## N-ary Trees

N-ary Trees — trees of data with any number of branches.

## Synopsis

    #include <glib.h>

    struct      GNode;
    GNode*      g_node_new                      (gpointer data);
    GNode*      g_node_copy                     (GNode *node);

    GNode*      g_node_insert                   (GNode *parent,
                                                 gint position,
                                                 GNode *node);
    GNode*      g_node_insert_before            (GNode *parent,
                                                 GNode *sibling,
                                                 GNode *node);
    GNode*      g_node_insert_after             (GNode *parent,
                                                 GNode *sibling,
                                                 GNode *node);
    #define     g_node_append                   (parent, node)
    GNode*      g_node_prepend                  (GNode *parent,
                                                 GNode *node);

    #define     g_node_insert_data              (parent, position, data)
    #define     g_node_insert_data_before       (parent, sibling, data)
    #define     g_node_append_data              (parent, data)
    #define     g_node_prepend_data             (parent, data)

    void        g_node_reverse_children         (GNode *node);
    void        g_node_traverse                 (GNode *root,
                                                 GTraverseType order,
                                                 GTraverseFlags flags,
                                                 gint max_depth,
                                                 GNodeTraverseFunc func,
                                                 gpointer data);
    enum        GTraverseFlags;
    gboolean    (*GNodeTraverseFunc)            (GNode *node,
                                                 gpointer data);
    void        g_node_children_foreach         (GNode *node,
                                                 GTraverseFlags flags,
                                                 GNodeForeachFunc func,
                                                 gpointer data);
    void        (*GNodeForeachFunc)             (GNode *node,
                                                 gpointer data);

    GNode*      g_node_get_root                 (GNode *node);
    GNode*      g_node_find                     (GNode *root,
                                                 GTraverseType order,
                                                 GTraverseFlags flags,
                                                 gpointer data);
    GNode*      g_node_find_child               (GNode *node,
                                                 GTraverseFlags flags,
                                                 gpointer data);
    gint        g_node_child_index              (GNode *node,
                                                 gpointer data);
    gint        g_node_child_position           (GNode *node,
                                                 GNode *child);
    #define     g_node_first_child              (node)
    GNode*      g_node_last_child               (GNode *node);
    GNode*      g_node_nth_child                (GNode *node,
                                                 guint n);
    GNode*      g_node_first_sibling            (GNode *node);
    #define     g_node_next_sibling             (node)
    #define     g_node_prev_sibling             (node)
    GNode*      g_node_last_sibling             (GNode *node);

    #define     G_NODE_IS_LEAF                  (node)
    #define     G_NODE_IS_ROOT                  (node)
    guint       g_node_depth                    (GNode *node);
    guint       g_node_n_nodes                  (GNode *root,
                                                 GTraverseFlags flags);
    guint       g_node_n_children               (GNode *node);
    gboolean    g_node_is_ancestor              (GNode *node,
                                                 GNode *descendant);
    guint       g_node_max_height               (GNode *root);

    void        g_node_unlink                   (GNode *node);
    void        g_node_destroy                  (GNode *root);

    void        g_node_push_allocator           (GAllocator *allocator);
    void        g_node_pop_allocator            (void);

## Description

The GNode struct and its associated functions provide a N-ary tree data structure, where nodes in the tree can contain arbitrary data.

To create a new tree use g_node_new().

To insert a node into a tree use g_node_insert(), g_node_insert_before(), g_node_append() and g_node_prepend().

To create a new node and insert it into a tree use g_node_insert_data(), g_node_insert_data_before(), g_node_append_data() and g_node_prepend_data().

To reverse the children of a node use g_node_reverse_children().

To find a node use g_node_get_root(), g_node_find(), g_node_find_child(), g_node_child_index(), g_node_child_position(), g_node_first_child(), g_node_last_child(), g_node_nth_child(), g_node_first_sibling(), g_node_prev_sibling(), g_node_next_sibling() or g_node_last_sibling().

To get information about a node or tree use G_NODE_IS_LEAF(), G_NODE_IS_ROOT(), g_node_depth(), g_node_n_nodes(), g_node_n_children(), g_node_is_ancestor() or g_node_max_height().

To traverse a tree, calling a function for each node visited in the traversal, use g_node_traverse() or g_node_children_foreach().

To remove a node or subtree from a tree use g_node_unlink() or g_node_destroy().

## Details

### struct GNode

    struct GNode {

      gpointer data;
      GNode	  *next;
      GNode	  *prev;
      GNode	  *parent;
      GNode	  *children;
    };

The GNode struct represents one node in a N-ary Tree. The `data` field contains the actual data of the node. The `next` and `prev` fields point to the node's siblings (a sibling is another GNode with the same parent). The `parent` field points to the parent of the GNode, or is `NULL` if the GNode is the root of the tree. The `children` field points to the first child of the GNode. The other children are accessed by using the `next` pointer of each child.

