1 files changed, 1055 insertions, 0 deletions
diff --git a/dom/base/ContentIterator.cpp b/dom/base/ContentIterator.cpp
new file mode 100644
index 0000000000..dbcb4627e2
--- /dev/null
+++ b/dom/base/ContentIterator.cpp
@@ -0,0 +1,1055 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#include "ContentIterator.h"
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/RangeBoundary.h"
+#include "mozilla/RangeUtils.h"
+#include "mozilla/Result.h"
+
+#include "nsContentUtils.h"
+#include "nsElementTable.h"
+#include "nsIContent.h"
+#include "nsRange.h"
+
+namespace mozilla {
+
+static bool ComparePostMode(const RawRangeBoundary& aStart,
+                            const RawRangeBoundary& aEnd, nsINode& aNode) {
+  nsINode* parent = aNode.GetParentNode();
+  if (!parent) {
+    return false;
+  }
+
+  // aNode should always be content, as we have a parent, but let's just be
+  // extra careful and check.
+  nsIContent* content =
+      NS_WARN_IF(!aNode.IsContent()) ? nullptr : aNode.AsContent();
+
+  // Post mode: start < node <= end.
+  RawRangeBoundary afterNode(parent, content);
+  const auto isStartLessThanAfterNode = [&]() {
+    const Maybe<int32_t> startComparedToAfterNode =
+        nsContentUtils::ComparePoints(aStart, afterNode);
+    return !NS_WARN_IF(!startComparedToAfterNode) &&
+           (*startComparedToAfterNode < 0);
+  };
+
+  const auto isAfterNodeLessOrEqualToEnd = [&]() {
+    const Maybe<int32_t> afterNodeComparedToEnd =
+        nsContentUtils::ComparePoints(afterNode, aEnd);
+    return !NS_WARN_IF(!afterNodeComparedToEnd) &&
+           (*afterNodeComparedToEnd <= 0);
+  };
+
+  return isStartLessThanAfterNode() && isAfterNodeLessOrEqualToEnd();
+}
+
+static bool ComparePreMode(const RawRangeBoundary& aStart,
+                           const RawRangeBoundary& aEnd, nsINode& aNode) {
+  nsINode* parent = aNode.GetParentNode();
+  if (!parent) {
+    return false;
+  }
+
+  // Pre mode: start <= node < end.
+  RawRangeBoundary beforeNode(parent, aNode.GetPreviousSibling());
+
+  const auto isStartLessOrEqualToBeforeNode = [&]() {
+    const Maybe<int32_t> startComparedToBeforeNode =
+        nsContentUtils::ComparePoints(aStart, beforeNode);
+    return !NS_WARN_IF(!startComparedToBeforeNode) &&
+           (*startComparedToBeforeNode <= 0);
+  };
+
+  const auto isBeforeNodeLessThanEndNode = [&]() {
+    const Maybe<int32_t> beforeNodeComparedToEnd =
+        nsContentUtils::ComparePoints(beforeNode, aEnd);
+    return !NS_WARN_IF(!beforeNodeComparedToEnd) &&
+           (*beforeNodeComparedToEnd < 0);
+  };
+
+  return isStartLessOrEqualToBeforeNode() && isBeforeNodeLessThanEndNode();
+}
+
+///////////////////////////////////////////////////////////////////////////
+// NodeIsInTraversalRange: returns true if content is visited during
+// the traversal of the range in the specified mode.
+//
+static bool NodeIsInTraversalRange(nsINode* aNode, bool aIsPreMode,
+                                   const RawRangeBoundary& aStart,
+                                   const RawRangeBoundary& aEnd) {
+  if (NS_WARN_IF(!aStart.IsSet()) || NS_WARN_IF(!aEnd.IsSet()) ||
+      NS_WARN_IF(!aNode)) {
+    return false;
+  }
+
+  // If a leaf node contains an end point of the traversal range, it is
+  // always in the traversal range.
+  if (aNode == aStart.Container() || aNode == aEnd.Container()) {
+    if (aNode->IsCharacterData()) {
+      return true;  // text node or something
+    }
+    if (!aNode->HasChildren()) {
+      MOZ_ASSERT(
+          aNode != aStart.Container() || aStart.IsStartOfContainer(),
+          "aStart.Container() doesn't have children and not a data node, "
+          "aStart should be at the beginning of its container");
+      MOZ_ASSERT(aNode != aEnd.Container() || aEnd.IsStartOfContainer(),
+                 "aEnd.Container() doesn't have children and not a data node, "
+                 "aEnd should be at the beginning of its container");
+      return true;
+    }
+  }
+
+  if (aIsPreMode) {
+    return ComparePreMode(aStart, aEnd, *aNode);
+  }
+
+  return ComparePostMode(aStart, aEnd, *aNode);
+}
+
+// Each concreate class of ContentIteratorBase may be owned by another class
+// which may be owned by JS.  Therefore, all of them should be in the cycle
+// collection.  However, we cannot make non-refcountable classes only with the
+// macros.  So, we need to make them cycle collectable without the macros.
