summaryrefslogtreecommitdiffstats
path: root/xpcom/base/StaticPtr.h
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--xpcom/base/StaticPtr.h235
1 files changed, 235 insertions, 0 deletions
diff --git a/xpcom/base/StaticPtr.h b/xpcom/base/StaticPtr.h
new file mode 100644
index 0000000000..38fcd82f97
--- /dev/null
+++ b/xpcom/base/StaticPtr.h
@@ -0,0 +1,235 @@
+/* -*- 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_StaticPtr_h
+#define mozilla_StaticPtr_h
+
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+
+/**
+ * StaticAutoPtr and StaticRefPtr are like UniquePtr and RefPtr, except they
+ * are suitable for use as global variables.
+ *
+ * In particular, a global instance of Static{Auto,Ref}Ptr doesn't cause the
+ * compiler to emit a static initializer.
+ *
+ * Since the compiler guarantees that all global variables are initialized to
+ * 0, the default constexpr constructors will result in no actual code being
+ * generated. Since we rely on this, the clang plugin, run as part of our
+ * "static analysis" builds, makes it a compile-time error to use
+ * Static{Auto,Ref}Ptr as anything except a global variable.
+ *
+ * Static{Auto,Ref}Ptr have a limited interface as compared to ns{Auto,Ref}Ptr;
+ * this is intentional, since their range of acceptable uses is smaller.
+ */
+
+template <class T>
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticAutoPtr {
+ public:
+ constexpr StaticAutoPtr() = default;
+ StaticAutoPtr(const StaticAutoPtr&) = delete;
+
+ StaticAutoPtr<T>& operator=(T* aRhs) {
+ Assign(aRhs);
+ return *this;
+ }
+
+ T* get() const { return mRawPtr; }
+
+ operator T*() const { return get(); }
+
+ T* operator->() const {
+ MOZ_ASSERT(mRawPtr);
+ return get();
+ }
+
+ T& operator*() const { return *get(); }
+
+ T* forget() {
+ T* temp = mRawPtr;
+ mRawPtr = nullptr;
+ return temp;
+ }
+
+ private:
+ void Assign(T* aNewPtr) {
+ MOZ_ASSERT(!aNewPtr || mRawPtr != aNewPtr);
+ T* oldPtr = mRawPtr;
+ mRawPtr = aNewPtr;
+ delete oldPtr;
+ }
+
+ T* mRawPtr = nullptr;
+};
+
+template <class T>
+class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticRefPtr {
+ public:
+ constexpr StaticRefPtr() = default;
+ StaticRefPtr(const StaticRefPtr&) = delete;
+
+ StaticRefPtr<T>& operator=(T* aRhs) {
+ AssignWithAddref(aRhs);
+ return *this;
+ }
+
+ StaticRefPtr<T>& operator=(const StaticRefPtr<T>& aRhs) {
+ return (this = aRhs.mRawPtr);
+ }
+
+ StaticRefPtr<T>& operator=(already_AddRefed<T>& aRhs) {
+ AssignAssumingAddRef(aRhs.take());
+ return *this;
+ }
+
+ template <typename U>
+ StaticRefPtr<T>& operator=(RefPtr<U>&& aRhs) {
+ AssignAssumingAddRef(aRhs.forget().take());
+ return *this;
+ }
+
+ StaticRefPtr<T>& operator=(already_AddRefed<T>&& aRhs) {
+ AssignAssumingAddRef(aRhs.take());
+ return *this;
+ }
+
+ already_AddRefed<T> forget() {
+ T* temp = mRawPtr;
+ mRawPtr = nullptr;
+ return already_AddRefed<T>(temp);
+ }
+
+ T* get() const { return mRawPtr; }
+
+ operator T*() const { return get(); }
+
+ T* operator->() const {
+ MOZ_ASSERT(mRawPtr);
+ return get();
+ }
+
+ T& operator*() const { return *get(); }
+
+ private:
+ void AssignWithAddref(T* aNewPtr) {
+ if (aNewPtr) {
+ RefPtrTraits<T>::AddRef(aNewPtr);
+ }
+ AssignAssumingAddRef(aNewPtr);
+ }
+
+ void AssignAssumingAddRef(T* aNewPtr) {
+ T* oldPtr = mRawPtr;
+ mRawPtr = aNewPtr;
+ if (oldPtr) {
+ RefPtrTraits<T>::Release(oldPtr);
+ }
+ }
+
+ T* MOZ_OWNING_REF mRawPtr = nullptr;
+};
+
+namespace StaticPtr_internal {
+class Zero;
+} // namespace StaticPtr_internal
+
+#define REFLEXIVE_EQUALITY_OPERATORS(type1, type2, eq_fn, ...) \
+ template <__VA_ARGS__> \
+ inline bool operator==(type1 lhs, type2 rhs) { \
+ return eq_fn; \
+ } \
+ \
+ template <__VA_ARGS__> \
+ inline bool operator==(type2 lhs, type1 rhs) { \
+ return rhs == lhs; \
+ } \
+ \
+ template <__VA_ARGS__> \
+ inline bool operator!=(type1 lhs, type2 rhs) { \
+ return !(lhs == rhs); \
+ } \
+ \
+ template <__VA_ARGS__> \
+ inline bool operator!=(type2 lhs, type1 rhs) { \
+ return !(lhs == rhs); \
+ }
+
+// StaticAutoPtr (in)equality operators
+
+template <class T, class U>
+inline bool operator==(const StaticAutoPtr<T>& aLhs,
+ const StaticAutoPtr<U>& aRhs) {
+ return aLhs.get() == aRhs.get();
+}
+
+template <class T, class U>
+inline bool operator!=(const StaticAutoPtr<T>& aLhs,
+ const StaticAutoPtr<U>& aRhs) {
+ return !(aLhs == aRhs);
+}
+
+REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, const U*,
+ lhs.get() == rhs, class T, class U)
+
+REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, U*, lhs.get() == rhs,
+ class T, class U)
+
+// Let us compare StaticAutoPtr to 0.
+REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, StaticPtr_internal::Zero*,
+ lhs.get() == nullptr, class T)
+
+// StaticRefPtr (in)equality operators
+
+template <class T, class U>
+inline bool operator==(const StaticRefPtr<T>& aLhs,
+ const StaticRefPtr<U>& aRhs) {
+ return aLhs.get() == aRhs.get();
+}
+
+template <class T, class U>
+inline bool operator!=(const StaticRefPtr<T>& aLhs,
+ const StaticRefPtr<U>& aRhs) {
+ return !(aLhs == aRhs);
+}
+
+REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, const U*, lhs.get() == rhs,
+ class T, class U)
+
+REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, U*, lhs.get() == rhs,
+ class T, class U)
+
+// Let us compare StaticRefPtr to 0.
+REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, StaticPtr_internal::Zero*,
+ lhs.get() == nullptr, class T)
+
+#undef REFLEXIVE_EQUALITY_OPERATORS
+
+} // namespace mozilla
+
+// Declared in mozilla/RefPtr.h
+template <class T>
+template <class U>
+RefPtr<T>::RefPtr(const mozilla::StaticRefPtr<U>& aOther)
+ : RefPtr(aOther.get()) {}
+
+template <class T>
+template <class U>
+RefPtr<T>& RefPtr<T>::operator=(const mozilla::StaticRefPtr<U>& aOther) {
+ return operator=(aOther.get());
+}
+
+template <class T>
+inline already_AddRefed<T> do_AddRef(const mozilla::StaticRefPtr<T>& aObj) {
+ RefPtr<T> ref(aObj);
+ return ref.forget();
+}
+
+#endif