typedef struct b_node_t b_node_t;
struct b_node_t {
    /* left child */
    b_node_t *left;
    /* right child */
    b_node_t *right;

    /* data contained by the node */
    void *data;
};

typedef struct b_tree_t b_tree_t;
struct b_tree_t {
    /* root of the tree */
    b_node_t *root;
};