+void ImplCycleCollectionTraverse(nsCycleCollectionTraversalCallback& aCallback,
+                                 ContentIteratorBase& aField, const char* aName,
+                                 uint32_t aFlags = 0) {
+  ImplCycleCollectionTraverse(aCallback, aField.mCurNode, aName, aFlags);
+  ImplCycleCollectionTraverse(aCallback, aField.mFirst, aName, aFlags);
+  ImplCycleCollectionTraverse(aCallback, aField.mLast, aName, aFlags);
+  ImplCycleCollectionTraverse(aCallback, aField.mClosestCommonInclusiveAncestor,
+                              aName, aFlags);
+}
+
+void ImplCycleCollectionUnlink(ContentIteratorBase& aField) {
+  ImplCycleCollectionUnlink(aField.mCurNode);
+  ImplCycleCollectionUnlink(aField.mFirst);
+  ImplCycleCollectionUnlink(aField.mLast);
+  ImplCycleCollectionUnlink(aField.mClosestCommonInclusiveAncestor);
+}
+
+ContentIteratorBase::ContentIteratorBase(Order aOrder) : mOrder(aOrder) {}
+
+ContentIteratorBase::~ContentIteratorBase() = default;
+
+/******************************************************
+ * Init routines
+ ******************************************************/
+
+nsresult ContentIteratorBase::Init(nsINode* aRoot) {
+  if (NS_WARN_IF(!aRoot)) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  if (mOrder == Order::Pre) {
+    mFirst = aRoot;
+    mLast = ContentIteratorBase::GetDeepLastChild(aRoot);
+    NS_WARNING_ASSERTION(mLast, "GetDeepLastChild returned null");
+  } else {
+    mFirst = ContentIteratorBase::GetDeepFirstChild(aRoot);
+    NS_WARNING_ASSERTION(mFirst, "GetDeepFirstChild returned null");
+    mLast = aRoot;
+  }
+
+  mClosestCommonInclusiveAncestor = aRoot;
+  mCurNode = mFirst;
+  return NS_OK;
+}
+
+nsresult ContentIteratorBase::Init(nsRange* aRange) {
+  if (NS_WARN_IF(!aRange)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (NS_WARN_IF(!aRange->IsPositioned())) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return InitInternal(aRange->StartRef().AsRaw(), aRange->EndRef().AsRaw());
+}
+
+nsresult ContentIteratorBase::Init(nsINode* aStartContainer,
+                                   uint32_t aStartOffset,
+                                   nsINode* aEndContainer,
+                                   uint32_t aEndOffset) {
+  if (NS_WARN_IF(!RangeUtils::IsValidPoints(aStartContainer, aStartOffset,
+                                            aEndContainer, aEndOffset))) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return InitInternal(RawRangeBoundary(aStartContainer, aStartOffset),
+                      RawRangeBoundary(aEndContainer, aEndOffset));
+}
+
+nsresult ContentIteratorBase::Init(const RawRangeBoundary& aStart,
+                                   const RawRangeBoundary& aEnd) {
+  if (NS_WARN_IF(!RangeUtils::IsValidPoints(aStart, aEnd))) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  return InitInternal(aStart, aEnd);
+}
+
+class MOZ_STACK_CLASS ContentIteratorBase::Initializer final {
+ public:
+  Initializer(ContentIteratorBase& aIterator, const RawRangeBoundary& aStart,
+              const RawRangeBoundary& aEnd)
+      : mIterator{aIterator},
+        mStart{aStart},
+        mEnd{aEnd},
+        mStartIsCharacterData{mStart.Container()->IsCharacterData()} {
+    MOZ_ASSERT(mStart.IsSetAndValid());
+    MOZ_ASSERT(mEnd.IsSetAndValid());
+  }
+
+  nsresult Run();
+
+ private:
+  /**
+   * @return may be nullptr.
+   */
+  nsINode* DetermineFirstNode() const;
+
+  /**
+   * @return may be nullptr.
