cmState: Extract a cmLinkedTree container adaptor.

This will be used to contain most of the content of the cmState
in several different trees.  Refer to the BuildsystemDirectory
state from the SnapshotData state.  Currently these trees have
the same structure, but that will change when we have more snapshot
types.

1 files changed, 164 insertions, 0 deletions

diff --git a/Source/cmLinkedTree.h b/Source/cmLinkedTree.h
new file mode 100644
index 0000000..d2339c4
--- /dev/null
+++ b/Source/cmLinkedTree.h
@@ -0,0 +1,164 @@
+/*============================================================================
+  CMake - Cross Platform Makefile Generator
+  Copyright 2015 Stephen Kelly <steveire@gmail.com>
+
+  Distributed under the OSI-approved BSD License (the "License");
+  see accompanying file Copyright.txt for details.
+
+  This software is distributed WITHOUT ANY WARRANTY; without even the
+  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  See the License for more information.
+============================================================================*/
+#ifndef cmLinkedTree_h
+#define cmLinkedTree_h
+
+#include "cmStandardIncludes.h"
+
+#include <assert.h>
+
+/**
+  @brief A adaptor for traversing a tree structure in a vector
+
+  This class is not intended to be wholly generic like a standard library
+  container adaptor.  Mostly it exists to facilitate code sharing for the
+  needs of the cmState.  For example, the Truncate() method is a specific
+  requirement of the cmState.
+
+  An empty cmLinkedTree provides a Root() method, and an Extend() method,
+  each of which return iterators.  A Tree can be built up by extending
+  from the root, and then extending from any other iterator.
+
+  An iterator resulting from this tree construction can be
+  forward-only-iterated toward the root.  Extending the tree never
+  invalidates existing iterators.
+ */
+template<typename T>
+class cmLinkedTree
+{
+  typedef typename std::vector<T>::size_type PositionType;
+  typedef T* PointerType;
+  typedef T& ReferenceType;
+public:
+  class iterator : public std::iterator<std::forward_iterator_tag, T>
+  {
+    friend class cmLinkedTree;
+    cmLinkedTree* Tree;
+
+    // The Position is always 'one past the end'.
+    PositionType Position;
+
+    iterator(cmLinkedTree* tree, PositionType pos)
+      : Tree(tree), Position(pos)
+    {
+
+    }
+
+  public:
+    iterator()
+      : Tree(0), Position(0)
+    {
+
+    }
+
+    void operator++()
+    {
+      assert(this->Tree);
+      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
+      assert(this->Position <= this->Tree->Data.size());
+      assert(this->Position > 0);
+      this->Position = this->Tree->UpPositions[this->Position - 1];
+    }
+
+    PointerType operator->() const
+    {
+      assert(this->Tree);
+      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
+      assert(this->Position <= this->Tree->Data.size());
+      assert(this->Position > 0);
+      return this->Tree->GetPointer(this->Position - 1);
+    }
+
+    PointerType operator->()
+    {
+      assert(this->Tree);
+      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
+      assert(this->Position <= this->Tree->Data.size());
+      assert(this->Position > 0);
+      return this->Tree->GetPointer(this->Position - 1);
+    }
+
+    bool operator==(iterator other) const
+    {
+      assert(this->Tree);
+      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
+      assert(this->Tree == other.Tree);
+      return this->Position == other.Position;
+    }
+
+    bool operator!=(iterator other) const
+    {
+      assert(this->Tree);
+      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
+      return !(*this == other);
+    }
+
+    bool IsValid() const
+    {
+      if (!this->Tree)
+        {
+        return false;
+        }
+      return this->Position <= this->Tree->Data.size();
+    }
+  };
+
+  iterator Root() const
+  {
+    return iterator(const_cast<cmLinkedTree*>(this), 0);
+  }
+
+  iterator Extend(iterator it)
+  {
+    return Extend_impl(it, T());
+  }
+
+  iterator Extend(iterator it, T t)
+  {
+    return Extend_impl(it, t);
+  }
+
+  iterator Truncate()
+  {
+    assert(this->UpPositions.size() > 0);
+    this->UpPositions.erase(this->UpPositions.begin() + 1,
+                            this->UpPositions.end());
+    assert(this->Data.size() > 0);
+    this->Data.erase(this->Data.begin() + 1, this->Data.end());
+    return iterator(this, 1);
+  }
+
+private:
+  T& GetReference(PositionType pos)
+  {
+    return this->Data[pos];
+  }
+
+  T* GetPointer(PositionType pos)
+  {
+    return &this->Data[pos];
+  }
+
+  iterator Extend_impl(iterator it, T t)
+  {
+    assert(this->UpPositions.size() == this->Data.size());
+    assert(it.Position <= this->UpPositions.size());
+    this->UpPositions.push_back(it.Position);
+    this->Data.push_back(t);
+    return iterator(this, this->UpPositions.size());
+  }
+
+  std::vector<T> Data;
+  std::vector<PositionType> UpPositions;
+};
+
+#endif