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/* -*- 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/. */
#ifndef TreeIterator_h
#define TreeIterator_h
#include "mozilla/Attributes.h"
#include "nsIContent.h"
/**
* A generic pre-order tree iterator on top of ChildIterator.
*
* See ChildIterator.h for the kind of iterators you can use as the template
* argument for this class.
*/
namespace mozilla {
namespace dom {
template <typename ChildIterator>
class MOZ_STACK_CLASS TreeIterator {
enum class Direction {
Forward,
Backwards,
};
template <Direction aDirection>
nsIContent* GetNextChild(ChildIterator& aIter) {
return aDirection == Direction::Forward ? aIter.GetNextChild()
: aIter.GetPreviousChild();
}
template <Direction>
inline void Advance();
template <Direction>
inline void AdvanceSkippingChildren();
public:
explicit TreeIterator(nsIContent& aRoot) : mRoot(aRoot), mCurrent(&aRoot) {}
nsIContent* GetCurrent() const { return mCurrent; }
// Note that this keeps the iterator state consistent in case of failure.
inline bool Seek(nsIContent&);
inline nsIContent* GetNext();
inline nsIContent* GetNextSkippingChildren();
inline nsIContent* GetPrev();
inline nsIContent* GetPrevSkippingChildren();
private:
using IteratorArray = AutoTArray<ChildIterator, 30>;
nsIContent& mRoot;
nsIContent* mCurrent;
IteratorArray mParentIterators;
};
template <typename ChildIterator>
template <typename TreeIterator<ChildIterator>::Direction aDirection>
inline void TreeIterator<ChildIterator>::AdvanceSkippingChildren() {
while (true) {
if (MOZ_UNLIKELY(mParentIterators.IsEmpty())) {
mCurrent = nullptr;
return;
}
if (nsIContent* nextSibling =
GetNextChild<aDirection>(mParentIterators.LastElement())) {
mCurrent = nextSibling;
return;
}
mParentIterators.RemoveLastElement();
}
}
template <typename ChildIterator>
inline bool TreeIterator<ChildIterator>::Seek(nsIContent& aContent) {
IteratorArray parentIterators;
nsIContent* current = &aContent;
while (current != &mRoot) {
nsIContent* parent = ChildIterator::GetParent(*current);
if (!parent) {
return false;
}
ChildIterator children(parent);
if (!children.Seek(current)) {
return false;
}
parentIterators.AppendElement(std::move(children));
current = parent;
}
parentIterators.Reverse();
mParentIterators = std::move(parentIterators);
mCurrent = &aContent;
return true;
}
template <typename ChildIterator>
template <typename TreeIterator<ChildIterator>::Direction aDirection>
inline void TreeIterator<ChildIterator>::Advance() {
MOZ_ASSERT(mCurrent);
const bool startAtBeginning = aDirection == Direction::Forward;
ChildIterator children(mCurrent, startAtBeginning);
if (nsIContent* first = GetNextChild<aDirection>(children)) {
mCurrent = first;
mParentIterators.AppendElement(std::move(children));
return;
}
AdvanceSkippingChildren<aDirection>();
}
template <typename ChildIterator>
inline nsIContent* TreeIterator<ChildIterator>::GetNext() {
Advance<Direction::Forward>();
return GetCurrent();
}
template <typename ChildIterator>
inline nsIContent* TreeIterator<ChildIterator>::GetPrev() {
Advance<Direction::Backwards>();
return GetCurrent();
}
template <typename ChildIterator>
inline nsIContent* TreeIterator<ChildIterator>::GetNextSkippingChildren() {
AdvanceSkippingChildren<Direction::Forward>();
return GetCurrent();
}
template <typename ChildIterator>
inline nsIContent* TreeIterator<ChildIterator>::GetPrevSkippingChildren() {
AdvanceSkippingChildren<Direction::Backwards>();
return GetCurrent();
}
} // namespace dom
} // namespace mozilla
#endif
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