text: // Copyright (c) 2020-2021 The Eleccoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <hash.h>
  #include <crypto/common.h>
  #include <crypto/hmac_sha512.h>
  
  #include <string>
  
  inline uint32_t ROTL32(uint32_t x, int8_t r)
  {
      return (x << r) | (x >> (32 - r));
  }
  
  unsigned int MurmurHash3(unsigned int nHashSeed, Span<const unsigned char> vDataToHash)
  {
      // The following is MurmurHash3 (x86_32), see https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
      uint32_t h1 = nHashSeed;
      const uint32_t c1 = 0xcc9e2d51;
      const uint32_t c2 = 0x1b873593;
  
      const int nblocks = vDataToHash.size() / 4;
  
      //----------
      // body
      const uint8_t* blocks = vDataToHash.data();
  
      for (int i = 0; i < nblocks; ++i) {
          uint32_t k1 = ReadLE32(blocks + i*4);
  
          k1 *= c1;
          k1 = ROTL32(k1, 15);
          k1 *= c2;
  
          h1 ^= k1;
          h1 = ROTL32(h1, 13);
          h1 = h1 * 5 + 0xe6546b64;
      }
  
      //----------
      // tail
      const uint8_t* tail = vDataToHash.data() + nblocks * 4;
  
      uint32_t k1 = 0;
  
      switch (vDataToHash.size() & 3) {
          case 3:
              k1 ^= tail[2] << 16;
              [[fallthrough]];
          case 2:
              k1 ^= tail[1] << 8;
              [[fallthrough]];
          case 1:
              k1 ^= tail[0];
              k1 *= c1;
              k1 = ROTL32(k1, 15);
              k1 *= c2;
              h1 ^= k1;
      }
  
      //----------
      // finalization
      h1 ^= vDataToHash.size();
      h1 ^= h1 >> 16;
      h1 *= 0x85ebca6b;
      h1 ^= h1 >> 13;
      h1 *= 0xc2b2ae35;
      h1 ^= h1 >> 16;
  
      return h1;
  }
  
  void BIP32Hash(const ChainCode &chainCode, unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64])
  {
      unsigned char num[4];
      num[0] = (nChild >> 24) & 0xFF;
      num[1] = (nChild >> 16) & 0xFF;
      num[2] = (nChild >>  8) & 0xFF;
      num[3] = (nChild >>  0) & 0xFF;
      CHMAC_SHA512(chainCode.begin(), chainCode.size()).Write(&header, 1).Write(data, 32).Write(num, 4).Finalize(output);
  }
  
  uint256 SHA256Uint256(const uint256& input)
  {
      uint256 result;
      CSHA256().Write(input.begin(), 32).Finalize(result.begin());
      return result;
  }
  
  CHashWriter TaggedHash(const std::string& tag)
  {
      CHashWriter writer(SER_GETHASH, 0);
      uint256 taghash;
      CSHA256().Write((const unsigned char*)tag.data(), tag.size()).Finalize(taghash.begin());
      writer << taghash << taghash;
      return writer;
  }
  