xpcom/base/nsWeakReference.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 // nsWeakReference.cpp
   8
   9 #include "mozilla/Attributes.h"
  10
  11 #include "nsWeakReference.h"
  12 #include "nsCOMPtr.h"
  13 #include "nsDebug.h"
  14
  15 class nsWeakReference final : public nsIWeakReference {
  16  public:
  17   // nsISupports...
  18   NS_DECL_ISUPPORTS
  19
  20   // nsIWeakReference...
  21   NS_DECL_NSIWEAKREFERENCE
  22
  23  private:
  24   friend class nsSupportsWeakReference;
  25
  26   explicit nsWeakReference(nsSupportsWeakReference* aReferent)
  27       : nsIWeakReference(aReferent)
  28   // ...I can only be constructed by an |nsSupportsWeakReference|
  29   {}
  30
  31   ~nsWeakReference()
  32   // ...I will only be destroyed by calling |delete| myself.
  33   {
  34     MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
  35     if (mObject) {
  36       static_cast<nsSupportsWeakReference*>(mObject)->NoticeProxyDestruction();
  37     }
  38   }
  39
  40   void NoticeReferentDestruction()
  41   // ...called (only) by an |nsSupportsWeakReference| from _its_ dtor.
  42   {
  43     MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
  44     mObject = nullptr;
  45   }
  46 };
  47
  48 nsresult nsQueryReferent::operator()(const nsIID& aIID, void** aAnswer) const {
  49   nsresult status;
  50   if (mWeakPtr) {
  51     if (NS_FAILED(status = mWeakPtr->QueryReferent(aIID, aAnswer))) {
  52       *aAnswer = 0;
  53     }
  54   } else {
  55     status = NS_ERROR_NULL_POINTER;
  56   }
  57
  58   if (mErrorPtr) {
  59     *mErrorPtr = status;
  60   }
  61   return status;
  62 }
  63
  64 nsIWeakReference* NS_GetWeakReference(nsISupportsWeakReference* aInstancePtr,
  65                                       nsresult* aErrorPtr) {
  66   nsresult status;
  67
  68   nsIWeakReference* result = nullptr;
  69
  70   if (aInstancePtr) {
  71     status = aInstancePtr->GetWeakReference(&result);
  72   } else {
  73     status = NS_ERROR_NULL_POINTER;
  74   }
  75
  76   if (aErrorPtr) {
  77     *aErrorPtr = status;
  78   }
  79
  80   return result;
  81 }
  82
  83 nsIWeakReference*  // or else |already_AddRefed<nsIWeakReference>|
  84 NS_GetWeakReference(nsISupports* aInstancePtr, nsresult* aErrorPtr) {
  85   nsresult status;
  86
  87   nsIWeakReference* result = nullptr;
  88
  89   if (aInstancePtr) {
  90     nsCOMPtr<nsISupportsWeakReference> factoryPtr =
  91         do_QueryInterface(aInstancePtr, &status);
  92     if (factoryPtr) {
  93       status = factoryPtr->GetWeakReference(&result);
  94     }
  95     // else, |status| has already been set by |do_QueryInterface|
  96   } else {
  97     status = NS_ERROR_NULL_POINTER;
  98   }
  99
 100   if (aErrorPtr) {
 101     *aErrorPtr = status;
 102   }
 103   return result;
 104 }
 105
 106 nsresult nsSupportsWeakReference::GetWeakReference(
 107     nsIWeakReference** aInstancePtr) {
 108   if (!aInstancePtr) {
 109     return NS_ERROR_NULL_POINTER;
 110   }
 111
 112   if (!mProxy) {
 113     mProxy = new nsWeakReference(this);
 114   } else {
 115     MOZ_WEAKREF_ASSERT_OWNINGTHREAD_DELEGATED(mProxy);
 116   }
 117   RefPtr<nsWeakReference> rval = mProxy;
 118   rval.forget(aInstancePtr);
 119
 120   return NS_OK;
 121 }
 122
 123 NS_IMPL_ISUPPORTS(nsWeakReference, nsIWeakReference)
 124
 125 NS_IMETHODIMP
 126 nsWeakReference::QueryReferentFromScript(const nsIID& aIID,
 127                                          void** aInstancePtr) {
 128   return QueryReferent(aIID, aInstancePtr);
 129 }
 130
 131 nsresult nsIWeakReference::QueryReferent(const nsIID& aIID,
 132                                          void** aInstancePtr) {
 133   MOZ_WEAKREF_ASSERT_OWNINGTHREAD;
 134
 135   if (!mObject) {
 136     return NS_ERROR_NULL_POINTER;
 137   }
 138
 139   return mObject->QueryInterface(aIID, aInstancePtr);
 140 }
 141
 142 size_t nsWeakReference::SizeOfOnlyThis(mozilla::MallocSizeOf aMallocSizeOf) {
 143   return aMallocSizeOf(this);
 144 }
 145
 146 void nsSupportsWeakReference::ClearWeakReferences() {
 147   if (mProxy) {
 148     mProxy->NoticeReferentDestruction();
 149     mProxy = nullptr;
 150   }
 151 }