/*
 * Copyright (c) 2009-2012 Zmanda, Inc.  All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * Contact information: Zmanda Inc., 465 S. Mathilda Ave., Suite 300
 * Sunnyvale, CA 94085, USA, or: http://www.zmanda.com
 */

%perlcode %{

=head1 NAME

Amanda::NDMP - communicate via NDMP

=head1 SYNOPSIS

  use Amanda::NDMP qw( :constants );

  my $conn = Amanda::NDMP::NDMPConnection->new($host, $port, $ident, $username,
					       $password, $auth);
  my ($ok, $blocksize, $file_num, $blockno) = $conn->tape_get_state();

=head1 DESCRIPTION

This package interfaces with the C class C<NDMPConnection> class declared in
C<ndmp-src/ndmpconnobj.h>.  It is only available in builds that did not specify
C<--without-ndmp>.  The C class, in turn, interfaces to the XDR code provided
by NDMJOB, which sends and receives NDMP messages on a TCP socket.

=head2 Constructor

  my $conn = Amanda::NDMP::NDMPConnection->new($host, $port, $ident, $username,
					       $password, $auth);
  if ($conn->err_code()) {
    # handle error..
  }

This gets a new connection object.  This will always return an object, but the
result should be checked for errors as described in the "Error Handling"
section, below.

The C<$host> and C<$port> give the NDMP server's host and port, respectively.
The C<$auth> parameter defines the authentication mechanism to use: "md5" or
"text"; "none" for no authentication; or "void" to not send any authentication
packets at all.  For md5 or text modes, C<$username> and C<$password> specify
the username and password for the NDMP server; these parameters must always be
included, but can be blank for none or void.

The C<$ident> parameter deserves some explanation.  NDMP scopes many
server-side variables to the NDMP connection - for example, the "current" tape
and taper state are associated with the NDMP connection.  To facilitate this,
the constructor returns the I<same connection> for any constructor invocation
with the same host, port, and identifier.  In cases where multiple connections
are required (e.g., when two tapes are in use simultaneously), callers should
provide different identifiers for each connection.

=head2 Methods

Note that not all NDMPConnection methods are available.  All of these methods
block until the appropriate reply is received.  The underlying C class provides
appropriate locking fundamentals to prevent corrupted on-the-wire messages.

All methods return a boolean "ok" status, with false indicating an error.

=head3 Error Handling

  my $code = $conn->err_code();
  my $msg = $conn->err_msg();

Get the error code and message from the last method that returned false, or
after the constructor is invoked.

  $conn->set_verbose(1);

This method will enable verbose logging of the NDMP transactions to the Amanda
debug logs.

=head3 SCSI Interface

  my $ok = $conn->scsi_open($device);	    # NDMP_SCSI_OPEN
  my $ok = $conn->scsi_close();		    # NDMP_SCSI_CLOSE
  # NDMP_SCSI_EXECUTE_CDB
  my $res = $conn->scsi_execute_cdb(
    flags => $flags,
    timeout => $timeout,
    cdb => $cdb,
    datain_len => $datain_len,	    # only if $flags == $NDMP9_SCSI_DATA_DIR_IN
    dataout => $dataout 	    # only if $flags == $NDMP9_SCSI_DATA_DIR_OUT
  )

The first two methods are clear; the third uses keyword parameters to simplify
a complex set of parameters.  The C<flags> argument can be
C<$NDMP9_SCSI_DATA_DIR_IN>, to take data I<into> the server from the SCSI
device, or C<$NDMP9_SCSI_DATA_DIR_OUT> to send data I<out> to the SCSI device.
The C<timeout> is in milliseconds.  The C<cdb> should be a SCSI control block
(the C<pack> function is useful here).  If the data direction is in, then
C<datain_len> indicates the maximum amount of data to expect; otherwise,
C<dataout> is the data to send to the device.

The result is C<undef> for an error, or a hashref with the following keys:

  status	    SCSI status byte
  ext_sense	    SCSI extended sense data
  datain	    data from the device
  dataout_len	    number of bytes actually transmitted to the device

=head3 Tape Interface

  my $ok = $conn->tape_open($device, $mode);
  my $ok = $conn->tape_close();

The first method opens a tape device, using the give mode -
C<$NDMP9_TAPE_READ_MODE> or C<$NDMP9_TAPE_RDRW_MODE>.  The second method closes
the tape device associated with this connection.

  my ($ok, $resid) = $conn->tape_mtio($op, $count);

This method sends C<NDMP_TAPE_MTIO> with the given operation and count.
Operations have the prefix C<$NDMP9_MTIO_>.  The number of incomplete
operations is returned in C<$resid>.

To read and write blocks, use these methods:

  my ($ok, $actual) = $conn->tape_write($data);
  my ($ok, $data) = $conn->tape_read($bufsize);

where C<$actual> and C<$bufsize> are byte counts, and C<$data> is a string of
data.  Finally, to get the state of the tape agent, use

  my ($ok, $blocksize, $file_num, $blockno) = $conn->tape_get_state();

=head2 Constants

The constants required for the interface exposed here are included in this
package.  They all begin with the prefix C<$NDMP9_>, which is an implementation
detail of the NDMJOB library.  The constants are available from the export tag
C<constants>:

  use Amanda::NDMP qw( :constants );

=cut


%}