util.java

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/* ============================================================
 * JRobin : Pure java implementation of RRDTool's functionality
 * ============================================================
 *
 * Project Info:  http://www.jrobin.org
 * Project Lead:  Sasa Markovic ([e-mail]);
 *
 * (C) Copyright 2003, by Sasa Markovic.
 *
 * Developers:    Sasa Markovic ([e-mail])
 *                Arne Vandamme ([e-mail])
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the GNU Lesser General Public License as published by the Free Software Foundation;
 * either version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */

package net.jumperz.ext.org.jrobin.core;

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Element;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Date;
import java.util.Locale;
import java.util.GregorianCalendar;
import java.util.ArrayList;
import java.io.*;

/**
 * Class defines various utility functions used in JRobin.
 *
 * @author <a href="mailto:[e-mail]">Sasa Markovic</a>
 */
public class Util {

	// pattern RRDTool uses to format doubles in XML files
	static final String PATTERN = "0.0000000000E00";
	// directory under $USER_HOME used for demo graphs storing
	static final String JROBIN_DIR = "jrobin-demo";

	static final DecimalFormat df;
	static {
		df = (DecimalFormat) NumberFormat.getNumberInstance(Locale.ENGLISH);
		df.applyPattern(PATTERN);
		df.setPositivePrefix("+");
	}

	/**
	 * Returns current timestamp in seconds (without milliseconds). Returned timestamp
	 * is obtained with the following expression: <p>
	 *
	 * <code>(System.currentTimeMillis() + 500L) / 1000L</code>
	 * @return Current timestamp
	 */
	public static long getTime() {
		return (System.currentTimeMillis() + 500L) / 1000L;
	}

	/**
	 * Just an alias for {@link #getTime()} method.
	 * @return Current timestamp (without milliseconds)
	 */
	public static long getTimestamp() {
		return getTime();
	}

	/**
	 * Rounds the given timestamp to the nearest whole &quote;step&quote;. Rounded value is obtained
	 * from the following expression:<p>
	 * <code>timestamp - timestamp % step;</code>
	 * @param timestamp Timestamp in seconds
	 * @param step Step in seconds
	 * @return "Rounded" timestamp
	 */
	public static long normalize(long timestamp, long step) {
		return timestamp - timestamp % step;
	}

	/**
	 * Returns the greater of two double values, but treats NaN as the smallest possible
	 * value. Note that <code>Math.max()</code> behaves differently for NaN arguments.
	 *
	 * @param x an argument
	 * @param y another argument
	 * @return the lager of arguments
	 */
	public static double max(double x, double y) {
		return Double.isNaN(x)? y: Double.isNaN(y)? x: Math.max(x, y);
	}

	/**
	 * Returns the smaller of two double values, but treats NaN as the greatest possible
	 * value. Note that <code>Math.min()</code> behaves differently for NaN arguments.
	 *
	 * @param x an argument
	 * @param y another argument
	 * @return the smaller of arguments
	 */
	public static double min(double x, double y) {
		return Double.isNaN(x)? y: Double.isNaN(y)? x: Math.min(x, y);
	}

	static double sum(double x, double y) {
		return Double.isNaN(x)? y: Double.isNaN(y)? x: x + y;
	}

	static String formatDouble(double x, String nanString, boolean forceExponents) {
		if(Double.isNaN(x)) {
			return nanString;
		}
		if(forceExponents) {
			return df.format(x);
		}
		return "" + x;
	}

	static String formatDouble(double x, boolean forceExponents) {
		return formatDouble(x, "" + Double.NaN, forceExponents);
	}

	/**
	 * Returns <code>Date</code> object for the given timestamp (in seconds, without
	 * milliseconds)
	 * @param timestamp Timestamp in seconds.
	 * @return Corresponding Date object.
	 */
	public static Date getDate(long timestamp) {
		return new Date(timestamp * 1000L);
	}

    /**
	 * Returns <code>GregorianCalendar</code> object for the given timestamp
	 * (in seconds, without milliseconds)
	 * @param timestamp Timestamp in seconds.
	 * @return Corresponding GregorianCalendar object.
	 */
	public static GregorianCalendar getGregorianCalendar(long timestamp) {
		GregorianCalendar gc = new GregorianCalendar();
		gc.setTimeInMillis(timestamp * 1000L);
		return gc;
	}

