import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

ipc/mscom/WeakRef.h

@@ -0,0 +1,104 @@
+/* -*- 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/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
+