mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-12-01 12:00:27 +00:00
d07309a180
Unfortunately adopt_ref requires a reference, which obviously does not work well with when attempting to harden against allocation failure. The adopt_ref_if_nonnull() variant will allow you to avoid using bare pointers, while still allowing you to handle allocation failure.
490 lines
14 KiB
C++
490 lines
14 KiB
C++
/*
|
|
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <AK/Atomic.h>
|
|
#include <AK/Format.h>
|
|
#include <AK/NonnullRefPtr.h>
|
|
#include <AK/StdLibExtras.h>
|
|
#include <AK/Traits.h>
|
|
#include <AK/Types.h>
|
|
#ifdef KERNEL
|
|
# include <Kernel/Arch/x86/CPU.h>
|
|
#endif
|
|
|
|
namespace AK {
|
|
|
|
template<typename T>
|
|
class OwnPtr;
|
|
|
|
template<typename T>
|
|
struct RefPtrTraits {
|
|
ALWAYS_INLINE static T* as_ptr(FlatPtr bits)
|
|
{
|
|
return (T*)(bits & ~(FlatPtr)1);
|
|
}
|
|
|
|
ALWAYS_INLINE static FlatPtr as_bits(T* ptr)
|
|
{
|
|
VERIFY(!((FlatPtr)ptr & 1));
|
|
return (FlatPtr)ptr;
|
|
}
|
|
|
|
template<typename U, typename PtrTraits>
|
|
ALWAYS_INLINE static FlatPtr convert_from(FlatPtr bits)
|
|
{
|
|
if (PtrTraits::is_null(bits))
|
|
return default_null_value;
|
|
return as_bits(PtrTraits::as_ptr(bits));
|
|
}
|
|
|
|
ALWAYS_INLINE static bool is_null(FlatPtr bits)
|
|
{
|
|
return !(bits & ~(FlatPtr)1);
|
|
}
|
|
|
|
ALWAYS_INLINE static FlatPtr exchange(Atomic<FlatPtr>& atomic_var, FlatPtr new_value)
|
|
{
|
|
// Only exchange when lock is not held
|
|
VERIFY(!(new_value & 1));
|
|
FlatPtr expected = atomic_var.load(AK::MemoryOrder::memory_order_relaxed);
|
|
for (;;) {
|
|
expected &= ~(FlatPtr)1; // only if lock bit is not set
|
|
if (atomic_var.compare_exchange_strong(expected, new_value, AK::MemoryOrder::memory_order_acq_rel))
|
|
break;
|
|
#ifdef KERNEL
|
|
Kernel::Processor::wait_check();
|
|
#endif
|
|
}
|
|
return expected;
|
|
}
|
|
|
|
ALWAYS_INLINE static bool exchange_if_null(Atomic<FlatPtr>& atomic_var, FlatPtr new_value)
|
|
{
|
|
// Only exchange when lock is not held
|
|
VERIFY(!(new_value & 1));
|
|
for (;;) {
|
|
FlatPtr expected = default_null_value; // only if lock bit is not set
|
|
if (atomic_var.compare_exchange_strong(expected, new_value, AK::MemoryOrder::memory_order_acq_rel))
|
|
break;
|
|
if (!is_null(expected))
|
|
return false;
|
|
#ifdef KERNEL
|
|
Kernel::Processor::wait_check();
|
|
#endif
|
|
}
|
|
return true;
|
|
}
|
|
|
|
ALWAYS_INLINE static FlatPtr lock(Atomic<FlatPtr>& atomic_var)
|
|
{
|
|
// This sets the lock bit atomically, preventing further modifications.
