base/metrics/histogram.cc

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This source file includes following definitions.
ReadHistogramArguments
ValidateRangeChecksum
FactoryGet
FactoryTimeGet
DebugNow
InitializeBucketRanges
FindCorruption
ranges
bucket_count
InspectConstructionArguments
GetHistogramType
HasConstructionArguments
Add
SnapshotSamples
AddSamples
AddSamplesFromPickle
WriteHTMLGraph
WriteAscii
SerializeInfoImpl
declared_max_
PrintEmptyBucket
GetBucketSize
GetAsciiBucketRange
DeserializeInfoImpl
SnapshotSampleVector
WriteAsciiImpl
GetPeakBucketSize
WriteAsciiHeader
WriteAsciiBucketContext
GetParameters
GetCountAndBucketData
FactoryGet
FactoryTimeGet
FactoryGetWithRangeDescription
GetHistogramType
GetBucketSize
GetAsciiBucketRange
PrintEmptyBucket
InitializeBucketRanges
DeserializeInfoImpl
FactoryGet
GetHistogramType
DeserializeInfoImpl
FactoryGet
GetHistogramType
ArrayToCustomRanges
SerializeInfoImpl
GetBucketSize
DeserializeInfoImpl
ValidateCustomRanges
CreateBucketRangesFromCustomRanges
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Histogram is an object that aggregates statistics, and can summarize them in
// various forms, including ASCII graphical, HTML, and numerically (as a
// vector of numbers corresponding to each of the aggregating buckets).
// See header file for details and examples.

#include "base/metrics/histogram.h"

#include <math.h>

#include <algorithm>
#include <string>

#include "base/compiler_specific.h"
#include "base/debug/alias.h"
#include "base/logging.h"
#include "base/metrics/sample_vector.h"
#include "base/metrics/statistics_recorder.h"
#include "base/pickle.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/synchronization/lock.h"
#include "base/values.h"

using std::string;
using std::vector;

namespace base {

namespace {

bool ReadHistogramArguments(PickleIterator* iter,
                            string* histogram_name,
                            int* flags,
                            int* declared_min,
                            int* declared_max,
                            uint64* bucket_count,
                            uint32* range_checksum) {
  if (!iter->ReadString(histogram_name) ||
      !iter->ReadInt(flags) ||
      !iter->ReadInt(declared_min) ||
      !iter->ReadInt(declared_max) ||
      !iter->ReadUInt64(bucket_count) ||
      !iter->ReadUInt32(range_checksum)) {
    DLOG(ERROR) << "Pickle error decoding Histogram: " << *histogram_name;
    return false;
  }

  // Since these fields may have come from an untrusted renderer, do additional
  // checks above and beyond those in Histogram::Initialize()
  if (*declared_max <= 0 ||
      *declared_min <= 0 ||
      *declared_max < *declared_min ||
      INT_MAX / sizeof(HistogramBase::Count) <= *bucket_count ||
      *bucket_count < 2) {
    DLOG(ERROR) << "Values error decoding Histogram: " << histogram_name;
    return false;
  }

  // We use the arguments to find or create the local version of the histogram
  // in this process, so we need to clear the IPC flag.
  DCHECK(*flags & HistogramBase::kIPCSerializationSourceFlag);
  *flags &= ~HistogramBase::kIPCSerializationSourceFlag;

  return true;
}

bool ValidateRangeChecksum(const HistogramBase& histogram,
                           uint32 range_checksum) {
  const Histogram& casted_histogram =
      static_cast<const Histogram&>(histogram);

  return casted_histogram.bucket_ranges()->checksum() == range_checksum;
}

}  // namespace

typedef HistogramBase::Count Count;
typedef HistogramBase::Sample Sample;

// static
const size_t Histogram::kBucketCount_MAX = 16384u;

HistogramBase* Histogram::FactoryGet(const string& name,
                                     Sample minimum,
                                     Sample maximum,
                                     size_t bucket_count,
                                     int32 flags) {
  bool valid_arguments =
      InspectConstructionArguments(name, &minimum, &maximum, &bucket_count);
  DCHECK(valid_arguments);

  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
  if (!histogram) {
    // To avoid racy destruction at shutdown, the following will be leaked.
    BucketRanges* ranges = new BucketRanges(bucket_count + 1);
    InitializeBucketRanges(minimum, maximum, ranges);
    const BucketRanges* registered_ranges =
        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);

