Pill.cpp

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