EDK: Move ref counting classes to mojo/edk/util.

mojo/edk/system/ref_ptr.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Provides a smart pointer class for intrusively reference-counted objects.
-
-#ifndef MOJO_EDK_SYSTEM_REF_PTR_H_
-#define MOJO_EDK_SYSTEM_REF_PTR_H_
-
-#include <assert.h>
-
-#include <cstddef>
-#include <utility>
-
-#include "mojo/edk/system/ref_ptr_internal.h"
-#include "mojo/public/cpp/system/macros.h"
-
-namespace mojo {
-namespace system {
-
-// A smart pointer class for intrusively reference-counted objects (e.g., those
-// subclassing |RefCountedThreadSafe| -- see ref_counted.h).
-//
-// Such objects require *adoption* to obtain the first |RefPtr|, which is
-// accomplished using |AdoptRef| (see below). (This is due to such objects being
-// constructed with a reference count of 1. The adoption requirement is
-// enforced, at least in Debug builds, by assertions.)
-//
-// E.g., if |Foo| is an intrusively reference-counted class:
-//
-//   // The |AdoptRef| may be put in a static factory method (e.g., if |Foo|'s
-//   // constructor is private).
-//   RefPtr<Foo> my_foo_ptr(AdoptRef(new Foo()));
-//
-//   // Now OK, since "my Foo" has been adopted ...
-//   RefPtr<Foo> another_ptr_to_my_foo(my_foo_ptr.get());
-//
-//   // ... though this would preferable in this situation.
-//   RefPtr<Foo> yet_another_ptr_to_my_foo(my_foo_ptr);
-//
-// Unlike Chromium's |scoped_refptr|, |RefPtr| is only explicitly constructible
-// from a plain pointer (and not assignable). It is however implicitly
-// constructible from |nullptr|. So:
-//
-//   RefPtr<Foo> foo(plain_ptr_to_adopted_foo);    // OK.
-//   foo = plain_ptr_to_adopted_foo;               // Not OK (doesn't compile).
-//   foo = RefPtr<Foo>(plain_ptr_to_adopted_foo);  // OK.
-//   foo = nullptr;                                // OK.
-//
-// And if we have |void MyFunction(RefPtr<Foo> foo)|, calling it using
-// |MyFunction(nullptr)| is also valid.
-//
-// Implementation note: For copy/move constructors/operator=s, we often have
-// templated versions, so that the operation can be done on a |RefPtr<U>|, where
-// |U| is a subclass of |T|. However, we also have non-templated versions with
-// |U = T|, since the templated versions don't count as copy/move
-// constructors/operator=s for the purposes of causing the default copy
-// constructor/operator= to be deleted. E.g., if we didn't declare any
-// non-templated versions, we'd get the default copy constructor/operator= (we'd
-// only not get the default move constructor/operator= by virtue of having a
-// destructor)! (In fact, it'd suffice to only declare a non-templated move
-// constructor or move operator=, which would cause the copy
-// constructor/operator= to be deleted, but for clarity we include explicit
-// non-templated versions of everything.)
-template <typename T>
-class RefPtr {
- public:
-  RefPtr() : ptr_(nullptr) {}
-  RefPtr(std::nullptr_t) : ptr_(nullptr) {}
-
-  // Explicit constructor from a plain pointer (to an object that must have
-  // already been adopted). (Note that in |T::T()|, references to |this| cannot
-  // be taken, since the object being constructed will not have been adopted
-  // yet.)
-  template <typename U>
-  explicit RefPtr(U* p)
-      : ptr_(p) {
-    if (ptr_)
-      ptr_->AddRef();
-  }
-
-  // Copy constructor.
-  RefPtr(const RefPtr<T>& r) : ptr_(r.ptr_) {
-    if (ptr_)
-      ptr_->AddRef();
-  }
-
-  template <typename U>
-  RefPtr(const RefPtr<U>& r)
-      : ptr_(r.ptr_) {
-    if (ptr_)
-      ptr_->AddRef();
-  }
-
-  // Move constructor.
-  RefPtr(RefPtr<T>&& r) : ptr_(r.ptr_) { r.ptr_ = nullptr; }
-
-  template <typename U>
-  RefPtr(RefPtr<U>&& r)
-      : ptr_(r.ptr_) {
-    r.ptr_ = nullptr;
-  }
-
-  // Destructor.
