1 files changed, 125 insertions, 0 deletions
diff --git a/ipc/mscom/Interceptor.h b/ipc/mscom/Interceptor.h
new file mode 100644
index 000000000..ecddbddf5
--- /dev/null
+++ b/ipc/mscom/Interceptor.h
@@ -0,0 +1,125 @@
+/* -*- 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_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