Function stepHash

pj_app/src/KeySequence.h:16–24

Maps a (position, key) pair to an opaque 32-bit value. The position acts as a salt, so the same key at different positions maps to different values (which keeps the configured step values from revealing repeats). constexpr so the comparison constants fold at compile time.

// keeps the configured step values from revealing repeats). constexpr so the
// comparison constants fold at compile time.
constexpr std::uint32_t stepHash(std::size_t pos, int key) {
  constexpr std::uint32_t kOffset = 0x811c9dc5u;
  constexpr std::uint32_t kPrime = 0x01000193u;
  constexpr std::uint32_t kSalt = 0x9e3779b9u;
  std::uint32_t h = kOffset;
  h = (h ^ (static_cast<std::uint32_t>(pos) + kSalt)) * kPrime;
  h = (h ^ static_cast<std::uint32_t>(key)) * kPrime;
  return h;
}

// A tiny fixed-sequence detector. It is configured with one step value per
// position (see stepHash). Feed key codes one at a time; feed() returns true