-  ~RefPtr() {
-    if (ptr_)
-      ptr_->Release();
-  }
-
-  T* get() const { return ptr_; }
-
-  T& operator*() const {
-    assert(ptr_);
-    return *ptr_;
-  }
-
-  T* operator->() const {
-    assert(ptr_);
-    return ptr_;
-  }
-
-  // Copy assignment.
-  RefPtr<T>& operator=(const RefPtr<T>& r) {
-    // Call |AddRef()| first so self-assignments work.
-    if (r.ptr_)
-      r.ptr_->AddRef();
-    T* old_ptr = ptr_;
-    ptr_ = r.ptr_;
-    if (old_ptr)
-      old_ptr->Release();
-    return *this;
-  }
-
-  template <typename U>
-  RefPtr<T>& operator=(const RefPtr<U>& r) {
-    // Call |AddRef()| first so self-assignments work.
-    if (r.ptr_)
-      r.ptr_->AddRef();
-    T* old_ptr = ptr_;
-    ptr_ = r.ptr_;
-    if (old_ptr)
-      old_ptr->Release();
-    return *this;
-  }
-
-  // Move assignment.
-  // Note: Like |std::shared_ptr|, we support self-move and move assignment is
-  // equivalent to |RefPtr<T>(std::move(r)).swap(*this)|.
-  RefPtr<T>& operator=(RefPtr<T>&& r) {
-    RefPtr<T>(std::move(r)).swap(*this);
-    return *this;
-  }
-
-  template <typename U>
-  RefPtr<T>& operator=(RefPtr<U>&& r) {
-    RefPtr<T>(std::move(r)).swap(*this);
-    return *this;
-  }
-
-  void swap(RefPtr<T>& r) {
-    T* p = ptr_;
-    ptr_ = r.ptr_;
-    r.ptr_ = p;
-  }
-
-  // Returns a new |RefPtr<T>| with the same contents as this pointer. Useful
-  // when a function takes a |RefPtr<T>&&| argument and the caller wants to
-  // retain its reference (rather than moving it).
-  RefPtr<T> Clone() const { return *this; }
-
-  // For compatibility with base.
-  // TODO(vtl): Remove this when we can.
-  RefPtr<T>&& Pass() MOJO_WARN_UNUSED_RESULT { return std::move(*this); }
-
-  explicit operator bool() const { return !!ptr_; }
-
-  template <typename U>
-  bool operator==(const RefPtr<U>& rhs) const {
-    return ptr_ == rhs.ptr_;
-  }
-
-  template <typename U>
-  bool operator!=(const RefPtr<U>& rhs) const {
-    return !operator==(rhs);
-  }
-
-  template <typename U>
-  bool operator<(const RefPtr<U>& rhs) const {
-    return ptr_ < rhs.ptr_;
-  }
-
- private:
-  template <typename U>
-  friend class RefPtr;
-
-  friend RefPtr<T> AdoptRef<T>(T*);
-
-  enum AdoptTag { ADOPT };
-  RefPtr(T* ptr, AdoptTag) : ptr_(ptr) { assert(ptr_); }
-
-  T* ptr_;
-};
-
-// Adopts a newly-created |T|. Typically used in a static factory method, like:
-//
-//   // static
-//   RefPtr<Foo> Foo::Create() {
-//     return AdoptRef(new Foo());
-//   }
-template <typename T>
-inline RefPtr<T> AdoptRef(T* ptr) {
-#ifndef NDEBUG
-  ptr->Adopt();
-#endif
-  return RefPtr<T>(ptr, RefPtr<T>::ADOPT);
-}
-
-// Creates an intrusively reference counted |T|, producing a |RefPtr<T>| (and
-// performing the required adoption). Use like:
-//
-//   auto my_foo = MakeRefCounted<Foo>(ctor_arg1, ctor_arg2);
-//
-// (|my_foo| will be of type |RefPtr<Foo>|.)
-template <typename T, typename... Args>
-RefPtr<T> MakeRefCounted(Args&&... args) {
-  return internal::MakeRefCountedHelper<T>::MakeRefCounted(
-      std::forward<Args>(args)...);
-}
-
-}  // namespace system
-}  // namespace mojo
-
-#endif  // MOJO_EDK_SYSTEM_REF_PTR_H_