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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/Mutex.h"
#include "nsTArray.h"
/**
* Thread-safe weak references for COM that works pre-Windows 8 and do not
* require WinRT.
*/
namespace mozilla {
namespace mscom {
// {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 Resolve(REFIID aIid, void** aOutStringReference) = 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();
virtual HRESULT ThreadSafeQueryInterface(REFIID aIid,
IUnknown** aOutInterface) = 0;
private:
void ClearWeakRefs();
private:
// Using a raw CRITICAL_SECTION here because it can be reentered
CRITICAL_SECTION mCS;
ULONG mRefCnt;
nsTArray<WeakRef*> mWeakRefs;
Flags mFlags;
};
class WeakRef : public IWeakReference
{
public:
// IUnknown
STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override;
STDMETHODIMP_(ULONG) AddRef() override;
STDMETHODIMP_(ULONG) Release() override;
// IWeakReference
STDMETHODIMP Resolve(REFIID aIid, void** aOutStrongReference) override;
explicit WeakRef(WeakReferenceSupport* aSupport);
void Clear();
private:
ULONG mRefCnt;
mozilla::Mutex mMutex; // Protects mSupport
WeakReferenceSupport* mSupport;
};
} // namespace mscom
} // namespace mozilla
#endif // mozilla_mscom_WeakRef_h
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