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MxScreen/Session/Medium/File.pm  view on Meta::CPAN

# -*- Mode: perl -*-
#
# $Id: File.pm,v 0.1 2001/04/22 17:57:04 ram Exp $
#
#  Copyright (c) 1998-2001, Raphael Manfredi
#  Copyright (c) 2000-2001, Christophe Dehaudt
#  
#  You may redistribute only under the terms of the Artistic License,
#  as specified in the README file that comes with the distribution.
#
# HISTORY
# $Log: File.pm,v $
# Revision 0.1  2001/04/22 17:57:04  ram
# Baseline for first Alpha release.
#
# $EndLog$
#

use strict;

package CGI::MxScreen::Session::Medium::File;

#
# Session storage is a file, indexed by a session ID.
#
# In the generated HTML, the session is identified by two parameters:
#
#    _mxscreen_session       the session ID
#    _mxscreen_token         a random token, saved with context
#
# The random token is generated each time the context is saved to the file.
# It is used at retrieve time to validate the session ID: noone could guess
# both the session ID and the associated token at the same time.
# 
# Note that since we generate a token each time we save, using "Back" from
# the browser to resubmit an old form is bound to fail, since the token
# will have changed.
#
# It is up to the user to ensure that old session files are removed from the
# file system, according to a suitable session expiring policy.
#

require CGI::MxScreen::Session::Medium;
use vars qw(@ISA);
@ISA = qw(CGI::MxScreen::Session::Medium);

use Carp::Datum;
use Getargs::Long;
use Log::Agent;
use Fcntl;
use File::Basename;
use File::Path;

require LockFile::Simple;
require CGI;

use constant MX_SESSION_ID 	=> "_mxscreen_session";
use constant MX_TOKEN 		=> "_mxscreen_token";

#
# ->make
#
# Creation routine.
#
# Arguments:
#   -directory	root directory where sessions are stored
#   -nfs		whether stored data are on a network filesystem
#	-max_hold	maximum expected lock holding time, for stale lock detection
#
sub make {
	DFEATURE my $f_;
	my $self = bless {}, shift;
	my $MAX_HOLD = 60;					# If CGI takes more than that, uh!

	my ($directory, $nfs, $max) = xgetargs(@_,
		-directory	=> 's',
		-nfs		=> ['i', 0],
		-max_hold	=> ['i', $MAX_HOLD],
	);

	$self->{directory} = $directory;
	$self->{shared} = $nfs;
	$self->{lockmgr} = LockFile::Simple->make(
		-delay		=> 1,
		-hold		=> $max,
		-max		=> $max,			# After that, will be stale
		-nfs		=> $nfs,
		-stale		=> 1,
	);

	return DVAL $self;
}