### g_node_new ()

    GNode*      g_node_new                      (gpointer data);

Creates a new GNode containing the given data. Used to create the first node in a tree.

`data` : | the data of the new node.
Returns : | a new GNode.

### g_node_copy ()

    GNode*      g_node_copy                     (GNode *node);

Recursively copies a GNode (but does not deep-copy the data inside the nodes, since there's no way for GLib to know how to do that).

`node` : | a GNode.
Returns : | a new GNode containing the same data pointers.

### g_node_insert ()

    GNode*      g_node_insert                   (GNode *parent,
                                                 gint position,
                                                 GNode *node);

Inserts a GNode beneath the parent at the given position.

`parent` : | the GNode to place `node` under.
`position` : | the position to place `node` at, with respect to its siblings. If position is -1, `node` is inserted as the last child of `parent`.
`node` : | the GNode to insert.
Returns : | the inserted GNode.

### g_node_insert_before ()

    GNode*      g_node_insert_before            (GNode *parent,
                                                 GNode *sibling,
                                                 GNode *node);

Inserts a GNode beneath the parent before the given sibling.

`parent` : | the GNode to place `node` under.
`sibling` : | the sibling GNode to place `node` before. If sibling is `NULL`, the node is inserted as the last child of `parent`.
`node` : | the GNode to insert.
Returns : | the inserted GNode.

### g_node_insert_after ()

    GNode*      g_node_insert_after             (GNode *parent,
                                                 GNode *sibling,
                                                 GNode *node);

Inserts a GNode beneath the parent after the given sibling.

`parent` : | the GNode to place `node` under.
`sibling` : | the sibling GNode to place `node` after. If sibling is `NULL`, the node is inserted as the first child of `parent`.
`node` : | the GNode to insert.
Returns : | the inserted GNode.

### g_node_append()

    #define     g_node_append(parent, node)

Inserts a GNode as the last child of the given parent.

`parent` : | the GNode to place the new GNode under.
`node` : | the GNode to insert.
Returns : | the inserted GNode.

### g_node_prepend ()

    GNode*      g_node_prepend                  (GNode *parent,
                                                 GNode *node);

Inserts a GNode as the first child of the given parent.

`parent` : | the GNode to place the new GNode under.
`node` : | the GNode to insert.
Returns : | the inserted GNode.

### g_node_insert_data()

    #define     g_node_insert_data(parent, position, data)

Inserts a new GNode at the given position.

`parent` : | the GNode to place the new GNode under.
`position` : | the position to place the new GNode at. If position is -1, the new GNode is inserted as the last child of `parent`.
`data` : | the data for the new GNode.
Returns : | the new GNode.

### g_node_insert_data_before()

    #define     g_node_insert_data_before(parent, sibling, data)

Inserts a new GNode before the given sibling.

`parent` : | the GNode to place the new GNode under.
`sibling` : | the sibling GNode to place the new GNode before.
`data` : | the data for the new GNode.
Returns : | the new GNode.

### g_node_append_data()

    #define     g_node_append_data(parent, data)

Inserts a new GNode as the last child of the given parent.

`parent` : | the GNode to place the new GNode under.
`data` : | the data for the new GNode.
Returns : | the new GNode.

### g_node_prepend_data()

    #define     g_node_prepend_data(parent, data)

Inserts a new GNode as the first child of the given parent.

`parent` : | the GNode to place the new GNode under.
`data` : | the data for the new GNode.
Returns : | the new GNode.

### g_node_reverse_children ()

    void        g_node_reverse_children         (GNode *node);

Reverses the order of the children of a GNode. (It doesn't change the order of the grandchildren.)

`node` : | a GNode.

### g_node_traverse ()

    void        g_node_traverse                 (GNode *root,
                                                 GTraverseType order,
                                                 GTraverseFlags flags,
                                                 gint max_depth,
                                                 GNodeTraverseFunc func,
                                                 gpointer data);

Traverses a tree starting at the given root GNode. It calls the given function for each node visited. The traversal can be halted at any point by returning `TRUE` from `func`.

`root` : | the root GNode of the tree to traverse.
`order` : | the order in which nodes are visited - `G_IN_ORDER`, `G_PRE_ORDER`, `G_POST_ORDER`, or `G_LEVEL_ORDER`.
`flags` : | which types of children are to be visited, one of `G_TRAVERSE_ALL`, `G_TRAVERSE_LEAFS` and `G_TRAVERSE_NON_LEAFS`.
`max_depth` : | the maximum depth of the traversal. Nodes below this depth will not be visited. If max_depth is -1 all nodes in the tree are visited. If depth is 1, only the root is visited. If depth is 2, the root and its children are visited. And so on.
`func` : | the function to call for each visited GNode.
`data` : | user data to pass to the function.

