#pragma once
#include <cstring>
#include <cstdint>
/** Хеш функция MurmurHash2
*@details Очень быстрая */
uint32_t murmur2(const uint8_t *data, std::size_t len) {
  const uint32_t m = 0x5bd1e995;
  const uint32_t seed = 0;
  const int r = 24;
  uint32_t h = seed ^ len;
  uint32_t k;
  while (len >= 4) {
    k = data[0];
    k |= data[1] << 8;
    k |= data[2] << 16;
    k |= data[3] << 24;
    k *= m;
    k ^= k >> r;
    k *= m;
    h *= m;
    h ^= k;
    data += 4;
    len -= 4;
  }
  switch (len) {
    case 3:
      h ^= data[2] << 16;
    case 2:
      h ^= data[1] << 8;
    case 1:
      h ^= data[0];
      h *= m;
  }
  h ^= h >> 13;
  h *= m;
  h ^= h >> 15;
  return h;
}
//! для murmur3
constexpr uint32_t murmur_32_scramble(uint32_t k) {
  k *= 0xcc9e2d51;
  k = (k << 15) | (k >> 17);
  k *= 0x1b873593;
  return k;
}
uint32_t murmur3(const uint8_t *key, std::size_t len, uint32_t seed = 0) {
  uint32_t h = seed;
  uint32_t k;
  /* Read in groups of 4. */
  for (std::size_t i = len >> 2; i; i--) {
    // Here is a source of differing results across endiannesses.
    // A swap here has no effects on hash properties though.
    memcpy(&k, key, sizeof(uint32_t));
    key += sizeof(uint32_t);
    h ^= murmur_32_scramble(k);
    h = (h << 13) | (h >> 19);
    h = h * 5 + 0xe6546b64;
  }
  /* Read the rest. */
  k = 0;
  for (std::size_t i = len & 3; i; i--) {
    k <<= 8;
    k |= key[i - 1];
  }
  // A swap is *not* necessary here because the preceding loop already
  // places the low bytes in the low places according to whatever endianness
  // we use. Swaps only apply when the memory is copied in a chunk.
  h ^= murmur_32_scramble(k);
  /* Finalize. */
  h ^= len;
  h ^= h >> 16;
  h *= 0x85ebca6b;
  h ^= h >> 13;
  h *= 0xc2b2ae35;
  h ^= h >> 16;
  return h;
}
/** where data is the location of the data in physical memory and 
* len is the length of the data in bytes */
uint32_t adler32(const uint8_t *data, std::size_t len) {
  constexpr uint32_t MOD_ADLER = 65521;
  uint32_t a = 1, b = 0; 
  // Process each byte of the data in order
  for (std::size_t index = 0; index < len; ++index) {
    a = (a + data[index]) % MOD_ADLER;
    b = (b + a) % MOD_ADLER;
  }
  return (b << 16) | a;
}
//! самая простая контрольная сумма байта
uint8_t xor8(const uint8_t *data, std::size_t len) {
  int lrc = 0;
  for (std::size_t i = 0; i < len; ++i)
    lrc = (lrc + data[i]) & 0xFF;
  lrc = ((lrc ^ 0xFF) + 1) & 0xFF;
}
/** сумма всех чисел
 *@details это быстрый алгоритм */
uint32_t crc_32b(const uint8_t *data, std::size_t len) {
  uint32_t ret = 0;
  for (std::size_t i = 0; i < len; ++i)
    ret += data[i];
  return ret;
}
//! таблица для расчётов crc32
const uint32_t Crc32Table[256] = {
  0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
  0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
  0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
  0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
  0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
  0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
  0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
  0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
  0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
  0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
  0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
  0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
  0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
  0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
  0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
  0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
  0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
  0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
  0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
  0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
  0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
  0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
  0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
  0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
  0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
  0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
  0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
  0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
  0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
  0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
  0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
  0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
  0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
  0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
  0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
  0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
  0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
  0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
  0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
  0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
  0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
  0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
  0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
  0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
  0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
  0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
  0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
  0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
  0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
  0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
  0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
  0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
  0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
  0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
  0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
  0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
  0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
  0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
  0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
  0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
  0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
  0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
  0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
  0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
};
//! расчёт crc32 по табличному методу
uint32_t crc32(const uint8_t* buf, std::size_t len) {
  uint32_t crc = 0xFFFFFFFF;
  while (len--)
    crc = (crc >> 8) ^ Crc32Table[(crc ^ *buf++) & 0xFF];
  return crc ^ 0xFFFFFFFF;
}