com.facebook.stats.EventCounterImpl.java Source code

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Here is the source code for com.facebook.stats.EventCounterImpl.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;

/**
 * reference implementation of a simple counter for a bounded period of time
 */
public class EventCounterImpl implements EventCounter {
    private final ReadableDateTime start;
    private final ReadableDateTime end;
    private final AtomicLong value;

    public EventCounterImpl(ReadableDateTime start, ReadableDateTime end, long initialValue) {
        if (start.isAfter(end)) {
            this.start = end;
            this.end = start;
        } else {
            this.start = start;
            this.end = end;
        }

        this.value = new AtomicLong(initialValue);
    }

    public EventCounterImpl(ReadableDateTime start, ReadableDateTime end) {
        this(start, end, 0L);
    }

    public void add(long delta) {
        value.addAndGet(delta);
    }

    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();
        }

        EventCounterImpl mergedCounter = new EventCounterImpl(mergedStart, mergedEnd);

        mergedCounter.add(value.get() + counter.getValue());

        return mergedCounter;
    }
}