    Histogram* tentative_histogram =
        new Histogram(name, minimum, maximum, registered_ranges);

    tentative_histogram->SetFlags(flags);
    histogram =
        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
  }

  DCHECK_EQ(HISTOGRAM, histogram->GetHistogramType());
  if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
    // The construction arguments do not match the existing histogram.  This can
    // come about if an extension updates in the middle of a chrome run and has
    // changed one of them, or simply by bad code within Chrome itself.  We
    // return NULL here with the expectation that bad code in Chrome will crash
    // on dereference, but extension/Pepper APIs will guard against NULL and not
    // crash.
    DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
    return NULL;
  }
  return histogram;
}

HistogramBase* Histogram::FactoryTimeGet(const string& name,
                                         TimeDelta minimum,
                                         TimeDelta maximum,
                                         size_t bucket_count,
                                         int32 flags) {
  return FactoryGet(name, minimum.InMilliseconds(), maximum.InMilliseconds(),
                    bucket_count, flags);
}

TimeTicks Histogram::DebugNow() {
#ifndef NDEBUG
  return TimeTicks::Now();
#else
  return TimeTicks();
#endif
}

// Calculate what range of values are held in each bucket.
// We have to be careful that we don't pick a ratio between starting points in
// consecutive buckets that is sooo small, that the integer bounds are the same
// (effectively making one bucket get no values).  We need to avoid:
//   ranges(i) == ranges(i + 1)
// To avoid that, we just do a fine-grained bucket width as far as we need to
// until we get a ratio that moves us along at least 2 units at a time.  From
// that bucket onward we do use the exponential growth of buckets.
//
// static
void Histogram::InitializeBucketRanges(Sample minimum,
                                       Sample maximum,
                                       BucketRanges* ranges) {
  double log_max = log(static_cast<double>(maximum));
  double log_ratio;
  double log_next;
  size_t bucket_index = 1;
  Sample current = minimum;
  ranges->set_range(bucket_index, current);
  size_t bucket_count = ranges->bucket_count();
  while (bucket_count > ++bucket_index) {
    double log_current;
    log_current = log(static_cast<double>(current));
    // Calculate the count'th root of the range.
    log_ratio = (log_max - log_current) / (bucket_count - bucket_index);
    // See where the next bucket would start.
    log_next = log_current + log_ratio;
    Sample next;
    next = static_cast<int>(floor(exp(log_next) + 0.5));
    if (next > current)
      current = next;
    else
      ++current;  // Just do a narrow bucket, and keep trying.
    ranges->set_range(bucket_index, current);
  }
  ranges->set_range(ranges->bucket_count(), HistogramBase::kSampleType_MAX);
  ranges->ResetChecksum();
}

// static
const int Histogram::kCommonRaceBasedCountMismatch = 5;

int Histogram::FindCorruption(const HistogramSamples& samples) const {
  int inconsistencies = NO_INCONSISTENCIES;
  Sample previous_range = -1;  // Bottom range is always 0.
  for (size_t index = 0; index < bucket_count(); ++index) {
    int new_range = ranges(index);
    if (previous_range >= new_range)
      inconsistencies |= BUCKET_ORDER_ERROR;
    previous_range = new_range;
  }

  if (!bucket_ranges()->HasValidChecksum())
    inconsistencies |= RANGE_CHECKSUM_ERROR;

  int64 delta64 = samples.redundant_count() - samples.TotalCount();
  if (delta64 != 0) {
    int delta = static_cast<int>(delta64);
    if (delta != delta64)
      delta = INT_MAX;  // Flag all giant errors as INT_MAX.
    if (delta > 0) {
      UMA_HISTOGRAM_COUNTS("Histogram.InconsistentCountHigh", delta);
      if (delta > kCommonRaceBasedCountMismatch)
        inconsistencies |= COUNT_HIGH_ERROR;
    } else {
      DCHECK_GT(0, delta);
      UMA_HISTOGRAM_COUNTS("Histogram.InconsistentCountLow", -delta);
      if (-delta > kCommonRaceBasedCountMismatch)
        inconsistencies |= COUNT_LOW_ERROR;
    }
  }
  return inconsistencies;
}

