Balanced Binary Trees

Balanced Binary Trees — a sorted collection of key/value pairs optimized for searching and traversing in order

Types and Values

  GTree

Includes

#include <glib.h>

Description

The GTree structure and its associated functions provide a sorted collection of key/value pairs optimized for searching and traversing in order.

To create a new GTree use g_tree_new().

To insert a key/value pair into a GTree use g_tree_insert().

To lookup the value corresponding to a given key, use g_tree_lookup() and g_tree_lookup_extended().

To find out the number of nodes in a GTree, use g_tree_nnodes(). To get the height of a GTree, use g_tree_height().

To traverse a GTree, calling a function for each node visited in the traversal, use g_tree_foreach().

To remove a key/value pair use g_tree_remove().

To destroy a GTree, use g_tree_destroy().

Functions

g_tree_new ()

GTree *
g_tree_new (GCompareFunc key_compare_func);

Creates a new GTree.

Parameters

key_compare_func

the function used to order the nodes in the GTree. It should return values similar to the standard strcmp() function - 0 if the two arguments are equal, a negative value if the first argument comes before the second, or a positive value if the first argument comes after the second.

 

Returns

a newly allocated GTree


g_tree_ref ()

GTree *
g_tree_ref (GTree *tree);

Increments the reference count of tree by one.

It is safe to call this function from any thread.

Parameters

tree

a GTree

 

Returns

the passed in GTree

Since: 2.22


g_tree_unref ()

void
g_tree_unref (GTree *tree);

Decrements the reference count of tree by one. If the reference count drops to 0, all keys and values will be destroyed (if destroy functions were specified) and all memory allocated by tree will be released.

It is safe to call this function from any thread.

Parameters

tree

a GTree

 

Since: 2.22


g_tree_new_with_data ()

GTree *
g_tree_new_with_data (GCompareDataFunc key_compare_func,
                      gpointer key_compare_data);

Creates a new GTree with a comparison function that accepts user data. See g_tree_new() for more details.

Parameters

key_compare_func

qsort()-style comparison function

 

key_compare_data

data to pass to comparison function

 

Returns

a newly allocated GTree


g_tree_new_full ()

GTree *
g_tree_new_full (GCompareDataFunc key_compare_func,
                 gpointer key_compare_data,
                 GDestroyNotify key_destroy_func,
                 GDestroyNotify value_destroy_func);

Creates a new GTree like g_tree_new() and allows to specify functions to free the memory allocated for the key and value that get called when removing the entry from the GTree.

Parameters

key_compare_func

qsort()-style comparison function

 

key_compare_data

data to pass to comparison function

 

key_destroy_func

a function to free the memory allocated for the key used when removing the entry from the GTree or NULL if you don't want to supply such a function

 

value_destroy_func

a function to free the memory allocated for the value used when removing the entry from the GTree or NULL if you don't want to supply such a function

 

Returns

a newly allocated GTree


g_tree_insert ()

void
g_tree_insert (GTree *tree,
               gpointer key,
               gpointer value);

Inserts a key/value pair into a GTree.

If the given key already exists in the GTree its corresponding value is set to the new value. If you supplied a value_destroy_func when creating the GTree, the old value is freed using that function. If you supplied a key_destroy_func when creating the GTree, the passed key is freed using that function.

The tree is automatically 'balanced' as new key/value pairs are added, so that the distance from the root to every leaf is as small as possible.

Parameters

tree

a GTree

 

key

the key to insert

 

value

the value corresponding to the key

 

g_tree_replace ()

void
g_tree_replace (GTree *tree,
                gpointer key,
                gpointer value);

Inserts a new key and value into a GTree similar to g_tree_insert(). The difference is that if the key already exists in the GTree, it gets replaced by the new key. If you supplied a value_destroy_func when creating the GTree, the old value is freed using that function. If you supplied a key_destroy_func when creating the GTree, the old key is freed using that function.

The tree is automatically 'balanced' as new key/value pairs are added, so that the distance from the root to every leaf is as small as possible.

Parameters

tree

a GTree

 

key

the key to insert

 

value

the value corresponding to the key

 

g_tree_nnodes ()

gint
g_tree_nnodes (GTree *tree);

Gets the number of nodes in a GTree.

Parameters

tree

a GTree

 

Returns

the number of nodes in tree


g_tree_height ()

gint
g_tree_height (GTree *tree);

Gets the height of a GTree.

If the GTree contains no nodes, the height is 0. If the GTree contains only one root node the height is 1. If the root node has children the height is 2, etc.

Parameters

tree

a GTree

 

Returns

the height of tree


g_tree_lookup ()

gpointer
g_tree_lookup (GTree *tree,
               gconstpointer key);

Gets the value corresponding to the given key. Since a GTree is automatically balanced as key/value pairs are added, key lookup is O(log n) (where n is the number of key/value pairs in the tree).

