content: /*
   * 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.bookkeeper.stats.codahale;
  
  import com.codahale.metrics.Snapshot;
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import java.io.OutputStream;
  
  /**
   * A snapshot of a FastTimer.
   */
  public class FastSnapshot extends Snapshot {
  
      private static final long[] EMPTY_VALUES = new long[] {};
  
      private final FastTimer timer;
      private final long min;
      private final long max;
      private final long sum;
      private final long cnt;
      private final long pcnt;
      private final long[] values;
  
      @SuppressFBWarnings(
              value = "EI_EXPOSE_REP2",
              justification = "long[] values is newly created array; FastTimer does not hold on to reference")
      public FastSnapshot(FastTimer timer, long min, long max, long sum, long cnt, long[] values) {
          this.timer = timer;
          this.min = min;
          this.max = max;
          this.sum = sum;
          this.cnt = cnt;
          this.pcnt = values != null ? sumOf(values) : 0;
          this.values = values;
      }
  
      @Override
      public double getValue(double quantile) {
          if (pcnt == 0 || values == null) {
              return 0;
          }
          long qcnt = 0;
          for (int i = 0; i < values.length; i++) {
              qcnt += values[i];
              if (((double) qcnt) / ((double) pcnt) > quantile) {
                  return timer.getBucketBound(i);
              }
          }
          return timer.getBucketBound(values.length);
      }
  
      @Override
      public long[] getValues() {
          return EMPTY_VALUES; // values in this snapshot represent percentile buckets, but not discrete values
      }
  
      @Override
      public int size() {
          return 0; // values in this snapshot represent percentile buckets, but not discrete values
      }
  
      @Override
      public long getMax() {
          return max;
      }
  
      @Override
      public double getMean() {
          return cnt > 0 ? ((double) sum) / ((double) cnt) : 0;
      }
  
      @Override
      public long getMin() {
          return min;
      }
  
      @Override
      public double getStdDev() {
          if (cnt < 2 || values == null) {
              return 0;
          }
          double avg = getMean();
          double var = 0;
          for (int i = 0; i < values.length; i++) {
              double val = timer.getBucketValue(i);
              var += ((double) values[i]) * Math.pow(val - avg, 2);
           }
          return Math.sqrt(var / ((double) cnt));
      }
  
      @Override
      public void dump(OutputStream output) {
          // values in this snapshot represent percentile buckets, but not discrete values
      }
  
      /**
       * Calculates the sum of values of an array.
       * @param a an array of values
       * @return the sum of all array values
       */
      private long sumOf(long[] a) {
          long sum = 0;
          for (long x : a) {
              sum += x;
          }
          return sum;
      }
  
  }