The Tor Browser: accessible/src/base/TreeWalker.cpp@97036ab72558

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

     1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

     2 /* This Source Code Form is subject to the terms of the Mozilla Public

     3  * License, v. 2.0. If a copy of the MPL was not distributed with this

     4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     6 #include "TreeWalker.h"

     8 #include "Accessible.h"

     9 #include "nsAccessibilityService.h"

    10 #include "DocAccessible.h"

    12 #include "mozilla/dom/Element.h"

    14 using namespace mozilla::a11y;

    16 ////////////////////////////////////////////////////////////////////////////////

    17 // WalkState

    18 ////////////////////////////////////////////////////////////////////////////////

    20 namespace mozilla {

    21 namespace a11y {

    23 struct WalkState

    24 {

    25   WalkState(nsIContent *aContent) :

    26     content(aContent), childIdx(0), prevState(nullptr) {}

    28   nsCOMPtr<nsIContent> content;

    29   nsCOMPtr<nsINodeList> childList;

    30   uint32_t childIdx;

    31   WalkState *prevState;

    32 };

    34 } // namespace a11y

    35 } // namespace mozilla

    37 ////////////////////////////////////////////////////////////////////////////////

    38 // TreeWalker

    39 ////////////////////////////////////////////////////////////////////////////////

    41 TreeWalker::

    42   TreeWalker(Accessible* aContext, nsIContent* aContent, uint32_t aFlags) :

    43   mDoc(aContext->Document()), mContext(aContext),

    44   mFlags(aFlags), mState(nullptr)

    45 {

    46   NS_ASSERTION(aContent, "No node for the accessible tree walker!");

    48   if (aContent)

    49     mState = new WalkState(aContent);

    51   mChildFilter = mContext->CanHaveAnonChildren() ?

    52     nsIContent::eAllChildren : nsIContent::eAllButXBL;

    54   mChildFilter |= nsIContent::eSkipPlaceholderContent;

    56   MOZ_COUNT_CTOR(TreeWalker);

    57 }

    59 TreeWalker::~TreeWalker()

    60 {

    61   // Clear state stack from memory

    62   while (mState)

    63     PopState();

    65   MOZ_COUNT_DTOR(TreeWalker);

    66 }

    68 ////////////////////////////////////////////////////////////////////////////////

    69 // TreeWalker: private

    71 Accessible*

    72 TreeWalker::NextChildInternal(bool aNoWalkUp)

    73 {

    74   if (!mState || !mState->content)

    75     return nullptr;

    77   if (!mState->childList)

    78     mState->childList = mState->content->GetChildren(mChildFilter);

    80   uint32_t length = 0;

    81   if (mState->childList)

    82     mState->childList->GetLength(&length);

    84   while (mState->childIdx < length) {

    85     nsIContent* childNode = mState->childList->Item(mState->childIdx);

    86     mState->childIdx++;

    88     bool isSubtreeHidden = false;

    89     Accessible* accessible = mFlags & eWalkCache ?

    90       mDoc->GetAccessible(childNode) :

    91       GetAccService()->GetOrCreateAccessible(childNode, mContext,

    92                                              &isSubtreeHidden);

    94     if (accessible)

    95       return accessible;

    97     // Walk down into subtree to find accessibles.

    98     if (!isSubtreeHidden) {

    99       PushState(childNode);

   100       accessible = NextChildInternal(true);

   101       if (accessible)

   102         return accessible;

   103     }

   104   }

   106   // No more children, get back to the parent.

   107   nsIContent* anchorNode = mState->content;

   108   PopState();

   109   if (aNoWalkUp)

   110     return nullptr;

   112   if (mState)

   113     return NextChildInternal(false);

   115   // If we traversed the whole subtree of the anchor node. Move to next node

   116   // relative anchor node within the context subtree if possible.

   117   if (mFlags != eWalkContextTree)

   118     return nullptr;

   120   while (anchorNode != mContext->GetNode()) {

   121     nsINode* parentNode = anchorNode->GetFlattenedTreeParent();

   122     if (!parentNode || !parentNode->IsElement())

   123       return nullptr;

   125     PushState(parentNode->AsElement());

   126     mState->childList = mState->content->GetChildren(mChildFilter);

   127     length = 0;

   128     if (mState->childList)

   129       mState->childList->GetLength(&length);

   131     while (mState->childIdx < length) {

   132       nsIContent* childNode = mState->childList->Item(mState->childIdx);

   133       mState->childIdx++;

   134       if (childNode == anchorNode)

   135         return NextChildInternal(false);

   136     }

   137     PopState();

   139     anchorNode = parentNode->AsElement();

   140   }

   142   return nullptr;

   143 }

   145 void

   146 TreeWalker::PopState()

   147 {

   148   WalkState* prevToLastState = mState->prevState;

   149   delete mState;

   150   mState = prevToLastState;

   151 }

   153 void

   154 TreeWalker::PushState(nsIContent* aContent)

   155 {

   156   WalkState* nextToLastState = new WalkState(aContent);

   157   nextToLastState->prevState = mState;

   158   mState = nextToLastState;

   159 }

The Tor Browser / file revision

accessible/src/base/TreeWalker.cpp@97036ab72558

accessible/src/base/TreeWalker.cpp