Sample Histogram::ranges(size_t i) const {
  return bucket_ranges_->range(i);
}

size_t Histogram::bucket_count() const {
  return bucket_ranges_->bucket_count();
}

// static
bool Histogram::InspectConstructionArguments(const string& name,
                                             Sample* minimum,
                                             Sample* maximum,
                                             size_t* bucket_count) {
  // Defensive code for backward compatibility.
  if (*minimum < 1) {
    DVLOG(1) << "Histogram: " << name << " has bad minimum: " << *minimum;
    *minimum = 1;
  }
  if (*maximum >= kSampleType_MAX) {
    DVLOG(1) << "Histogram: " << name << " has bad maximum: " << *maximum;
    *maximum = kSampleType_MAX - 1;
  }
  if (*bucket_count >= kBucketCount_MAX) {
    DVLOG(1) << "Histogram: " << name << " has bad bucket_count: "
             << *bucket_count;
    *bucket_count = kBucketCount_MAX - 1;
  }

  if (*minimum >= *maximum)
    return false;
  if (*bucket_count < 3)
    return false;
  if (*bucket_count > static_cast<size_t>(*maximum - *minimum + 2))
    return false;
  return true;
}

HistogramType Histogram::GetHistogramType() const {
  return HISTOGRAM;
}

bool Histogram::HasConstructionArguments(Sample expected_minimum,
                                         Sample expected_maximum,
                                         size_t expected_bucket_count) const {
  return ((expected_minimum == declared_min_) &&
          (expected_maximum == declared_max_) &&
          (expected_bucket_count == bucket_count()));
}

void Histogram::Add(int value) {
  DCHECK_EQ(0, ranges(0));
  DCHECK_EQ(kSampleType_MAX, ranges(bucket_count()));

  if (value > kSampleType_MAX - 1)
    value = kSampleType_MAX - 1;
  if (value < 0)
    value = 0;
  samples_->Accumulate(value, 1);
}

scoped_ptr<HistogramSamples> Histogram::SnapshotSamples() const {
  return SnapshotSampleVector().PassAs<HistogramSamples>();
}

void Histogram::AddSamples(const HistogramSamples& samples) {
  samples_->Add(samples);
}

bool Histogram::AddSamplesFromPickle(PickleIterator* iter) {
  return samples_->AddFromPickle(iter);
}

// The following methods provide a graphical histogram display.
void Histogram::WriteHTMLGraph(string* output) const {
  // TBD(jar) Write a nice HTML bar chart, with divs an mouse-overs etc.
  output->append("<PRE>");
  WriteAsciiImpl(true, "<br>", output);
  output->append("</PRE>");
}

void Histogram::WriteAscii(string* output) const {
  WriteAsciiImpl(true, "\n", output);
}

bool Histogram::SerializeInfoImpl(Pickle* pickle) const {
  DCHECK(bucket_ranges()->HasValidChecksum());
  return pickle->WriteString(histogram_name()) &&
      pickle->WriteInt(flags()) &&
      pickle->WriteInt(declared_min()) &&
      pickle->WriteInt(declared_max()) &&
      pickle->WriteUInt64(bucket_count()) &&
      pickle->WriteUInt32(bucket_ranges()->checksum());
}

Histogram::Histogram(const string& name,
                     Sample minimum,
                     Sample maximum,
                     const BucketRanges* ranges)
  : HistogramBase(name),
    bucket_ranges_(ranges),
    declared_min_(minimum),
    declared_max_(maximum) {
  if (ranges)
    samples_.reset(new SampleVector(ranges));
}

Histogram::~Histogram() {
}

bool Histogram::PrintEmptyBucket(size_t index) const {
  return true;
}

// Use the actual bucket widths (like a linear histogram) until the widths get
// over some transition value, and then use that transition width.  Exponentials
// get so big so fast (and we don't expect to see a lot of entries in the large
// buckets), so we need this to make it possible to see what is going on and
// not have 0-graphical-height buckets.
double Histogram::GetBucketSize(Count current, size_t i) const {
  DCHECK_GT(ranges(i + 1), ranges(i));
  static const double kTransitionWidth = 5;
  double denominator = ranges(i + 1) - ranges(i);
  if (denominator > kTransitionWidth)
    denominator = kTransitionWidth;  // Stop trying to normalize.
  return current/denominator;
}

const string Histogram::GetAsciiBucketRange(size_t i) const {
  return GetSimpleAsciiBucketRange(ranges(i));
}

