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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_mscom_WeakRef_h
#define mozilla_mscom_WeakRef_h
#include <guiddef.h>
#include <unknwn.h>
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/RefPtr.h"
#include "nsISupportsImpl.h"
/**
* Thread-safe weak references for COM that works pre-Windows 8 and do not
* require WinRT.
*/
namespace mozilla {
namespace mscom {
struct IWeakReferenceSource;
class WeakReferenceSupport;
namespace detail {
class SharedRef final {
public:
explicit SharedRef(WeakReferenceSupport* aSupport);
void Lock();
void Unlock();
HRESULT ToStrongRef(IWeakReferenceSource** aOutStringReference);
HRESULT Resolve(REFIID aIid, void** aOutStrongReference);
void Clear();
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SharedRef)
SharedRef(const SharedRef&) = delete;
SharedRef(SharedRef&&) = delete;
SharedRef& operator=(const SharedRef&) = delete;
SharedRef& operator=(SharedRef&&) = delete;
private:
~SharedRef();
private:
CRITICAL_SECTION mCS;
WeakReferenceSupport* mSupport;
};
} // namespace detail
// {F841AEFA-064C-49A4-B73D-EBD14A90F012}
DEFINE_GUID(IID_IWeakReference, 0xf841aefa, 0x64c, 0x49a4, 0xb7, 0x3d, 0xeb,
0xd1, 0x4a, 0x90, 0xf0, 0x12);
struct IWeakReference : public IUnknown {
virtual STDMETHODIMP ToStrongRef(
IWeakReferenceSource** aOutStrongReference) = 0;
virtual STDMETHODIMP Resolve(REFIID aIid, void** aOutStrongReference) = 0;
};
// {87611F0C-9BBB-4F78-9D43-CAC5AD432CA1}
DEFINE_GUID(IID_IWeakReferenceSource, 0x87611f0c, 0x9bbb, 0x4f78, 0x9d, 0x43,
0xca, 0xc5, 0xad, 0x43, 0x2c, 0xa1);
struct IWeakReferenceSource : public IUnknown {
virtual STDMETHODIMP GetWeakReference(IWeakReference** aOutWeakRef) = 0;
};
class WeakRef;
class WeakReferenceSupport : public IWeakReferenceSource {
public:
enum class Flags { eNone = 0, eDestroyOnMainThread = 1 };
// IUnknown
STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override;
STDMETHODIMP_(ULONG) AddRef() override;
STDMETHODIMP_(ULONG) Release() override;
// IWeakReferenceSource
STDMETHODIMP GetWeakReference(IWeakReference** aOutWeakRef) override;
protected:
explicit WeakReferenceSupport(Flags aFlags);
virtual ~WeakReferenceSupport() = default;
virtual HRESULT WeakRefQueryInterface(REFIID aIid,
IUnknown** aOutInterface) = 0;
class MOZ_RAII StabilizeRefCount final {
public:
explicit StabilizeRefCount(WeakReferenceSupport& aObject);
~StabilizeRefCount();
StabilizeRefCount(const StabilizeRefCount&) = delete;
StabilizeRefCount(StabilizeRefCount&&) = delete;
StabilizeRefCount& operator=(const StabilizeRefCount&) = delete;
StabilizeRefCount& operator=(StabilizeRefCount&&) = delete;
private:
WeakReferenceSupport& mObject;
};
friend class StabilizeRefCount;
private:
RefPtr<detail::SharedRef> mSharedRef;
ULONG mRefCnt;
Flags mFlags;
};
class WeakRef final : public IWeakReference {
public:
// IUnknown
STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override;
STDMETHODIMP_(ULONG) AddRef() override;
STDMETHODIMP_(ULONG) Release() override;
// IWeakReference
STDMETHODIMP ToStrongRef(IWeakReferenceSource** aOutStrongReference) override;
STDMETHODIMP Resolve(REFIID aIid, void** aOutStrongReference) override;
explicit WeakRef(RefPtr<detail::SharedRef>& aSharedRef);
private:
~WeakRef() = default;
Atomic<ULONG> mRefCnt;
RefPtr<detail::SharedRef> mSharedRef;
};
} // namespace mscom
} // namespace mozilla
#endif // mozilla_mscom_WeakRef_h
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