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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_interceptor_h
#define mozilla_mscom_interceptor_h
#include "mozilla/Move.h"
#include "mozilla/Mutex.h"
#include "nsTArray.h"
#include "mozilla/mscom/Ptr.h"
#include "mozilla/mscom/WeakRef.h"
#include "mozilla/RefPtr.h"
#include <callobj.h>
namespace mozilla {
namespace mscom {
// {8831EB53-A937-42BC-9921-B3E1121FDF86}
DEFINE_GUID(IID_IInterceptorSink,
0x8831eb53, 0xa937, 0x42bc, 0x99, 0x21, 0xb3, 0xe1, 0x12, 0x1f, 0xdf, 0x86);
struct IInterceptorSink : public ICallFrameEvents
{
virtual STDMETHODIMP SetInterceptor(IWeakReference* aInterceptor) = 0;
};
// {3710799B-ECA2-4165-B9B0-3FA1E4A9B230}
DEFINE_GUID(IID_IInterceptor,
0x3710799b, 0xeca2, 0x4165, 0xb9, 0xb0, 0x3f, 0xa1, 0xe4, 0xa9, 0xb2, 0x30);
struct IInterceptor : public IUnknown
{
virtual STDMETHODIMP GetTargetForIID(REFIID aIid, InterceptorTargetPtr& aTarget) = 0;
virtual STDMETHODIMP GetInterceptorForIID(REFIID aIid,
void** aOutInterceptor) = 0;
};
/**
* The COM interceptor is the core functionality in mscom that allows us to
* redirect method calls to different threads. It emulates the vtable of a
* target interface. When a call is made on this emulated vtable, the call is
* packaged up into an instance of the ICallFrame interface which may be passed
* to other contexts for execution.
*
* In order to accomplish this, COM itself provides the CoGetInterceptor
* function, which instantiates an ICallInterceptor. Note, however, that
* ICallInterceptor only works on a single interface; we need to be able to
* interpose QueryInterface calls so that we can instantiate a new
* ICallInterceptor for each new interface that is requested.
*
* We accomplish this by using COM aggregation, which means that the
* ICallInterceptor delegates its IUnknown implementation to its outer object
* (the mscom::Interceptor we implement and control).
*/
class Interceptor final : public WeakReferenceSupport
, public IInterceptor
{
public:
static HRESULT Create(STAUniquePtr<IUnknown> aTarget, IInterceptorSink* aSink,
REFIID aIid, void** aOutput);
// IUnknown
STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override;
STDMETHODIMP_(ULONG) AddRef() override;
STDMETHODIMP_(ULONG) Release() override;
// IInterceptor
STDMETHODIMP GetTargetForIID(REFIID aIid, InterceptorTargetPtr& aTarget) override;
STDMETHODIMP GetInterceptorForIID(REFIID aIid, void** aOutInterceptor) override;
private:
struct MapEntry
{
MapEntry(REFIID aIid, IUnknown* aInterceptor, IUnknown* aTargetInterface)
: mIID(aIid)
, mInterceptor(aInterceptor)
, mTargetInterface(aTargetInterface)
{}
IID mIID;
IUnknown* mInterceptor;
IUnknown* mTargetInterface;
};
private:
Interceptor(STAUniquePtr<IUnknown> aTarget, IInterceptorSink* aSink);
~Interceptor();
MapEntry* Lookup(REFIID aIid);
HRESULT QueryInterfaceTarget(REFIID aIid, void** aOutput);
HRESULT ThreadSafeQueryInterface(REFIID aIid,
IUnknown** aOutInterface) override;
HRESULT CreateInterceptor(REFIID aIid, IUnknown* aOuter, IUnknown** aOutput);
private:
STAUniquePtr<IUnknown> mTarget;
RefPtr<IInterceptorSink> mEventSink;
mozilla::Mutex mMutex; // Guards mInterceptorMap
// Using a nsTArray since the # of interfaces is not going to be very high
nsTArray<MapEntry> mInterceptorMap;
};
template <typename InterfaceT>
inline HRESULT
CreateInterceptor(STAUniquePtr<InterfaceT> aTargetInterface,
IInterceptorSink* aEventSink,
InterfaceT** aOutInterface)
{
if (!aTargetInterface || !aEventSink) {
return E_INVALIDARG;
}
REFIID iidTarget = __uuidof(aTargetInterface);
STAUniquePtr<IUnknown> targetUnknown(aTargetInterface.release());
return Interceptor::Create(Move(targetUnknown), aEventSink, iidTarget,
(void**)aOutInterface);
}
} // namespace mscom
} // namespace mozilla
#endif // mozilla_mscom_interceptor_h
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