src/string_util.cc

#include "string_util.h"

#include <array>
#ifdef BENCHMARK_STL_ANDROID_GNUSTL
#include <cerrno>
#endif
#include <cmath>
#include <cstdarg>
#include <cstdio>
#include <memory>
#include <sstream>

#include "arraysize.h"
#include "benchmark/types.h"

namespace benchmark {
namespace {
// kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta.
const char* const kBigSIUnits[] = {"k", "M", "G", "T", "P", "E", "Z", "Y"};
// Kibi, Mebi, Gibi, Tebi, Pebi, Exbi, Zebi, Yobi.
const char* const kBigIECUnits[] = {"Ki", "Mi", "Gi", "Ti",
                                    "Pi", "Ei", "Zi", "Yi"};
// milli, micro, nano, pico, femto, atto, zepto, yocto.
const char* const kSmallSIUnits[] = {"m", "u", "n", "p", "f", "a", "z", "y"};

// We require that all three arrays have the same size.
static_assert(arraysize(kBigSIUnits) == arraysize(kBigIECUnits),
              "SI and IEC unit arrays must be the same size");
static_assert(arraysize(kSmallSIUnits) == arraysize(kBigSIUnits),
              "Small SI and Big SI unit arrays must be the same size");

const int64_t kUnitsSize = arraysize(kBigSIUnits);

std::pair<std::string, int64_t> ToExponentAndMantissa(double val, int precision,
                                                      double one_k) {
  std::string mantissa;
  int64_t exponent = 0;
  if (val < 0) {
    mantissa = "-";
    val = -val;
  } else {
    mantissa.clear();
  }

  // Adjust threshold so that it never excludes things which can't be rendered
  // in 'precision' digits.
  const double adjusted_threshold =
      std::max(1.0, 1.0 / std::pow(10.0, precision));
  const double big_threshold = (adjusted_threshold * one_k) - 1;
  const double small_threshold = adjusted_threshold;
  // Values in ]simple_threshold,small_threshold[ will be printed as-is
  const double simple_threshold = 0.01;

  auto format_mantissa = [&](double v) { mantissa += StrFormat("%g", v); };

  // Positive powers
  if (val > big_threshold) {
    double scaled = val;
    for (size_t i = 0; i < arraysize(kBigSIUnits); ++i) {
      scaled /= one_k;
      if (scaled <= big_threshold) {
        format_mantissa(scaled);
        exponent = static_cast<int64_t>(i + 1);
        return std::make_pair(mantissa, exponent);
      }
    }
    format_mantissa(val);
    exponent = 0;
    return std::make_pair(mantissa, exponent);
  }

  // Negative powers
  if (val < small_threshold) {
    if (val < simple_threshold) {
      double scaled = val;
      for (size_t i = 0; i < arraysize(kSmallSIUnits); ++i) {
        scaled *= one_k;
        if (scaled >= small_threshold) {
          format_mantissa(scaled);
          exponent = -static_cast<int64_t>(i + 1);
          return std::make_pair(mantissa, exponent);
        }
      }
    }
    format_mantissa(val);
    exponent = 0;
    return std::make_pair(mantissa, exponent);
  }

  format_mantissa(val);
  exponent = 0;
  return std::make_pair(mantissa, exponent);
}

std::string ExponentToPrefix(int64_t exponent, bool iec) {
  if (exponent == 0) {
    return {};
  }

  const int64_t index = (exponent > 0 ? exponent - 1 : -exponent - 1);
  if (index >= kUnitsSize) {
    return {};
  }

  const char* const* array =
      (exponent > 0 ? (iec ? kBigIECUnits : kBigSIUnits) : kSmallSIUnits);

  return std::string(array[index]);
}

std::string ToBinaryStringFullySpecified(double value, int precision,
                                         Counter::OneK one_k) {
  auto [mantissa, exponent] = ToExponentAndMantissa(
      value, precision, one_k == Counter::kIs1024 ? 1024.0 : 1000.0);
  return mantissa + ExponentToPrefix(exponent, one_k == Counter::kIs1024);
}

PRINTF_FORMAT_STRING_FUNC(1, 0)
std::string StrFormatImp(const char* msg, va_list args) {
  // we might need a second shot at this, so pre-emptivly make a copy
  va_list args_cp;
  va_copy(args_cp, args);

  // Use std::array for first attempt to avoid one memory allocation guess what
  // the size might be
  std::array<char, 256> local_buff = {};

  // 2015-10-08: vsnprintf is used instead of snd::vsnprintf due to a limitation
  // in the android-ndk
  auto ret = vsnprintf(local_buff.data(), local_buff.size(), msg, args_cp);

  va_end(args_cp);

