/**
    *
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.hadoop.hbase.metrics.impl;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.metrics.Histogram;
  import org.apache.hadoop.hbase.metrics.Snapshot;
  
  /**
   * Custom histogram implementation based on FastLongHistogram. Dropwizard-based histograms are
   * slow compared to this implementation, so we are using our implementation here.
   * See HBASE-15222.
   */
  @InterfaceAudience.Private
  public class HistogramImpl implements Histogram {
    // Double buffer the two FastLongHistograms.
    // As they are reset they learn how the buckets should be spaced
    // So keep two around and use them
    protected final FastLongHistogram histogram;
    private final CounterImpl counter;
  
    public HistogramImpl() {
      this((long) Integer.MAX_VALUE << 2);
    }
  
    public HistogramImpl(long maxExpected) {
      this(FastLongHistogram.DEFAULT_NBINS, 1, maxExpected);
    }
  
    public HistogramImpl(int numBins, long min, long maxExpected) {
      this.counter = new CounterImpl();
      this.histogram = new FastLongHistogram(numBins, min, maxExpected);
    }
  
    protected HistogramImpl(CounterImpl counter, FastLongHistogram histogram) {
      this.counter = counter;
      this.histogram = histogram;
    }
  
    @Override
    public void update(int value) {
      counter.increment();
      histogram.add(value, 1);
    }
  
    @Override
    public void update(long value) {
      counter.increment();
      histogram.add(value, 1);
    }
  
    @Override
    public long getCount() {
      return counter.getCount();
    }
  
    public long getMax() {
      return this.histogram.getMax();
    }
  
    @Override
    public Snapshot snapshot() {
      return histogram.snapshotAndReset();
    }
  }