gtree.c

/* GLIB - Library of useful routines for C programming
 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
 * file for a list of people on the GLib Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GLib at ftp://ftp.gtk.org/pub/gtk/. 
 */

/* 
 * MT safe
 */

#include "gtypes.h"
#include "gtree.h"
//#include "gatomic.h"
//#include "gtestutils.h"
#include "gslice.h"
#include "gmessages.h"
#include "gnode.h"

/**
 * SECTION:trees-binary
 * @title: Balanced Binary Trees
 * @short_description: a sorted collection of key/value pairs optimized
 *                     for searching and traversing in order
 *
 * 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 look up 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().
 **/

#undef G_TREE_DEBUG

#define MAX_GTREE_HEIGHT 40

typedef struct _GTreeNode  GTreeNode;

/**
 * GTree:
 *
 * The GTree struct is an opaque data structure representing a
 * [balanced binary tree][glib-Balanced-Binary-Trees]. It should be
 * accessed only by using the following functions.
 */
struct _GTree
{
    GTreeNode        *root;
    GCompareDataFunc  key_compare;
    GDestroyNotify    key_destroy_func;
    GDestroyNotify    value_destroy_func;
    gpointer          key_compare_data;
    guint             nnodes;
    gint              ref_count;
};

struct _GTreeNode
{
    gpointer   key;         /* key for this node */
    gpointer   value;       /* value stored at this node */
    GTreeNode *left;        /* left subtree */
    GTreeNode *right;       /* right subtree */
    gint8      balance;     /* height (right) - height (left) */
    guint8     left_child;
    guint8     right_child;
};


static GTreeNode* g_tree_node_new                   (gpointer       key,
        gpointer       value);
static void       g_tree_insert_internal            (GTree         *tree,
        gpointer       key,
        gpointer       value,
        gboolean       replace);
static gboolean   g_tree_remove_internal            (GTree         *tree,
        gconstpointer  key,
        gboolean       steal);
static GTreeNode* g_tree_node_balance               (GTreeNode     *node);
static GTreeNode *g_tree_find_node                  (GTree         *tree,
        gconstpointer  key);
static gint       g_tree_node_pre_order             (GTreeNode     *node,
        GTraverseFunc  traverse_func,
        gpointer       data);
static gint       g_tree_node_in_order              (GTreeNode     *node,
        GTraverseFunc  traverse_func,
        gpointer       data);
static gint       g_tree_node_post_order            (GTreeNode     *node,
        GTraverseFunc  traverse_func,
        gpointer       data);
static gpointer   g_tree_node_search                (GTreeNode     *node,
        GCompareFunc   search_func,
        gconstpointer  data);
static GTreeNode* g_tree_node_rotate_left           (GTreeNode     *node);
static GTreeNode* g_tree_node_rotate_right          (GTreeNode     *node);
#ifdef G_TREE_DEBUG
static void       g_tree_node_check                 (GTreeNode     *node);
#endif


static GTreeNode *g_tree_node_new (gpointer key, gpointer value)
{
    GTreeNode *node = g_slice_new (GTreeNode);

    node->balance = 0;
    node->left = NULL;
    node->right = NULL;
    node->left_child = FALSE;
    node->right_child = FALSE;
    node->key = key;
    node->value = value;

    return node;
}

/**
 * g_tree_new:
 * @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.
 * 
 * Creates a new #GTree.
 * 
 * Returns: a newly allocated #GTree
 */
GTree *g_tree_new (GCompareFunc key_compare_func)
{
    g_return_val_if_fail (key_compare_func != NULL, NULL);

    return g_tree_new_full ((GCompareDataFunc) key_compare_func, NULL,
            NULL, NULL);
}

