# subroutine name: GetFileLock
# Locks a file on flock-disabled systems like Win9x, so that no one 
# else can get to it while it is being accessed.
# It checks for the existance of a lock file and if it finds it, it 
# waits until the lock file disappears, but not more than 20 sec. 
# After the lock file is gone, it opens the lock file up itself.
#
# Input:
#      $lock_file = filename to use as a temporary lock file
#
# Global variables used:
#	$no_flock - disable flock or not
#	%LOCK_HANDLES - hash of locked file handles
sub GetFileLock {
	if ($no_flock) {
		my ($lock_file) = @_;
		my $endtime = time + 10;
	
		my $delta = 20/86400; # 20 seconds
	
		if (-e $lock_file && -M $lock_file > $delta) {
			unlink($lock_file);
		}
	
		while (-e $lock_file && time < $endtime) {
			sleep(1);  # Wait 1 sec.
		}
		local *LOCK_FILE;
		$LOCK_HANDLES{$lock_file}=*LOCK_FILE;
		# Create lock file
		open(LOCK_FILE, ">$lock_file") or
			die("Error in subroutine GetFileLock: Can't open $lock_file. Reason: $!");
	}
}