Add move support for scoped_refptr.

base/memory/ref_counted.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_MEMORY_REF_COUNTED_H_
 #define BASE_MEMORY_REF_COUNTED_H_
 
 #include <cassert>
 #include <iosfwd>
 
 #include "base/atomic_ref_count.h"
 #include "base/base_export.h"
 #include "base/compiler_specific.h"
 #ifndef NDEBUG
 #include "base/logging.h"
 #endif
+#include "base/move.h"
 #include "base/threading/thread_collision_warner.h"
 #include "build/build_config.h"
 
 namespace base {
 
 namespace subtle {
 
 class BASE_EXPORT RefCountedBase {
  public:
   bool HasOneRef() const { return ref_count_ == 1; }
@@ skipping 230 matching lines @@
 //   {
 //     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.
 //   }
 //
 template <class T>
 class scoped_refptr {
+  TYPE_WITH_MOVE_CONSTRUCTOR_FOR_CPP_03(scoped_refptr)
  public:
   typedef T element_type;
 
   scoped_refptr() : ptr_(NULL) {
   }
 
   scoped_refptr(T* p) : ptr_(p) {
     if (ptr_)
       AddRef(ptr_);
   }
 
   scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
     if (ptr_)
       AddRef(ptr_);
   }
 
   template <typename U>
   scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
     if (ptr_)
       AddRef(ptr_);
   }
 
+  template <typename U>
+  scoped_refptr(scoped_refptr<U>&& r) : ptr_(r.get()) {
+    r.ptr_ = nullptr;
+  }
+
   ~scoped_refptr() {
     if (ptr_)
       Release(ptr_);
   }
 
   T* get() const { return ptr_; }
 
   T& operator*() const {
     assert(ptr_ != NULL);
     return *ptr_;
@@ skipping 17 matching lines @@
 
   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();
   }
 
+  template <typename U>
+  scoped_refptr<T>& operator=(scoped_refptr<U>&& r) {
+    scoped_refptr<T>(r.Pass()).swap(*this);

[danakj, 2015/04/10 19:44:24]

This is:
temp.ptr_ = r.ptr_;
r.ptr_ = nullptr;
T* p = ptr_;
ptr_ = temp.ptr_;
temp.ptr_ = p;

You could do this as:
T* p = r.ptr_;
r.ptr_ = nullptr;
ptr_ = p;

And get the same thing?

[Kibeom Kim (inactive), 2015/04/12 07:35:14]

Yeah you're right. it also needs |if (ptr_) Release(ptr_);| to be identical.
(corresponds to the temp destructor)

T* p = r.get();
r.ptr_ = nullptr;
if (ptr_)
  Release(ptr_);
ptr_ = p;

+    return *this;
+  }
+
   void swap(T** pp) {
     T* p = ptr_;
     ptr_ = *pp;
     *pp = p;
   }
 
   void swap(scoped_refptr<T>& r) {
     swap(&r.ptr_);
   }
 
  private:
+  template <typename U> friend class scoped_refptr;
+
   // Allow scoped_refptr<T> to be used in boolean expressions, but not
   // implicitly convertible to a real bool (which is dangerous).
   //
   // Note that this trick is only safe when the == and != operators
   // are declared explicitly, as otherwise "refptr1 == refptr2"
   // will compile but do the wrong thing (i.e., convert to Testable
   // and then do the comparison).
   typedef T* scoped_refptr::*Testable;
 
  public:
@@ skipping 64 matching lines @@
 bool operator!=(const T* lhs, const scoped_refptr<U>& rhs) {
   return !operator==(lhs, rhs);
 }
 
 template <typename T>
 std::ostream& operator<<(std::ostream& out, const scoped_refptr<T>& p) {
   return out << p.get();
 }
 
 #endif  // BASE_MEMORY_REF_COUNTED_H_