# subroutine name: readdata
# Reads all data from datafile
# If error occurs (e.g. file doesn't exist), makes CGI process exit with error
# Returns: reference to the array of lines, trailing "\n" in each 
#          line is not removed
# Global variables used:
#	$no_flock - disable flock or not
sub readdata {
	my($datafile) = @_;
	my @data;
	# If OS (like Win95) desn't support flock, we have to
	# go unreliable and slow way and create "lock" file
	GetFileLock("$datafile.lock");
	local *DATA;
	if (open(DATA,"<$datafile")) {
		# shared locking
		flock(DATA, 1) unless ($no_flock);
		my $line;
		while ($line = <DATA>) {
			push (@data, $line);
		};
		# unlock file
		flock(DATA, 8) unless ($no_flock);
		close(DATA);
		ReleaseFileLock("$datafile.lock");
	} else {
  		ReleaseFileLock("$datafile.lock");
		die("Error in subroutine readdata: Can't open $datafile. Reason: $!");
	};
	return \@data;
}