RID.hpp

// Copyright 2022 ShenMian
// License(Apache-2.0)
 
#pragma once
 
#include <atomic>
#include <cassert>
#include <random>
#include <set>
 
class RID
{
public:
    enum class State
    {
        Unloaded,
        Loading,
        Loaded
    };
 
    RID();
 
    // RID(const RID&) = delete;
 
    operator uint32_t() const;
 
private:
    uint32_t           id_;
    std::atomic<State> state_ = State::Unloaded;
 
    inline static std::set<uint32_t> used_ids_;
 
    inline static std::uniform_int_distribution<uint32_t> distrib_;
    inline static std::mt19937                            generator_ = std::mt19937(std::random_device()());
};
 
inline RID::RID()
{
    assert(used_ids_.size() <= std::numeric_limits<uint32_t>::max());
#if 1
    do
    {
        id_ = distrib_(generator_);
    } while(used_ids_.contains(id_));
#else
    id = distrib(generator);
#endif
}
 
inline RID::operator uint32_t() const
{
    return id_;
}