ros2_introspection/include/ros2_introspection/tree.hpp

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#pragma once

#include <vector>
#include <deque>
#include <iostream>
#include <memory>
#include <boost/container/stable_vector.hpp>
#include <boost/noncopyable.hpp>


namespace Ros2Introspection {

template <typename T> class TreeNode
{
public:

  typedef std::vector<TreeNode> ChildrenVector; // dangerous because of pointer invalidation (but faster)

  TreeNode(const TreeNode* parent );

  const TreeNode* parent() const  { return _parent; }

  const T& value() const          { return _value; }
  void setValue( const T& value)  { _value = value; }

  const ChildrenVector& children()const   { return _children; }
  ChildrenVector& children()              { return _children; }

  const TreeNode* child(size_t index) const { return &(_children[index]); }
  TreeNode* child(size_t index) { return &(_children[index]); }

  TreeNode *addChild(const T& child );

  bool isLeaf() const { return _children.empty(); }

private:
  const TreeNode*   _parent;
  T                 _value;
  ChildrenVector    _children;
};


template <typename T> class Tree
{
public:
  Tree(): _root( new TreeNode<T>(nullptr) ) {}

  TreeNode<T>* root() { return _root.get(); }

  const TreeNode<T>* root() const { return _root.get(); }

  friend std::ostream& operator<<(std::ostream& os, const Tree& _this){
    _this.print_impl(os, _this.croot() , 0);
    return os;
  }

private:

  void print_impl(std::ostream& os, const TreeNode<T> *node, int indent ) const;

  std::unique_ptr<TreeNode<T>> _root;
};

//-----------------------------------------


template <typename T> inline
std::ostream& operator<<(std::ostream &os, const std::pair<const TreeNode<T>*, const TreeNode<T>* >& tail_head )
{
  const TreeNode<T>* tail = tail_head.first;
  const TreeNode<T>* head = tail_head.second;

  if( !head ) return os;

  const TreeNode<T>* array[64];
  int index = 0;
  array[index++] = head;

  while( !head || head != tail)
  {
    head = head->parent();
    array[index++] = head;
  };
  array[index] = nullptr;
  index--;

  while ( index >=0)
  {
    if( array[index] ){
      os << array[index]->value();
    }
    if( index >0 )  os << ".";
    index--;
  }
  return os;
}

template <typename T> inline
void Tree<T>::print_impl(std::ostream &os, const TreeNode<T>* node, int indent) const
{
  for (int i=0; i<indent; i++) os << " ";
  os << node->value() << std::endl;

  for (const auto& child: node->children() )
  {
    print_impl(os, &child, indent+3);
  }
}

template <typename T> inline
TreeNode<T>::TreeNode(const TreeNode *parent):
  _parent(parent)
{

}

template <typename T> inline
TreeNode<T> *TreeNode<T>::addChild(const T& value)
{
  assert(_children.capacity() > _children.size() );
  _children.push_back( TreeNode<T>(this) );
  _children.back().setValue( value );
  return &_children.back();
}

}