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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "base/memory/weak_ptr.h"
6 
7 namespace base {
8 namespace internal {
9 
Flag()10 WeakReference::Flag::Flag() : is_valid_(true) {
11   // Flags only become bound when checked for validity, or invalidated,
12   // so that we can check that later validity/invalidation operations on
13   // the same Flag take place on the same sequenced thread.
14   sequence_checker_.DetachFromSequence();
15 }
16 
Invalidate()17 void WeakReference::Flag::Invalidate() {
18   // The flag being invalidated with a single ref implies that there are no
19   // weak pointers in existence. Allow deletion on other thread in this case.
20   DCHECK(sequence_checker_.CalledOnValidSequencedThread() || HasOneRef())
21       << "WeakPtrs must be invalidated on the same sequenced thread.";
22   is_valid_ = false;
23 }
24 
IsValid() const25 bool WeakReference::Flag::IsValid() const {
26   DCHECK(sequence_checker_.CalledOnValidSequencedThread())
27       << "WeakPtrs must be checked on the same sequenced thread.";
28   return is_valid_;
29 }
30 
~Flag()31 WeakReference::Flag::~Flag() {
32 }
33 
WeakReference()34 WeakReference::WeakReference() {
35 }
36 
WeakReference(const Flag * flag)37 WeakReference::WeakReference(const Flag* flag) : flag_(flag) {
38 }
39 
~WeakReference()40 WeakReference::~WeakReference() {
41 }
42 
43 WeakReference::WeakReference(WeakReference&& other) = default;
44 
45 WeakReference::WeakReference(const WeakReference& other) = default;
46 
is_valid() const47 bool WeakReference::is_valid() const { return flag_.get() && flag_->IsValid(); }
48 
WeakReferenceOwner()49 WeakReferenceOwner::WeakReferenceOwner() {
50 }
51 
~WeakReferenceOwner()52 WeakReferenceOwner::~WeakReferenceOwner() {
53   Invalidate();
54 }
55 
GetRef() const56 WeakReference WeakReferenceOwner::GetRef() const {
57   // If we hold the last reference to the Flag then create a new one.
58   if (!HasRefs())
59     flag_ = new WeakReference::Flag();
60 
61   return WeakReference(flag_.get());
62 }
63 
Invalidate()64 void WeakReferenceOwner::Invalidate() {
65   if (flag_.get()) {
66     flag_->Invalidate();
67     flag_ = NULL;
68   }
69 }
70 
WeakPtrBase()71 WeakPtrBase::WeakPtrBase() {
72 }
73 
~WeakPtrBase()74 WeakPtrBase::~WeakPtrBase() {
75 }
76 
WeakPtrBase(const WeakReference & ref)77 WeakPtrBase::WeakPtrBase(const WeakReference& ref) : ref_(ref) {
78 }
79 
80 }  // namespace internal
81 }  // namespace base
82