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
7namespace base {
8namespace internal {
9
10WeakReference::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
17void 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
25bool 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
31WeakReference::Flag::~Flag() {
32}
33
34WeakReference::WeakReference() {
35}
36
37WeakReference::WeakReference(const Flag* flag) : flag_(flag) {
38}
39
40WeakReference::~WeakReference() {
41}
42
43bool WeakReference::is_valid() const { return flag_.get() && flag_->IsValid(); }
44
45WeakReferenceOwner::WeakReferenceOwner() {
46}
47
48WeakReferenceOwner::~WeakReferenceOwner() {
49  Invalidate();
50}
51
52WeakReference WeakReferenceOwner::GetRef() const {
53  // If we hold the last reference to the Flag then create a new one.
54  if (!HasRefs())
55    flag_ = new WeakReference::Flag();
56
57  return WeakReference(flag_.get());
58}
59
60void WeakReferenceOwner::Invalidate() {
61  if (flag_.get()) {
62    flag_->Invalidate();
63    flag_ = NULL;
64  }
65}
66
67WeakPtrBase::WeakPtrBase() {
68}
69
70WeakPtrBase::~WeakPtrBase() {
71}
72
73WeakPtrBase::WeakPtrBase(const WeakReference& ref) : ref_(ref) {
74}
75
76}  // namespace internal
77}  // namespace base
78