void Histogram::print()

in util/Stats.cpp [226:285]

• 47 lines of code
• 7 McCabe index (conditional complexity)

void Histogram::print(std::ostream& os) const {
  const int64_t multiplier = divider_;

  // calculate the last bucket index
  int32_t lastIdx = -1;
  for (int i = kLastIndex; i >= 0; --i) {
    if (hdata_[i] > 0) {
      lastIdx = i;
      break;
    }
  }
  if (lastIdx == -1) {
    os << "no data" << std::endl;
    return;
  }

  // comment out header in gnuplot data file
  os << "# ";
  Counter::printCounterHeader(os);
  os << ",";           // awk -F, '/^count/ {sum+=$6} END {print "sum is", sum}'
  Counter::print(os);  // the base counter part
  os << std::endl << "# range, mid point, percentile, count" << std::endl;
  int64_t prev = 0;
  int64_t total = 0;
  const int64_t ctrTotal = getCount();
  auto oldPrecision = os.precision(5);
  // we can combine this loop and the calcPercentile() one but it's
  // easier to read/maintain/test when separated and it's only 2 pass on
  // very little data

  // output the data of each bucket of the histogram
  for (size_t i = 0; i <= static_cast<size_t>(lastIdx); ++i) {
    total += hdata_[i];

    // data in each row is separated by comma (",")
    if (i > 0) {
      os << ">= " << multiplier * prev + offset_ << " ";
    }
    double perc = 100. * (double)total / ctrTotal;
    if (i < kLastIndex) {
      int64_t cur = Histogram::kHistogramBuckets[i];
      os << "< " << multiplier * cur + offset_ << " ";
      double midpt = multiplier * (prev + cur) / 2 + offset_;
      os << ", " << midpt << " ";
      prev = cur;
    } else {
      os << ", " << multiplier * prev + offset_ << " ";
    }
    os << ", " << perc << ", " << hdata_[i] << std::endl;
  }

  // print the information of target percentiles
  os.precision(1);
  os << std::fixed << "# target " << percentile1_ << "%,"
     << calcPercentile(percentile1_) << std::endl
     << "# target " << percentile2_ << "%," << calcPercentile(percentile2_)
     << std::endl;
  os.unsetf(std::ios_base::floatfield);
  os.precision(oldPrecision);
}