|
|
// This is important when e.g. copying a RefPtr where the source
|
|
// might be released and freed too quickly. This allows us
|
|
// to temporarily lock the pointer so we can add a reference, then
|
|
// unlock it
|
|
FlatPtr bits;
|
|
for (;;) {
|
|
bits = atomic_var.fetch_or(1, AK::MemoryOrder::memory_order_acq_rel);
|
|
if (!(bits & 1))
|
|
break;
|
|
#ifdef KERNEL
|
|
Kernel::Processor::wait_check();
|
|
#endif
|
|
}
|
|
VERIFY(!(bits & 1));
|
|
return bits;
|
|
}
|
|
|
|
ALWAYS_INLINE static void unlock(Atomic<FlatPtr>& atomic_var, FlatPtr new_value)
|
|
{
|
|
VERIFY(!(new_value & 1));
|
|
atomic_var.store(new_value, AK::MemoryOrder::memory_order_release);
|
|
}
|
|
|
|
static constexpr FlatPtr default_null_value = 0;
|
|
|
|
using NullType = std::nullptr_t;
|
|
};
|
|
|
|
template<typename T, typename PtrTraits>
|
|
class RefPtr {
|
|
template<typename U, typename P>
|
|
friend class RefPtr;
|
|
template<typename U>
|
|
friend class WeakPtr;
|
|
|
|
public:
|
|
enum AdoptTag {
|
|
Adopt
|
|
};
|
|
|
|
RefPtr() = default;
|
|
RefPtr(const T* ptr)
|
|
: m_bits(PtrTraits::as_bits(const_cast<T*>(ptr)))
|
|
{
|
|
ref_if_not_null(const_cast<T*>(ptr));
|
|
}
|
|
RefPtr(const T& object)
|
|
: m_bits(PtrTraits::as_bits(const_cast<T*>(&object)))
|
|
{
|
|
T* ptr = const_cast<T*>(&object);
|
|
VERIFY(ptr);
|
|
VERIFY(!is_null());
|
|
ptr->ref();
|
|
}
|
|
RefPtr(AdoptTag, T& object)
|
|
: m_bits(PtrTraits::as_bits(&object))
|
|
{
|
|
VERIFY(!is_null());
|
|
}
|
|
RefPtr(RefPtr&& other)
|
|
: m_bits(other.leak_ref_raw())
|
|
{
|
|
}
|
|
ALWAYS_INLINE RefPtr(const NonnullRefPtr<T>& other)
|
|
: m_bits(PtrTraits::as_bits(const_cast<T*>(other.add_ref())))
|
|
{
|
|
}
|
|
template<typename U>
|
|
ALWAYS_INLINE RefPtr(const NonnullRefPtr<U>& other)
|
|
: m_bits(PtrTraits::as_bits(const_cast<U*>(other.add_ref())))
|
|
{
|
|
}
|
|
template<typename U>
|
|
ALWAYS_INLINE RefPtr(NonnullRefPtr<U>&& other)
|
|
: m_bits(PtrTraits::as_bits(&other.leak_ref()))
|
|
{
|
|
VERIFY(!is_null());
|
|
}
|
|
template<typename U, typename P = RefPtrTraits<U>>
|
|
RefPtr(RefPtr<U, P>&& other)
|
|
: m_bits(PtrTraits::template convert_from<U, P>(other.leak_ref_raw()))
|
|
{
|
|
}
|
|
RefPtr(const RefPtr& other)
|
|
: m_bits(other.add_ref_raw())
|
|
{
|
|
}
|
|
template<typename U, typename P = RefPtrTraits<U>>
|
|
RefPtr(const RefPtr<U, P>& other)
|
|
: m_bits(other.add_ref_raw())
|
|
{
|
|
}
|
|
ALWAYS_INLINE ~RefPtr()
|
|
{
|
|
clear();
|
|
#ifdef SANITIZE_PTRS
|
|
if constexpr (sizeof(T*) == 8)
|
|
m_bits.store(0xe0e0e0e0e0e0e0e0, AK::MemoryOrder::memory_order_relaxed);
|
|
else
|
|
m_bits.store(0xe0e0e0e0, AK::MemoryOrder::memory_order_relaxed);
|
|
#endif
|
|
}
|
|
|
|
template<typename U>
|
|
RefPtr(const OwnPtr<U>&) = delete;
|
|
template<typename U>
|
|
RefPtr& operator=(const OwnPtr<U>&) = delete;
|
|
|
|
void swap(RefPtr& other)
|
|
{
|
|
if (this == &other)
|
|
return;
|
|
|
|
// NOTE: swap is not atomic!
|
|
FlatPtr other_bits = PtrTraits::exchange(other.m_bits, PtrTraits::default_null_value);
|
|
FlatPtr bits = PtrTraits::exchange(m_bits, other_bits);
|
|
PtrTraits::exchange(other.m_bits, bits);
|
|
}
|
|
|
|
template<typename U, typename P = RefPtrTraits<U>>
|
|
void swap(RefPtr<U, P>& other)
|
|
{
|
|
// NOTE: swap is not atomic!
