sousa-gecko/dom/base/TreeWalker.cpp

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * Implementation of DOM Traversal's TreeWalker
 */

#include "mozilla/dom/TreeWalker.h"

#include "mozilla/dom/NodeFilterBinding.h"
#include "mozilla/dom/TreeWalkerBinding.h"
#include "nsContentUtils.h"
#include "nsError.h"
#include "nsIContent.h"
#include "nsINode.h"

namespace mozilla::dom {

/*
 * Factories, constructors and destructors
 */

TreeWalker::TreeWalker(nsINode* aRoot, uint32_t aWhatToShow,
                       NodeFilter* aFilter)
    : nsTraversal(aRoot, aWhatToShow, aFilter), mCurrentNode(aRoot) {}

TreeWalker::~TreeWalker() = default;

/*
 * nsISupports and cycle collection stuff
 */

NS_IMPL_CYCLE_COLLECTION(TreeWalker, mFilter, mCurrentNode, mRoot)

// QueryInterface implementation for TreeWalker
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(TreeWalker)
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

// Have to pass in dom::TreeWalker because a11y has an a11y::TreeWalker that
// passes TreeWalker so refcount logging would get confused on the name
// collision.
NS_IMPL_CYCLE_COLLECTING_ADDREF(dom::TreeWalker)
NS_IMPL_CYCLE_COLLECTING_RELEASE(dom::TreeWalker)

void TreeWalker::SetCurrentNode(nsINode& aNode, ErrorResult& aResult) {
  aResult = nsContentUtils::CheckSameOrigin(mRoot, &aNode);
  if (aResult.Failed()) {
    return;
  }

  mCurrentNode = &aNode;
}

already_AddRefed<nsINode> TreeWalker::ParentNode(ErrorResult& aResult) {
  nsCOMPtr<nsINode> node = mCurrentNode;

  while (node && node != mRoot) {
    node = node->GetParentNode();

    if (node) {
      int16_t filtered = TestNode(node, aResult);
      if (aResult.Failed()) {
        return nullptr;
      }
      if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
        mCurrentNode = node;
        return node.forget();
      }
    }
  }

  return nullptr;
}

already_AddRefed<nsINode> TreeWalker::FirstChild(ErrorResult& aResult) {
  return FirstChildInternal(false, aResult);
}

already_AddRefed<nsINode> TreeWalker::LastChild(ErrorResult& aResult) {
  return FirstChildInternal(true, aResult);
}

already_AddRefed<nsINode> TreeWalker::PreviousSibling(ErrorResult& aResult) {
  return NextSiblingInternal(true, aResult);
}

already_AddRefed<nsINode> TreeWalker::NextSibling(ErrorResult& aResult) {
  return NextSiblingInternal(false, aResult);
}

already_AddRefed<nsINode> TreeWalker::PreviousNode(ErrorResult& aResult) {
  nsCOMPtr<nsINode> node = mCurrentNode;

  while (node != mRoot) {
    while (nsINode* previousSibling = node->GetPreviousSibling()) {
      node = previousSibling;

      int16_t filtered = TestNode(node, aResult);
      if (aResult.Failed()) {
        return nullptr;
      }

      nsINode* lastChild;
      while (filtered != NodeFilter_Binding::FILTER_REJECT &&
             (lastChild = node->GetLastChild())) {
        node = lastChild;
        filtered = TestNode(node, aResult);
        if (aResult.Failed()) {
          return nullptr;
        }
      }

      if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
        mCurrentNode = node;
        return node.forget();
      }
    }

    if (node == mRoot) {
      break;
    }

    node = node->GetParentNode();
    if (!node) {
      break;
    }

    int16_t filtered = TestNode(node, aResult);
    if (aResult.Failed()) {
      return nullptr;
    }

    if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
      mCurrentNode = node;
      return node.forget();
    }
  }

  return nullptr;
}

static already_AddRefed<nsINode> EnsureAddRefed(nsCOMPtr<nsINode>& aNode) {
  return aNode.forget();
}

static already_AddRefed<nsINode> EnsureAddRefed(nsINode*& aNode) {
  return do_AddRef(aNode);
}

already_AddRefed<nsINode> TreeWalker::NextNode(ErrorResult& aResult) {
  // With no filter TestNode() cannot run script, and the loop performs no
  // refcount decrements before its final assignment to mCurrentNode, so
  // nothing can destroy a node mid-walk.
  if (!mFilter) {
    return NextNodeInternal<nsINode*>(aResult);
  }
  return NextNodeInternal<nsCOMPtr<nsINode>>(aResult);
}

template <typename NodePtr>
already_AddRefed<nsINode> TreeWalker::NextNodeInternal(ErrorResult& aResult) {
  int16_t filtered =
      NodeFilter_Binding::FILTER_ACCEPT;  // pre-init for inner loop