//------------------------------------------------------------------------------
// Private methods

// static
HistogramBase* Histogram::DeserializeInfoImpl(PickleIterator* iter) {
  string histogram_name;
  int flags;
  int declared_min;
  int declared_max;
  uint64 bucket_count;
  uint32 range_checksum;

  if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
                              &declared_max, &bucket_count, &range_checksum)) {
    return NULL;
  }

  // Find or create the local version of the histogram in this process.
  HistogramBase* histogram = Histogram::FactoryGet(
      histogram_name, declared_min, declared_max, bucket_count, flags);

  if (!ValidateRangeChecksum(*histogram, range_checksum)) {
    // The serialized histogram might be corrupted.
    return NULL;
  }
  return histogram;
}

scoped_ptr<SampleVector> Histogram::SnapshotSampleVector() const {
  scoped_ptr<SampleVector> samples(new SampleVector(bucket_ranges()));
  samples->Add(*samples_);
  return samples.Pass();
}

void Histogram::WriteAsciiImpl(bool graph_it,
                               const string& newline,
                               string* output) const {
  // Get local (stack) copies of all effectively volatile class data so that we
  // are consistent across our output activities.
  scoped_ptr<SampleVector> snapshot = SnapshotSampleVector();
  Count sample_count = snapshot->TotalCount();

  WriteAsciiHeader(*snapshot, sample_count, output);
  output->append(newline);

  // Prepare to normalize graphical rendering of bucket contents.
  double max_size = 0;
  if (graph_it)
    max_size = GetPeakBucketSize(*snapshot);

  // Calculate space needed to print bucket range numbers.  Leave room to print
  // nearly the largest bucket range without sliding over the histogram.
  size_t largest_non_empty_bucket = bucket_count() - 1;
  while (0 == snapshot->GetCountAtIndex(largest_non_empty_bucket)) {
    if (0 == largest_non_empty_bucket)
      break;  // All buckets are empty.
    --largest_non_empty_bucket;
  }

  // Calculate largest print width needed for any of our bucket range displays.
  size_t print_width = 1;
  for (size_t i = 0; i < bucket_count(); ++i) {
    if (snapshot->GetCountAtIndex(i)) {
      size_t width = GetAsciiBucketRange(i).size() + 1;
      if (width > print_width)
        print_width = width;
    }
  }

  int64 remaining = sample_count;
  int64 past = 0;
  // Output the actual histogram graph.
  for (size_t i = 0; i < bucket_count(); ++i) {
    Count current = snapshot->GetCountAtIndex(i);
    if (!current && !PrintEmptyBucket(i))
      continue;
    remaining -= current;
    string range = GetAsciiBucketRange(i);
    output->append(range);
    for (size_t j = 0; range.size() + j < print_width + 1; ++j)
      output->push_back(' ');
    if (0 == current && i < bucket_count() - 1 &&
        0 == snapshot->GetCountAtIndex(i + 1)) {
      while (i < bucket_count() - 1 &&
             0 == snapshot->GetCountAtIndex(i + 1)) {
        ++i;
      }
      output->append("... ");
      output->append(newline);
      continue;  // No reason to plot emptiness.
    }
    double current_size = GetBucketSize(current, i);
    if (graph_it)
      WriteAsciiBucketGraph(current_size, max_size, output);
    WriteAsciiBucketContext(past, current, remaining, i, output);
    output->append(newline);
    past += current;
  }
  DCHECK_EQ(sample_count, past);
}

double Histogram::GetPeakBucketSize(const SampleVector& samples) const {
  double max = 0;
  for (size_t i = 0; i < bucket_count() ; ++i) {
    double current_size = GetBucketSize(samples.GetCountAtIndex(i), i);
    if (current_size > max)
      max = current_size;
  }
  return max;
}

void Histogram::WriteAsciiHeader(const SampleVector& samples,
                                 Count sample_count,
                                 string* output) const {
  StringAppendF(output,
                "Histogram: %s recorded %d samples",
                histogram_name().c_str(),
                sample_count);
  if (0 == sample_count) {
    DCHECK_EQ(samples.sum(), 0);
  } else {
    double average = static_cast<float>(samples.sum()) / sample_count;