+   */
+  [[nodiscard]] Result<nsINode*, nsresult> DetermineLastNode() const;
+
+  bool IsCollapsedNonCharacterRange() const;
+  bool IsSingleNodeCharacterRange() const;
+
+  ContentIteratorBase& mIterator;
+  const RawRangeBoundary& mStart;
+  const RawRangeBoundary& mEnd;
+  const bool mStartIsCharacterData;
+};
+
+nsresult ContentIteratorBase::InitInternal(const RawRangeBoundary& aStart,
+                                           const RawRangeBoundary& aEnd) {
+  Initializer initializer{*this, aStart, aEnd};
+  return initializer.Run();
+}
+
+bool ContentIteratorBase::Initializer::IsCollapsedNonCharacterRange() const {
+  return !mStartIsCharacterData && mStart == mEnd;
+}
+
+bool ContentIteratorBase::Initializer::IsSingleNodeCharacterRange() const {
+  return mStartIsCharacterData && mStart.Container() == mEnd.Container();
+}
+
+nsresult ContentIteratorBase::Initializer::Run() {
+  // get common content parent
+  mIterator.mClosestCommonInclusiveAncestor =
+      nsContentUtils::GetClosestCommonInclusiveAncestor(mStart.Container(),
+                                                        mEnd.Container());
+  if (NS_WARN_IF(!mIterator.mClosestCommonInclusiveAncestor)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Check to see if we have a collapsed range, if so, there is nothing to
+  // iterate over.
+  //
+  // XXX: CharacterDataNodes (text nodes) are currently an exception, since
+  //      we always want to be able to iterate text nodes at the end points
+  //      of a range.
+
+  if (IsCollapsedNonCharacterRange()) {
+    mIterator.SetEmpty();
+    return NS_OK;
+  }
+
+  if (IsSingleNodeCharacterRange()) {
+    mIterator.mFirst = mStart.Container()->AsContent();
+    mIterator.mLast = mIterator.mFirst;
+    mIterator.mCurNode = mIterator.mFirst;
+
+    return NS_OK;
+  }
+
+  mIterator.mFirst = DetermineFirstNode();
+
+  if (Result<nsINode*, nsresult> lastNode = DetermineLastNode();
+      NS_WARN_IF(lastNode.isErr())) {
+    return lastNode.unwrapErr();
+  } else {
+    mIterator.mLast = lastNode.unwrap();
+  }
+
+  // If either first or last is null, they both have to be null!
+  if (!mIterator.mFirst || !mIterator.mLast) {
+    mIterator.SetEmpty();
+  }
+
+  mIterator.mCurNode = mIterator.mFirst;
+
+  return NS_OK;
+}
+
+nsINode* ContentIteratorBase::Initializer::DetermineFirstNode() const {
+  nsIContent* cChild = nullptr;
+
+  // Try to get the child at our starting point. This might return null if
+  // mStart is immediately after the last node in mStart.Container().
+  if (!mStartIsCharacterData) {
+    cChild = mStart.GetChildAtOffset();
+  }
+
+  if (!cChild) {
+    // No children (possibly a <br> or text node), or index is after last child.
+
+    if (mIterator.mOrder == Order::Pre) {
+      // XXX: In the future, if start offset is after the last
+      //      character in the cdata node, should we set mFirst to
+      //      the next sibling?
+
+      // Normally we would skip the start node because the start node is outside
+      // of the range in pre mode. However, if aStartOffset == 0, and the node
+      // is a non-container node (e.g. <br>), we don't skip the node in this
+      // case in order to address bug 1215798.
+      bool startIsContainer = true;
+      if (mStart.Container()->IsHTMLElement()) {
+        nsAtom* name = mStart.Container()->NodeInfo()->NameAtom();
+        startIsContainer =
+            nsHTMLElement::IsContainer(nsHTMLTags::AtomTagToId(name));
+      }
+      if (!mStartIsCharacterData &&
+          (startIsContainer || !mStart.IsStartOfContainer())) {
+        nsINode* const result =
+            ContentIteratorBase::GetNextSibling(mStart.Container());
+        NS_WARNING_ASSERTION(result, "GetNextSibling returned null");
+
+        // Does mFirst node really intersect the range?  The range could be
+        // 'degenerate', i.e., not collapsed but still contain no content.
+        if (result &&
+            NS_WARN_IF(!NodeIsInTraversalRange(
+                result, mIterator.mOrder == Order::Pre, mStart, mEnd))) {
+          return nullptr;
+        }
+
+        return result;
+      }
+      return mStart.Container()->AsContent();
+    }
+
+    // post-order
+    if (NS_WARN_IF(!mStart.Container()->IsContent())) {
+      // What else can we do?
+      return nullptr;
+    }
+    return mStart.Container()->AsContent();
+  }
+
+  if (mIterator.mOrder == Order::Pre) {
+    return cChild;
+  }
+
+  // post-order
+  nsINode* const result = ContentIteratorBase::GetDeepFirstChild(cChild);
+  NS_WARNING_ASSERTION(result, "GetDeepFirstChild returned null");
+
+  // Does mFirst node really intersect the range?  The range could be
+  // 'degenerate', i.e., not collapsed but still contain no content.
