base/memory/weak_ptr.cc

   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
  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
  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
  25 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
  31 WeakReference::Flag::~Flag() {
  32 }
  33
  34 WeakReference::WeakReference() {
  35 }
  36
  37 WeakReference::WeakReference(const Flag* flag) : flag_(flag) {
  38 }
  39
  40 WeakReference::~WeakReference() {
  41 }
  42
  43 bool WeakReference::is_valid() const { return flag_.get() && flag_->IsValid(); }
  44
  45 WeakReferenceOwner::WeakReferenceOwner() {
  46 }
  47
  48 WeakReferenceOwner::~WeakReferenceOwner() {
  49   Invalidate();
  50 }
  51
  52 WeakReference 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
  60 void WeakReferenceOwner::Invalidate() {
  61   if (flag_.get()) {
  62     flag_->Invalidate();
  63     flag_ = NULL;
  64   }
  65 }
  66
  67 WeakPtrBase::WeakPtrBase() {
  68 }
  69
  70 WeakPtrBase::~WeakPtrBase() {
  71 }
  72
  73 WeakPtrBase::WeakPtrBase(const WeakReference& ref) : ref_(ref) {
  74 }
  75
  76 }  // namespace internal
  77 }  // namespace base