ShatteredPrism/launcher/Usable.h

#pragma once

#include <cstddef>
#include <memory>

#include "QObjectPtr.h"

class Usable;

/**
 * Base class for things that can be used by multiple other things and we want to track the use count.
 *
 * @see UseLock
 */
class Usable {
    friend class UseLock;

   public:
    virtual ~Usable() {}

    std::size_t useCount() const { return m_useCount; }
    bool isInUse() const { return m_useCount > 0; }

   protected:
    virtual void decrementUses() { m_useCount--; }
    virtual void incrementUses() { m_useCount++; }

   private:
    std::size_t m_useCount = 0;
};

/**
 * Lock class to use for keeping track of uses of other things derived from Usable
 *
 * @see Usable
 */
class UseLock {
   public:
    UseLock(shared_qobject_ptr<Usable> usable) : m_usable(usable)
    {
        // this doesn't use shared pointer use count, because that wouldn't be correct. this count is separate.
        m_usable->incrementUses();
    }
    ~UseLock() { m_usable->decrementUses(); }

   private:
    shared_qobject_ptr<Usable> m_usable;
};