base/metrics/histogram.cc

   1 // Copyright (c) 2012 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 // Histogram is an object that aggregates statistics, and can summarize them in
   6 // various forms, including ASCII graphical, HTML, and numerically (as a
   7 // vector of numbers corresponding to each of the aggregating buckets).
   8 // See header file for details and examples.
   9
  10 #include "base/metrics/histogram.h"
  11
  12 #include <math.h>
  13
  14 #include <algorithm>
  15 #include <string>
  16
  17 #include "base/compiler_specific.h"
  18 #include "base/debug/alias.h"
  19 #include "base/logging.h"
  20 #include "base/metrics/histogram_macros.h"
  21 #include "base/metrics/sample_vector.h"
  22 #include "base/metrics/statistics_recorder.h"
  23 #include "base/pickle.h"
  24 #include "base/strings/string_util.h"
  25 #include "base/strings/stringprintf.h"
  26 #include "base/synchronization/lock.h"
  27 #include "base/values.h"
  28
  29 namespace base {
  30
  31 namespace {
  32
  33 bool ReadHistogramArguments(PickleIterator* iter,
  34                             std::string* histogram_name,
  35                             int* flags,
  36                             int* declared_min,
  37                             int* declared_max,
  38                             size_t* bucket_count,
  39                             uint32* range_checksum) {
  40   if (!iter->ReadString(histogram_name) ||
  41       !iter->ReadInt(flags) ||
  42       !iter->ReadInt(declared_min) ||
  43       !iter->ReadInt(declared_max) ||
  44       !iter->ReadSizeT(bucket_count) ||
  45       !iter->ReadUInt32(range_checksum)) {
  46     DLOG(ERROR) << "Pickle error decoding Histogram: " << *histogram_name;
  47     return false;
  48   }
  49
  50   // Since these fields may have come from an untrusted renderer, do additional
  51   // checks above and beyond those in Histogram::Initialize()
  52   if (*declared_max <= 0 ||
  53       *declared_min <= 0 ||
  54       *declared_max < *declared_min ||
  55       INT_MAX / sizeof(HistogramBase::Count) <= *bucket_count ||
  56       *bucket_count < 2) {
  57     DLOG(ERROR) << "Values error decoding Histogram: " << histogram_name;
  58     return false;
  59   }
  60
  61   // We use the arguments to find or create the local version of the histogram
  62   // in this process, so we need to clear the IPC flag.
  63   DCHECK(*flags & HistogramBase::kIPCSerializationSourceFlag);
  64   *flags &= ~HistogramBase::kIPCSerializationSourceFlag;
  65
  66   return true;
  67 }
  68
  69 bool ValidateRangeChecksum(const HistogramBase& histogram,
  70                            uint32 range_checksum) {
  71   const Histogram& casted_histogram =
  72       static_cast<const Histogram&>(histogram);
  73
  74   return casted_histogram.bucket_ranges()->checksum() == range_checksum;
  75 }
  76
  77 }  // namespace
  78
  79 typedef HistogramBase::Count Count;
  80 typedef HistogramBase::Sample Sample;
  81
  82 // static
  83 const size_t Histogram::kBucketCount_MAX = 16384u;
  84
  85 HistogramBase* Histogram::FactoryGet(const std::string& name,
  86                                      Sample minimum,
  87                                      Sample maximum,
  88                                      size_t bucket_count,
  89                                      int32 flags) {
  90   bool valid_arguments =
  91       InspectConstructionArguments(name, &minimum, &maximum, &bucket_count);
  92   DCHECK(valid_arguments);
  93
  94   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
  95   if (!histogram) {
  96     // To avoid racy destruction at shutdown, the following will be leaked.
  97     BucketRanges* ranges = new BucketRanges(bucket_count + 1);
  98     InitializeBucketRanges(minimum, maximum, ranges);
  99     const BucketRanges* registered_ranges =
 100         StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
 101
 102     Histogram* tentative_histogram =
 103         new Histogram(name, minimum, maximum, registered_ranges);
 104
 105     tentative_histogram->SetFlags(flags);
 106     histogram =
 107         StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
 108   }
 109
 110   DCHECK_EQ(HISTOGRAM, histogram->GetHistogramType());
 111   if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
 112     // The construction arguments do not match the existing histogram.  This can
 113     // come about if an extension updates in the middle of a chrome run and has
 114     // changed one of them, or simply by bad code within Chrome itself.  We
 115     // return NULL here with the expectation that bad code in Chrome will crash
 116     // on dereference, but extension/Pepper APIs will guard against NULL and not
 117     // crash.
