chromium/third_party/webrtc/system_wrappers/source/metrics.cc

// Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS.  All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
//

#include "system_wrappers/include/metrics.h"

#include <algorithm>

#include "absl/strings/string_view.h"
#include "rtc_base/string_utils.h"
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/thread_annotations.h"

// Default implementation of histogram methods for WebRTC clients that do not
// want to provide their own implementation.

namespace webrtc {
namespace metrics {
class Histogram;

namespace {
// Limit for the maximum number of sample values that can be stored.
// TODO(asapersson): Consider using bucket count (and set up
// linearly/exponentially spaced buckets) if samples are logged more frequently.
const int kMaxSampleMapSize = …;

class RtcHistogram { … };

class RtcHistogramMap { … };

// RtcHistogramMap is allocated upon call to Enable().
// The histogram getter functions, which return pointer values to the histograms
// in the map, are cached in WebRTC. Therefore, this memory is not freed by the
// application (the memory will be reclaimed by the OS).
static std::atomic<RtcHistogramMap*> g_rtc_histogram_map(nullptr);

void CreateMap() { … }

// Set the first time we start using histograms. Used to make sure Enable() is
// not called thereafter.
#if RTC_DCHECK_IS_ON
static std::atomic<int> g_rtc_histogram_called(0);
#endif

// Gets the map (or nullptr).
RtcHistogramMap* GetMap() { … }
}  // namespace

#ifndef WEBRTC_EXCLUDE_METRICS_DEFAULT
// Implementation of histogram methods in
// webrtc/system_wrappers/interface/metrics.h.

// Histogram with exponentially spaced buckets.
// Creates (or finds) histogram.
// The returned histogram pointer is cached (and used for adding samples in
// subsequent calls).
Histogram* HistogramFactoryGetCounts(absl::string_view name,
                                     int min,
                                     int max,
                                     int bucket_count) {
  // TODO(asapersson): Alternative implementation will be needed if this
  // histogram type should be truly exponential.
  return HistogramFactoryGetCountsLinear(name, min, max, bucket_count);
}

// Histogram with linearly spaced buckets.
// Creates (or finds) histogram.
// The returned histogram pointer is cached (and used for adding samples in
// subsequent calls).
Histogram* HistogramFactoryGetCountsLinear(absl::string_view name,
                                           int min,
                                           int max,
                                           int bucket_count) {
  RtcHistogramMap* map = GetMap();
  if (!map)
    return nullptr;

  return map->GetCountsHistogram(name, min, max, bucket_count);
}

// Histogram with linearly spaced buckets.
// Creates (or finds) histogram.
// The returned histogram pointer is cached (and used for adding samples in
// subsequent calls).
Histogram* HistogramFactoryGetEnumeration(absl::string_view name,
                                          int boundary) {
  RtcHistogramMap* map = GetMap();
  if (!map)
    return nullptr;

  return map->GetEnumerationHistogram(name, boundary);
}

// Our default implementation reuses the non-sparse histogram.
Histogram* SparseHistogramFactoryGetEnumeration(absl::string_view name,
                                                int boundary) {
  return HistogramFactoryGetEnumeration(name, boundary);
}

// Fast path. Adds `sample` to cached `histogram_pointer`.
void HistogramAdd(Histogram* histogram_pointer, int sample) {
  RtcHistogram* ptr = reinterpret_cast<RtcHistogram*>(histogram_pointer);
  ptr->Add(sample);
}

#endif  // WEBRTC_EXCLUDE_METRICS_DEFAULT

SampleInfo::SampleInfo(absl::string_view name,
                       int min,
                       int max,
                       size_t bucket_count)
    : … { … }

SampleInfo::~SampleInfo() { … }

// Implementation of global functions in metrics.h.
void Enable() { … }

void GetAndReset(
    std::map<std::string, std::unique_ptr<SampleInfo>, rtc::AbslStringViewCmp>*
        histograms) { … }

void Reset() { … }

int NumEvents(absl::string_view name, int sample) { … }

int NumSamples(absl::string_view name) { … }

int MinSample(absl::string_view name) { … }

std::map<int, int> Samples(absl::string_view name) { … }

}  // namespace metrics
}  // namespace webrtc