Pill.cpp

   1 #include "Pill.hpp"
   2
   3 #include <limits>
   4
   5 #if __has_include(<experimental/random>)
   6 #include <experimental/random>
   7 #define HAS_RANDINT
   8 #else
   9 #include <random>
  10 #endif
  11
  12 #include <boost/config.hpp>
  13
  14 Pill::Pill()
  15 {
  16   using s_t = decltype(s_);
  17
  18 #ifdef HAS_RANDINT
  19   auto constexpr min = std::numeric_limits<s_t>::min();
  20   auto constexpr max = std::numeric_limits<s_t>::max();
  21   s_                 = std::experimental::randint(min, max);
  22 #else
  23   std::random_device                 rd;
  24   std::uniform_int_distribution<s_t> uni_dist;
  25   s_ = uni_dist(rd);
  26 #endif
  27
  28   auto resp{b32_ndigits_};
  29   b32_str_[resp] = '\0';
  30
  31   // <http://philzimmermann.com/docs/human-oriented-base-32-encoding.txt>
  32
  33   constexpr char b32_charset[]{"ybndrfg8ejkmcpqxot1uwisza345h769"};
  34
  35   auto const os{reinterpret_cast<const unsigned char*>(&s_)};
  36   auto       osp{os + sizeof(s_)};
  37   auto       x{0ul};
  38
  39   switch ((osp - os) % 5) { // Duff's device
  40   case 0:
  41     do {
  42       x                = *--osp;
  43       b32_str_[--resp] = b32_charset[x % 32];
  44       x /= 32;
  45       [[fallthrough]];
  46
  47     case 4:
  48       x |= (static_cast<unsigned long>(*--osp)) << 3;
  49       b32_str_[--resp] = b32_charset[x % 32];
  50       x /= 32;
  51       b32_str_[--resp] = b32_charset[x % 32];
  52       x /= 32;
  53       [[fallthrough]];
  54
  55     case 3:
  56       x |= (static_cast<unsigned long>(*--osp)) << 1;
  57       b32_str_[--resp] = b32_charset[x % 32];
  58       x /= 32;
  59       [[fallthrough]];
  60
  61     case 2:
  62       x |= (static_cast<unsigned long>(*--osp)) << 4;
  63       b32_str_[--resp] = b32_charset[x % 32];
  64       x /= 32;
  65       b32_str_[--resp] = b32_charset[x % 32];
  66       x /= 32;
  67       [[fallthrough]];
  68
  69     case 1:
  70       x |= (static_cast<unsigned long>(*--osp)) << 2;
  71       b32_str_[--resp] = b32_charset[x % 32];
  72       x /= 32;
  73       b32_str_[--resp] = b32_charset[x];
  74     } while (osp > os);
  75   }
  76 }