  // handle empty expansion
  if (ret == 0) {
    return {};
  }
  if (static_cast<std::size_t>(ret) < local_buff.size()) {
    return std::string(local_buff.data());
  }

  // we did not provide a long enough buffer on our first attempt.
  // add 1 to size to account for null-byte in size cast to prevent overflow
  std::size_t size = static_cast<std::size_t>(ret) + 1;
  auto buff_ptr = std::unique_ptr<char[]>(new char[size]);
  // 2015-10-08: vsnprintf is used instead of snd::vsnprintf due to a limitation
  // in the android-ndk
  va_list args_cp2;
  va_copy(args_cp2, args);
  vsnprintf(buff_ptr.get(), size, msg, args_cp2);
  va_end(args_cp2);
  return std::string(buff_ptr.get());
}

}  // end namespace

std::string HumanReadableNumber(double n, Counter::OneK one_k) {
  return ToBinaryStringFullySpecified(n, 1, one_k);
}

std::string StrFormat(const char* format, ...) {
  va_list args;
  va_start(args, format);
  std::string tmp = StrFormatImp(format, args);
  va_end(args);
  return tmp;
}

std::vector<std::string> StrSplit(const std::string& str, char delim) {
  if (str.empty()) {
    return {};
  }
  std::vector<std::string> ret;
  size_t first = 0;
  size_t next = str.find(delim);
  for (; next != std::string::npos;
       first = next + 1, next = str.find(delim, first)) {
    ret.push_back(str.substr(first, next - first));
  }
  ret.push_back(str.substr(first));
  return ret;
}

#ifdef BENCHMARK_STL_ANDROID_GNUSTL
/*
 * GNU STL in Android NDK lacks support for some C++11 functions, including
 * stoul, stoi, stod. We reimplement them here using C functions strtoul,
 * strtol, strtod. Note that reimplemented functions are in benchmark::
 * namespace, not std:: namespace.
 */
unsigned long stoul(const std::string& str, size_t* pos, int base) {
  /* Record previous errno */
  const int oldErrno = errno;
  errno = 0;

  const char* strStart = str.c_str();
  char* strEnd = const_cast<char*>(strStart);
  const unsigned long result = strtoul(strStart, &strEnd, base);

  const int strtoulErrno = errno;
  /* Restore previous errno */
  errno = oldErrno;

  /* Check for errors and return */
  if (strtoulErrno == ERANGE) {
    throw std::out_of_range("stoul failed: " + str +
                            " is outside of range of unsigned long");
  } else if (strEnd == strStart || strtoulErrno != 0) {
    throw std::invalid_argument("stoul failed: " + str + " is not an integer");
  }
  if (pos != nullptr) {
    *pos = static_cast<size_t>(strEnd - strStart);
  }
  return result;
}

int stoi(const std::string& str, size_t* pos, int base) {
  /* Record previous errno */
  const int oldErrno = errno;
  errno = 0;

  const char* strStart = str.c_str();
  char* strEnd = const_cast<char*>(strStart);
  const long result = strtol(strStart, &strEnd, base);

  const int strtolErrno = errno;
  /* Restore previous errno */
  errno = oldErrno;

  /* Check for errors and return */
  if (strtolErrno == ERANGE || long(int(result)) != result) {
    throw std::out_of_range("stoul failed: " + str +
                            " is outside of range of int");
  } else if (strEnd == strStart || strtolErrno != 0) {
    throw std::invalid_argument("stoul failed: " + str + " is not an integer");
  }
  if (pos != nullptr) {
    *pos = static_cast<size_t>(strEnd - strStart);
  }
  return int(result);
}

double stod(const std::string& str, size_t* pos) {
  /* Record previous errno */
  const int oldErrno = errno;
  errno = 0;

  const char* strStart = str.c_str();
  char* strEnd = const_cast<char*>(strStart);
  const double result = strtod(strStart, &strEnd);

  /* Restore previous errno */
  const int strtodErrno = errno;
  errno = oldErrno;

  /* Check for errors and return */
  if (strtodErrno == ERANGE) {
    throw std::out_of_range("stoul failed: " + str +
                            " is outside of range of int");
  } else if (strEnd == strStart || strtodErrno != 0) {
    throw std::invalid_argument("stoul failed: " + str + " is not an integer");
  }
  if (pos != nullptr) {
    *pos = static_cast<size_t>(strEnd - strStart);
  }
  return result;
}
#endif

}  // end namespace benchmark