utils/benchmark/src/string_util.cc

   1 #include "string_util.h"
   2
   3 #include <array>
   4 #include <cmath>
   5 #include <cstdarg>
   6 #include <cstdio>
   7 #include <memory>
   8 #include <sstream>
   9
  10 #include "arraysize.h"
  11
  12 namespace benchmark {
  13 namespace {
  14
  15 // kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta.
  16 const char kBigSIUnits[] = "kMGTPEZY";
  17 // Kibi, Mebi, Gibi, Tebi, Pebi, Exbi, Zebi, Yobi.
  18 const char kBigIECUnits[] = "KMGTPEZY";
  19 // milli, micro, nano, pico, femto, atto, zepto, yocto.
  20 const char kSmallSIUnits[] = "munpfazy";
  21
  22 // We require that all three arrays have the same size.
  23 static_assert(arraysize(kBigSIUnits) == arraysize(kBigIECUnits),
  24               "SI and IEC unit arrays must be the same size");
  25 static_assert(arraysize(kSmallSIUnits) == arraysize(kBigSIUnits),
  26               "Small SI and Big SI unit arrays must be the same size");
  27
  28 static const int64_t kUnitsSize = arraysize(kBigSIUnits);
  29
  30 void ToExponentAndMantissa(double val, double thresh, int precision,
  31                            double one_k, std::string* mantissa,
  32                            int64_t* exponent) {
  33   std::stringstream mantissa_stream;
  34
  35   if (val < 0) {
  36     mantissa_stream << "-";
  37     val = -val;
  38   }
  39
  40   // Adjust threshold so that it never excludes things which can't be rendered
  41   // in 'precision' digits.
  42   const double adjusted_threshold =
  43       std::max(thresh, 1.0 / std::pow(10.0, precision));
  44   const double big_threshold = adjusted_threshold * one_k;
  45   const double small_threshold = adjusted_threshold;
  46   // Values in ]simple_threshold,small_threshold[ will be printed as-is
  47   const double simple_threshold = 0.01;
  48
  49   if (val > big_threshold) {
  50     // Positive powers
  51     double scaled = val;
  52     for (size_t i = 0; i < arraysize(kBigSIUnits); ++i) {
  53       scaled /= one_k;
  54       if (scaled <= big_threshold) {
  55         mantissa_stream << scaled;
  56         *exponent = i + 1;
  57         *mantissa = mantissa_stream.str();
  58         return;
  59       }
  60     }
  61     mantissa_stream << val;
  62     *exponent = 0;
  63   } else if (val < small_threshold) {
  64     // Negative powers
  65     if (val < simple_threshold) {
  66       double scaled = val;
  67       for (size_t i = 0; i < arraysize(kSmallSIUnits); ++i) {
  68         scaled *= one_k;
  69         if (scaled >= small_threshold) {
  70           mantissa_stream << scaled;
  71           *exponent = -static_cast<int64_t>(i + 1);
  72           *mantissa = mantissa_stream.str();
  73           return;
  74         }
  75       }
  76     }
  77     mantissa_stream << val;
  78     *exponent = 0;
  79   } else {
  80     mantissa_stream << val;
  81     *exponent = 0;
  82   }
  83   *mantissa = mantissa_stream.str();
  84 }
  85
  86 std::string ExponentToPrefix(int64_t exponent, bool iec) {
  87   if (exponent == 0) return "";
  88
  89   const int64_t index = (exponent > 0 ? exponent - 1 : -exponent - 1);
  90   if (index >= kUnitsSize) return "";
  91
  92   const char* array =
  93       (exponent > 0 ? (iec ? kBigIECUnits : kBigSIUnits) : kSmallSIUnits);
  94   if (iec)
  95     return array[index] + std::string("i");
  96   else
  97     return std::string(1, array[index]);
  98 }
  99
 100 std::string ToBinaryStringFullySpecified(double value, double threshold,
 101                                          int precision, double one_k = 1024.0) {
 102   std::string mantissa;
 103   int64_t exponent;
 104   ToExponentAndMantissa(value, threshold, precision, one_k, &mantissa,
 105                         &exponent);
 106   return mantissa + ExponentToPrefix(exponent, false);
 107 }
 108
 109 }  // end namespace
 110
 111 void AppendHumanReadable(int n, std::string* str) {
 112   std::stringstream ss;
 113   // Round down to the nearest SI prefix.
 114   ss << ToBinaryStringFullySpecified(n, 1.0, 0);
 115   *str += ss.str();
 116 }
 117
 118 std::string HumanReadableNumber(double n, double one_k) {
 119   // 1.1 means that figures up to 1.1k should be shown with the next unit down;
 120   // this softens edge effects.
 121   // 1 means that we should show one decimal place of precision.
 122   return ToBinaryStringFullySpecified(n, 1.1, 1, one_k);
 123 }
 124
 125 std::string StrFormatImp(const char* msg, va_list args) {
 126   // we might need a second shot at this, so pre-emptivly make a copy
 127   va_list args_cp;
 128   va_copy(args_cp, args);
 129
 130   // TODO(ericwf): use std::array for first attempt to avoid one memory
 131   // allocation guess what the size might be
 132   std::array<char, 256> local_buff;
 133   std::size_t size = local_buff.size();
 134   // 2015-10-08: vsnprintf is used instead of snd::vsnprintf due to a limitation
 135   // in the android-ndk
 136   auto ret = vsnprintf(local_buff.data(), size, msg, args_cp);
 137
 138   va_end(args_cp);
 139
 140   // handle empty expansion
 141   if (ret == 0) return std::string{};
 142   if (static_cast<std::size_t>(ret) < size)
 143     return std::string(local_buff.data());
 144
 145   // we did not provide a long enough buffer on our first attempt.
 146   // add 1 to size to account for null-byte in size cast to prevent overflow
 147   size = static_cast<std::size_t>(ret) + 1;
 148   auto buff_ptr = std::unique_ptr<char[]>(new char[size]);
 149   // 2015-10-08: vsnprintf is used instead of snd::vsnprintf due to a limitation
 150   // in the android-ndk
 151   ret = vsnprintf(buff_ptr.get(), size, msg, args);
 152   return std::string(buff_ptr.get());
 153 }
 154
 155 std::string StrFormat(const char* format, ...) {
 156   va_list args;
 157   va_start(args, format);
 158   std::string tmp = StrFormatImp(format, args);
 159   va_end(args);
 160   return tmp;
 161 }
 162
 163 void ReplaceAll(std::string* str, const std::string& from,
 164                 const std::string& to) {
 165   std::size_t start = 0;
 166   while ((start = str->find(from, start)) != std::string::npos) {
 167     str->replace(start, from.length(), to);
 168     start += to.length();
 169   }
 170 }
 171
 172 }  // end namespace benchmark