 118     DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
 119     return NULL;
 120   }
 121   return histogram;
 122 }
 123
 124 HistogramBase* Histogram::FactoryTimeGet(const std::string& name,
 125                                          TimeDelta minimum,
 126                                          TimeDelta maximum,
 127                                          size_t bucket_count,
 128                                          int32 flags) {
 129   return FactoryGet(name, static_cast<Sample>(minimum.InMilliseconds()),
 130                     static_cast<Sample>(maximum.InMilliseconds()), bucket_count,
 131                     flags);
 132 }
 133
 134 HistogramBase* Histogram::FactoryGet(const char* name,
 135                                      Sample minimum,
 136                                      Sample maximum,
 137                                      size_t bucket_count,
 138                                      int32 flags) {
 139   return FactoryGet(std::string(name), minimum, maximum, bucket_count, flags);
 140 }
 141
 142 HistogramBase* Histogram::FactoryTimeGet(const char* name,
 143                                          TimeDelta minimum,
 144                                          TimeDelta maximum,
 145                                          size_t bucket_count,
 146                                          int32 flags) {
 147   return FactoryTimeGet(std::string(name), minimum, maximum, bucket_count,
 148                         flags);
 149 }
 150
 151 // Calculate what range of values are held in each bucket.
 152 // We have to be careful that we don't pick a ratio between starting points in
 153 // consecutive buckets that is sooo small, that the integer bounds are the same
 154 // (effectively making one bucket get no values).  We need to avoid:
 155 //   ranges(i) == ranges(i + 1)
 156 // To avoid that, we just do a fine-grained bucket width as far as we need to
 157 // until we get a ratio that moves us along at least 2 units at a time.  From
 158 // that bucket onward we do use the exponential growth of buckets.
 159 //
 160 // static
 161 void Histogram::InitializeBucketRanges(Sample minimum,
 162                                        Sample maximum,
 163                                        BucketRanges* ranges) {
 164   double log_max = log(static_cast<double>(maximum));
 165   double log_ratio;
 166   double log_next;
 167   size_t bucket_index = 1;
 168   Sample current = minimum;
 169   ranges->set_range(bucket_index, current);
 170   size_t bucket_count = ranges->bucket_count();
 171   while (bucket_count > ++bucket_index) {
 172     double log_current;
 173     log_current = log(static_cast<double>(current));
 174     // Calculate the count'th root of the range.
 175     log_ratio = (log_max - log_current) / (bucket_count - bucket_index);
 176     // See where the next bucket would start.
 177     log_next = log_current + log_ratio;
 178     Sample next;
 179     next = static_cast<int>(floor(exp(log_next) + 0.5));
 180     if (next > current)
 181       current = next;
 182     else
 183       ++current;  // Just do a narrow bucket, and keep trying.
 184     ranges->set_range(bucket_index, current);
 185   }
 186   ranges->set_range(ranges->bucket_count(), HistogramBase::kSampleType_MAX);
 187   ranges->ResetChecksum();
 188 }
 189
 190 // static
 191 const int Histogram::kCommonRaceBasedCountMismatch = 5;
 192
 193 int Histogram::FindCorruption(const HistogramSamples& samples) const {
 194   int inconsistencies = NO_INCONSISTENCIES;
 195   Sample previous_range = -1;  // Bottom range is always 0.
 196   for (size_t index = 0; index < bucket_count(); ++index) {
 197     int new_range = ranges(index);
 198     if (previous_range >= new_range)
 199       inconsistencies |= BUCKET_ORDER_ERROR;
 200     previous_range = new_range;
 201   }
 202
 203   if (!bucket_ranges()->HasValidChecksum())
 204     inconsistencies |= RANGE_CHECKSUM_ERROR;
 205
 206   int64 delta64 = samples.redundant_count() - samples.TotalCount();
 207   if (delta64 != 0) {
 208     int delta = static_cast<int>(delta64);
 209     if (delta != delta64)
 210       delta = INT_MAX;  // Flag all giant errors as INT_MAX.
