Source code of Windows XP (NT5)
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#---------------------------------------------------------------------
package LockProc;
#
# Copyright (c) Microsoft Corporation. All rights reserved.
#
# Version: 1.00 (01/01/2001) : BPerkins
# 2.00 (10/16/2001) : SuemiaoR
# Purpose: Create locking to prevent multiple processes at the same time.
#---------------------------------------------------------------------
use strict;
use vars qw($VERSION);
$VERSION = '1.00';
use Win32::ChangeNotify;
use Win32::Event;
use Logmsg;
use comlib;
#---------------------------------------------------------------------
sub new
{
my $class = shift;
my $spool_path = shift;
my $timeout = shift;
return 0 if not defined $spool_path;
my $instance =
{
Path => $spool_path,
Timeout => $timeout || INFINITE, # default timeout is INFINITE
File => "$ENV{COMPUTERNAME}.txt",
NotificationObj => undef,
LocalSyncObj => undef,
fHaveLocalSync => 0,
Count => 0
};
return bless $instance;
}
#---------------------------------------------------------------------
sub Lock
{
my $self = shift;
my $wait_return;
return 0 unless ref $self;
# If we already hold the lock just bump up the ref-count
if ( $self->{Count} )
{
$self->{Count}++;
return 1;
}
# Need to synchronize local access (only one program
# at a time from the same machine can hold the lock)
dbgmsg( "Creating a local request event..." );
if ( !defined $self->{LocalSyncObj} )
{
my $lock_path = $self->{Path};
$lock_path =~ s/\\\\/remote\\/;
$lock_path =~ s/\\/\//g;
if( !($self->{LocalSyncObj} = new Win32::Event ( 0, 1, "Global\\$lock_path" ) ))
{
errmsg( "Unable to create a local event ($^E)." );
errmsg( "Check if the same process is running in this machine." );
return 0;
}
}
dbgmsg( "Checking global lock status ..." );
if ( !$self->{fHaveLocalSync} )
{
# Handle timeout
if( !($wait_return = $self->{LocalSyncObj}->wait( $self->{Timeout} ) ) )
{
dbgmsg( "Waiting on another process on machine." );
return 2;
}
# Handle error condition
elsif ( $wait_return != 1 )
{
errmsg( "Unexpected error waiting for local synchronization (wait returned ". $wait_return. ")" );
return 0;
}
$self->{fHaveLocalSync} = 1;
}
# Check for our existence before we create a file in the queue
# (this will be the case if something bad happened on the last run and we are
# rerunning the command to recover)
if ( ! -e "$self->{Path}\\$self->{File}" )
{
if( !open SPOOLFILE, "> $self->{Path}\\$self->{File}" )
{
errmsg( "Failed to create synchronization file '$self->{Path}\\$self->{File}' ($!)." );
return 0;
}
print SPOOLFILE "This file is used to synchronize access among machines.";
close SPOOLFILE;
}
# Create the notification object if this is the first time we were called
dbgmsg( "Creating the notification object..." );
if( !$self->{NotificationObj} )
{
if( !($self->{NotificationObj} = new Win32::ChangeNotify( $self->{Path}, 0, FILE_NOTIFY_CHANGE_FILE_NAME ) ))
{
errmsg( "Failed creating monitor object ($^E)." );
return 0;
}
}
# Check our position in the 'queue' at the beginning
dbgmsg( "Looking up the waiting queue..." );
my $tmpfile = "$ENV{TEMP}\\tmpfile";
if ( system("dir /b /od $self->{Path} > $tmpfile") )
{
errmsg( "Unable to view directory $self->{Path}." );
return 0;
}
my @ordered_spool_directory = &comlib::ReadFile($tmpfile);
dbgmsg( "The Waiting queue [@ordered_spool_directory]" ) if( @ordered_spool_directory > 1 );
# We are at the top
if ( $ordered_spool_directory[0] eq $self->{File} )
{
$self->{Count}++;
dbgmsg( "Pass semaphore verification.");
return 1;
}
# Recheck our position in the 'queue' everytime the state of the directory changes
# until we are in the top position
# or we hit the timeout value with no activity
while ( 1 )
{
$self->{NotificationObj}->reset();
$wait_return = $self->{NotificationObj}->wait( $self->{Timeout} );
if ( system("dir /b /od $self->{Path} > $tmpfile") )
{
errmsg( "Unable to view directory $self->{Path}." );
return 0;
}
@ordered_spool_directory = &comlib::ReadFile($tmpfile);
# We are at the top
if ( $ordered_spool_directory[0] eq $self->{File} )
{
$self->{Count}++;
return 1;
}
# Still waiting for others
# But need to Make sure we are still in the queue
my $found_self = 0;
for ( @ordered_spool_directory )
{
if ( $_ eq "$self->{File}" ){ $found_self = 1; last;}
}
if ( !$found_self )
{
# Lost our synchronization file -- recreating...
if ( !(open SPOOLFILE, "> $self->{Path}\\$self->{File}" ) )
{
errmsg( "Lost our synchronization file '$self->{Path}\\$self->{File}' -- failed to recreate. ($!)." );
return 0;
}
print SPOOLFILE "This file is used to synchronize access among machines.";
close SPOOLFILE;
}
# Handle timeout
if ( !$wait_return )
{
my $machine_name = $ordered_spool_directory[0];
$machine_name =~ s/\.txt$//;
wrnmsg ( "Waiting on $machine_name ($self->{Path}\\$ordered_spool_directory[0])." );
return 2;
}
# Handle error condition
elsif ( $wait_return != 1 )
{
errmsg( "Unexpected error waiting on directory to change (wait returned ". $wait_return. ")" );
return 0;
}
}
errmsg( "Jumped out of an infinte loop -- no idea how we got here" );
return 1;
}
#---------------------------------------------------------------------
sub Unlock
{
my $self = shift;
return unless ref $self;
# Can't release a lock we don't hold
return 0 if ( !$self->{Count} );
# Decrement lock count
if ( !( --$self->{Count} ) )
{
if ( ! unlink "$self->{Path}\\$self->{File}" )
{
errmsg("Failed to delete synchronization file ($self->{Path}\\$self->{File}).");
errmsg("May need to delete by hand." );
return 0;
}
$self->{LocalSyncObj}->set();
}
return 1;
}
#---------------------------------------------------------------------
sub GetLastError
{
my $self = shift;
return unless ref $self;
#return $self->{LastErrorValue};
}
#---------------------------------------------------------------------
sub GetLastErrorMessage
{
my $self = shift;
return unless ref $self;
#return $self->{LastErrorMsg};
}
#---------------------------------------------------------------------
sub DESTROY
{
my $self = shift;
return unless ref $self;
if ( $self->{Count} > 0 )
{
#print "Abandoning lock file -- attempting to delete.";
$self->{Count} = 1;
return $self->Unlock();
}
else
{
$self->{LocalSyncObj}->set() if ( $self->{fHaveLocalSync} ) ;
return 1;
}
}
#---------------------------------------------------------------------
1;
__END__
=head1 NAME
<<mypackage>> - <<short description>>
=head1 SYNOPSIS
<<A short code example>>
=head1 DESCRIPTION
<<The purpose and functionality of this module>>
=head1 AUTHOR
<<your alias>>
=head1 COPYRIGHT
Copyright (c) Microsoft Corporation. All rights reserved.
=cut