mirror of
https://github.com/SerenityOS/serenity
synced 2024-07-22 02:26:11 +00:00
d7b6cc6421
Our existing implementation did not check the element type of the other pointer in the constructors and move assignment operators. This meant that some operations that would require explicit casting on raw pointers were done implicitly, such as: - downcasting a base class to a derived class (e.g. `Kernel::Inode` => `Kernel::ProcFSDirectoryInode` in Kernel/ProcFS.cpp), - casting to an unrelated type (e.g. `Promise<bool>` => `Promise<Empty>` in LibIMAP/Client.cpp) This, of course, allows gross violations of the type system, and makes the need to type-check less obvious before downcasting. Luckily, while adding the `static_ptr_cast`s, only two truly incorrect usages were found; in the other instances, our casts just needed to be made explicit.
360 lines
9.1 KiB
C++
360 lines
9.1 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Atomic.h>
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#include <AK/Format.h>
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#include <AK/Traits.h>
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#include <AK/Types.h>
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#ifdef KERNEL
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# include <Kernel/Arch/x86/Processor.h>
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# include <Kernel/Arch/x86/ScopedCritical.h>
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#endif
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namespace AK {
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template<typename T>
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class OwnPtr;
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template<typename T, typename PtrTraits>
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class RefPtr;
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template<typename T>
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ALWAYS_INLINE void ref_if_not_null(T* ptr)
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{
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if (ptr)
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ptr->ref();
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}
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template<typename T>
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ALWAYS_INLINE void unref_if_not_null(T* ptr)
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{
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if (ptr)
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ptr->unref();
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}
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template<typename T>
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class NonnullRefPtr {
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template<typename U, typename P>
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friend class RefPtr;
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template<typename U>
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friend class NonnullRefPtr;
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template<typename U>
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friend class WeakPtr;
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public:
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using ElementType = T;
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enum AdoptTag { Adopt };
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ALWAYS_INLINE NonnullRefPtr(const T& object)
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: m_bits((FlatPtr)&object)
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{
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VERIFY(!(m_bits & 1));
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const_cast<T&>(object).ref();
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}
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template<typename U>
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ALWAYS_INLINE NonnullRefPtr(const U& object) requires(IsConvertible<U*, T*>)
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: m_bits((FlatPtr) static_cast<const T*>(&object))
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{
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VERIFY(!(m_bits & 1));
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const_cast<T&>(static_cast<const T&>(object)).ref();
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}
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ALWAYS_INLINE NonnullRefPtr(AdoptTag, T& object)
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: m_bits((FlatPtr)&object)
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{
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VERIFY(!(m_bits & 1));
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}
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ALWAYS_INLINE NonnullRefPtr(NonnullRefPtr&& other)
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: m_bits((FlatPtr)&other.leak_ref())
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{
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VERIFY(!(m_bits & 1));
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}
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template<typename U>
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ALWAYS_INLINE NonnullRefPtr(NonnullRefPtr<U>&& other) requires(IsConvertible<U*, T*>)
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: m_bits((FlatPtr)&other.leak_ref())
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{
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VERIFY(!(m_bits & 1));
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}
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ALWAYS_INLINE NonnullRefPtr(const NonnullRefPtr& other)
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: m_bits((FlatPtr)other.add_ref())
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{
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VERIFY(!(m_bits & 1));
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}
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template<typename U>
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ALWAYS_INLINE NonnullRefPtr(const NonnullRefPtr<U>& other) requires(IsConvertible<U*, T*>)
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: m_bits((FlatPtr)other.add_ref())
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{
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VERIFY(!(m_bits & 1));
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}
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ALWAYS_INLINE ~NonnullRefPtr()
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{
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assign(nullptr);
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#ifdef SANITIZE_PTRS
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m_bits.store(explode_byte(0xb0), AK::MemoryOrder::memory_order_relaxed);
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#endif
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}
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template<typename U>
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NonnullRefPtr(const OwnPtr<U>&) = delete;