 211     if (delta > 0) {
 212       UMA_HISTOGRAM_COUNTS("Histogram.InconsistentCountHigh", delta);
 213       if (delta > kCommonRaceBasedCountMismatch)
 214         inconsistencies |= COUNT_HIGH_ERROR;
 215     } else {
 216       DCHECK_GT(0, delta);
 217       UMA_HISTOGRAM_COUNTS("Histogram.InconsistentCountLow", -delta);
 218       if (-delta > kCommonRaceBasedCountMismatch)
 219         inconsistencies |= COUNT_LOW_ERROR;
 220     }
 221   }
 222   return inconsistencies;
 223 }
 224
 225 Sample Histogram::ranges(size_t i) const {
 226   return bucket_ranges_->range(i);
 227 }
 228
 229 size_t Histogram::bucket_count() const {
 230   return bucket_ranges_->bucket_count();
 231 }
 232
 233 // static
 234 bool Histogram::InspectConstructionArguments(const std::string& name,
 235                                              Sample* minimum,
 236                                              Sample* maximum,
 237                                              size_t* bucket_count) {
 238   // Defensive code for backward compatibility.
 239   if (*minimum < 1) {
 240     DVLOG(1) << "Histogram: " << name << " has bad minimum: " << *minimum;
 241     *minimum = 1;
 242   }
 243   if (*maximum >= kSampleType_MAX) {
 244     DVLOG(1) << "Histogram: " << name << " has bad maximum: " << *maximum;
 245     *maximum = kSampleType_MAX - 1;
 246   }
 247   if (*bucket_count >= kBucketCount_MAX) {
 248     DVLOG(1) << "Histogram: " << name << " has bad bucket_count: "
 249              << *bucket_count;
 250     *bucket_count = kBucketCount_MAX - 1;
 251   }
 252
 253   if (*minimum >= *maximum)
 254     return false;
 255   if (*bucket_count < 3)
 256     return false;
 257   if (*bucket_count > static_cast<size_t>(*maximum - *minimum + 2))
 258     return false;
 259   return true;
 260 }
 261
 262 HistogramType Histogram::GetHistogramType() const {
 263   return HISTOGRAM;
 264 }
 265
 266 bool Histogram::HasConstructionArguments(Sample expected_minimum,
 267                                          Sample expected_maximum,
 268                                          size_t expected_bucket_count) const {
 269   return ((expected_minimum == declared_min_) &&
 270           (expected_maximum == declared_max_) &&
 271           (expected_bucket_count == bucket_count()));
 272 }
 273
 274 void Histogram::Add(int value) {
 275   DCHECK_EQ(0, ranges(0));
 276   DCHECK_EQ(kSampleType_MAX, ranges(bucket_count()));
 277
 278   if (value > kSampleType_MAX - 1)
 279     value = kSampleType_MAX - 1;
 280   if (value < 0)
 281     value = 0;
 282   samples_->Accumulate(value, 1);
 283
 284   FindAndRunCallback(value);
 285 }
 286
 287 scoped_ptr<HistogramSamples> Histogram::SnapshotSamples() const {
 288   return SnapshotSampleVector().Pass();
 289 }
 290
 291 void Histogram::AddSamples(const HistogramSamples& samples) {
 292   samples_->Add(samples);
 293 }
 294
 295 bool Histogram::AddSamplesFromPickle(PickleIterator* iter) {
 296   return samples_->AddFromPickle(iter);
 297 }
 298
 299 // The following methods provide a graphical histogram display.
 300 void Histogram::WriteHTMLGraph(std::string* output) const {
 301   // TBD(jar) Write a nice HTML bar chart, with divs an mouse-overs etc.
 302   output->append("<PRE>");
 303   WriteAsciiImpl(true, "<br>", output);
 304   output->append("</PRE>");
 305 }
 306
 307 void Histogram::WriteAscii(std::string* output) const {
 308   WriteAsciiImpl(true, "\n", output);
 309 }
 310
 311 bool Histogram::SerializeInfoImpl(Pickle* pickle) const {
 312   DCHECK(bucket_ranges()->HasValidChecksum());
 313   return pickle->WriteString(histogram_name()) &&
 314       pickle->WriteInt(flags()) &&
 315       pickle->WriteInt(declared_min()) &&
 316       pickle->WriteInt(declared_max()) &&
 317       pickle->WriteSizeT(bucket_count()) &&
 318       pickle->WriteUInt32(bucket_ranges()->checksum());
 319 }
 320
 321 Histogram::Histogram(const std::string& name,
 322                      Sample minimum,
 323                      Sample maximum,
 324                      const BucketRanges* ranges)
 325   : HistogramBase(name),
 326     bucket_ranges_(ranges),
 327     declared_min_(minimum),
 328     declared_max_(maximum) {
 329   if (ranges)
 330     samples_.reset(new SampleVector(ranges));
 331 }
 332
 333 Histogram::~Histogram() {
 334 }
 335
 336 bool Histogram::PrintEmptyBucket(size_t index) const {
 337   return true;
 338 }
 339
 340 // Use the actual bucket widths (like a linear histogram) until the widths get
 341 // over some transition value, and then use that transition width.  Exponentials
 342 // get so big so fast (and we don't expect to see a lot of entries in the large
 343 // buckets), so we need this to make it possible to see what is going on and
 344 // not have 0-graphical-height buckets.
