DataChunk.java

package org.rrd4j.core.jrrd;

import java.util.Map;

import org.rrd4j.data.LinearInterpolator;
import org.rrd4j.data.Plottable;

/**
 * Models a chunk of result data from an RRDatabase.
 *
 * @author <a href="mailto:ciaran@codeloop.com">Ciaran Treanor</a>
 * @version $Revision: 1.1 $
 */
public class DataChunk {

    private static final String NEWLINE = System.getProperty("line.separator");
    /** Start time in seconds since epoch */
    private final long startTime;
    /** Row number offset relative to current row. Can be negative */
    final int startOffset;
    /** Row number offset relative to current row */
    final int endOffset;
    /** Step in seconds */
    private final long step;
    /** Number of datasources must be equal to number of datasources in file */
    final int dsCount;
    final double[][] data;
    private final int rows;
    /** Map datasource name to datasource index */
    private final Map<String, Integer> nameindex;

    DataChunk(Map<String, Integer> nameindex, long startTime, int startOffset, int endOffset, long step, int dsCount, int rows) {
        this.nameindex = nameindex;
        this.startTime = startTime;
        this.startOffset = startOffset;
        this.endOffset = endOffset;
        this.step = step;
        this.dsCount = dsCount;
        this.rows = rows;
        data = new double[rows][dsCount];
    }

    /**
     * Returns a summary of the contents of this data chunk. The first column is
     * the time (RRD format) and the following columns are the data source
     * values.
     *
     * @return a summary of the contents of this data chunk.
     */
    public String toString() {

        StringBuilder sb = new StringBuilder();
        long time = startTime;

        for (int row = 0; row < rows; row++, time += step) {
            sb.append(time);
            sb.append(": ");

            for (int ds = 0; ds < dsCount; ds++) {
                sb.append(data[row][ds]);
                sb.append(" ");
            }

            sb.append(NEWLINE);
        }

        return sb.toString();
    }

    public int getStart() {
        return startOffset;
    }

    public int getEnd() {
        return endOffset;
    }

    public long getStep() {
        return step;
    }

    public int getDsCount() {
        return dsCount;
    }

    /**
     * <p>Getter for the field <code>data</code>.</p>
     *
     * @return the data
     */
    public double[][] getData() {
        return data;
    }

    /**
     * <p>Getter for the time stamps values.</p>
     *
     * @return array of time stamps in seconds
     */
    public long[] getTimestamps() {
        long[] date =  new long[rows];
        long time = startTime;
        for (int row = 0; row < rows; row++, time += step) {
            date[row] = time;
        }
        return date;
    }

    /**
     * Extract a datasource from the datachunck given is name as a Plottable
     *
     * @param name the datasource name
     * @return a plottable for the datasource
     */
    public Plottable toPlottable(String name) {
        Integer dsId = nameindex.get(name);
        if(dsId == null)
            throw new RuntimeException("datasource not not found: " + name);
        long[] date =  new long[rows];
        double[] results =  new double[rows];
        long time = startTime;
        for (int row = 0; row < rows; row++, time += step) {
            date[row] = time;
            results[row] = data[row][dsId];
        }
        return new LinearInterpolator(date, results);
    }

}