Move webrtc/{base => rtc_base}

webrtc/base/weak_ptr.h

 /*
  *  Copyright 2016 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.
  */
 
 #ifndef WEBRTC_BASE_WEAK_PTR_H_
 #define WEBRTC_BASE_WEAK_PTR_H_
 
-#include <memory>
 
-#include <utility>
-
-#include "webrtc/base/refcount.h"
-#include "webrtc/base/scoped_ref_ptr.h"
-#include "webrtc/base/sequenced_task_checker.h"
-
-// The implementation is borrowed from chromium except that it does not
-// implement SupportsWeakPtr.
-
-// Weak pointers are pointers to an object that do not affect its lifetime,
-// and which may be invalidated (i.e. reset to nullptr) by the object, or its
-// owner, at any time, most commonly when the object is about to be deleted.
-
-// Weak pointers are useful when an object needs to be accessed safely by one
-// or more objects other than its owner, and those callers can cope with the
-// object vanishing and e.g. tasks posted to it being silently dropped.
-// Reference-counting such an object would complicate the ownership graph and
-// make it harder to reason about the object's lifetime.
-
-// EXAMPLE:
-//
-//  class Controller {
-//   public:
-//    Controller() : weak_factory_(this) {}
-//    void SpawnWorker() { Worker::StartNew(weak_factory_.GetWeakPtr()); }
-//    void WorkComplete(const Result& result) { ... }
-//   private:
-//    // Member variables should appear before the WeakPtrFactory, to ensure
-//    // that any WeakPtrs to Controller are invalidated before its members
-//    // variable's destructors are executed, rendering them invalid.
-//    WeakPtrFactory<Controller> weak_factory_;
-//  };
-//
-//  class Worker {
-//   public:
-//    static void StartNew(const WeakPtr<Controller>& controller) {
-//      Worker* worker = new Worker(controller);
-//      // Kick off asynchronous processing...
-//    }
-//   private:
-//    Worker(const WeakPtr<Controller>& controller)
-//        : controller_(controller) {}
-//    void DidCompleteAsynchronousProcessing(const Result& result) {
-//      if (controller_)
-//        controller_->WorkComplete(result);
-//    }
-//    WeakPtr<Controller> controller_;
-//  };
-//
-// With this implementation a caller may use SpawnWorker() to dispatch multiple
-// Workers and subsequently delete the Controller, without waiting for all
-// Workers to have completed.
-
-// ------------------------- IMPORTANT: Thread-safety -------------------------
-
-// Weak pointers may be passed safely between threads, but must always be
-// dereferenced and invalidated on the same TaskQueue or thread, otherwise
-// checking the pointer would be racey.
-//
-// To ensure correct use, the first time a WeakPtr issued by a WeakPtrFactory
-// is dereferenced, the factory and its WeakPtrs become bound to the calling
-// TaskQueue/thread, and cannot be dereferenced or
-// invalidated on any other TaskQueue/thread. Bound WeakPtrs can still be handed
-// off to other TaskQueues, e.g. to use to post tasks back to object on the
-// bound sequence.
-//
-// Thus, at least one WeakPtr object must exist and have been dereferenced on
-// the correct thread to enforce that other WeakPtr objects will enforce they
-// are used on the desired thread.
-
-namespace rtc {
-
-namespace internal {
-
-class WeakReference {
- public:
-  // Although Flag is bound to a specific sequence, it may be
-  // deleted from another via base::WeakPtr::~WeakPtr().
-  class Flag : public RefCountInterface {
-   public:
-    Flag();
-
-    void Invalidate();
-    bool IsValid() const;
-
-   private:
-    friend class RefCountedObject<Flag>;
-
-    ~Flag() override;
-
-    SequencedTaskChecker checker_;
-    bool is_valid_;
-  };
-
-  WeakReference();
-  explicit WeakReference(const Flag* flag);
-  ~WeakReference();
-
-  WeakReference(WeakReference&& other);
-  WeakReference(const WeakReference& other);
-  WeakReference& operator=(WeakReference&& other) = default;
-  WeakReference& operator=(const WeakReference& other) = default;
-
-  bool is_valid() const;
-
- private:
-  scoped_refptr<const Flag> flag_;
-};
-
-class WeakReferenceOwner {
- public:
-  WeakReferenceOwner();
-  ~WeakReferenceOwner();
-
-  WeakReference GetRef() const;
-
-  bool HasRefs() const { return flag_.get() && !flag_->HasOneRef(); }
-
-  void Invalidate();
-
- private:
-  SequencedTaskChecker checker_;