+  if (result && !NodeIsInTraversalRange(result, mIterator.mOrder == Order::Pre,
+                                        mStart, mEnd)) {
+    return nullptr;
+  }
+
+  return result;
+}
+
+Result<nsINode*, nsresult> ContentIteratorBase::Initializer::DetermineLastNode()
+    const {
+  const bool endIsCharacterData = mEnd.Container()->IsCharacterData();
+
+  if (endIsCharacterData || !mEnd.Container()->HasChildren() ||
+      mEnd.IsStartOfContainer()) {
+    if (mIterator.mOrder == Order::Pre) {
+      if (NS_WARN_IF(!mEnd.Container()->IsContent())) {
+        // Not much else to do here...
+        return nullptr;
+      }
+
+      // If the end node is a non-container element and the end offset is 0,
+      // the last element should be the previous node (i.e., shouldn't
+      // include the end node in the range).
+      bool endIsContainer = true;
+      if (mEnd.Container()->IsHTMLElement()) {
+        nsAtom* name = mEnd.Container()->NodeInfo()->NameAtom();
+        endIsContainer =
+            nsHTMLElement::IsContainer(nsHTMLTags::AtomTagToId(name));
+      }
+      if (!endIsCharacterData && !endIsContainer && mEnd.IsStartOfContainer()) {
+        nsINode* const result = mIterator.PrevNode(mEnd.Container());
+        NS_WARNING_ASSERTION(result, "PrevNode returned null");
+        if (result && result != mIterator.mFirst &&
+            NS_WARN_IF(!NodeIsInTraversalRange(
+                result, mIterator.mOrder == Order::Pre,
+                RawRangeBoundary(mIterator.mFirst, 0u), mEnd))) {
+          return nullptr;
+        }
+
+        return result;
+      }
+
+      return mEnd.Container()->AsContent();
+    }
+
+    // post-order
+    //
+    // XXX: In the future, if end offset is before the first character in the
+    //      cdata node, should we set mLast to the prev sibling?
+
+    if (!endIsCharacterData) {
+      nsINode* const result =
+          ContentIteratorBase::GetPrevSibling(mEnd.Container());
+      NS_WARNING_ASSERTION(result, "GetPrevSibling returned null");
+
+      if (!NodeIsInTraversalRange(result, mIterator.mOrder == Order::Pre,
+                                  mStart, mEnd)) {
+        return nullptr;
+      }
+      return result;
+    }
+    return mEnd.Container()->AsContent();
+  }
+
+  nsIContent* cChild = mEnd.Ref();
+
+  if (NS_WARN_IF(!cChild)) {
+    // No child at offset!
+    MOZ_ASSERT_UNREACHABLE("ContentIterator::ContentIterator");
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  if (mIterator.mOrder == Order::Pre) {
+    nsINode* const result = ContentIteratorBase::GetDeepLastChild(cChild);
+    NS_WARNING_ASSERTION(result, "GetDeepLastChild returned null");
+
+    if (NS_WARN_IF(!NodeIsInTraversalRange(
+            result, mIterator.mOrder == Order::Pre, mStart, mEnd))) {
+      return nullptr;
+    }
+
+    return result;
+  }
+
+  // post-order
+  return cChild;
+}
+
+void ContentIteratorBase::SetEmpty() {
+  mCurNode = nullptr;
+  mFirst = nullptr;
+  mLast = nullptr;
+  mClosestCommonInclusiveAncestor = nullptr;
+}
+
+// static
+nsINode* ContentIteratorBase::GetDeepFirstChild(nsINode* aRoot) {
+  if (NS_WARN_IF(!aRoot) || !aRoot->HasChildren()) {
+    return aRoot;
+  }
+
+  return ContentIteratorBase::GetDeepFirstChild(aRoot->GetFirstChild());
+}
+
+// static
+nsIContent* ContentIteratorBase::GetDeepFirstChild(nsIContent* aRoot) {
+  if (NS_WARN_IF(!aRoot)) {
+    return nullptr;
+  }
+
+  nsIContent* node = aRoot;
+  nsIContent* child = node->GetFirstChild();
+
+  while (child) {
+    node = child;
+    child = node->GetFirstChild();
+  }
+
+  return node;
+}
+
+// static
+nsINode* ContentIteratorBase::GetDeepLastChild(nsINode* aRoot) {
+  if (NS_WARN_IF(!aRoot) || !aRoot->HasChildren()) {
+    return aRoot;
+  }
+
+  return ContentIteratorBase::GetDeepLastChild(aRoot->GetLastChild());
+}
+
+// static
+nsIContent* ContentIteratorBase::GetDeepLastChild(nsIContent* aRoot) {
+  if (NS_WARN_IF(!aRoot)) {
+    return nullptr;
+  }
+
+  nsIContent* node = aRoot;
+  while (node->HasChildren()) {
+    nsIContent* child = node->GetLastChild();
+    node = child;
+  }
+  return node;
+}
+
+// Get the next sibling, or parent's next sibling, or grandpa's next sibling...