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template<typename U>
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NonnullRefPtr& operator=(const OwnPtr<U>&) = delete;
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template<typename U>
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NonnullRefPtr(const RefPtr<U>&) = delete;
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template<typename U>
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NonnullRefPtr& operator=(const RefPtr<U>&) = delete;
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NonnullRefPtr(const RefPtr<T>&) = delete;
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NonnullRefPtr& operator=(const RefPtr<T>&) = delete;
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NonnullRefPtr& operator=(const NonnullRefPtr& other)
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{
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if (this != &other)
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assign(other.add_ref());
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return *this;
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}
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template<typename U>
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NonnullRefPtr& operator=(const NonnullRefPtr<U>& other) requires(IsConvertible<U*, T*>)
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{
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assign(other.add_ref());
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return *this;
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}
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ALWAYS_INLINE NonnullRefPtr& operator=(NonnullRefPtr&& other)
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{
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if (this != &other)
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assign(&other.leak_ref());
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return *this;
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}
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template<typename U>
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NonnullRefPtr& operator=(NonnullRefPtr<U>&& other) requires(IsConvertible<U*, T*>)
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{
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assign(&other.leak_ref());
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return *this;
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}
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NonnullRefPtr& operator=(const T& object)
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{
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const_cast<T&>(object).ref();
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assign(const_cast<T*>(&object));
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return *this;
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}
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[[nodiscard]] ALWAYS_INLINE T& leak_ref()
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{
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T* ptr = exchange(nullptr);
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VERIFY(ptr);
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return *ptr;
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}
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ALWAYS_INLINE RETURNS_NONNULL T* ptr()
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{
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return as_nonnull_ptr();
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}
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ALWAYS_INLINE RETURNS_NONNULL const T* ptr() const
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{
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return as_nonnull_ptr();
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}
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ALWAYS_INLINE RETURNS_NONNULL T* operator->()
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{
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return as_nonnull_ptr();
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}
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ALWAYS_INLINE RETURNS_NONNULL const T* operator->() const
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{
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return as_nonnull_ptr();
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}
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ALWAYS_INLINE T& operator*()
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{
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return *as_nonnull_ptr();
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}
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ALWAYS_INLINE const T& operator*() const
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{
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return *as_nonnull_ptr();
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}
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ALWAYS_INLINE RETURNS_NONNULL operator T*()
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{
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return as_nonnull_ptr();
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}
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ALWAYS_INLINE RETURNS_NONNULL operator const T*() const
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{
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return as_nonnull_ptr();
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}
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ALWAYS_INLINE operator T&()
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{
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return *as_nonnull_ptr();
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}
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ALWAYS_INLINE operator const T&() const
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{
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return *as_nonnull_ptr();
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}
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operator bool() const = delete;
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bool operator!() const = delete;
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void swap(NonnullRefPtr& other)
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{
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if (this == &other)
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return;
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// NOTE: swap is not atomic!
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T* other_ptr = other.exchange(nullptr);
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T* ptr = exchange(other_ptr);
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other.exchange(ptr);
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}
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template<typename U>
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void swap(NonnullRefPtr<U>& other) requires(IsConvertible<U*, T*>)
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{
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// NOTE: swap is not atomic!