    StringAppendF(output, ", average = %.1f", average);
  }
  if (flags() & ~kHexRangePrintingFlag)
    StringAppendF(output, " (flags = 0x%x)", flags() & ~kHexRangePrintingFlag);
}

void Histogram::WriteAsciiBucketContext(const int64 past,
                                        const Count current,
                                        const int64 remaining,
                                        const size_t i,
                                        string* output) const {
  double scaled_sum = (past + current + remaining) / 100.0;
  WriteAsciiBucketValue(current, scaled_sum, output);
  if (0 < i) {
    double percentage = past / scaled_sum;
    StringAppendF(output, " {%3.1f%%}", percentage);
  }
}

void Histogram::GetParameters(DictionaryValue* params) const {
  params->SetString("type", HistogramTypeToString(GetHistogramType()));
  params->SetInteger("min", declared_min());
  params->SetInteger("max", declared_max());
  params->SetInteger("bucket_count", static_cast<int>(bucket_count()));
}

void Histogram::GetCountAndBucketData(Count* count,
                                      int64* sum,
                                      ListValue* buckets) const {
  scoped_ptr<SampleVector> snapshot = SnapshotSampleVector();
  *count = snapshot->TotalCount();
  *sum = snapshot->sum();
  size_t index = 0;
  for (size_t i = 0; i < bucket_count(); ++i) {
    Sample count = snapshot->GetCountAtIndex(i);
    if (count > 0) {
      scoped_ptr<DictionaryValue> bucket_value(new DictionaryValue());
      bucket_value->SetInteger("low", ranges(i));
      if (i != bucket_count() - 1)
        bucket_value->SetInteger("high", ranges(i + 1));
      bucket_value->SetInteger("count", count);
      buckets->Set(index, bucket_value.release());
      ++index;
    }
  }
}

//------------------------------------------------------------------------------
// LinearHistogram: This histogram uses a traditional set of evenly spaced
// buckets.
//------------------------------------------------------------------------------

LinearHistogram::~LinearHistogram() {}

HistogramBase* LinearHistogram::FactoryGet(const string& name,
                                           Sample minimum,
                                           Sample maximum,
                                           size_t bucket_count,
                                           int32 flags) {
  return FactoryGetWithRangeDescription(
      name, minimum, maximum, bucket_count, flags, NULL);
}

HistogramBase* LinearHistogram::FactoryTimeGet(const string& name,
                                               TimeDelta minimum,
                                               TimeDelta maximum,
                                               size_t bucket_count,
                                               int32 flags) {
  return FactoryGet(name, minimum.InMilliseconds(), maximum.InMilliseconds(),
                    bucket_count, flags);
}

HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
      const std::string& name,
      Sample minimum,
      Sample maximum,
      size_t bucket_count,
      int32 flags,
      const DescriptionPair descriptions[]) {
  bool valid_arguments = Histogram::InspectConstructionArguments(
      name, &minimum, &maximum, &bucket_count);
  DCHECK(valid_arguments);

  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
  if (!histogram) {
    // To avoid racy destruction at shutdown, the following will be leaked.
    BucketRanges* ranges = new BucketRanges(bucket_count + 1);
    InitializeBucketRanges(minimum, maximum, ranges);
    const BucketRanges* registered_ranges =
        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);

    LinearHistogram* tentative_histogram =
        new LinearHistogram(name, minimum, maximum, registered_ranges);

    // Set range descriptions.
    if (descriptions) {
      for (int i = 0; descriptions[i].description; ++i) {
        tentative_histogram->bucket_description_[descriptions[i].sample] =
            descriptions[i].description;
      }
    }

    tentative_histogram->SetFlags(flags);
    histogram =
        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
  }

  DCHECK_EQ(LINEAR_HISTOGRAM, histogram->GetHistogramType());
  if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
    // The construction arguments do not match the existing histogram.  This can
    // come about if an extension updates in the middle of a chrome run and has
    // changed one of them, or simply by bad code within Chrome itself.  We
    // return NULL here with the expectation that bad code in Chrome will crash
    // on dereference, but extension/Pepper APIs will guard against NULL and not
    // crash.
    DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
    return NULL;
  }
  return histogram;
}

