sha3.hpp

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#ifndef SHA_3_IMPL_HPP
#define SHA_3_IMPL_HPP
 
#include <cstring>
#include <utility>
 
#include "constant.hh"
 
#define UNROLL(A, F)                                                             \
  [&]<uint64_t... I>(std::index_sequence<I...>) __attribute__((always_inline)) { \
    ((A), ...);                                                                  \
  } (std::make_index_sequence<(F)>());
 
template <std::size_t m_mode>
class SHA3 {
  alignas(32) uint64_t s[b >> 6] = {0};  
 public:
  static constexpr auto block_size() {
    return (b - (m_mode << 1)) >> 3;
  }
 
  void update(const void* __restrict in, const uint64_t sz) {
    alignas(32) uint64_t c[5], t[25];
    for (uint64_t i{}; i < sz; i += block_size()) {
      UNROLL(s[I] ^= ((const uint64_t* __restrict)&((char*)in)[i])[I], block_size() >> 3);
      for (uint64_t rnd{}; rnd < nr; rnd++) {
        UNROLL(c[I] = s[I] ^ s[I + 5] ^ s[I + 10] ^ s[I + 15] ^ s[I + 20], 5);
        UNROLL(s[I] ^= (c[(I + 1) % 5] << 1 | c[(I + 1) % 5] >> 63) ^ c[(I + 4) % 5], 25);
        UNROLL(t[I] = s[pi[I]] << rot[pi[I]] | s[pi[I]] >> (64 - rot[pi[I]]), 25);
        UNROLL(s[I] = (~t[I / 5 * 5 + (I + 1) % 5] & t[I / 5 * 5 + (I + 2) % 5]) ^ t[I], 25);
        s[0] ^= rc[rnd];
      }
    }
  }
 
  void finalize(void* __restrict out, const void* __restrict in, const uint64_t sz) {
    uint64_t resid = sz % block_size();
    update(in, sz - resid);
 
    alignas(32) uint8_t buff[block_size()] = {0};
    buff[block_size() - 1] = 0x80;
    buff[resid] |= 0x06;
    memcpy(buff, &((char*)in)[sz - resid], resid);
    update(buff, block_size());
    memcpy(out, s, m_mode >> 3);
    memset(s, 0, sizeof(s));
  }
 
  auto operator()(auto&&... args) {
    return finalize(std::forward<decltype(args)>(args)...);
  }
};
 
template <std::size_t m_mode>
void sha3(auto&&... args) {
  SHA3<m_mode>{}(std::forward<decltype(args)>(args)...);
}
 
#endif  // SHA_3_IMPL_HPP