Id.h

/*
 * Gamedev Framework (gf)
 * Copyright (C) 2016-2018 Julien Bernard
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */
#ifndef GF_ID_H
#define GF_ID_H

#include <cstdint>
#include <string>

#include "Portability.h"
#include "StringRef.h"

namespace gf {
#ifndef DOXYGEN_SHOULD_SKIP_THIS
inline namespace v1 {
#endif

  using Id = uint64_t;

  constexpr Id InvalidId = 0;

  constexpr Id hash(const char *str, std::size_t sz) {
    Id value = UINT64_C(0xcbf29ce484222325);

    for (std::size_t i = 0; i < sz; ++i) {
      value ^= static_cast<unsigned char>(str[i]);
      value *= UINT64_C(0x100000001b3);
    }

    return value;
  }

  constexpr Id hash(StringRef str) {
    return hash(str.getData(), str.getSize());
  }

  namespace literals {

    constexpr gf::Id operator"" _id(const char *str, std::size_t sz) {
      return gf::hash(str, sz);
    }

  }

#ifndef DOXYGEN_SHOULD_SKIP_THIS
}
#endif
}

#endif // GF_ID_H