Normalizer.java

package org.rrd4j.graph;

import org.rrd4j.core.Util;

import java.util.Arrays;

class Normalizer {
    private final double[] timestamps;
    final int count;
    final double step;

    Normalizer(long tStart, long tEnd, int count) {
        this.count = count;
        this.step = (tEnd - tStart) / (count - 1);
        this.timestamps = new double[count];
        for (int i = 0; i < count; i++) {
            this.timestamps[i] = tStart + ((double) i / (double) (count - 1)) * (tEnd - tStart);
        }
    }

    double[] getTimestamps() {
        return timestamps;
    }

    double[] normalize(long[] rawTimestamps, double[] rawValues) {
        int rawCount = rawTimestamps.length;
        long rawStep = rawTimestamps[1] - rawTimestamps[0];
        // check if we have a simple match
        if (rawCount == count && rawStep == step && rawTimestamps[0] == timestamps[0]) {
            return getCopyOf(rawValues);
        }
        // reset all normalized values to NaN
        double[] values = new double[count];
        Arrays.fill(values, Double.NaN);
        for (int rawSeg = 0, seg = 0; rawSeg < rawCount && seg < count; rawSeg++) {
            double rawValue = rawValues[rawSeg];
            if (!Double.isNaN(rawValue)) {
                long rawLeft = rawTimestamps[rawSeg] - rawStep;
                while (seg < count && rawLeft >= timestamps[seg]) {
                    seg++;
                }
                boolean overlap = true;
                for (int fillSeg = seg; overlap && fillSeg < count; fillSeg++) {
                    double left = timestamps[fillSeg] - step;
                    double t1 = Math.max(rawLeft, left);
                    double t2 = Math.min(rawTimestamps[rawSeg], timestamps[fillSeg]);
                    if (t1 < t2) {
                        values[fillSeg] = Util.sum(values[fillSeg], (t2 - t1) * rawValues[rawSeg]);
                    }
                    else {
                        overlap = false;
                    }
                }
            }
        }
        for (int seg = 0; seg < count; seg++) {
            values[seg] /= step;
        }
        return values;
    }

    private static double[] getCopyOf(double[] rawValues) {
        int n = rawValues.length;
        double[] values = new double[n];
        System.arraycopy(rawValues, 0, values, 0, n);
        return values;
    }
}