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// Copyright 2023 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef SRC_DAWN_COMMON_WEAKREFSUPPORT_H_
#define SRC_DAWN_COMMON_WEAKREFSUPPORT_H_
#include "dawn/common/Compiler.h"
#include "dawn/common/Ref.h"
namespace dawn {
template <typename T>
class WeakRef;
namespace detail {
// Indirection layer to provide external ref-counting for WeakRefs.
class WeakRefData : public RefCounted {
public:
explicit WeakRefData(RefCounted* value);
void Invalidate();
// Tries to return a valid Ref to `mValue` if it's internal refcount is not already 0. If the
// internal refcount has already reached 0, returns nullptr instead.
Ref<RefCounted> TryGetRef();
// Returns the raw pointer to the RefCounted. In general, this is an unsafe operation because
// the RefCounted can become invalid after being retrieved.
RefCounted* UnsafeGet() const;
private:
std::mutex mMutex;
RefCounted* mValue = nullptr;
};
// Interface base class used to enable compile-time verification of WeakRefSupport functions.
class WeakRefSupportBase {
protected:
explicit WeakRefSupportBase(Ref<detail::WeakRefData> data);
virtual ~WeakRefSupportBase();
private:
template <typename T>
friend class ::dawn::WeakRef;
Ref<detail::WeakRefData> mData;
};
} // namespace detail
// Class that should be extended to enable WeakRefs for the type.
template <typename T>
class WeakRefSupport : public detail::WeakRefSupportBase {
public:
#if DAWN_COMPILER_IS(CLANG)
// Note that the static cast below fails CFI builds due to the cast. The cast itself is
// safe so we suppress the failure. See the following link regarding the cast:
// https://stackoverflow.com/questions/73172193/can-you-static-cast-this-to-a-derived-class-in-a-base-class-constructor-then-u,
DAWN_NO_SANITIZE("cfi-derived-cast")
#endif
WeakRefSupport()
: WeakRefSupportBase(AcquireRef(new detail::WeakRefData(static_cast<T*>(this)))) {}
};
} // namespace dawn
#endif // SRC_DAWN_COMMON_WEAKREFSUPPORT_H_