components/metrics/histogram_encoder.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/metrics/histogram_encoder.h"
   6
   7 #include <string>
   8
   9 #include "base/basictypes.h"
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/metrics/histogram.h"
  12 #include "base/metrics/histogram_samples.h"
  13 #include "components/metrics/metrics_hashes.h"
  14
  15 using base::SampleCountIterator;
  16
  17 namespace metrics {
  18
  19 void EncodeHistogramDelta(const std::string& histogram_name,
  20                           const base::HistogramSamples& snapshot,
  21                           ChromeUserMetricsExtension* uma_proto) {
  22   DCHECK_NE(0, snapshot.TotalCount());
  23   DCHECK(uma_proto);
  24
  25   // We will ignore the MAX_INT/infinite value in the last element of range[].
  26
  27   HistogramEventProto* histogram_proto = uma_proto->add_histogram_event();
  28   histogram_proto->set_name_hash(HashMetricName(histogram_name));
  29   histogram_proto->set_sum(snapshot.sum());
  30
  31   for (scoped_ptr<SampleCountIterator> it = snapshot.Iterator(); !it->Done();
  32        it->Next()) {
  33     base::Histogram::Sample min;
  34     base::Histogram::Sample max;
  35     base::Histogram::Count count;
  36     it->Get(&min, &max, &count);
  37     HistogramEventProto::Bucket* bucket = histogram_proto->add_bucket();
  38     bucket->set_min(min);
  39     bucket->set_max(max);
  40     bucket->set_count(count);
  41   }
  42
  43   // Omit fields to save space (see rules in histogram_event.proto comments).
  44   for (int i = 0; i < histogram_proto->bucket_size(); ++i) {
  45     HistogramEventProto::Bucket* bucket = histogram_proto->mutable_bucket(i);
  46     if (i + 1 < histogram_proto->bucket_size() &&
  47         bucket->max() == histogram_proto->bucket(i + 1).min()) {
  48       bucket->clear_max();
  49     } else if (bucket->max() == bucket->min() + 1) {
  50       bucket->clear_min();
  51     }
  52   }
  53 }
  54
  55 }  // namespace metrics