 345 double Histogram::GetBucketSize(Count current, size_t i) const {
 346   DCHECK_GT(ranges(i + 1), ranges(i));
 347   static const double kTransitionWidth = 5;
 348   double denominator = ranges(i + 1) - ranges(i);
 349   if (denominator > kTransitionWidth)
 350     denominator = kTransitionWidth;  // Stop trying to normalize.
 351   return current/denominator;
 352 }
 353
 354 const std::string Histogram::GetAsciiBucketRange(size_t i) const {
 355   return GetSimpleAsciiBucketRange(ranges(i));
 356 }
 357
 358 //------------------------------------------------------------------------------
 359 // Private methods
 360
 361 // static
 362 HistogramBase* Histogram::DeserializeInfoImpl(PickleIterator* iter) {
 363   std::string histogram_name;
 364   int flags;
 365   int declared_min;
 366   int declared_max;
 367   size_t bucket_count;
 368   uint32 range_checksum;
 369
 370   if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
 371                               &declared_max, &bucket_count, &range_checksum)) {
 372     return NULL;
 373   }
 374
 375   // Find or create the local version of the histogram in this process.
 376   HistogramBase* histogram = Histogram::FactoryGet(
 377       histogram_name, declared_min, declared_max, bucket_count, flags);
 378
 379   if (!ValidateRangeChecksum(*histogram, range_checksum)) {
 380     // The serialized histogram might be corrupted.
 381     return NULL;
 382   }
 383   return histogram;
 384 }
 385
 386 scoped_ptr<SampleVector> Histogram::SnapshotSampleVector() const {
 387   scoped_ptr<SampleVector> samples(new SampleVector(bucket_ranges()));
 388   samples->Add(*samples_);
 389   return samples.Pass();
 390 }
 391
 392 void Histogram::WriteAsciiImpl(bool graph_it,
 393                                const std::string& newline,
 394                                std::string* output) const {
 395   // Get local (stack) copies of all effectively volatile class data so that we
 396   // are consistent across our output activities.
 397   scoped_ptr<SampleVector> snapshot = SnapshotSampleVector();
 398   Count sample_count = snapshot->TotalCount();
 399
 400   WriteAsciiHeader(*snapshot, sample_count, output);
 401   output->append(newline);
 402
 403   // Prepare to normalize graphical rendering of bucket contents.
 404   double max_size = 0;
 405   if (graph_it)
 406     max_size = GetPeakBucketSize(*snapshot);
 407
 408   // Calculate space needed to print bucket range numbers.  Leave room to print
 409   // nearly the largest bucket range without sliding over the histogram.
 410   size_t largest_non_empty_bucket = bucket_count() - 1;
 411   while (0 == snapshot->GetCountAtIndex(largest_non_empty_bucket)) {
 412     if (0 == largest_non_empty_bucket)
 413       break;  // All buckets are empty.
 414     --largest_non_empty_bucket;
 415   }
 416
 417   // Calculate largest print width needed for any of our bucket range displays.
 418   size_t print_width = 1;
 419   for (size_t i = 0; i < bucket_count(); ++i) {
 420     if (snapshot->GetCountAtIndex(i)) {
 421       size_t width = GetAsciiBucketRange(i).size() + 1;
 422       if (width > print_width)
 423         print_width = width;
 424     }
 425   }
 426
 427   int64 remaining = sample_count;
 428   int64 past = 0;
 429   // Output the actual histogram graph.
 430   for (size_t i = 0; i < bucket_count(); ++i) {
 431     Count current = snapshot->GetCountAtIndex(i);
 432     if (!current && !PrintEmptyBucket(i))
 433       continue;
 434     remaining -= current;
 435     std::string range = GetAsciiBucketRange(i);
 436     output->append(range);
 437     for (size_t j = 0; range.size() + j < print_width + 1; ++j)
 438       output->push_back(' ');
 439     if (0 == current && i < bucket_count() - 1 &&
 440         0 == snapshot->GetCountAtIndex(i + 1)) {
 441       while (i < bucket_count() - 1 &&
 442              0 == snapshot->GetCountAtIndex(i + 1)) {
 443         ++i;
 444       }
 445       output->append("... ");
 446       output->append(newline);
 447       continue;  // No reason to plot emptiness.