### enum GTraverseFlags

    typedef enum
    {
      G_TRAVERSE_LEAFS      = 1 << 0,
      G_TRAVERSE_NON_LEAFS  = 1 << 1,
      G_TRAVERSE_ALL        = G_TRAVERSE_LEAFS | G_TRAVERSE_NON_LEAFS,
      G_TRAVERSE_MASK       = 0x03
    } GTraverseFlags;

Specifies which nodes are visited during several of the tree functions, including g_node_traverse() and g_node_find().

`G_TRAVERSE_LEAFS` | only leaf nodes should be visited.
`G_TRAVERSE_NON_LEAFS` | only non-leaf nodes should be visited.
`G_TRAVERSE_ALL` | all nodes should be visited.
`G_TRAVERSE_MASK` |

### GNodeTraverseFunc ()

    gboolean    (*GNodeTraverseFunc)            (GNode *node,
                                                 gpointer data);

Specifies the type of function passed to g_node_traverse(). The function is called with each of the nodes visited, together with the user data passed to g_node_traverse(). If the function returns `TRUE`, then the traversal is stopped.

`node` : | a GNode.
`data` : | user data passed to g_node_traverse().
Returns : | `TRUE` to stop the traversal.

### g_node_children_foreach ()

    void        g_node_children_foreach         (GNode *node,
                                                 GTraverseFlags flags,
                                                 GNodeForeachFunc func,
                                                 gpointer data);

Calls a function for each of the children of a GNode. Note that it doesn't descend beneath the child nodes.

`node` : | a GNode.
`flags` : | which types of children are to be visited, one of `G_TRAVERSE_ALL`, `G_TRAVERSE_LEAFS` and `G_TRAVERSE_NON_LEAFS`.
`func` : | the function to call for each visited node.
`data` : | user data to pass to the function.

### GNodeForeachFunc ()

    void        (*GNodeForeachFunc)             (GNode *node,
                                                 gpointer data);

Specifies the type of function passed to g_node_children_foreach(). The function is called with each child node, together with the user data passed to g_node_children_foreach().

`node` : | a GNode.
`data` : | user data passed to g_node_children_foreach().

### g_node_get_root ()

    GNode*      g_node_get_root                 (GNode *node);

Gets the root of a tree.

`node` : | a GNode.
Returns : | the root of the tree.

### g_node_find ()

    GNode*      g_node_find                     (GNode *root,
                                                 GTraverseType order,
                                                 GTraverseFlags flags,
                                                 gpointer data);

Finds a GNode in a tree.

`root` : | the root GNode of the tree to search.
`order` : | the order in which nodes are visited - `G_IN_ORDER`, `G_PRE_ORDER`, `G_POST_ORDER`, or `G_LEVEL_ORDER`.
`flags` : | which types of children are to be searched, one of `G_TRAVERSE_ALL`, `G_TRAVERSE_LEAFS` and `G_TRAVERSE_NON_LEAFS`.
`data` : | the data to find.
Returns : | the found GNode, or `NULL` if the data is not found.

### g_node_find_child ()

    GNode*      g_node_find_child               (GNode *node,
                                                 GTraverseFlags flags,
                                                 gpointer data);

Finds the first child of a GNode with the given data.

`node` : | a GNode.
`flags` : | which types of children are to be searched, one of `G_TRAVERSE_ALL`, `G_TRAVERSE_LEAFS` and `G_TRAVERSE_NON_LEAFS`.
`data` : | the data to find.
Returns : | the found child GNode, or `NULL` if the data is not found.

### g_node_child_index ()

    gint        g_node_child_index              (GNode *node,
                                                 gpointer data);

Gets the position of the first child of a GNode which contains the given data.

`node` : | a GNode.
`data` : | the data to find.
Returns : | the index of the child of `node` which contains `data`, or -1 if the data is not found.

### g_node_child_position ()

    gint        g_node_child_position           (GNode *node,
                                                 GNode *child);

Gets the position of a GNode with respect to its siblings. `child` must be a child of `node`. The first child is numbered 0, the second 1, and so on.

`node` : | a GNode.
`child` : | a child of `node`.
Returns : | the position of `child` with respect to its siblings.

### g_node_first_child()

    #define     g_node_first_child(node)

Gets the first child of a GNode.

