com.facebook.stats.AssociativeAggregationCounter.java Source code

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Here is the source code for com.facebook.stats.AssociativeAggregationCounter.java

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/*
 * Copyright (C) 2012 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.facebook.stats;

import org.joda.time.Duration;
import org.joda.time.ReadableDateTime;

import java.util.concurrent.atomic.AtomicLong;

public class AssociativeAggregationCounter implements EventCounter {
    private final ReadableDateTime start;
    private final ReadableDateTime end;
    private final long initialValue;
    private final AssociativeAggregation associativeAggregation;
    protected final AtomicLong value;

    public AssociativeAggregationCounter(ReadableDateTime start, ReadableDateTime end,
            AssociativeAggregation associativeAggregation, long initialValue) {
        if (start.isAfter(end)) {
            this.start = end;
            this.end = start;
        } else {
            this.start = start;
            this.end = end;
        }
        this.initialValue = initialValue;
        this.associativeAggregation = associativeAggregation;
        this.value = new AtomicLong(initialValue);
    }

    public void add(long delta) {
        long val = value.get();
        while (!value.compareAndSet(val, associativeAggregation.combine(val, delta))) {
            val = value.get();
        }
    }

    public long getValue() {
        return value.get();
    }

    public ReadableDateTime getStart() {
        return start;
    }

    public ReadableDateTime getEnd() {
        return end;
    }

    @Override
    public Duration getLength() {
        return new Duration(start, end);
    }

    @Override
    public EventCounter merge(EventCounter counter) {
        ReadableDateTime mergedStart = start;
        ReadableDateTime mergedEnd = end;

        if (counter.getStart().isBefore(mergedStart)) {
            mergedStart = counter.getStart();
        }

        if (counter.getEnd().isAfter(mergedEnd)) {
            mergedEnd = counter.getEnd();
        }

        AssociativeAggregationCounter mergedCounter = new AssociativeAggregationCounter(mergedStart, mergedEnd,
                associativeAggregation, initialValue);

        mergedCounter.add(associativeAggregation.combine(value.get(), counter.getValue()));

        return mergedCounter;
    }
}