robin.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.
 *
 * 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.
 *
 * Developers:    Sasa Markovic ([e-mail])
 *                Arne Vandamme ([e-mail])
 *
 * 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 java.io.IOException;

/**
 * Class to represent archive values for a single datasource. Robin class is the heart of
 * the so-called "round robin database" concept. Basically, each Robin object is a
 * fixed length array of double values. Each double value reperesents consolidated, archived
 * value for the specific timestamp. When the underlying array of double values gets completely
 * filled, new values will replace the oldest ones.<p>
 *
 * Robin object does not hold values in memory - such object could be quite large.
 * Instead of it, Robin reads them from the backend I/O only when necessary.
 *
 * @author <a href="mailto:[e-mail]">Sasa Markovic</a>
 */
public class Robin implements RrdUpdater {
	private Archive parentArc;
	private RrdInt pointer;
	private RrdDoubleArray values;
	private int rows;

	Robin(Archive parentArc, int rows, boolean shouldInitialize) throws IOException {
		this.parentArc = parentArc;
		this.pointer = new RrdInt(this);
		this.values = new RrdDoubleArray(this, rows);
		this.rows = rows;
		if(shouldInitialize) {
			pointer.set(0);
			values.set(0, Double.NaN, rows);
		}
	}

	/**
	 * Fetches all archived values.
	 *
	 * @return Array of double archive values, starting from the oldest one.
	 * @throws IOException Thrown in case of I/O specific error.
	 */
	public double[] getValues() throws IOException {
		return getValues(0, rows);
	}

	// stores single value
	void store(double newValue) throws IOException {
		int position = pointer.get();
		values.set(position, newValue);
		pointer.set((position + 1) % rows);
	}

	// stores the same value several times
	void bulkStore(double newValue, int bulkCount) throws IOException {
		//assert bulkCount <= rows: "Invalid number of bulk updates: " + bulkCount + " rows=" + rows;
		int position = pointer.get();
		// update tail
		int tailUpdateCount = Math.min(rows - position, bulkCount);
		values.set(position, newValue, tailUpdateCount);
		pointer.set((position + tailUpdateCount) % rows);
		// do we need to update from the start?
		int headUpdateCount = bulkCount - tailUpdateCount;
		if(headUpdateCount > 0) {
			values.set(0, newValue, headUpdateCount);
			pointer.set(headUpdateCount);
		}
	}

	// updates Robin values in bulk
	void update(double[] newValues) throws IOException {
		//assert rows == newValues.length: "Invalid number of values supplied: " + newValues.length +
		//	" rows=" + rows;
		pointer.set(0);
		values.writeDouble(0, newValues);
	}

	String dump() throws IOException {
		StringBuffer buffer = new StringBuffer("Robin " + pointer.get() + "/" + rows + ": ");
		double[] values = getValues();
		for(int i = 0; i < values.length; i++) {
			buffer.append(Util.formatDouble(values[i], true) + " ");
		}
		buffer.append("\n");
		return buffer.toString();
	}

	/**
	 * Returns the i-th value from the Robin archive.
	 * @param index Value index
	 * @return Value stored in the i-th position (the oldest value has zero index)
	 * @throws IOException Thrown in case of I/O specific error.
	 */
	public double getValue(int index) throws IOException {
		int arrayIndex = (pointer.get() + index) % rows;
		return values.get(arrayIndex);
	}

	double[] getValues(int index, int count) throws IOException {
		//assert count <= rows: "Too many values requested: " + count + " rows=" + rows;
		int startIndex = (pointer.get() + index) % rows;
		int tailReadCount = Math.min(rows - startIndex, count);
		double[] tailValues = values.get(startIndex, tailReadCount);
		if(tailReadCount < count) {
            int headReadCount = count - tailReadCount;
			double[] headValues = values.get(0, headReadCount);
			double[] values = new double[count];
			int k = 0;
			for(int i = 0; i < tailValues.length; i++) {
				values[k++] = tailValues[i];
			}
			for(int i = 0; i < headValues.length; i++) {
				values[k++] = headValues[i];
			}
			return values;
		}
		else {
			return tailValues;
		}
	}

	/**
	 * Returns the Archive object to which this Robin object belongs.
	 *
	 * @return Parent Archive object
	 */
	public Archive getParent() {
		return parentArc;
	}

	/**
	 * Returns the size of the underlying array of archived values.
	 *
	 * @return Number of stored values
	 */
	public int getSize() {
		return rows;
	}

	/**
	 * Copies object's internal state to another Robin object.
	 * @param other New Robin object to copy state to
	 * @throws IOException Thrown in case of I/O error
	 * @throws RrdException Thrown if supplied argument is not a Robin object
	 */
	public void copyStateTo(RrdUpdater other) throws IOException, RrdException {
		if(!(other instanceof Robin)) {
			throw new RrdException(
				"Cannot copy Robin object to " + other.getClass().getName());
		}
		Robin robin = (Robin) other;
		int rowsDiff = rows - robin.rows;
		if(rowsDiff == 0) {
			// Identical dimensions. Do copy in BULK to speed things up
			robin.pointer.set(pointer.get());
			robin.values.writeBytes(values.readBytes());
		}
		else {
			// different sizes
			for(int i = 0; i < robin.rows; i++) {
				int j = i + rowsDiff;
				robin.store(j >= 0? getValue(j): Double.NaN);
			}
		}
	}

	void filterValues(double minValue, double maxValue) throws IOException {
		for(int i = 0; i < rows; i++) {
			double value = values.get(i);
			if(!Double.isNaN(minValue) && !Double.isNaN(value) && minValue > value) {
				values.set(i, Double.NaN);
			}
			if(!Double.isNaN(maxValue) && !Double.isNaN(value) && maxValue < value) {
				values.set(i, Double.NaN);
			}
		}
	}

	/**
	 * Returns the underlying storage (backend) object which actually performs all
	 * I/O operations.
	 * @return I/O backend object
	 */
	public RrdBackend getRrdBackend() {
		return parentArc.getRrdBackend();
	}

	/**
	 * Required to implement RrdUpdater interface. You should never call this method directly.
	 * @return Allocator object
	 */
	public RrdAllocator getRrdAllocator() {
		return parentArc.getRrdAllocator();
	}
}