|
|
FlatPtr other_bits = P::exchange(other.m_bits, P::default_null_value);
|
|
FlatPtr bits = PtrTraits::exchange(m_bits, PtrTraits::template convert_from<U, P>(other_bits));
|
|
P::exchange(other.m_bits, P::template convert_from<U, P>(bits));
|
|
}
|
|
|
|
ALWAYS_INLINE RefPtr& operator=(RefPtr&& other)
|
|
{
|
|
if (this != &other)
|
|
assign_raw(other.leak_ref_raw());
|
|
return *this;
|
|
}
|
|
|
|
template<typename U, typename P = RefPtrTraits<U>>
|
|
ALWAYS_INLINE RefPtr& operator=(RefPtr<U, P>&& other)
|
|
{
|
|
assign_raw(PtrTraits::template convert_from<U, P>(other.leak_ref_raw()));
|
|
return *this;
|
|
}
|
|
|
|
template<typename U>
|
|
ALWAYS_INLINE RefPtr& operator=(NonnullRefPtr<U>&& other)
|
|
{
|
|
assign_raw(PtrTraits::as_bits(&other.leak_ref()));
|
|
return *this;
|
|
}
|
|
|
|
ALWAYS_INLINE RefPtr& operator=(const NonnullRefPtr<T>& other)
|
|
{
|
|
assign_raw(PtrTraits::as_bits(other.add_ref()));
|
|
return *this;
|
|
}
|
|
|
|
template<typename U>
|
|
ALWAYS_INLINE RefPtr& operator=(const NonnullRefPtr<U>& other)
|
|
{
|
|
assign_raw(PtrTraits::as_bits(other.add_ref()));
|
|
return *this;
|
|
}
|
|
|
|
ALWAYS_INLINE RefPtr& operator=(const RefPtr& other)
|
|
{
|
|
if (this != &other)
|
|
assign_raw(other.add_ref_raw());
|
|
return *this;
|
|
}
|
|
|
|
template<typename U>
|
|
ALWAYS_INLINE RefPtr& operator=(const RefPtr<U>& other)
|
|
{
|
|
assign_raw(other.add_ref_raw());
|
|
return *this;
|
|
}
|
|
|
|
ALWAYS_INLINE RefPtr& operator=(const T* ptr)
|
|
{
|
|
ref_if_not_null(const_cast<T*>(ptr));
|
|
assign_raw(PtrTraits::as_bits(const_cast<T*>(ptr)));
|
|
return *this;
|
|
}
|
|
|
|
ALWAYS_INLINE RefPtr& operator=(const T& object)
|
|
{
|
|
const_cast<T&>(object).ref();
|
|
assign_raw(PtrTraits::as_bits(const_cast<T*>(&object)));
|
|
return *this;
|
|
}
|
|
|
|
RefPtr& operator=(std::nullptr_t)
|
|
{
|
|
clear();
|
|
return *this;
|
|
}
|
|
|
|
ALWAYS_INLINE bool assign_if_null(RefPtr&& other)
|
|
{
|
|
if (this == &other)
|
|
return is_null();
|
|
return PtrTraits::exchange_if_null(m_bits, other.leak_ref_raw());
|
|
}
|
|
|
|
template<typename U, typename P = RefPtrTraits<U>>
|
|
ALWAYS_INLINE bool assign_if_null(RefPtr<U, P>&& other)
|
|
{
|
|
if (this == &other)
|
|
return is_null();
|
|
return PtrTraits::exchange_if_null(m_bits, PtrTraits::template convert_from<U, P>(other.leak_ref_raw()));
|
|
}
|
|
|
|
ALWAYS_INLINE void clear()
|
|
{
|
|
assign_raw(PtrTraits::default_null_value);
|
|
}
|
|
|
|
bool operator!() const { return PtrTraits::is_null(m_bits.load(AK::MemoryOrder::memory_order_relaxed)); }
|
|
|
|
[[nodiscard]] T* leak_ref()
|
|
{
|
|
FlatPtr bits = PtrTraits::exchange(m_bits, PtrTraits::default_null_value);
|
|
return PtrTraits::as_ptr(bits);
|
|
}
|
|
|
|
NonnullRefPtr<T> release_nonnull()
|
|
{
|
|
FlatPtr bits = PtrTraits::exchange(m_bits, PtrTraits::default_null_value);
|
|
VERIFY(!PtrTraits::is_null(bits));
|
|