 448     }
 449     double current_size = GetBucketSize(current, i);
 450     if (graph_it)
 451       WriteAsciiBucketGraph(current_size, max_size, output);
 452     WriteAsciiBucketContext(past, current, remaining, i, output);
 453     output->append(newline);
 454     past += current;
 455   }
 456   DCHECK_EQ(sample_count, past);
 457 }
 458
 459 double Histogram::GetPeakBucketSize(const SampleVector& samples) const {
 460   double max = 0;
 461   for (size_t i = 0; i < bucket_count() ; ++i) {
 462     double current_size = GetBucketSize(samples.GetCountAtIndex(i), i);
 463     if (current_size > max)
 464       max = current_size;
 465   }
 466   return max;
 467 }
 468
 469 void Histogram::WriteAsciiHeader(const SampleVector& samples,
 470                                  Count sample_count,
 471                                  std::string* output) const {
 472   StringAppendF(output,
 473                 "Histogram: %s recorded %d samples",
 474                 histogram_name().c_str(),
 475                 sample_count);
 476   if (0 == sample_count) {
 477     DCHECK_EQ(samples.sum(), 0);
 478   } else {
 479     double average = static_cast<float>(samples.sum()) / sample_count;
 480
 481     StringAppendF(output, ", average = %.1f", average);
 482   }
 483   if (flags() & ~kHexRangePrintingFlag)
 484     StringAppendF(output, " (flags = 0x%x)", flags() & ~kHexRangePrintingFlag);
 485 }
 486
 487 void Histogram::WriteAsciiBucketContext(const int64 past,
 488                                         const Count current,
 489                                         const int64 remaining,
 490                                         const size_t i,
 491                                         std::string* output) const {
 492   double scaled_sum = (past + current + remaining) / 100.0;
 493   WriteAsciiBucketValue(current, scaled_sum, output);
 494   if (0 < i) {
 495     double percentage = past / scaled_sum;
 496     StringAppendF(output, " {%3.1f%%}", percentage);
 497   }
 498 }
 499
 500 void Histogram::GetParameters(DictionaryValue* params) const {
 501   params->SetString("type", HistogramTypeToString(GetHistogramType()));
 502   params->SetInteger("min", declared_min());
 503   params->SetInteger("max", declared_max());
 504   params->SetInteger("bucket_count", static_cast<int>(bucket_count()));
 505 }
 506
 507 void Histogram::GetCountAndBucketData(Count* count,
 508                                       int64* sum,
 509                                       ListValue* buckets) const {
 510   scoped_ptr<SampleVector> snapshot = SnapshotSampleVector();
 511   *count = snapshot->TotalCount();
 512   *sum = snapshot->sum();
 513   size_t index = 0;
 514   for (size_t i = 0; i < bucket_count(); ++i) {
 515     Sample count_at_index = snapshot->GetCountAtIndex(i);
 516     if (count_at_index > 0) {
 517       scoped_ptr<DictionaryValue> bucket_value(new DictionaryValue());
 518       bucket_value->SetInteger("low", ranges(i));
 519       if (i != bucket_count() - 1)
 520         bucket_value->SetInteger("high", ranges(i + 1));
 521       bucket_value->SetInteger("count", count_at_index);
 522       buckets->Set(index, bucket_value.release());
 523       ++index;
 524     }
 525   }
 526 }
 527
 528 //------------------------------------------------------------------------------
 529 // LinearHistogram: This histogram uses a traditional set of evenly spaced
 530 // buckets.