+// static
+nsIContent* ContentIteratorBase::GetNextSibling(nsINode* aNode) {
+  if (NS_WARN_IF(!aNode)) {
+    return nullptr;
+  }
+
+  if (aNode->GetNextSibling()) {
+    return aNode->GetNextSibling();
+  }
+
+  nsINode* parent = aNode->GetParentNode();
+  if (NS_WARN_IF(!parent)) {
+    return nullptr;
+  }
+
+  // XXX This is a hack to preserve previous behaviour: This should be fixed
+  // in bug 1404916. If we were positioned on anonymous content, move to
+  // the first child of our parent.
+  if (parent->GetLastChild() && parent->GetLastChild() != aNode) {
+    return parent->GetFirstChild();
+  }
+
+  return ContentIteratorBase::GetNextSibling(parent);
+}
+
+// Get the prev sibling, or parent's prev sibling, or grandpa's prev sibling...
+// static
+nsIContent* ContentIteratorBase::GetPrevSibling(nsINode* aNode) {
+  if (NS_WARN_IF(!aNode)) {
+    return nullptr;
+  }
+
+  if (aNode->GetPreviousSibling()) {
+    return aNode->GetPreviousSibling();
+  }
+
+  nsINode* parent = aNode->GetParentNode();
+  if (NS_WARN_IF(!parent)) {
+    return nullptr;
+  }
+
+  // XXX This is a hack to preserve previous behaviour: This should be fixed
+  // in bug 1404916. If we were positioned on anonymous content, move to
+  // the last child of our parent.
+  if (parent->GetFirstChild() && parent->GetFirstChild() != aNode) {
+    return parent->GetLastChild();
+  }
+
+  return ContentIteratorBase::GetPrevSibling(parent);
+}
+
+nsINode* ContentIteratorBase::NextNode(nsINode* aNode) {
+  nsINode* node = aNode;
+
+  // if we are a Pre-order iterator, use pre-order
+  if (mOrder == Order::Pre) {
+    // if it has children then next node is first child
+    if (node->HasChildren()) {
+      nsIContent* firstChild = node->GetFirstChild();
+      MOZ_ASSERT(firstChild);
+
+      return firstChild;
+    }
+
+    // else next sibling is next
+    return ContentIteratorBase::GetNextSibling(node);
+  }
+
+  // post-order
+  nsINode* parent = node->GetParentNode();
+  if (NS_WARN_IF(!parent)) {
+    MOZ_ASSERT(parent, "The node is the root node but not the last node");
+    mCurNode = nullptr;
+    return node;
+  }
+
+  if (nsIContent* sibling = node->GetNextSibling()) {
+    // next node is sibling's "deep left" child
+    return ContentIteratorBase::GetDeepFirstChild(sibling);
+  }
+
+  return parent;
+}
+
+nsINode* ContentIteratorBase::PrevNode(nsINode* aNode) {
+  nsINode* node = aNode;
+
+  // if we are a Pre-order iterator, use pre-order
+  if (mOrder == Order::Pre) {
+    nsINode* parent = node->GetParentNode();
+    if (NS_WARN_IF(!parent)) {
+      MOZ_ASSERT(parent, "The node is the root node but not the first node");
+      mCurNode = nullptr;
+      return aNode;
+    }
+
+    nsIContent* sibling = node->GetPreviousSibling();
+    if (sibling) {
+      return ContentIteratorBase::GetDeepLastChild(sibling);
+    }
+
+    return parent;
+  }
+
+  // post-order
+  if (node->HasChildren()) {
+    return node->GetLastChild();
+  }
+
+  // else prev sibling is previous
+  return ContentIteratorBase::GetPrevSibling(node);
+}
+
+/******************************************************
+ * ContentIteratorBase routines
+ ******************************************************/
+
+void ContentIteratorBase::First() {
+  if (!mFirst) {
+    MOZ_ASSERT(IsDone());
+    mCurNode = nullptr;
+    return;
+  }
+
+  mozilla::DebugOnly<nsresult> rv = PositionAt(mFirst);
+  NS_ASSERTION(NS_SUCCEEDED(rv), "Failed to position iterator!");
+}
+
+void ContentIteratorBase::Last() {
+  // Note that mLast can be nullptr if SetEmpty() is called in Init()
+  // since at that time, Init() returns NS_OK.