return NonnullRefPtr<T>(NonnullRefPtr<T>::Adopt, *PtrTraits::as_ptr(bits));
|
|
}
|
|
|
|
ALWAYS_INLINE T* ptr() { return as_ptr(); }
|
|
ALWAYS_INLINE const T* ptr() const { return as_ptr(); }
|
|
|
|
ALWAYS_INLINE T* operator->()
|
|
{
|
|
return as_nonnull_ptr();
|
|
}
|
|
|
|
ALWAYS_INLINE const T* operator->() const
|
|
{
|
|
return as_nonnull_ptr();
|
|
}
|
|
|
|
ALWAYS_INLINE T& operator*()
|
|
{
|
|
return *as_nonnull_ptr();
|
|
}
|
|
|
|
ALWAYS_INLINE const T& operator*() const
|
|
{
|
|
return *as_nonnull_ptr();
|
|
}
|
|
|
|
ALWAYS_INLINE operator const T*() const { return as_ptr(); }
|
|
ALWAYS_INLINE operator T*() { return as_ptr(); }
|
|
|
|
ALWAYS_INLINE operator bool() { return !is_null(); }
|
|
|
|
bool operator==(std::nullptr_t) const { return is_null(); }
|
|
bool operator!=(std::nullptr_t) const { return !is_null(); }
|
|
|
|
bool operator==(const RefPtr& other) const { return as_ptr() == other.as_ptr(); }
|
|
bool operator!=(const RefPtr& other) const { return as_ptr() != other.as_ptr(); }
|
|
|
|
bool operator==(RefPtr& other) { return as_ptr() == other.as_ptr(); }
|
|
bool operator!=(RefPtr& other) { return as_ptr() != other.as_ptr(); }
|
|
|
|
bool operator==(const T* other) const { return as_ptr() == other; }
|
|
bool operator!=(const T* other) const { return as_ptr() != other; }
|
|
|
|
bool operator==(T* other) { return as_ptr() == other; }
|
|
bool operator!=(T* other) { return as_ptr() != other; }
|
|
|
|
ALWAYS_INLINE bool is_null() const { return PtrTraits::is_null(m_bits.load(AK::MemoryOrder::memory_order_relaxed)); }
|
|
|
|
template<typename U = T, typename EnableIf<IsSame<U, T> && !IsNullPointer<typename PtrTraits::NullType>>::Type* = nullptr>
|
|
typename PtrTraits::NullType null_value() const
|
|
{
|
|
// make sure we are holding a null value
|
|
FlatPtr bits = m_bits.load(AK::MemoryOrder::memory_order_relaxed);
|
|
VERIFY(PtrTraits::is_null(bits));
|
|
return PtrTraits::to_null_value(bits);
|
|
}
|
|
template<typename U = T, typename EnableIf<IsSame<U, T> && !IsNullPointer<typename PtrTraits::NullType>>::Type* = nullptr>
|
|
void set_null_value(typename PtrTraits::NullType value)
|
|
{
|
|
// make sure that new null value would be interpreted as a null value
|
|
FlatPtr bits = PtrTraits::from_null_value(value);
|
|
VERIFY(PtrTraits::is_null(bits));
|
|
assign_raw(bits);
|
|
}
|
|
|
|
private:
|
|
template<typename F>
|
|
void do_while_locked(F f) const
|
|
{
|
|
#ifdef KERNEL
|
|
// We don't want to be pre-empted while we have the lock bit set
|
|
Kernel::ScopedCritical critical;
|
|
#endif
|
|
FlatPtr bits = PtrTraits::lock(m_bits);
|
|
T* ptr = PtrTraits::as_ptr(bits);
|
|
f(ptr);
|
|
PtrTraits::unlock(m_bits, bits);
|
|
}
|
|
|
|
[[nodiscard]] ALWAYS_INLINE FlatPtr leak_ref_raw()
|
|
{
|
|
return PtrTraits::exchange(m_bits, PtrTraits::default_null_value);
|
|
}
|
|
|
|
[[nodiscard]] ALWAYS_INLINE FlatPtr add_ref_raw() const