 531 //------------------------------------------------------------------------------
 532
 533 LinearHistogram::~LinearHistogram() {}
 534
 535 HistogramBase* LinearHistogram::FactoryGet(const std::string& name,
 536                                            Sample minimum,
 537                                            Sample maximum,
 538                                            size_t bucket_count,
 539                                            int32 flags) {
 540   return FactoryGetWithRangeDescription(
 541       name, minimum, maximum, bucket_count, flags, NULL);
 542 }
 543
 544 HistogramBase* LinearHistogram::FactoryTimeGet(const std::string& name,
 545                                                TimeDelta minimum,
 546                                                TimeDelta maximum,
 547                                                size_t bucket_count,
 548                                                int32 flags) {
 549   return FactoryGet(name, static_cast<Sample>(minimum.InMilliseconds()),
 550                     static_cast<Sample>(maximum.InMilliseconds()), bucket_count,
 551                     flags);
 552 }
 553
 554 HistogramBase* LinearHistogram::FactoryGet(const char* name,
 555                                            Sample minimum,
 556                                            Sample maximum,
 557                                            size_t bucket_count,
 558                                            int32 flags) {
 559   return FactoryGet(std::string(name), minimum, maximum, bucket_count, flags);
 560 }
 561
 562 HistogramBase* LinearHistogram::FactoryTimeGet(const char* name,
 563                                                TimeDelta minimum,
 564                                                TimeDelta maximum,
 565                                                size_t bucket_count,
 566                                                int32 flags) {
 567   return FactoryTimeGet(std::string(name),  minimum, maximum, bucket_count,
 568                         flags);
 569 }
 570
 571 HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
 572       const std::string& name,
 573       Sample minimum,
 574       Sample maximum,
 575       size_t bucket_count,
 576       int32 flags,
 577       const DescriptionPair descriptions[]) {
 578   bool valid_arguments = Histogram::InspectConstructionArguments(
 579       name, &minimum, &maximum, &bucket_count);
 580   DCHECK(valid_arguments);
 581
 582   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
 583   if (!histogram) {
 584     // To avoid racy destruction at shutdown, the following will be leaked.
 585     BucketRanges* ranges = new BucketRanges(bucket_count + 1);
 586     InitializeBucketRanges(minimum, maximum, ranges);
 587     const BucketRanges* registered_ranges =
 588         StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
 589
 590     LinearHistogram* tentative_histogram =
 591         new LinearHistogram(name, minimum, maximum, registered_ranges);
 592
 593     // Set range descriptions.
 594     if (descriptions) {
 595       for (int i = 0; descriptions[i].description; ++i) {
 596         tentative_histogram->bucket_description_[descriptions[i].sample] =
 597             descriptions[i].description;
 598       }
 599     }
 600
 601     tentative_histogram->SetFlags(flags);
 602     histogram =
 603         StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
 604   }
 605
 606   DCHECK_EQ(LINEAR_HISTOGRAM, histogram->GetHistogramType());
 607   if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
 608     // The construction arguments do not match the existing histogram.  This can
 609     // come about if an extension updates in the middle of a chrome run and has
 610     // changed one of them, or simply by bad code within Chrome itself.  We
 611     // return NULL here with the expectation that bad code in Chrome will crash
 612     // on dereference, but extension/Pepper APIs will guard against NULL and not
 613     // crash.
 614     DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
 615     return NULL;
 616   }
 617   return histogram;
 618 }
 619
 620 HistogramType LinearHistogram::GetHistogramType() const {
 621   return LINEAR_HISTOGRAM;
 622 }
 623
 624 LinearHistogram::LinearHistogram(const std::string& name,
 625                                  Sample minimum,
 626                                  Sample maximum,
 627                                  const BucketRanges* ranges)
 628     : Histogram(name, minimum, maximum, ranges) {
 629 }
 630
 631 double LinearHistogram::GetBucketSize(Count current, size_t i) const {
 632   DCHECK_GT(ranges(i + 1), ranges(i));
 633   // Adjacent buckets with different widths would have "surprisingly" many (few)
 634   // samples in a histogram if we didn't normalize this way.
