sunxfancy / DSViz

A C++ data structure visualization library using GraphViz

DSViz

DSViz is a header-only C++11 library for visualization node-based data structure for generating GraphViz dot files. You can copy and put it anywhere you like.

To visualize your data structure, there are two approaches: invasive or non-invasive

Basic invasive approach

The invasive approach is very simple, you need to inherit the interface DSViz::IDataStructure and implement the dsviz_show method in the data structure that you want to visualize. The bad thing is that you need to modify your data structure.

struct Node : public DSViz::IDataStructure {
    string name;
    float sum;

    Node* parent;
    Node* left;
    Node* right;

    Node(string name, float sum, Node* left, Node* right) 
        : name(name), sum(sum), parent(nullptr), left(left), right(right) {
        if (left)  left->parent  = this;
        if (right) right->parent = this;
    } 

    virtual void dsviz_show(DSViz::IViz& viz) {
        DSViz::TableNode node(viz, 2);
        viz.setName(this, node.name);
        node.addPointer("parent", parent, "", "", "", "[constraint=false]");
        node.add("name", name);
        node.add("sum", sum);
        node.addEdge(left,  "left");
        node.addEdge(right, "right");
    }
};

TableNode is the class used for printing table nodes in GraphViz.

• addPointer can set a pointer which is another node
• add can add a new field
• addEdge links nodes and influence the layout of the graph

Generate a *.dot file for your data structure

Once you have the data structures, create a Dot object and load data structures using the API load_ds. You can load any node that can used to access the whole data structure (by keep tracing pointers). Usually, a root node is the one you want to load. We will do a depth-first order traversal to load all nodes in the graph.

Then, dot.print will print the GraphViz *.dot format in string. You can output it to a file or print it into stdout.

    Node A {string("A"), 10.0f, nullptr, nullptr};
    Node B {string("B"), 12.0f, nullptr, nullptr};
    Node hello {string("hello"), 11.5f, &A, &B};

    DSViz::Dot dot;
    dot.load_ds(&hello);
    std::cout << dot.print();

You can use xdot in Linux to open the graphviz dot file or using dot to convert it into a png image:

  dot -Tpng filename.dot -o outfile.png

Non-invasive approach

The non-invasive approach is more flexible, you don't need to modify your data structure. You can use a mock class that contains the pointer of nodes and provide a dsviz_show function to visualize the data structure.

Use binary search tree as an example, we may have some code that implements the BST:

struct bintree_node {
    bintree_node *left;
    bintree_node *right;
    int           data;
};

class bst {
    bintree_node *root;

  public:
    bst() { root = NULL; }
    int  isempty() { return (root == NULL); }
    bintree_node *getRoot() { return root; }
    void insert(int item);
    void displayBinTree();
    void printBinTree(bintree_node *);
};

The individual function dsviz_show is used to visualize the data structure. It has the following signature:

void dsviz_show(bintree_node* P, DSViz::IViz &viz);

P is the pointer of the node, viz is the interface for adding nodes and edges.

Then we need to define a mock class which use this function. DSViz::Mock is a template that has two parameters: the type of the node and the function for visualization:

typedef DSViz::Mock<bintree_node, dsviz_show> mock;

Finally, we use mock::get to map the pointer of the original node to the mock node. It should be used everywhere in the dsviz_show function:

#include "dsv.hpp"
void dsviz_show(bintree_node* P, DSViz::IViz &viz);
typedef DSViz::Mock<bintree_node, dsviz_show> mock;

void dsviz_show(bintree_node* P, DSViz::IViz &viz) {
    DSViz::TableNode node(viz);
    viz.setName(mock::get(P), node.name);
    node.add("data", P->data);
    if (P->left) node.addEdge(mock::get(P->left), "left");
    if (P->right) node.addEdge(mock::get(P->right), "right");
}

Then we can print the dot file:

    DSViz::Dot dot;
    dot.load_ds(mock::get(bst.getRoot()));
    std::cout << dot.print();