ladybird/AK/Retained.h

#pragma once

#include <AK/Assertions.h>
#include <AK/Types.h>

#ifdef __clang__
#define CONSUMABLE(initial_state) __attribute__((consumable(initial_state)))
#define CALLABLE_WHEN(...) __attribute__((callable_when(__VA_ARGS__)))
#define SET_TYPESTATE(state) __attribute__((set_typestate(state)))
#define RETURN_TYPESTATE(state) __attribute__((return_typestate(state)))
#else
#define CONSUMABLE(initial_state)
#define CALLABLE_WHEN(state)
#define SET_TYPESTATE(state)
#define RETURN_TYPESTATE(state)
#endif

namespace AK {

template<typename T>
inline void retain_if_not_null(T* ptr)
{
    if (ptr)
        ptr->retain();
}

template<typename T>
inline void release_if_not_null(T* ptr)
{
    if (ptr)
        ptr->release();
}

template<typename T>
class CONSUMABLE(unconsumed) Retained {
public:
    enum AdoptTag { Adopt };

    RETURN_TYPESTATE(unconsumed) Retained(const T& object) : m_ptr(const_cast<T*>(&object)) { m_ptr->retain(); }
    RETURN_TYPESTATE(unconsumed) Retained(T& object) : m_ptr(&object) { m_ptr->retain(); }
    template<typename U> RETURN_TYPESTATE(unconsumed) Retained(U& object) : m_ptr(&static_cast<T&>(object)) { m_ptr->retain(); }
    RETURN_TYPESTATE(unconsumed) Retained(AdoptTag, T& object) : m_ptr(&object) { }
    RETURN_TYPESTATE(unconsumed) Retained(Retained& other) : m_ptr(&other.copy_ref().leak_ref()) { }
    RETURN_TYPESTATE(unconsumed) Retained(Retained&& other) : m_ptr(&other.leak_ref()) { }
    template<typename U> RETURN_TYPESTATE(unconsumed) Retained(Retained<U>&& other) : m_ptr(static_cast<T*>(&other.leak_ref())) { }
    RETURN_TYPESTATE(unconsumed) Retained(const Retained& other) : m_ptr(&const_cast<Retained&>(other).copy_ref().leak_ref()) { }
    template<typename U> RETURN_TYPESTATE(unconsumed) Retained(const Retained<U>& other) : m_ptr(&const_cast<Retained<U>&>(other).copy_ref().leak_ref()) { }
    ~Retained()
    {
        release_if_not_null(m_ptr);
        m_ptr = nullptr;
#ifdef SANITIZE_PTRS
        if constexpr(sizeof(T*) == 8)
            m_ptr = (T*)(0xb0b0b0b0b0b0b0b0);
        else
            m_ptr = (T*)(0xb0b0b0b0);
#endif
    }

    CALLABLE_WHEN(unconsumed) Retained& operator=(Retained&& other)
    {
        if (this != &other) {
            release_if_not_null(m_ptr);
            m_ptr = &other.leak_ref();
        }
        return *this;
    }

    template<typename U>
    CALLABLE_WHEN(unconsumed) Retained& operator=(Retained<U>&& other)
    {
        if (this != static_cast<void*>(&other)) {
            release_if_not_null(m_ptr);
            m_ptr = &other.leak_ref();
        }
        return *this;
    }

    CALLABLE_WHEN(unconsumed) Retained& operator=(T& object)
    {
        if (m_ptr != &object)
            release_if_not_null(m_ptr);
        m_ptr = &object;
        m_ptr->retain();
        return *this;
    }

    CALLABLE_WHEN(unconsumed) Retained copy_ref() const
    {
        return Retained(*m_ptr);
    }

    CALLABLE_WHEN(unconsumed) SET_TYPESTATE(consumed)
    T& leak_ref()
    {
        ASSERT(m_ptr);
        T* leakedPtr = m_ptr;
        m_ptr = nullptr;
        return *leakedPtr;
    }

    CALLABLE_WHEN(unconsumed) T* ptr() { ASSERT(m_ptr); return m_ptr; }
    CALLABLE_WHEN(unconsumed) const T* ptr() const { ASSERT(m_ptr); return m_ptr; }

    CALLABLE_WHEN(unconsumed) T* operator->() { ASSERT(m_ptr); return m_ptr; }
    CALLABLE_WHEN(unconsumed) const T* operator->() const { ASSERT(m_ptr); return m_ptr; }

    CALLABLE_WHEN(unconsumed) T& operator*() { ASSERT(m_ptr); return *m_ptr; }
    CALLABLE_WHEN(unconsumed) const T& operator*() const { ASSERT(m_ptr); return *m_ptr; }

    CALLABLE_WHEN(unconsumed) operator T*() { ASSERT(m_ptr); return m_ptr; }
    CALLABLE_WHEN(unconsumed) operator const T*() const { ASSERT(m_ptr); return m_ptr; }

private:
    Retained() { }

    T* m_ptr { nullptr };
};

template<typename T>
inline Retained<T> adopt(T& object)
{
    return Retained<T>(Retained<T>::Adopt, object);
}

}

using AK::Retained;
using AK::adopt;