    /**
	 * Returns <code>GregorianCalendar</code> object for the given Date object
	 * @param date Date object
	 * @return Corresponding GregorianCalendar object.
	 */
	public static GregorianCalendar getGregorianCalendar(Date date) {
		GregorianCalendar gc = new GregorianCalendar();
		gc.setTime(date);
		return gc;
	}

	/**
	 * Returns timestamp (unix epoch) for the given Date object
	 * @param date Date object
	 * @return Corresponding timestamp (without milliseconds)
	 */
	public static long getTimestamp(Date date) {
		// round to whole seconds, ignore milliseconds
		return (date.getTime() + 499L) / 1000L;
	}

	/**
	 * Returns timestamp (unix epoch) for the given GregorianCalendar object
	 * @param gc GregorianCalendar object
	 * @return Corresponding timestamp (without milliseconds)
	 */
	public static long getTimestamp(GregorianCalendar gc) {
		return getTimestamp(gc.getTime());
	}

	/**
	 * Returns timestamp (unix epoch) for the given year, month, day, hour and minute.
	 * @param year Year
	 * @param month Month (zero-based)
	 * @param day Day in month
	 * @param hour Hour
	 * @param min Minute
	 * @return Corresponding timestamp
	 */
	public static long getTimestamp(int year, int month, int day, int hour, int min) {
		GregorianCalendar gc = new GregorianCalendar(year, month, day, hour, min);
		return Util.getTimestamp(gc);
	}

	/**
	 * Returns timestamp (unix epoch) for the given year, month and day.
	 * @param year Year
	 * @param month Month (zero-based)
	 * @param day Day in month
	 * @return Corresponding timestamp
	 */
	public static long getTimestamp(int year, int month, int day) {
		return Util.getTimestamp(year, month, day, 0, 0);
	}

	/**
	 * Parses input string as a double value. If the value cannot be parsed, Double.NaN
	 * is returned (NumberFormatException is never thrown).
	 * @param valueStr String representing double value
	 * @return a double corresponding to the input string
	 */
	public static double parseDouble(String valueStr) {
		double value;
		try {
			value = Double.parseDouble(valueStr);
		}
		catch(NumberFormatException nfe) {
			value = Double.NaN;
		}
		return value;
	}

	/**
	 * Parses input string as a boolean value. The parser is case insensitive.
	 * @param valueStr String representing boolean value
	 * @return <code>true</code>, if valueStr equals to 'true', 'on', 'yes', 'y' or '1';
	 * <code>false</code> in all other cases.
	 */
	public static boolean parseBoolean(String valueStr) {
		return valueStr.equalsIgnoreCase("true") ||
			valueStr.equalsIgnoreCase("on") ||
			valueStr.equalsIgnoreCase("yes") ||
			valueStr.equalsIgnoreCase("y") ||
			valueStr.equalsIgnoreCase("1");
	}

	/**
	 * Returns file system separator string.
	 * @return File system separator ("/" on Unix, "\" on Windows)
	 */
	public static String getFileSeparator() {
		return System.getProperty("file.separator");
	}

	/**
	 * Returns path to user's home directory.
	 * @return Path to users home directory, with file separator appended.
	 */
	public static String getUserHomeDirectory() {
		return System.getProperty("user.home") + getFileSeparator();
	}

	private static final File homeDirFile;
	private static final String homeDirPath;

	static {
		homeDirPath = getUserHomeDirectory() + JROBIN_DIR + getFileSeparator();
		homeDirFile = new File(homeDirPath);
	}

	/**
	 * Returns path to directory used for placement of JRobin demo graphs and creates it
	 * if necessary.
	 * @return Path to demo directory (defaults to $HOME/jrobin/) if directory exists or
	 * was successfully created. Null if such directory could not be created.
	 */
	public static String getJRobinDemoDirectory() {
		return (homeDirFile.exists() || homeDirFile.mkdirs())? homeDirPath: null;
	}

	/**