HistogramType LinearHistogram::GetHistogramType() const {
  return LINEAR_HISTOGRAM;
}

LinearHistogram::LinearHistogram(const string& name,
                                 Sample minimum,
                                 Sample maximum,
                                 const BucketRanges* ranges)
    : Histogram(name, minimum, maximum, ranges) {
}

double LinearHistogram::GetBucketSize(Count current, size_t i) const {
  DCHECK_GT(ranges(i + 1), ranges(i));
  // Adjacent buckets with different widths would have "surprisingly" many (few)
  // samples in a histogram if we didn't normalize this way.
  double denominator = ranges(i + 1) - ranges(i);
  return current/denominator;
}

const string LinearHistogram::GetAsciiBucketRange(size_t i) const {
  int range = ranges(i);
  BucketDescriptionMap::const_iterator it = bucket_description_.find(range);
  if (it == bucket_description_.end())
    return Histogram::GetAsciiBucketRange(i);
  return it->second;
}

bool LinearHistogram::PrintEmptyBucket(size_t index) const {
  return bucket_description_.find(ranges(index)) == bucket_description_.end();
}

// static
void LinearHistogram::InitializeBucketRanges(Sample minimum,
                                             Sample maximum,
                                             BucketRanges* ranges) {
  double min = minimum;
  double max = maximum;
  size_t bucket_count = ranges->bucket_count();
  for (size_t i = 1; i < bucket_count; ++i) {
    double linear_range =
        (min * (bucket_count - 1 - i) + max * (i - 1)) / (bucket_count - 2);
    ranges->set_range(i, static_cast<Sample>(linear_range + 0.5));
  }
  ranges->set_range(ranges->bucket_count(), HistogramBase::kSampleType_MAX);
  ranges->ResetChecksum();
}

// static
HistogramBase* LinearHistogram::DeserializeInfoImpl(PickleIterator* iter) {
  string histogram_name;
  int flags;
  int declared_min;
  int declared_max;
  uint64 bucket_count;
  uint32 range_checksum;

  if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
                              &declared_max, &bucket_count, &range_checksum)) {
    return NULL;
  }

  HistogramBase* histogram = LinearHistogram::FactoryGet(
      histogram_name, declared_min, declared_max, bucket_count, flags);
  if (!ValidateRangeChecksum(*histogram, range_checksum)) {
    // The serialized histogram might be corrupted.
    return NULL;
  }
  return histogram;
}

//------------------------------------------------------------------------------
// This section provides implementation for BooleanHistogram.
//------------------------------------------------------------------------------

HistogramBase* BooleanHistogram::FactoryGet(const string& name, int32 flags) {
  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
  if (!histogram) {
    // To avoid racy destruction at shutdown, the following will be leaked.
    BucketRanges* ranges = new BucketRanges(4);
    LinearHistogram::InitializeBucketRanges(1, 2, ranges);
    const BucketRanges* registered_ranges =
        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);

    BooleanHistogram* tentative_histogram =
        new BooleanHistogram(name, registered_ranges);

    tentative_histogram->SetFlags(flags);
    histogram =
        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
  }

  DCHECK_EQ(BOOLEAN_HISTOGRAM, histogram->GetHistogramType());
  return histogram;
}

HistogramType BooleanHistogram::GetHistogramType() const {
  return BOOLEAN_HISTOGRAM;
}

BooleanHistogram::BooleanHistogram(const string& name,
                                   const BucketRanges* ranges)
    : LinearHistogram(name, 1, 2, ranges) {}

HistogramBase* BooleanHistogram::DeserializeInfoImpl(PickleIterator* iter) {
  string histogram_name;
  int flags;
  int declared_min;
  int declared_max;
  uint64 bucket_count;
  uint32 range_checksum;

  if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
                              &declared_max, &bucket_count, &range_checksum)) {
    return NULL;
  }

  HistogramBase* histogram = BooleanHistogram::FactoryGet(
      histogram_name, flags);
  if (!ValidateRangeChecksum(*histogram, range_checksum)) {
    // The serialized histogram might be corrupted.
    return NULL;
  }
  return histogram;
}

//------------------------------------------------------------------------------
// CustomHistogram:
//------------------------------------------------------------------------------