+  if (!mLast) {
+    MOZ_ASSERT(IsDone());
+    mCurNode = nullptr;
+    return;
+  }
+
+  mozilla::DebugOnly<nsresult> rv = PositionAt(mLast);
+  NS_ASSERTION(NS_SUCCEEDED(rv), "Failed to position iterator!");
+}
+
+void ContentIteratorBase::Next() {
+  if (IsDone()) {
+    return;
+  }
+
+  if (mCurNode == mLast) {
+    mCurNode = nullptr;
+    return;
+  }
+
+  mCurNode = NextNode(mCurNode);
+}
+
+void ContentIteratorBase::Prev() {
+  if (IsDone()) {
+    return;
+  }
+
+  if (mCurNode == mFirst) {
+    mCurNode = nullptr;
+    return;
+  }
+
+  mCurNode = PrevNode(mCurNode);
+}
+
+// Keeping arrays of indexes for the stack of nodes makes PositionAt
+// interesting...
+nsresult ContentIteratorBase::PositionAt(nsINode* aCurNode) {
+  if (NS_WARN_IF(!aCurNode)) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  // take an early out if this doesn't actually change the position
+  if (mCurNode == aCurNode) {
+    return NS_OK;
+  }
+  mCurNode = aCurNode;
+
+  // Check to see if the node falls within the traversal range.
+
+  RawRangeBoundary first(mFirst, 0u);
+  RawRangeBoundary last(mLast, 0u);
+
+  if (mFirst && mLast) {
+    if (mOrder == Order::Pre) {
+      // In pre we want to record the point immediately before mFirst, which is
+      // the point immediately after mFirst's previous sibling.
+      first = {mFirst->GetParentNode(), mFirst->GetPreviousSibling()};
+
+      // If mLast has no children, then we want to make sure to include it.
+      if (!mLast->HasChildren()) {
+        last = {mLast->GetParentNode(), mLast->AsContent()};
+      }
+    } else {
+      // If the first node has any children, we want to be immediately after the
+      // last. Otherwise we want to be immediately before mFirst.
+      if (mFirst->HasChildren()) {
+        first = {mFirst, mFirst->GetLastChild()};
+      } else {
+        first = {mFirst->GetParentNode(), mFirst->GetPreviousSibling()};
+      }
+
+      // Set the last point immediately after the final node.
+      last = {mLast->GetParentNode(), mLast->AsContent()};
+    }
+  }
+
+  NS_WARNING_ASSERTION(first.IsSetAndValid(), "first is not valid");
+  NS_WARNING_ASSERTION(last.IsSetAndValid(), "last is not valid");
+
+  // The end positions are always in the range even if it has no parent.  We
+  // need to allow that or 'iter->Init(root)' would assert in Last() or First()
+  // for example, bug 327694.
+  if (mFirst != mCurNode && mLast != mCurNode &&
+      (NS_WARN_IF(!first.IsSet()) || NS_WARN_IF(!last.IsSet()) ||
+       NS_WARN_IF(!NodeIsInTraversalRange(mCurNode, mOrder == Order::Pre, first,
+                                          last)))) {
+    mCurNode = nullptr;
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+/******************************************************
+ * ContentSubtreeIterator init routines
+ ******************************************************/
+
+nsresult ContentSubtreeIterator::Init(nsINode* aRoot) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+nsresult ContentSubtreeIterator::Init(nsRange* aRange) {
+  MOZ_ASSERT(aRange);
+
+  if (NS_WARN_IF(!aRange->IsPositioned())) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  mRange = aRange;
+
+  return InitWithRange();
+}
+
+nsresult ContentSubtreeIterator::Init(nsINode* aStartContainer,
+                                      uint32_t aStartOffset,
+                                      nsINode* aEndContainer,
+                                      uint32_t aEndOffset) {
+  return Init(RawRangeBoundary(aStartContainer, aStartOffset),
+              RawRangeBoundary(aEndContainer, aEndOffset));
+}
+
+nsresult ContentSubtreeIterator::Init(const RawRangeBoundary& aStartBoundary,
+                                      const RawRangeBoundary& aEndBoundary) {
+  RefPtr<nsRange> range =
+      nsRange::Create(aStartBoundary, aEndBoundary, IgnoreErrors());
+  if (NS_WARN_IF(!range) || NS_WARN_IF(!range->IsPositioned())) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (NS_WARN_IF(range->StartRef() != aStartBoundary) ||
+      NS_WARN_IF(range->EndRef() != aEndBoundary)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  mRange = std::move(range);
+
+  return InitWithRange();
+}
+
+void ContentSubtreeIterator::CacheInclusiveAncestorsOfEndContainer() {
+  mInclusiveAncestorsOfEndContainer.Clear();
+  nsINode* const endContainer = mRange->GetEndContainer();
+  nsIContent* endNode =
+      endContainer->IsContent() ? endContainer->AsContent() : nullptr;
+  while (endNode) {
+    mInclusiveAncestorsOfEndContainer.AppendElement(endNode);
+    endNode = endNode->GetParent();
+  }
+}
+
+nsIContent* ContentSubtreeIterator::DetermineCandidateForFirstContent() const {
+  nsINode* startContainer = mRange->GetStartContainer();
+  nsIContent* firstCandidate = nullptr;
+  // find first node in range
+  nsINode* node = nullptr;
+  if (!startContainer->GetChildCount()) {
+    // no children, start at the node itself
+    node = startContainer;
+  } else {
+    nsIContent* child = mRange->GetChildAtStartOffset();
+    MOZ_ASSERT(child ==
+               startContainer->GetChildAt_Deprecated(mRange->StartOffset()));
+    if (!child) {
+      // offset after last child
+      node = startContainer;
+    } else {
+      firstCandidate = child;
+    }
+  }
+
+  if (!firstCandidate) {
+    // then firstCandidate is next node after node
+    firstCandidate = ContentIteratorBase::GetNextSibling(node);
+  }
+
+  if (firstCandidate) {
+    firstCandidate = ContentIteratorBase::GetDeepFirstChild(firstCandidate);
+  }
+
+  return firstCandidate;
+}
+
+nsIContent* ContentSubtreeIterator::DetermineFirstContent() const {
+  nsIContent* firstCandidate = DetermineCandidateForFirstContent();
+  if (!firstCandidate) {
+    return nullptr;
+  }
+
+  // confirm that this first possible contained node is indeed contained.  Else
+  // we have a range that does not fully contain any node.
