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/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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file Copyright.txt or https://cmake.org/licensing for details. */
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#ifndef cmLinkedTree_h
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#define cmLinkedTree_h
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#include "cmConfigure.h" // IWYU pragma: keep
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#include <assert.h>
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#include <vector>
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/**
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@brief A adaptor for traversing a tree structure in a vector
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This class is not intended to be wholly generic like a standard library
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container adaptor. Mostly it exists to facilitate code sharing for the
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needs of the cmState. For example, the Truncate() method is a specific
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requirement of the cmState.
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An empty cmLinkedTree provides a Root() method, and an Push() method,
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each of which return iterators. A Tree can be built up by extending
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from the root, and then extending from any other iterator.
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An iterator resulting from this tree construction can be
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forward-only-iterated toward the root. Extending the tree never
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invalidates existing iterators.
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*/
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template <typename T>
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class cmLinkedTree
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{
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typedef typename std::vector<T>::size_type PositionType;
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typedef T* PointerType;
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typedef T& ReferenceType;
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public:
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class iterator
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{
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friend class cmLinkedTree;
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cmLinkedTree* Tree;
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// The Position is always 'one past the end'.
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PositionType Position;
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iterator(cmLinkedTree* tree, PositionType pos)
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: Tree(tree)
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, Position(pos)
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{
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}
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public:
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iterator()
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: Tree(nullptr)
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, Position(0)
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{
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}
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void operator++()
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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assert(this->Position <= this->Tree->Data.size());
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assert(this->Position > 0);
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this->Position = this->Tree->UpPositions[this->Position - 1];
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}
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PointerType operator->() const
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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assert(this->Position <= this->Tree->Data.size());
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assert(this->Position > 0);
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return this->Tree->GetPointer(this->Position - 1);
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}
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PointerType operator->()
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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assert(this->Position <= this->Tree->Data.size());
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assert(this->Position > 0);
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return this->Tree->GetPointer(this->Position - 1);
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}
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ReferenceType operator*() const
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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assert(this->Position <= this->Tree->Data.size());
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assert(this->Position > 0);
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return this->Tree->GetReference(this->Position - 1);
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}
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ReferenceType operator*()
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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assert(this->Position <= this->Tree->Data.size());
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assert(this->Position > 0);
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return this->Tree->GetReference(this->Position - 1);
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}
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bool operator==(iterator other) const
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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assert(this->Tree == other.Tree);
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return this->Position == other.Position;
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}
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bool operator!=(iterator other) const
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{
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assert(this->Tree);
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assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
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return !(*this == other);
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}
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bool IsValid() const
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{
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if (!this->Tree) {
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return false;
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}
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return this->Position <= this->Tree->Data.size();
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}
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bool StrictWeakOrdered(iterator other) const
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{
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assert(this->Tree);
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assert(this->Tree == other.Tree);
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return this->Position < other.Position;
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}
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};
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iterator Root() const
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{
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return iterator(const_cast<cmLinkedTree*>(this), 0);
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}
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iterator Push(iterator it) { return Push_impl(it, T()); }
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iterator Push(iterator it, T t) { return Push_impl(it, std::move(t)); }
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bool IsLast(iterator it) { return it.Position == this->Data.size(); }
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iterator Pop(iterator it)
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{
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assert(!this->Data.empty());
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assert(this->UpPositions.size() == this->Data.size());
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bool const isLast = this->IsLast(it);
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++it;
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// If this is the last entry then no other entry can refer
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// to it so we can drop its storage.
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if (isLast) {
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this->Data.pop_back();
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this->UpPositions.pop_back();
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}
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return it;
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}
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iterator Truncate()
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{
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assert(!this->UpPositions.empty());
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this->UpPositions.erase(this->UpPositions.begin() + 1,
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this->UpPositions.end());
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assert(!this->Data.empty());
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this->Data.erase(this->Data.begin() + 1, this->Data.end());
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return iterator(this, 1);
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}
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void Clear()
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{
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this->UpPositions.clear();
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this->Data.clear();
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}
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private:
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T& GetReference(PositionType pos) { return this->Data[pos]; }
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T* GetPointer(PositionType pos) { return &this->Data[pos]; }
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iterator Push_impl(iterator it, T&& t)
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{
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assert(this->UpPositions.size() == this->Data.size());
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assert(it.Position <= this->UpPositions.size());
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this->UpPositions.push_back(it.Position);
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this->Data.push_back(std::move(t));
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return iterator(this, this->UpPositions.size());
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}
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std::vector<T> Data;
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std::vector<PositionType> UpPositions;
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};
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#endif
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