|
|
{
|
|
#ifdef KERNEL
|
|
// We don't want to be pre-empted while we have the lock bit set
|
|
Kernel::ScopedCritical critical;
|
|
#endif
|
|
// This prevents a race condition between thread A and B:
|
|
// 1. Thread A copies RefPtr, e.g. through assignment or copy constructor,
|
|
// gets the pointer from source, but is pre-empted before adding
|
|
// another reference
|
|
// 2. Thread B calls clear, leak_ref, or release_nonnull on source, and
|
|
// then drops the last reference, causing the object to be deleted
|
|
// 3. Thread A finishes step #1 by attempting to add a reference to
|
|
// the object that was already deleted in step #2
|
|
FlatPtr bits = PtrTraits::lock(m_bits);
|
|
if (T* ptr = PtrTraits::as_ptr(bits))
|
|
ptr->ref();
|
|
PtrTraits::unlock(m_bits, bits);
|
|
return bits;
|
|
}
|
|
|
|
ALWAYS_INLINE void assign_raw(FlatPtr bits)
|
|
{
|
|
FlatPtr prev_bits = PtrTraits::exchange(m_bits, bits);
|
|
unref_if_not_null(PtrTraits::as_ptr(prev_bits));
|
|
}
|
|
|
|
ALWAYS_INLINE T* as_ptr() const
|
|
{
|
|
return PtrTraits::as_ptr(m_bits.load(AK::MemoryOrder::memory_order_relaxed));
|
|
}
|
|
|
|
ALWAYS_INLINE T* as_nonnull_ptr() const
|
|
{
|
|
return as_nonnull_ptr(m_bits.load(AK::MemoryOrder::memory_order_relaxed));
|
|
}
|
|
|
|
ALWAYS_INLINE T* as_nonnull_ptr(FlatPtr bits) const
|
|
{
|
|
VERIFY(!PtrTraits::is_null(bits));
|
|
return PtrTraits::as_ptr(bits);
|
|
}
|
|
|
|
mutable Atomic<FlatPtr> m_bits { PtrTraits::default_null_value };
|
|
};
|
|
|
|
template<typename T>
|
|
struct Formatter<RefPtr<T>> : Formatter<const T*> {
|
|
void format(FormatBuilder& builder, const RefPtr<T>& value)
|
|
{
|
|
Formatter<const T*>::format(builder, value.ptr());
|
|
}
|
|
};
|
|
|
|
template<typename T>
|
|
struct Traits<RefPtr<T>> : public GenericTraits<RefPtr<T>> {
|
|
using PeekType = T*;
|
|
using ConstPeekType = const T*;
|
|
static unsigned hash(const RefPtr<T>& p) { return ptr_hash(p.ptr()); }
|
|
static bool equals(const RefPtr<T>& a, const RefPtr<T>& b) { return a.ptr() == b.ptr(); }
|
|
};
|
|
|
|
template<typename T, typename U>
|
|
inline NonnullRefPtr<T> static_ptr_cast(const NonnullRefPtr<U>& ptr)
|
|
{
|
|
return NonnullRefPtr<T>(static_cast<const T&>(*ptr));
|
|
}
|
|
|
|
template<typename T, typename U, typename PtrTraits = RefPtrTraits<T>>
|
|
inline RefPtr<T> static_ptr_cast(const RefPtr<U>& ptr)
|
|
{
|
|
return RefPtr<T, PtrTraits>(static_cast<const T*>(ptr.ptr()));
|
|
}
|
|
|
|
template<typename T, typename PtrTraitsT, typename U, typename PtrTraitsU>
|
|
inline void swap(RefPtr<T, PtrTraitsT>& a, RefPtr<U, PtrTraitsU>& b)
|
|
{
|
|
a.swap(b);
|
|
}
|
|
|
|
template<typename T>
|
|
inline RefPtr<T> adopt_ref_if_nonnull(T* object)
|
|
{
|
|
if (object)
|
|
return RefPtr<T>(RefPtr<T>::Adopt, *object);
|
|
return {};
|
|
}
|
|
|
|
}
|
|
|
|
using AK::adopt_ref_if_nonnull;
|
|
using AK::RefPtr;
|
|
using AK::static_ptr_cast;
|