+  const Maybe<bool> isNodeContainedInRange =
+      RangeUtils::IsNodeContainedInRange(*firstCandidate, mRange);
+  MOZ_ALWAYS_TRUE(isNodeContainedInRange);
+  if (!isNodeContainedInRange.value()) {
+    return nullptr;
+  }
+
+  // cool, we have the first node in the range.  Now we walk up its ancestors
+  // to find the most senior that is still in the range.  That's the real first
+  // node.
+  return GetTopAncestorInRange(firstCandidate);
+}
+
+nsIContent* ContentSubtreeIterator::DetermineCandidateForLastContent() const {
+  nsIContent* lastCandidate{nullptr};
+  nsINode* endContainer = mRange->GetEndContainer();
+  // now to find the last node
+  int32_t offset = mRange->EndOffset();
+  int32_t numChildren = endContainer->GetChildCount();
+
+  nsINode* node = nullptr;
+  if (offset > numChildren) {
+    // Can happen for text nodes
+    offset = numChildren;
+  }
+  if (!offset || !numChildren) {
+    node = endContainer;
+  } else {
+    lastCandidate = mRange->EndRef().Ref();
+    MOZ_ASSERT(lastCandidate == endContainer->GetChildAt_Deprecated(--offset));
+    NS_ASSERTION(lastCandidate,
+                 "tree traversal trouble in ContentSubtreeIterator::Init");
+  }
+
+  if (!lastCandidate) {
+    // then lastCandidate is prev node before node
+    lastCandidate = ContentIteratorBase::GetPrevSibling(node);
+  }
+
+  if (lastCandidate) {
+    lastCandidate = ContentIteratorBase::GetDeepLastChild(lastCandidate);
+  }
+
+  return lastCandidate;
+}
+
+nsresult ContentSubtreeIterator::InitWithRange() {
+  MOZ_ASSERT(mRange);
+  MOZ_ASSERT(mRange->IsPositioned());
+
+  // get the start node and offset, convert to nsINode
+  mClosestCommonInclusiveAncestor = mRange->GetClosestCommonInclusiveAncestor();
+  nsINode* startContainer = mRange->GetStartContainer();
+  const int32_t startOffset = mRange->StartOffset();
+  nsINode* endContainer = mRange->GetEndContainer();
+  const int32_t endOffset = mRange->EndOffset();
+  MOZ_ASSERT(mClosestCommonInclusiveAncestor && startContainer && endContainer);
+  // Bug 767169
+  MOZ_ASSERT(uint32_t(startOffset) <= startContainer->Length() &&
+             uint32_t(endOffset) <= endContainer->Length());
+
+  // short circuit when start node == end node
+  if (startContainer == endContainer) {
+    nsINode* child = startContainer->GetFirstChild();
+
+    if (!child || startOffset == endOffset) {
+      // Text node, empty container, or collapsed
+      SetEmpty();
+      return NS_OK;
+    }
+  }
+
+  CacheInclusiveAncestorsOfEndContainer();
+
+  mFirst = DetermineFirstContent();
+  if (!mFirst) {
+    SetEmpty();
+    return NS_OK;
+  }
+
+  mLast = DetermineLastContent();
+  if (!mLast) {
+    SetEmpty();
+    return NS_OK;
+  }
+
+  mCurNode = mFirst;
+
+  return NS_OK;
+}
+
+nsIContent* ContentSubtreeIterator::DetermineLastContent() const {
+  nsIContent* lastCandidate = DetermineCandidateForLastContent();
+  if (!lastCandidate) {
+    return nullptr;
+  }
+
+  // confirm that this last possible contained node is indeed contained.  Else
+  // we have a range that does not fully contain any node.