 635   double denominator = ranges(i + 1) - ranges(i);
 636   return current/denominator;
 637 }
 638
 639 const std::string LinearHistogram::GetAsciiBucketRange(size_t i) const {
 640   int range = ranges(i);
 641   BucketDescriptionMap::const_iterator it = bucket_description_.find(range);
 642   if (it == bucket_description_.end())
 643     return Histogram::GetAsciiBucketRange(i);
 644   return it->second;
 645 }
 646
 647 bool LinearHistogram::PrintEmptyBucket(size_t index) const {
 648   return bucket_description_.find(ranges(index)) == bucket_description_.end();
 649 }
 650
 651 // static
 652 void LinearHistogram::InitializeBucketRanges(Sample minimum,
 653                                              Sample maximum,
 654                                              BucketRanges* ranges) {
 655   double min = minimum;
 656   double max = maximum;
 657   size_t bucket_count = ranges->bucket_count();
 658   for (size_t i = 1; i < bucket_count; ++i) {
 659     double linear_range =
 660         (min * (bucket_count - 1 - i) + max * (i - 1)) / (bucket_count - 2);
 661     ranges->set_range(i, static_cast<Sample>(linear_range + 0.5));
 662   }
 663   ranges->set_range(ranges->bucket_count(), HistogramBase::kSampleType_MAX);
 664   ranges->ResetChecksum();
 665 }
 666
 667 // static
 668 HistogramBase* LinearHistogram::DeserializeInfoImpl(PickleIterator* iter) {
 669   std::string histogram_name;
 670   int flags;
 671   int declared_min;
 672   int declared_max;
 673   size_t bucket_count;
 674   uint32 range_checksum;
 675
 676   if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
 677                               &declared_max, &bucket_count, &range_checksum)) {
 678     return NULL;
 679   }
 680
 681   HistogramBase* histogram = LinearHistogram::FactoryGet(
 682       histogram_name, declared_min, declared_max, bucket_count, flags);
 683   if (!ValidateRangeChecksum(*histogram, range_checksum)) {
 684     // The serialized histogram might be corrupted.
 685     return NULL;
 686   }
 687   return histogram;
 688 }
 689
 690 //------------------------------------------------------------------------------
 691 // This section provides implementation for BooleanHistogram.
 692 //------------------------------------------------------------------------------
 693
 694 HistogramBase* BooleanHistogram::FactoryGet(const std::string& name,
 695                                             int32 flags) {
 696   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
 697   if (!histogram) {
 698     // To avoid racy destruction at shutdown, the following will be leaked.
 699     BucketRanges* ranges = new BucketRanges(4);
 700     LinearHistogram::InitializeBucketRanges(1, 2, ranges);
 701     const BucketRanges* registered_ranges =
 702         StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
 703
 704     BooleanHistogram* tentative_histogram =
 705         new BooleanHistogram(name, registered_ranges);
 706
 707     tentative_histogram->SetFlags(flags);
 708     histogram =
 709         StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
 710   }
 711
 712   DCHECK_EQ(BOOLEAN_HISTOGRAM, histogram->GetHistogramType());
 713   return histogram;
 714 }
 715
 716 HistogramBase* BooleanHistogram::FactoryGet(const char* name, int32 flags) {
 717   return FactoryGet(std::string(name), flags);
 718 }
 719
 720 HistogramType BooleanHistogram::GetHistogramType() const {
 721   return BOOLEAN_HISTOGRAM;
 722 }
 723
 724 BooleanHistogram::BooleanHistogram(const std::string& name,
 725                                    const BucketRanges* ranges)
 726     : LinearHistogram(name, 1, 2, ranges) {}
 727
 728 HistogramBase* BooleanHistogram::DeserializeInfoImpl(PickleIterator* iter) {
 729   std::string histogram_name;
 730   int flags;
 731   int declared_min;
 732   int declared_max;
 733   size_t bucket_count;
 734   uint32 range_checksum;
 735
 736   if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
 737                               &declared_max, &bucket_count, &range_checksum)) {
 738     return NULL;
 739   }
 740
 741   HistogramBase* histogram = BooleanHistogram::FactoryGet(
 742       histogram_name, flags);
 743   if (!ValidateRangeChecksum(*histogram, range_checksum)) {
 744     // The serialized histogram might be corrupted.
 745     return NULL;
 746   }
 747   return histogram;
 748 }
 749
 750 //------------------------------------------------------------------------------
 751 // CustomHistogram:
 752 //------------------------------------------------------------------------------
 753
 754 HistogramBase* CustomHistogram::FactoryGet(
 755     const std::string& name,
 756     const std::vector<Sample>& custom_ranges,
 757     int32 flags) {
 758   CHECK(ValidateCustomRanges(custom_ranges));
 759
 760   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
 761   if (!histogram) {
 762     BucketRanges* ranges = CreateBucketRangesFromCustomRanges(custom_ranges);
 763     const BucketRanges* registered_ranges =
 764         StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
 765
 766     // To avoid racy destruction at shutdown, the following will be leaked.