  NodePtr node = mCurrentNode;

  while (true) {
    nsINode* firstChild;
    while (filtered != NodeFilter_Binding::FILTER_REJECT &&
           (firstChild = node->GetFirstChild())) {
      node = firstChild;

      filtered = TestNode(node, aResult);
      if (aResult.Failed()) {
        return nullptr;
      }

      if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
        // Node found
        mCurrentNode = node;
        return EnsureAddRefed(node);
      }
    }

    nsINode* sibling = nullptr;
    nsINode* temp = node;
    do {
      if (temp == mRoot) break;

      sibling = temp->GetNextSibling();
      if (sibling) break;

      temp = temp->GetParentNode();
    } while (temp);

    if (!sibling) break;

    node = sibling;

    // Found a sibling. Either ours or ancestor's
    filtered = TestNode(node, aResult);
    if (aResult.Failed()) {
      return nullptr;
    }

    if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
      // Node found
      mCurrentNode = node;
      return EnsureAddRefed(node);
    }
  }

  return nullptr;
}

/*
 * TreeWalker helper functions
 */

/*
 * Implements FirstChild and LastChild which only vary in which direction
 * they search.
 * @param aReversed Controls whether we search forwards or backwards
 * @param aResult   Whether we threw or not.
 * @returns         The desired node. Null if no child is found
 */
already_AddRefed<nsINode> TreeWalker::FirstChildInternal(bool aReversed,
                                                         ErrorResult& aResult) {
  nsCOMPtr<nsINode> node =
      aReversed ? mCurrentNode->GetLastChild() : mCurrentNode->GetFirstChild();

  while (node) {
    int16_t filtered = TestNode(node, aResult);
    if (aResult.Failed()) {
      return nullptr;
    }

    switch (filtered) {
      case NodeFilter_Binding::FILTER_ACCEPT:
        // Node found
        mCurrentNode = node;
        return node.forget();
      case NodeFilter_Binding::FILTER_SKIP: {
        nsINode* child =
            aReversed ? node->GetLastChild() : node->GetFirstChild();
        if (child) {
          node = child;
          continue;
        }
        break;
      }
      case NodeFilter_Binding::FILTER_REJECT:
        // Keep searching
        break;
    }

    do {
      nsINode* sibling =
          aReversed ? node->GetPreviousSibling() : node->GetNextSibling();
      if (sibling) {
        node = sibling;
        break;
      }

      nsINode* parent = node->GetParentNode();

      if (!parent || parent == mRoot || parent == mCurrentNode) {
        return nullptr;
      }

      node = parent;

    } while (node);
  }

  return nullptr;
}

/*
 * Implements NextSibling and PreviousSibling which only vary in which
 * direction they search.
 * @param aReversed Controls whether we search forwards or backwards
 * @param aResult   Whether we threw or not.
 * @returns         The desired node. Null if no child is found
 */
already_AddRefed<nsINode> TreeWalker::NextSiblingInternal(
    bool aReversed, ErrorResult& aResult) {
  nsCOMPtr<nsINode> node = mCurrentNode;

  if (node == mRoot) {
    return nullptr;
  }

  while (true) {
    nsINode* sibling =
        aReversed ? node->GetPreviousSibling() : node->GetNextSibling();

    while (sibling) {
      node = sibling;

      int16_t filtered = TestNode(node, aResult);
      if (aResult.Failed()) {
        return nullptr;
      }

      if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
        // Node found
        mCurrentNode = node;
        return node.forget();
      }

      // If rejected or no children, try a sibling
      if (filtered == NodeFilter_Binding::FILTER_REJECT ||
          !(sibling =
                aReversed ? node->GetLastChild() : node->GetFirstChild())) {
        sibling =
            aReversed ? node->GetPreviousSibling() : node->GetNextSibling();
      }
    }

    node = node->GetParentNode();

    if (!node || node == mRoot) {
      return nullptr;
    }

    // Is parent transparent in filtered view?
    int16_t filtered = TestNode(node, aResult);
    if (aResult.Failed()) {
      return nullptr;
    }
    if (filtered == NodeFilter_Binding::FILTER_ACCEPT) {
      return nullptr;
    }
  }
}

bool TreeWalker::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto,
                            JS::MutableHandle<JSObject*> aReflector) {
  return TreeWalker_Binding::Wrap(aCx, this, aGivenProto, aReflector);
}

}  // namespace mozilla::dom