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/*
* Copyright (c) 2018-2022, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/Checked.h>
#include <AK/Noncopyable.h>
#include <AK/Platform.h>
#include <AK/StdLibExtras.h>
namespace AK {
class AtomicRefCountedBase {
AK_MAKE_NONCOPYABLE(AtomicRefCountedBase);
AK_MAKE_NONMOVABLE(AtomicRefCountedBase);
public:
using RefCountType = unsigned int;
using AllowOwnPtr = FalseType;
void ref() const
{
auto old_ref_count = m_ref_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed);
VERIFY(old_ref_count > 0);
VERIFY(!Checked<RefCountType>::addition_would_overflow(old_ref_count, 1));
}
[[nodiscard]] bool try_ref() const
{
RefCountType expected = m_ref_count.load(AK::MemoryOrder::memory_order_relaxed);
for (;;) {
if (expected == 0)
return false;
VERIFY(!Checked<RefCountType>::addition_would_overflow(expected, 1));
if (m_ref_count.compare_exchange_strong(expected, expected + 1, AK::MemoryOrder::memory_order_acquire))
return true;
}
}
[[nodiscard]] RefCountType ref_count() const
{
return m_ref_count.load(AK::MemoryOrder::memory_order_relaxed);
}
protected:
AtomicRefCountedBase() = default;
~AtomicRefCountedBase()
{
VERIFY(m_ref_count.load(AK::MemoryOrder::memory_order_relaxed) == 0);
}
RefCountType deref_base() const
{
auto old_ref_count = m_ref_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
VERIFY(old_ref_count > 0);
return old_ref_count - 1;
}
mutable Atomic<RefCountType> m_ref_count { 1 };
};
template<typename T>
class AtomicRefCounted : public AtomicRefCountedBase {
public:
bool unref() const
{
auto* that = const_cast<T*>(static_cast<T const*>(this));
auto new_ref_count = deref_base();
if (new_ref_count == 0) {
if constexpr (requires { that->will_be_destroyed(); })
that->will_be_destroyed();
delete that;
return true;
}
return false;
}
};
}
using AK::AtomicRefCounted;
using AK::AtomicRefCountedBase;
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