HistogramBase* CustomHistogram::FactoryGet(const string& name,
                                           const vector<Sample>& custom_ranges,
                                           int32 flags) {
  CHECK(ValidateCustomRanges(custom_ranges));

  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
  if (!histogram) {
    BucketRanges* ranges = CreateBucketRangesFromCustomRanges(custom_ranges);
    const BucketRanges* registered_ranges =
        StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);

    // To avoid racy destruction at shutdown, the following will be leaked.
    CustomHistogram* tentative_histogram =
        new CustomHistogram(name, registered_ranges);

    tentative_histogram->SetFlags(flags);

    histogram =
        StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
  }

  DCHECK_EQ(histogram->GetHistogramType(), CUSTOM_HISTOGRAM);
  return histogram;
}

HistogramType CustomHistogram::GetHistogramType() const {
  return CUSTOM_HISTOGRAM;
}

// static
vector<Sample> CustomHistogram::ArrayToCustomRanges(
    const Sample* values, size_t num_values) {
  vector<Sample> all_values;
  for (size_t i = 0; i < num_values; ++i) {
    Sample value = values[i];
    all_values.push_back(value);

    // Ensure that a guard bucket is added. If we end up with duplicate
    // values, FactoryGet will take care of removing them.
    all_values.push_back(value + 1);
  }
  return all_values;
}

CustomHistogram::CustomHistogram(const string& name,
                                 const BucketRanges* ranges)
    : Histogram(name,
                ranges->range(1),
                ranges->range(ranges->bucket_count() - 1),
                ranges) {}

bool CustomHistogram::SerializeInfoImpl(Pickle* pickle) const {
  if (!Histogram::SerializeInfoImpl(pickle))
    return false;

  // Serialize ranges. First and last ranges are alwasy 0 and INT_MAX, so don't
  // write them.
  for (size_t i = 1; i < bucket_ranges()->bucket_count(); ++i) {
    if (!pickle->WriteInt(bucket_ranges()->range(i)))
      return false;
  }
  return true;
}

double CustomHistogram::GetBucketSize(Count current, size_t i) const {
  return 1;
}

// static
HistogramBase* CustomHistogram::DeserializeInfoImpl(PickleIterator* iter) {
  string histogram_name;
  int flags;
  int declared_min;
  int declared_max;
  uint64 bucket_count;
  uint32 range_checksum;

  if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
                              &declared_max, &bucket_count, &range_checksum)) {
    return NULL;
  }

  // First and last ranges are not serialized.
  vector<Sample> sample_ranges(bucket_count - 1);

  for (size_t i = 0; i < sample_ranges.size(); ++i) {
    if (!iter->ReadInt(&sample_ranges[i]))
      return NULL;
  }

  HistogramBase* histogram = CustomHistogram::FactoryGet(
      histogram_name, sample_ranges, flags);
  if (!ValidateRangeChecksum(*histogram, range_checksum)) {
    // The serialized histogram might be corrupted.
    return NULL;
  }
  return histogram;
}

// static
bool CustomHistogram::ValidateCustomRanges(
    const vector<Sample>& custom_ranges) {
  bool has_valid_range = false;
  for (size_t i = 0; i < custom_ranges.size(); i++) {
    Sample sample = custom_ranges[i];
    if (sample < 0 || sample > HistogramBase::kSampleType_MAX - 1)
      return false;
    if (sample != 0)
      has_valid_range = true;
  }
  return has_valid_range;
}

// static
BucketRanges* CustomHistogram::CreateBucketRangesFromCustomRanges(
      const vector<Sample>& custom_ranges) {
  // Remove the duplicates in the custom ranges array.
  vector<int> ranges = custom_ranges;
  ranges.push_back(0);  // Ensure we have a zero value.
  ranges.push_back(HistogramBase::kSampleType_MAX);
  std::sort(ranges.begin(), ranges.end());
  ranges.erase(std::unique(ranges.begin(), ranges.end()), ranges.end());

  BucketRanges* bucket_ranges = new BucketRanges(ranges.size());
  for (size_t i = 0; i < ranges.size(); i++) {
    bucket_ranges->set_range(i, ranges[i]);
  }
  bucket_ranges->ResetChecksum();
  return bucket_ranges;
}

}  // namespace base
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root/base/metrics/histogram.cc

DEFINITIONS