 767     CustomHistogram* tentative_histogram =
 768         new CustomHistogram(name, registered_ranges);
 769
 770     tentative_histogram->SetFlags(flags);
 771
 772     histogram =
 773         StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
 774   }
 775
 776   DCHECK_EQ(histogram->GetHistogramType(), CUSTOM_HISTOGRAM);
 777   return histogram;
 778 }
 779
 780 HistogramBase* CustomHistogram::FactoryGet(
 781     const char* name,
 782     const std::vector<Sample>& custom_ranges,
 783     int32 flags) {
 784   return FactoryGet(std::string(name), custom_ranges, flags);
 785 }
 786
 787 HistogramType CustomHistogram::GetHistogramType() const {
 788   return CUSTOM_HISTOGRAM;
 789 }
 790
 791 // static
 792 std::vector<Sample> CustomHistogram::ArrayToCustomRanges(
 793     const Sample* values, size_t num_values) {
 794   std::vector<Sample> all_values;
 795   for (size_t i = 0; i < num_values; ++i) {
 796     Sample value = values[i];
 797     all_values.push_back(value);
 798
 799     // Ensure that a guard bucket is added. If we end up with duplicate
 800     // values, FactoryGet will take care of removing them.
 801     all_values.push_back(value + 1);
 802   }
 803   return all_values;
 804 }
 805
 806 CustomHistogram::CustomHistogram(const std::string& name,
 807                                  const BucketRanges* ranges)
 808     : Histogram(name,
 809                 ranges->range(1),
 810                 ranges->range(ranges->bucket_count() - 1),
 811                 ranges) {}
 812
 813 bool CustomHistogram::SerializeInfoImpl(Pickle* pickle) const {
 814   if (!Histogram::SerializeInfoImpl(pickle))
 815     return false;
 816
 817   // Serialize ranges. First and last ranges are alwasy 0 and INT_MAX, so don't
 818   // write them.
 819   for (size_t i = 1; i < bucket_ranges()->bucket_count(); ++i) {
 820     if (!pickle->WriteInt(bucket_ranges()->range(i)))
 821       return false;
 822   }
 823   return true;
 824 }
 825
 826 double CustomHistogram::GetBucketSize(Count current, size_t i) const {
 827   return 1;
 828 }
 829
 830 // static
 831 HistogramBase* CustomHistogram::DeserializeInfoImpl(PickleIterator* iter) {
 832   std::string histogram_name;
 833   int flags;
 834   int declared_min;
 835   int declared_max;
 836   size_t bucket_count;
 837   uint32 range_checksum;
 838
 839   if (!ReadHistogramArguments(iter, &histogram_name, &flags, &declared_min,
 840                               &declared_max, &bucket_count, &range_checksum)) {
 841     return NULL;
 842   }
 843
 844   // First and last ranges are not serialized.
 845   std::vector<Sample> sample_ranges(bucket_count - 1);
 846
 847   for (size_t i = 0; i < sample_ranges.size(); ++i) {
 848     if (!iter->ReadInt(&sample_ranges[i]))
 849       return NULL;
 850   }
 851
 852   HistogramBase* histogram = CustomHistogram::FactoryGet(
 853       histogram_name, sample_ranges, flags);
 854   if (!ValidateRangeChecksum(*histogram, range_checksum)) {
 855     // The serialized histogram might be corrupted.
 856     return NULL;
 857   }
 858   return histogram;
 859 }
 860
 861 // static
 862 bool CustomHistogram::ValidateCustomRanges(
 863     const std::vector<Sample>& custom_ranges) {
 864   bool has_valid_range = false;
 865   for (size_t i = 0; i < custom_ranges.size(); i++) {
 866     Sample sample = custom_ranges[i];
 867     if (sample < 0 || sample > HistogramBase::kSampleType_MAX - 1)
 868       return false;
 869     if (sample != 0)
 870       has_valid_range = true;
 871   }
 872   return has_valid_range;
 873 }
 874
 875 // static
 876 BucketRanges* CustomHistogram::CreateBucketRangesFromCustomRanges(
 877       const std::vector<Sample>& custom_ranges) {
 878   // Remove the duplicates in the custom ranges array.
 879   std::vector<int> ranges = custom_ranges;
 880   ranges.push_back(0);  // Ensure we have a zero value.
 881   ranges.push_back(HistogramBase::kSampleType_MAX);
 882   std::sort(ranges.begin(), ranges.end());
 883   ranges.erase(std::unique(ranges.begin(), ranges.end()), ranges.end());
 884
 885   BucketRanges* bucket_ranges = new BucketRanges(ranges.size());
 886   for (size_t i = 0; i < ranges.size(); i++) {
 887     bucket_ranges->set_range(i, ranges[i]);
 888   }
 889   bucket_ranges->ResetChecksum();
 890   return bucket_ranges;
 891 }
 892
 893 }  // namespace base