#ifndef CPP_HTMLPARSER_HASH_H_

#define CPP_HTMLPARSER_HASH_H_

#include <string_view>

namespace htmlparser {

// Source: https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function

class Hash {

 public:

  static uint32_t FNVHash(std::string_view s, uint32_t h = 2166136261) {

    for (unsigned char c : s) {

      h ^= c;

      h *= 16777619;  // FNV prime.

    }

    return h;

  }

  static uint64_t FNVHash64(std::string_view s,

                            uint64_t h = 14695981039346656037u) {

    for (unsigned char c : s) {

      h ^= c;

      h *= 1099511628211;  // FNV prime.

    }

    return h;

  }

  // FNV-1a. Alternate. Same as above except the order of XOR and multiply

  // is reversed.

  static uint64_t FNV_AHash64(std::string_view s,

                              uint64_t h = 14695981039346656037u) {

    for (unsigned char c : s) {

      h *= 1099511628211;  // FNV prime.

      h ^= c;

    }

    return h;

  }

 private:

  // No objects of this class.

  Hash() = delete;

};

}  // namespace htmlparser

#endif  // CPP_HTMLPARSER_HASH_H_