Parameters

tree

a GTree

 

key

the key to look up

 

Returns

the value corresponding to the key, or NULL if the key was not found


g_tree_lookup_extended ()

gboolean
g_tree_lookup_extended (GTree *tree,
                        gconstpointer lookup_key,
                        gpointer *orig_key,
                        gpointer *value);

Looks up a key in the GTree, returning the original key and the associated value. This is useful if you need to free the memory allocated for the original key, for example before calling g_tree_remove().

Parameters

tree

a GTree

 

lookup_key

the key to look up

 

orig_key

returns the original key.

[optional][nullable]

value

returns the value associated with the key.

[optional][nullable]

Returns

TRUE if the key was found in the GTree


g_tree_foreach ()

void
g_tree_foreach (GTree *tree,
                GTraverseFunc func,
                gpointer user_data);

Calls the given function for each of the key/value pairs in the GTree. The function is passed the key and value of each pair, and the given data parameter. The tree is traversed in sorted order.

The tree may not be modified while iterating over it (you can't add/remove items). To remove all items matching a predicate, you need to add each item to a list in your GTraverseFunc as you walk over the tree, then walk the list and remove each item.

Parameters

tree

a GTree

 

func

the function to call for each node visited. If this function returns TRUE, the traversal is stopped.

 

user_data

user data to pass to the function

 

g_tree_traverse ()

void
g_tree_traverse (GTree *tree,
                 GTraverseFunc traverse_func,
                 GTraverseType traverse_type,
                 gpointer user_data);

g_tree_traverse has been deprecated since version 2.2 and should not be used in newly-written code.

The order of a balanced tree is somewhat arbitrary. If you just want to visit all nodes in sorted order, use g_tree_foreach() instead. If you really need to visit nodes in a different order, consider using an n-ary tree.

Calls the given function for each node in the GTree.

Parameters

tree

a GTree

 

traverse_func

the function to call for each node visited. If this function returns TRUE, the traversal is stopped.

 

traverse_type

the order in which nodes are visited, one of G_IN_ORDER, G_PRE_ORDER and G_POST_ORDER

 

user_data

user data to pass to the function

 

GTraverseFunc ()

gboolean
(*GTraverseFunc) (gpointer key,
                  gpointer value,
                  gpointer data);

Specifies the type of function passed to g_tree_traverse(). It is passed the key and value of each node, together with the user_data parameter passed to g_tree_traverse(). If the function returns TRUE, the traversal is stopped.

Parameters

key

a key of a GTree node

 

value

the value corresponding to the key

 

data

user data passed to g_tree_traverse()

 

Returns

TRUE to stop the traversal


g_tree_search ()

gpointer
g_tree_search (GTree *tree,
               GCompareFunc search_func,
               gconstpointer user_data);

Searches a GTree using search_func .

The search_func is called with a pointer to the key of a key/value pair in the tree, and the passed in user_data . If search_func returns 0 for a key/value pair, then the corresponding value is returned as the result of g_tree_search(). If search_func returns -1, searching will proceed among the key/value pairs that have a smaller key; if search_func returns 1, searching will proceed among the key/value pairs that have a larger key.

Parameters

tree

a GTree

 

search_func

a function used to search the GTree

 

user_data

the data passed as the second argument to search_func

 

Returns

the value corresponding to the found key, or NULL if the key was not found


g_tree_remove ()

gboolean
g_tree_remove (GTree *tree,
               gconstpointer key);

Removes a key/value pair from a GTree.

If the GTree was created using g_tree_new_full(), the key and value are freed using the supplied destroy functions, otherwise you have to make sure that any dynamically allocated values are freed yourself. If the key does not exist in the GTree, the function does nothing.

Parameters

tree

a GTree

 

key

the key to remove

 

Returns

TRUE if the key was found (prior to 2.8, this function returned nothing)


g_tree_steal ()

gboolean
g_tree_steal (GTree *tree,
              gconstpointer key);

Removes a key and its associated value from a GTree without calling the key and value destroy functions.

If the key does not exist in the GTree, the function does nothing.

Parameters

tree

a GTree

 

key

the key to remove

 

Returns

TRUE if the key was found (prior to 2.8, this function returned nothing)


g_tree_destroy ()

void
g_tree_destroy (GTree *tree);

Removes all keys and values from the GTree and decreases its reference count by one. If keys and/or values are dynamically allocated, you should either free them first or create the GTree using g_tree_new_full(). In the latter case the destroy functions you supplied will be called on all keys and values before destroying the GTree.

Parameters

tree

a GTree

 

Types and Values

GTree

typedef struct _GTree GTree;

The GTree struct is an opaque data structure representing a balanced binary tree. It should be accessed only by using the following functions.