`node` : | a GNode.
Returns : | the last child of `node`, or `NULL` if `node` is `NULL` or has no children.

### g_node_last_child ()

    GNode*      g_node_last_child               (GNode *node);

Gets the last child of a GNode.

`node` : | a GNode (must not be `NULL`).
Returns : | the last child of `node`, or `NULL` if `node` has no children.

### g_node_nth_child ()

    GNode*      g_node_nth_child                (GNode *node,
                                                 guint n);

Gets a child of a GNode, using the given index. The first child is at index 0. If the index is too big, `NULL` is returned.

`node` : | a GNode.
`n` : | the index of the desired child.
Returns : | the child of `node` at index `n`.

### g_node_first_sibling ()

    GNode*      g_node_first_sibling            (GNode *node);

Gets the first sibling of a GNode. This could possibly be the node itself.

`node` : | a GNode.
Returns : | the first sibling of `node`.

### g_node_next_sibling()

    #define     g_node_next_sibling(node)

Gets the next sibling of a GNode.

`node` : | a GNode.
Returns : | the next sibling of `node`, or `NULL` if `node` is `NULL`.

### g_node_prev_sibling()

    #define     g_node_prev_sibling(node)

Gets the previous sibling of a GNode.

`node` : | a GNode.
Returns : | the previous sibling of `node`, or `NULL` if `node` is `NULL`.

### g_node_last_sibling ()

    GNode*      g_node_last_sibling             (GNode *node);

Gets the last sibling of a GNode. This could possibly be the node itself.

`node` : | a GNode.
Returns : | the last sibling of `node`.

### G_NODE_IS_LEAF()

    #define	 G_NODE_IS_LEAF(node)	(((GNode*) (node))->children == NULL)

Returns `TRUE` if a GNode is a leaf node.

`node` : | a GNode.
Returns : | `TRUE` if the GNode is a leaf node (i.e. it has no children).

### G_NODE_IS_ROOT()

    #define     G_NODE_IS_ROOT(node)

Returns `TRUE` if a GNode is the root of a tree.

`node` : | a GNode.
Returns : | `TRUE` if the GNode is the root of a tree (i.e. it has no parent or siblings).

### g_node_depth ()

    guint       g_node_depth                    (GNode *node);

Gets the depth of a GNode.

If `node` is `NULL` the depth is 0. The root node has a depth of 1. For the children of the root node the depth is 2. And so on.

`node` : | a GNode.
Returns : | the depth of the GNode.

### g_node_n_nodes ()

    guint       g_node_n_nodes                  (GNode *root,
                                                 GTraverseFlags flags);

Gets the number of nodes in a tree.

`root` : | a GNode.
`flags` : | which types of children are to be counted, one of `G_TRAVERSE_ALL`, `G_TRAVERSE_LEAFS` and `G_TRAVERSE_NON_LEAFS`.
Returns : | the number of nodes in the tree.

### g_node_n_children ()

    guint       g_node_n_children               (GNode *node);

Gets the number of children of a GNode.

`node` : | a GNode.
Returns : | the number of children of `node`.

### g_node_is_ancestor ()

    gboolean    g_node_is_ancestor              (GNode *node,
                                                 GNode *descendant);

Returns `TRUE` if `node` is an ancestor of `descendant`. This is true if node is the parent of `descendant`, or if node is the grandparent of `descendant` etc.

`node` : | a GNode.
`descendant` : | a GNode.
Returns : | `TRUE` if `node` is an ancestor of `descendant`.

### g_node_max_height ()

    guint       g_node_max_height               (GNode *root);

Gets the maximum height of all branches beneath a GNode. This is the maximum distance from the GNode to all leaf nodes.

If `root` is `NULL`, 0 is returned. If `root` has no children, 1 is returned. If `root` has children, 2 is returned. And so on.

`root` : | a GNode.
Returns : | the maximum height of the tree beneath `root`.

### g_node_unlink ()

    void        g_node_unlink                   (GNode *node);

Unlinks a GNode from a tree, resulting in two separate trees.

`node` : | the GNode to unlink, which becomes the root of a new tree.

### g_node_destroy ()

    void        g_node_destroy                  (GNode *root);

Removes the GNode and its children from the tree, freeing any memory allocated.

`root` : | the root of the tree/subtree to destroy.

### g_node_push_allocator ()

    void        g_node_push_allocator           (GAllocator *allocator);

Sets the allocator to use to allocate GNode elements. Use g_node_pop_allocator() to restore the previous allocator.

`allocator` : | the GAllocator to use when allocating GNode elements.

### g_node_pop_allocator ()

    void        g_node_pop_allocator            (void);

Restores the previous GAllocator, used when allocating GNode elements.