sn, $csn) =
         unpack($DCI_FORMAT, $pk_dci);

      my @guid = unpack($GUID_FORMAT, $pk_guid);
      my $guid = Win32::API::Struct->new('GUID');
      @{$guid}{qw( Data1 Data2 Data3 Data4 )} = @guid;

      if (!(my $rv = $NetApiBufferFree->Call( $ptr_to_pk_dci ))) {
         # It uses the same codes as GetLastError
         $^E = $rv;
         # Don't use carp since it's likely a bug in this sub.
         warn("Warning: Error from NetApiBufferFree: $^E");
      }

      return {
         DomainControllerName        => $dcn,
         DomainControllerAddress     => $dca,
         DomainControllerAddressType => $dcat,
         DomainGuid                  => \@guid,
         DomainName                  => $dn,
         DnsForestName               => $dfn,
         Flags                       => $flags,
         DcSiteName                  => $sn,
         ClientSiteName              => $csn,
      };
   }
}

my $domainguid = Win32::API::Struct->new('GUID');

my $dci = DsGetDcName(
   'mymachine',
   'mydomain',
   $domainguid,
   'myADsite',
   DS_IS_DNS_NAME,
);

use Data::Dumper qw( Dumper );
print Dumper $dci;