Pill.cpp

   1 #include "Pill.hpp"
   2
   3 #include <limits>
   4
   5 Pill::Pill()
   6 {
   7   using s_t = decltype(s_);
   8
   9   std::uniform_int_distribution<s_t> uni_dist;
  10   s_ = uni_dist(rng_);
  11
  12   auto resp{b32_ndigits_};
  13   b32_str_[resp] = '\0';
  14
  15   // <http://philzimmermann.com/docs/human-oriented-base-32-encoding.txt>
  16
  17   constexpr char b32_charset[]{"ybndrfg8ejkmcpqxot1uwisza345h769"};
  18
  19   auto const os{reinterpret_cast<const unsigned char*>(&s_)};
  20   auto       osp{os + sizeof(s_)};
  21   auto       x{0ul};
  22
  23   switch ((osp - os) % 5) { // Duff's device
  24   case 0:
  25     do {
  26       x                = *--osp;
  27       b32_str_[--resp] = b32_charset[x % 32];
  28       x /= 32;
  29       [[fallthrough]];
  30
  31     case 4:
  32       x |= (static_cast<unsigned long>(*--osp)) << 3;
  33       b32_str_[--resp] = b32_charset[x % 32];
  34       x /= 32;
  35       b32_str_[--resp] = b32_charset[x % 32];
  36       x /= 32;
  37       [[fallthrough]];
  38
  39     case 3:
  40       x |= (static_cast<unsigned long>(*--osp)) << 1;
  41       b32_str_[--resp] = b32_charset[x % 32];
  42       x /= 32;
  43       [[fallthrough]];
  44
  45     case 2:
  46       x |= (static_cast<unsigned long>(*--osp)) << 4;
  47       b32_str_[--resp] = b32_charset[x % 32];
  48       x /= 32;
  49       b32_str_[--resp] = b32_charset[x % 32];
  50       x /= 32;
  51       [[fallthrough]];
  52
  53     case 1:
  54       x |= (static_cast<unsigned long>(*--osp)) << 2;
  55       b32_str_[--resp] = b32_charset[x % 32];
  56       x /= 32;
  57       b32_str_[--resp] = b32_charset[x];
  58     } while (osp > os);
  59   }
  60 }