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+/*
+ * Copyright 2011 The WebRTC Project Authors. All rights reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+// Originally these classes are from Chromium.
+// http://src.chromium.org/viewvc/chrome/trunk/src/base/memory/ref_counted.h?view=markup
+
+//
+// A smart pointer class for reference counted objects. Use this class instead
+// of calling AddRef and Release manually on a reference counted object to
+// avoid common memory leaks caused by forgetting to Release an object
+// reference. Sample usage:
+//
+// class MyFoo : public RefCounted<MyFoo> {
+// ...
+// };
+//
+// void some_function() {
+// scoped_refptr<MyFoo> foo = new MyFoo();
+// foo->Method(param);
+// // `foo` is released when this function returns
+// }
+//
+// void some_other_function() {
+// scoped_refptr<MyFoo> foo = new MyFoo();
+// ...
+// foo = nullptr; // explicitly releases `foo`
+// ...
+// if (foo)
+// foo->Method(param);
+// }
+//
+// The above examples show how scoped_refptr<T> acts like a pointer to T.
+// Given two scoped_refptr<T> classes, it is also possible to exchange
+// references between the two objects, like so:
+//
+// {
+// scoped_refptr<MyFoo> a = new MyFoo();
+// scoped_refptr<MyFoo> b;
+//
+// b.swap(a);
+// // now, `b` references the MyFoo object, and `a` references null.
+// }
+//
+// To make both `a` and `b` in the above example reference the same MyFoo
+// object, simply use the assignment operator:
+//
+// {
+// scoped_refptr<MyFoo> a = new MyFoo();
+// scoped_refptr<MyFoo> b;
+//
+// b = a;
+// // now, `a` and `b` each own a reference to the same MyFoo object.
+// }
+//
+
+#ifndef API_SCOPED_REFPTR_H_
+#define API_SCOPED_REFPTR_H_
+
+#include <memory>
+#include <utility>
+
+namespace rtc {
+
+template <class T>
+class scoped_refptr {
+ public:
+ typedef T element_type;
+
+ scoped_refptr() : ptr_(nullptr) {}
+ scoped_refptr(std::nullptr_t) : ptr_(nullptr) {} // NOLINT(runtime/explicit)
+
+ explicit scoped_refptr(T* p) : ptr_(p) {
+ if (ptr_)
+ ptr_->AddRef();
+ }
+
+ scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
+ if (ptr_)
+ ptr_->AddRef();
+ }
+
+ template <typename U>
+ scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
+ if (ptr_)
+ ptr_->AddRef();
+ }
+
+ // Move constructors.
+ scoped_refptr(scoped_refptr<T>&& r) noexcept : ptr_(r.release()) {}
+
+ template <typename U>
+ scoped_refptr(scoped_refptr<U>&& r) noexcept : ptr_(r.release()) {}
+
+ ~scoped_refptr() {
+ if (ptr_)
+ ptr_->Release();
+ }
+
+ T* get() const { return ptr_; }
+ explicit operator bool() const { return ptr_ != nullptr; }
+ T& operator*() const { return *ptr_; }
+ T* operator->() const { return ptr_; }
+
+ // Returns the (possibly null) raw pointer, and makes the scoped_refptr hold a
+ // null pointer, all without touching the reference count of the underlying
+ // pointed-to object. The object is still reference counted, and the caller of
+ // release() is now the proud owner of one reference, so it is responsible for
+ // calling Release() once on the object when no longer using it.
+ T* release() {
+ T* retVal = ptr_;
+ ptr_ = nullptr;
+ return retVal;
+ }
+
+ scoped_refptr<T>& operator=(T* p) {
+ // AddRef first so that self assignment should work
+ if (p)
+ p->AddRef();
+ if (ptr_)
+ ptr_->Release();
+ ptr_ = p;
+ return *this;
+ }
+
+ scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
+ return *this = r.ptr_;
+ }
+
+ template <typename U>
+ scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
+ return *this = r.get();
+ }
+
+ scoped_refptr<T>& operator=(scoped_refptr<T>&& r) noexcept {
+ scoped_refptr<T>(std::move(r)).swap(*this);
+ return *this;
+ }
+
+ template <typename U>
+ scoped_refptr<T>& operator=(scoped_refptr<U>&& r) noexcept {
+ scoped_refptr<T>(std::move(r)).swap(*this);
+ return *this;
+ }
+
+ void swap(T** pp) noexcept {
+ T* p = ptr_;
+ ptr_ = *pp;
+ *pp = p;
+ }
+
+ void swap(scoped_refptr<T>& r) noexcept { swap(&r.ptr_); }
+
+ protected:
+ T* ptr_;
+};
+
+template <typename T, typename U>
+bool operator==(const rtc::scoped_refptr<T>& a,
+ const rtc::scoped_refptr<U>& b) {
+ return a.get() == b.get();
+}
+template <typename T, typename U>
+bool operator!=(const rtc::scoped_refptr<T>& a,
+ const rtc::scoped_refptr<U>& b) {
+ return !(a == b);
+}
+
+template <typename T>
+bool operator==(const rtc::scoped_refptr<T>& a, std::nullptr_t) {
+ return a.get() == nullptr;
+}
+
+template <typename T>
+bool operator!=(const rtc::scoped_refptr<T>& a, std::nullptr_t) {
+ return !(a == nullptr);
+}
+
+template <typename T>
+bool operator==(std::nullptr_t, const rtc::scoped_refptr<T>& a) {
+ return a.get() == nullptr;
+}
+
+template <typename T>
+bool operator!=(std::nullptr_t, const rtc::scoped_refptr<T>& a) {
+ return !(a == nullptr);
+}
+
+// Comparison with raw pointer.
+template <typename T, typename U>
+bool operator==(const rtc::scoped_refptr<T>& a, const U* b) {
+ return a.get() == b;
+}
+template <typename T, typename U>
+bool operator!=(const rtc::scoped_refptr<T>& a, const U* b) {
+ return !(a == b);
+}
+
+template <typename T, typename U>
+bool operator==(const T* a, const rtc::scoped_refptr<U>& b) {
+ return a == b.get();
+}
+template <typename T, typename U>
+bool operator!=(const T* a, const rtc::scoped_refptr<U>& b) {
+ return !(a == b);
+}
+
+// Ordered comparison, needed for use as a std::map key.
+template <typename T, typename U>
+bool operator<(const rtc::scoped_refptr<T>& a, const rtc::scoped_refptr<U>& b) {
+ return a.get() < b.get();
+}
+
+} // namespace rtc
+
+#endif // API_SCOPED_REFPTR_H_