+
+  const Maybe<bool> isNodeContainedInRange =
+      RangeUtils::IsNodeContainedInRange(*lastCandidate, mRange);
+  MOZ_ALWAYS_TRUE(isNodeContainedInRange);
+  if (!isNodeContainedInRange.value()) {
+    return nullptr;
+  }
+
+  // cool, we have the last node in the range.  Now we walk up its ancestors to
+  // find the most senior that is still in the range.  That's the real first
+  // node.
+  return GetTopAncestorInRange(lastCandidate);
+}
+
+/****************************************************************
+ * ContentSubtreeIterator overrides of ContentIterator routines
+ ****************************************************************/
+
+// we can't call PositionAt in a subtree iterator...
+void ContentSubtreeIterator::First() { mCurNode = mFirst; }
+
+// we can't call PositionAt in a subtree iterator...
+void ContentSubtreeIterator::Last() { mCurNode = mLast; }
+
+void ContentSubtreeIterator::Next() {
+  if (IsDone()) {
+    return;
+  }
+
+  if (mCurNode == mLast) {
+    mCurNode = nullptr;
+    return;
+  }
+
+  nsINode* nextNode = ContentIteratorBase::GetNextSibling(mCurNode);
+  NS_ASSERTION(nextNode, "No next sibling!?! This could mean deadlock!");
+
+  int32_t i = mInclusiveAncestorsOfEndContainer.IndexOf(nextNode);
+  while (i != -1) {
+    // as long as we are finding ancestors of the endpoint of the range,
+    // dive down into their children
+    nextNode = nextNode->GetFirstChild();
+    NS_ASSERTION(nextNode, "Iterator error, expected a child node!");
+
+    // should be impossible to get a null pointer.  If we went all the way
+    // down the child chain to the bottom without finding an interior node,
+    // then the previous node should have been the last, which was
+    // was tested at top of routine.
+    i = mInclusiveAncestorsOfEndContainer.IndexOf(nextNode);
+  }
+
+  mCurNode = nextNode;
+}
+
+void ContentSubtreeIterator::Prev() {
+  // Prev should be optimized to use the mStartNodes, just as Next
+  // uses mInclusiveAncestorsOfEndContainer.
+  if (IsDone()) {
+    return;
+  }
+
+  if (mCurNode == mFirst) {
+    mCurNode = nullptr;
+    return;
+  }
+
+  // If any of these function calls return null, so will all succeeding ones,
+  // so mCurNode will wind up set to null.
+  nsINode* prevNode = ContentIteratorBase::GetDeepFirstChild(mCurNode);
+
+  prevNode = PrevNode(prevNode);
+
+  prevNode = ContentIteratorBase::GetDeepLastChild(prevNode);
+
+  mCurNode = GetTopAncestorInRange(prevNode);
+}
+
+nsresult ContentSubtreeIterator::PositionAt(nsINode* aCurNode) {
+  NS_ERROR("Not implemented!");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+/****************************************************************
+ * ContentSubtreeIterator helper routines
+ ****************************************************************/
+
+nsIContent* ContentSubtreeIterator::GetTopAncestorInRange(
+    nsINode* aNode) const {
+  if (!aNode || !aNode->GetParentNode()) {
+    return nullptr;
+  }
+
+  // aNode has a parent, so it must be content.
+  nsIContent* content = aNode->AsContent();
+
+  // sanity check: aNode is itself in the range
+  Maybe<bool> isNodeContainedInRange =
+      RangeUtils::IsNodeContainedInRange(*aNode, mRange);
+  NS_ASSERTION(isNodeContainedInRange && isNodeContainedInRange.value(),
+               "aNode isn't in mRange, or something else weird happened");
+  if (!isNodeContainedInRange || !isNodeContainedInRange.value()) {
+    return nullptr;
+  }
+
+  while (content) {
+    nsIContent* parent = content->GetParent();
+    // content always has a parent.  If its parent is the root, however --
+    // i.e., either it's not content, or it is content but its own parent is
+    // null -- then we're finished, since we don't go up to the root.
+    //
+    // We have to special-case this because CompareNodeToRange treats the root
+    // node differently -- see bug 765205.
+    if (!parent || !parent->GetParentNode()) {
+      return content;
+    }
+
+    isNodeContainedInRange =
+        RangeUtils::IsNodeContainedInRange(*parent, mRange);
+    MOZ_ALWAYS_TRUE(isNodeContainedInRange);
+    if (!isNodeContainedInRange.value()) {
+      return content;
+    }
+
+    content = parent;
+  }
+
+  MOZ_CRASH("This should only be possible if aNode was null");
+}
+
+}  // namespace mozilla