-  mutable scoped_refptr<RefCountedObject<WeakReference::Flag>> flag_;
-};
-
-// This class simplifies the implementation of WeakPtr's type conversion
-// constructor by avoiding the need for a public accessor for ref_.  A
-// WeakPtr<T> cannot access the private members of WeakPtr<U>, so this
-// base class gives us a way to access ref_ in a protected fashion.
-class WeakPtrBase {
- public:
-  WeakPtrBase();
-  ~WeakPtrBase();
-
-  WeakPtrBase(const WeakPtrBase& other) = default;
-  WeakPtrBase(WeakPtrBase&& other) = default;
-  WeakPtrBase& operator=(const WeakPtrBase& other) = default;
-  WeakPtrBase& operator=(WeakPtrBase&& other) = default;
-
- protected:
-  explicit WeakPtrBase(const WeakReference& ref);
-
-  WeakReference ref_;
-};
-
-}  // namespace internal
-
-template <typename T>
-class WeakPtrFactory;
-
-template <typename T>
-class WeakPtr : public internal::WeakPtrBase {
- public:
-  WeakPtr() : ptr_(nullptr) {}
-
-  // Allow conversion from U to T provided U "is a" T. Note that this
-  // is separate from the (implicit) copy and move constructors.
-  template <typename U>
-  WeakPtr(const WeakPtr<U>& other)
-      : internal::WeakPtrBase(other), ptr_(other.ptr_) {}
-  template <typename U>
-  WeakPtr(WeakPtr<U>&& other)
-      : internal::WeakPtrBase(std::move(other)), ptr_(other.ptr_) {}
-
-  T* get() const { return ref_.is_valid() ? ptr_ : nullptr; }
-
-  T& operator*() const {
-    RTC_DCHECK(get() != nullptr);
-    return *get();
-  }
-  T* operator->() const {
-    RTC_DCHECK(get() != nullptr);
-    return get();
-  }
-
-  void reset() {
-    ref_ = internal::WeakReference();
-    ptr_ = nullptr;
-  }
-
-  // Allow conditionals to test validity, e.g. if (weak_ptr) {...};
-  explicit operator bool() const { return get() != nullptr; }
-
- private:
-  template <typename U>
-  friend class WeakPtr;
-  friend class WeakPtrFactory<T>;
-
-  WeakPtr(const internal::WeakReference& ref, T* ptr)
-      : internal::WeakPtrBase(ref), ptr_(ptr) {}
-
-  // This pointer is only valid when ref_.is_valid() is true.  Otherwise, its
-  // value is undefined (as opposed to nullptr).
-  T* ptr_;
-};
-
-// Allow callers to compare WeakPtrs against nullptr to test validity.
-template <class T>
-bool operator!=(const WeakPtr<T>& weak_ptr, std::nullptr_t) {
-  return !(weak_ptr == nullptr);
-}
-template <class T>
-bool operator!=(std::nullptr_t, const WeakPtr<T>& weak_ptr) {
-  return weak_ptr != nullptr;
-}
-template <class T>
-bool operator==(const WeakPtr<T>& weak_ptr, std::nullptr_t) {
-  return weak_ptr.get() == nullptr;
-}
-template <class T>
-bool operator==(std::nullptr_t, const WeakPtr<T>& weak_ptr) {
-  return weak_ptr == nullptr;
-}
-
-// A class may be composed of a WeakPtrFactory and thereby
-// control how it exposes weak pointers to itself.  This is helpful if you only
-// need weak pointers within the implementation of a class.  This class is also
-// useful when working with primitive types.  For example, you could have a
-// WeakPtrFactory<bool> that is used to pass around a weak reference to a bool.
-
-// Note that GetWeakPtr must be called on one and only one TaskQueue or thread
-// and the WeakPtr must only be dereferenced and invalidated on that same
-// TaskQueue/thread. A WeakPtr instance can be copied and posted to other
-// sequences though as long as it is not dereferenced (WeakPtr<T>::get()).
-template <class T>
-class WeakPtrFactory {
- public:
-  explicit WeakPtrFactory(T* ptr) : ptr_(ptr) {}
-
-  ~WeakPtrFactory() { ptr_ = nullptr; }
-
-  WeakPtr<T> GetWeakPtr() {
-    RTC_DCHECK(ptr_);
-    return WeakPtr<T>(weak_reference_owner_.GetRef(), ptr_);
-  }
-
-  // Call this method to invalidate all existing weak pointers.
-  void InvalidateWeakPtrs() {
-    RTC_DCHECK(ptr_);
-    weak_reference_owner_.Invalidate();
-  }
-
-  // Call this method to determine if any weak pointers exist.
-  bool HasWeakPtrs() const {
-    RTC_DCHECK(ptr_);
-    return weak_reference_owner_.HasRefs();
-  }
-
- private:
-  internal::WeakReferenceOwner weak_reference_owner_;
-  T* ptr_;
-  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(WeakPtrFactory);
-};
-
-}  // namespace rtc
+// This header is deprecated and is just left here temporarily during
+// refactoring. See https://bugs.webrtc.org/7634 for more details.
+#include "webrtc/rtc_base/weak_ptr.h"
 
 #endif  // WEBRTC_BASE_WEAK_PTR_H_