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-rw-r--r--xpcom/base/OwningNonNull.h198
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diff --git a/xpcom/base/OwningNonNull.h b/xpcom/base/OwningNonNull.h
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+/* -*- 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/. */
+
+/* A class for non-null strong pointers to reference-counted objects. */
+
+#ifndef mozilla_OwningNonNull_h
+#define mozilla_OwningNonNull_h
+
+#include "nsAutoPtr.h"
+#include "nsCycleCollectionNoteChild.h"
+
+namespace mozilla {
+
+template<class T>
+class OwningNonNull
+{
+public:
+ OwningNonNull() {}
+
+ MOZ_IMPLICIT OwningNonNull(T& aValue)
+ {
+ init(&aValue);
+ }
+
+ template<class U>
+ MOZ_IMPLICIT OwningNonNull(already_AddRefed<U>&& aValue)
+ {
+ init(aValue);
+ }
+
+ template<class U>
+ MOZ_IMPLICIT OwningNonNull(const OwningNonNull<U>& aValue)
+ {
+ init(aValue);
+ }
+
+ // This is no worse than get() in terms of const handling.
+ operator T&() const
+ {
+ MOZ_ASSERT(mInited);
+ MOZ_ASSERT(mPtr, "OwningNonNull<T> was set to null");
+ return *mPtr;
+ }
+
+ operator T*() const
+ {
+ MOZ_ASSERT(mInited);
+ MOZ_ASSERT(mPtr, "OwningNonNull<T> was set to null");
+ return mPtr;
+ }
+
+ // Conversion to bool is always true, so delete to catch errors
+ explicit operator bool() const = delete;
+
+ T*
+ operator->() const
+ {
+ MOZ_ASSERT(mInited);
+ MOZ_ASSERT(mPtr, "OwningNonNull<T> was set to null");
+ return mPtr;
+ }
+
+ OwningNonNull<T>&
+ operator=(T* aValue)
+ {
+ init(aValue);
+ return *this;
+ }
+
+ OwningNonNull<T>&
+ operator=(T& aValue)
+ {
+ init(&aValue);
+ return *this;
+ }
+
+ template<class U>
+ OwningNonNull<T>&
+ operator=(already_AddRefed<U>&& aValue)
+ {
+ init(aValue);
+ return *this;
+ }
+
+ template<class U>
+ OwningNonNull<T>&
+ operator=(const OwningNonNull<U>& aValue)
+ {
+ init(aValue);
+ return *this;
+ }
+
+ // Don't allow assigning nullptr, it makes no sense
+ void operator=(decltype(nullptr)) = delete;
+
+ already_AddRefed<T> forget()
+ {
+#ifdef DEBUG
+ mInited = false;
+#endif
+ return mPtr.forget();
+ }
+
+ template<class U>
+ void
+ forget(U** aOther)
+ {
+#ifdef DEBUG
+ mInited = false;
+#endif
+ mPtr.forget(aOther);
+ }
+
+ // Make us work with smart pointer helpers that expect a get().
+ T* get() const
+ {
+ MOZ_ASSERT(mInited);
+ MOZ_ASSERT(mPtr);
+ return mPtr;
+ }
+
+ template<typename U>
+ void swap(U& aOther)
+ {
+ mPtr.swap(aOther);
+#ifdef DEBUG
+ mInited = mPtr;
+#endif
+ }
+
+ // We have some consumers who want to check whether we're inited in non-debug
+ // builds as well. Luckily, we have the invariant that we're inited precisely
+ // when mPtr is non-null.
+ bool isInitialized() const
+ {
+ MOZ_ASSERT(!!mPtr == mInited, "mInited out of sync with mPtr?");
+ return mPtr;
+ }
+
+protected:
+ template<typename U>
+ void init(U&& aValue)
+ {
+ mPtr = aValue;
+ MOZ_ASSERT(mPtr);
+#ifdef DEBUG
+ mInited = true;
+#endif
+ }
+
+ RefPtr<T> mPtr;
+#ifdef DEBUG
+ bool mInited = false;
+#endif
+};
+
+template <typename T>
+inline void
+ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
+ OwningNonNull<T>& aField,
+ const char* aName,
+ uint32_t aFlags = 0)
+{
+ CycleCollectionNoteChild(aCallback, aField.get(), aName, aFlags);
+}
+
+} // namespace mozilla
+
+// Declared in nsCOMPtr.h
+template<class T> template<class U>
+nsCOMPtr<T>::nsCOMPtr(const mozilla::OwningNonNull<U>& aOther)
+ : nsCOMPtr(aOther.get())
+{}
+
+template<class T> template<class U>
+nsCOMPtr<T>&
+nsCOMPtr<T>::operator=(const mozilla::OwningNonNull<U>& aOther)
+{
+ return operator=(aOther.get());
+}
+
+// Declared in mozilla/RefPtr.h
+template<class T> template<class U>
+RefPtr<T>::RefPtr(const mozilla::OwningNonNull<U>& aOther)
+ : RefPtr(aOther.get())
+{}
+
+template<class T> template<class U>
+RefPtr<T>&
+RefPtr<T>::operator=(const mozilla::OwningNonNull<U>& aOther)
+{
+ return operator=(aOther.get());
+}
+
+#endif // mozilla_OwningNonNull_h