/*

 * This file is part of PowerDNS or dnsdist.

 * Copyright -- PowerDNS.COM B.V. and its contributors

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of version 2 of the GNU General Public License as

 * published by the Free Software Foundation.

 *

 * In addition, for the avoidance of any doubt, permission is granted to

 * link this program with OpenSSL and to (re)distribute the binaries

 * produced as the result of such linking.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */

#pragma once

#include <cinttypes>

inline void burtlemix(uint32_t& a, uint32_t& b, uint32_t& c)

{

  a -= b;

  a -= c;

  a ^= (c >> 13);

  b -= c;

  b -= a;

  b ^= (a << 8);

  c -= a;

  c -= b;

  c ^= (b >> 13);

  a -= b;

  a -= c;

  a ^= (c >> 12);

  b -= c;

  b -= a;

  b ^= (a << 16);

  c -= a;

  c -= b;

  c ^= (b >> 5);

  a -= b;

  a -= c;

  a ^= (c >> 3);

  b -= c;

  b -= a;

  b ^= (a << 10);

  c -= a;

  c -= b;

  c ^= (b >> 15);

}

inline uint32_t burtle(const unsigned char* k, uint32_t length, uint32_t initval)

{

  uint32_t a, b, c, len;

  /* Set up the internal state */

  len = length;

  a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */

  c = initval; /* the previous hash value */

  /*---------------------------------------- handle most of the key */

  while (len >= 12) {

    a += (k[0] + ((uint32_t)k[1] << 8) + ((uint32_t)k[2] << 16) + ((uint32_t)k[3] << 24));

    b += (k[4] + ((uint32_t)k[5] << 8) + ((uint32_t)k[6] << 16) + ((uint32_t)k[7] << 24));

    c += (k[8] + ((uint32_t)k[9] << 8) + ((uint32_t)k[10] << 16) + ((uint32_t)k[11] << 24));

    burtlemix(a, b, c);

    k += 12;

    len -= 12;

  }

  /*------------------------------------- handle the last 11 bytes */

  c += length;

  switch (len) { /* all the case statements fall through */

  case 11:

    c += ((uint32_t)k[10] << 24);

    /* fall-through */

  case 10:

    c += ((uint32_t)k[9] << 16);

    /* fall-through */

  case 9:

    c += ((uint32_t)k[8] << 8);

    /* the first byte of c is reserved for the length */

    /* fall-through */

  case 8:

    b += ((uint32_t)k[7] << 24);

    /* fall-through */

  case 7:

    b += ((uint32_t)k[6] << 16);

    /* fall-through */

  case 6:

    b += ((uint32_t)k[5] << 8);

    /* fall-through */

  case 5:

    b += k[4];

    /* fall-through */

  case 4:

    a += ((uint32_t)k[3] << 24);

    /* fall-through */

  case 3:

    a += ((uint32_t)k[2] << 16);

    /* fall-through */

  case 2:

    a += ((uint32_t)k[1] << 8);

    /* fall-through */

  case 1:

    a += k[0];

    /* case 0: nothing left to add */

  }

  burtlemix(a, b, c);

  /*-------------------------------------------- report the result */

  return c;

}

inline uint32_t burtleCI(const unsigned char* k, uint32_t length, uint32_t initval)

{

  uint32_t a, b, c, len;

  /* Set up the internal state */

  len = length;

  a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */

  c = initval; /* the previous hash value */

  /*---------------------------------------- handle most of the key */

  while (len >= 12) {

    a += (dns_tolower(k[0]) + ((uint32_t)dns_tolower(k[1]) << 8) + ((uint32_t)dns_tolower(k[2]) << 16) + ((uint32_t)dns_tolower(k[3]) << 24));

    b += (dns_tolower(k[4]) + ((uint32_t)dns_tolower(k[5]) << 8) + ((uint32_t)dns_tolower(k[6]) << 16) + ((uint32_t)dns_tolower(k[7]) << 24));

    c += (dns_tolower(k[8]) + ((uint32_t)dns_tolower(k[9]) << 8) + ((uint32_t)dns_tolower(k[10]) << 16) + ((uint32_t)dns_tolower(k[11]) << 24));

    burtlemix(a, b, c);

    k += 12;

    len -= 12;

  }

  /*------------------------------------- handle the last 11 bytes */

  c += length;

  switch (len) { /* all the case statements fall through */

  case 11:

    c += ((uint32_t)dns_tolower(k[10]) << 24);

    /* fall-through */

  case 10:

    c += ((uint32_t)dns_tolower(k[9]) << 16);

    /* fall-through */

  case 9:

    c += ((uint32_t)dns_tolower(k[8]) << 8);

    /* the first byte of c is reserved for the length */

    /* fall-through */

  case 8:

    b += ((uint32_t)dns_tolower(k[7]) << 24);

    /* fall-through */

  case 7:

    b += ((uint32_t)dns_tolower(k[6]) << 16);

    /* fall-through */

  case 6:

    b += ((uint32_t)dns_tolower(k[5]) << 8);

    /* fall-through */

  case 5:

    b += dns_tolower(k[4]);

    /* fall-through */

  case 4:

    a += ((uint32_t)dns_tolower(k[3]) << 24);

    /* fall-through */

  case 3:

    a += ((uint32_t)dns_tolower(k[2]) << 16);

    /* fall-through */

  case 2:

    a += ((uint32_t)dns_tolower(k[1]) << 8);

    /* fall-through */

  case 1:

    a += dns_tolower(k[0]);

    /* case 0: nothing left to add */

  }

  burtlemix(a, b, c);

  /*-------------------------------------------- report the result */

  return c;

}

template <typename T>

inline uint32_t burtleCI(const T& k, uint32_t initval)

{

  return burtleCI(reinterpret_cast<const unsigned char*>(k.data()), k.length(), initval); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast): can't static_cast because of sign difference

}