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U* other_ptr = other.exchange(nullptr);
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T* ptr = exchange(other_ptr);
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other.exchange(ptr);
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}
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private:
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NonnullRefPtr() = delete;
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ALWAYS_INLINE T* as_ptr() const
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{
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return (T*)(m_bits.load(AK::MemoryOrder::memory_order_relaxed) & ~(FlatPtr)1);
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}
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ALWAYS_INLINE RETURNS_NONNULL T* as_nonnull_ptr() const
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{
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T* ptr = (T*)(m_bits.load(AK::MemoryOrder::memory_order_relaxed) & ~(FlatPtr)1);
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VERIFY(ptr);
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return ptr;
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}
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template<typename F>
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void do_while_locked(F f) const
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{
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#ifdef KERNEL
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// We don't want to be pre-empted while we have the lock bit set
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Kernel::ScopedCritical critical;
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#endif
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FlatPtr bits;
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for (;;) {
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bits = m_bits.fetch_or(1, AK::MemoryOrder::memory_order_acq_rel);
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if (!(bits & 1))
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break;
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#ifdef KERNEL
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Kernel::Processor::wait_check();
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#endif
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}
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VERIFY(!(bits & 1));
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f((T*)bits);
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m_bits.store(bits, AK::MemoryOrder::memory_order_release);
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}
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ALWAYS_INLINE void assign(T* new_ptr)
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{
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T* prev_ptr = exchange(new_ptr);
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unref_if_not_null(prev_ptr);
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}
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ALWAYS_INLINE T* exchange(T* new_ptr)
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{
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VERIFY(!((FlatPtr)new_ptr & 1));
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#ifdef KERNEL
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// We don't want to be pre-empted while we have the lock bit set
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Kernel::ScopedCritical critical;
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#endif
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// Only exchange while not locked
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FlatPtr expected = m_bits.load(AK::MemoryOrder::memory_order_relaxed);
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for (;;) {
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expected &= ~(FlatPtr)1; // only if lock bit is not set
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if (m_bits.compare_exchange_strong(expected, (FlatPtr)new_ptr, AK::MemoryOrder::memory_order_acq_rel))
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break;
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#ifdef KERNEL
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Kernel::Processor::wait_check();
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#endif
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}
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VERIFY(!(expected & 1));
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return (T*)expected;
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}
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T* add_ref() const
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{
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#ifdef KERNEL
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// We don't want to be pre-empted while we have the lock bit set
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Kernel::ScopedCritical critical;
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#endif
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// Lock the pointer
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FlatPtr expected = m_bits.load(AK::MemoryOrder::memory_order_relaxed);
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for (;;) {
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expected &= ~(FlatPtr)1; // only if lock bit is not set
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if (m_bits.compare_exchange_strong(expected, expected | 1, AK::MemoryOrder::memory_order_acq_rel))
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break;
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#ifdef KERNEL
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Kernel::Processor::wait_check();
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#endif
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}
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// Add a reference now that we locked the pointer
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ref_if_not_null((T*)expected);
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// Unlock the pointer again
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m_bits.store(expected, AK::MemoryOrder::memory_order_release);
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return (T*)expected;
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}
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mutable Atomic<FlatPtr> m_bits { 0 };
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};
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template<typename T>
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inline NonnullRefPtr<T> adopt_ref(T& object)
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{
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return NonnullRefPtr<T>(NonnullRefPtr<T>::Adopt, object);
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}
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template<typename T>
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struct Formatter<NonnullRefPtr<T>> : Formatter<const T*> {
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void format(FormatBuilder& builder, const NonnullRefPtr<T>& value)
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{
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Formatter<const T*>::format(builder, value.ptr());
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}
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};
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template<typename T, typename U>
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inline void swap(NonnullRefPtr<T>& a, NonnullRefPtr<U>& b) requires(IsConvertible<U*, T*>)
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{
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a.swap(b);
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}
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template<typename T, class... Args>
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requires(IsConstructible<T, Args...>) inline NonnullRefPtr<T> make_ref_counted(Args&&... args)
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{
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return NonnullRefPtr<T>(NonnullRefPtr<T>::Adopt, *new T(forward<Args>(args)...));
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}
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// FIXME: Remove once P0960R3 is available in Clang.
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template<typename T, class... Args>
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inline NonnullRefPtr<T> make_ref_counted(Args&&... args)
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{
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return NonnullRefPtr<T>(NonnullRefPtr<T>::Adopt, *new T { forward<Args>(args)... });
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}
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}
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template<typename T>
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struct Traits<NonnullRefPtr<T>> : public GenericTraits<NonnullRefPtr<T>> {
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using PeekType = T*;
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using ConstPeekType = const T*;
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static unsigned hash(const NonnullRefPtr<T>& p) { return ptr_hash(p.ptr()); }
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static bool equals(const NonnullRefPtr<T>& a, const NonnullRefPtr<T>& b) { return a.ptr() == b.ptr(); }
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};
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using AK::adopt_ref;
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using AK::make_ref_counted;
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using AK::NonnullRefPtr;
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