/**
 * g_tree_new_with_data:
 * @key_compare_func: qsort()-style comparison function
 * @key_compare_data: data to pass to comparison function
 * 
 * Creates a new #GTree with a comparison function that accepts user data.
 * See g_tree_new() for more details.
 * 
 * Returns: a newly allocated #GTree
 */
GTree *g_tree_new_with_data (GCompareDataFunc key_compare_func, gpointer key_compare_data)
{
    g_return_val_if_fail (key_compare_func != NULL, NULL);

    return g_tree_new_full (key_compare_func, key_compare_data, NULL, NULL);
}

/**
 * g_tree_new_full:
 * @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
 * 
 * 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.
 * 
 * Returns: a newly allocated #GTree
 */
GTree *g_tree_new_full (GCompareDataFunc key_compare_func,
        gpointer         key_compare_data,
        GDestroyNotify   key_destroy_func,
        GDestroyNotify   value_destroy_func)
{
    GTree *tree;

    g_return_val_if_fail (key_compare_func != NULL, NULL);

    tree = g_slice_new (GTree);
    tree->root               = NULL;
    tree->key_compare        = key_compare_func;
    tree->key_destroy_func   = key_destroy_func;
    tree->value_destroy_func = value_destroy_func;
    tree->key_compare_data   = key_compare_data;
    tree->nnodes             = 0;
    tree->ref_count          = 1;

    return tree;
}

static inline GTreeNode *g_tree_first_node (GTree *tree)
{
    GTreeNode *tmp;

    if (!tree->root)
        return NULL;

    tmp = tree->root;

    while (tmp->left_child)
        tmp = tmp->left;

    return tmp;
} 

static inline GTreeNode *g_tree_node_previous (GTreeNode *node)
{
    GTreeNode *tmp;

    tmp = node->left;

    if (node->left_child)
        while (tmp->right_child)
            tmp = tmp->right;

    return tmp;
}

static inline GTreeNode *g_tree_node_next (GTreeNode *node)
{
    GTreeNode *tmp;

    tmp = node->right;

    if (node->right_child)
        while (tmp->left_child)
            tmp = tmp->left;

    return tmp;
}

void g_tree_remove_all (GTree *tree)
{
    GTreeNode *node;
    GTreeNode *next;

    g_return_if_fail (tree != NULL);

    node = g_tree_first_node (tree);

    while (node)
    {
        next = g_tree_node_next (node);

        if (tree->key_destroy_func)
            tree->key_destroy_func (node->key);
        if (tree->value_destroy_func)
            tree->value_destroy_func (node->value);
        g_slice_free (GTreeNode, node);

        node = next;
    }

    tree->root = NULL;
    tree->nnodes = 0;
}

/**
 * g_tree_ref:
 * @tree: a #GTree
 *
 * Increments the reference count of @tree by one.
 *
 * It is safe to call this function from any thread.
 *
 * Returns: the passed in #GTree
 *
 * Since: 2.22
 */
GTree *g_tree_ref (GTree *tree)
{
    g_return_val_if_fail (tree != NULL, NULL);

    tree->ref_count++;

    return tree;
}

/**
 * g_tree_unref:
 * @tree: a #GTree
 *
 * 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.
 *
 * Since: 2.22
 */
void g_tree_unref (GTree *tree)
{
    g_return_if_fail (tree != NULL);

    tree->ref_count--;

    if (!tree->ref_count)
    {
        g_tree_remove_all (tree);
        g_slice_free (GTree, tree);
    }
}

/**
 * g_tree_destroy:
 * @tree: a #GTree
 * 
 * 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.
 */
void g_tree_destroy (GTree *tree)
{
    g_return_if_fail (tree != NULL);

    g_tree_remove_all (tree);
    g_tree_unref (tree);
}

/**
 * g_tree_insert:
 * @tree: a #GTree
 * @key: the key to insert
 * @value: the value corresponding to the key
 * 
 * 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.
 */
void g_tree_insert (GTree *tree, gpointer  key, gpointer  value)
{
    g_return_if_fail (tree != NULL);

    g_tree_insert_internal (tree, key, value, FALSE);

#ifdef G_TREE_DEBUG
    g_tree_node_check (tree->root);
#endif
}

/**
 * g_tree_replace:
 * @tree: a #GTree
 * @key: the key to insert
 * @value: the value corresponding to the key
 * 
 * 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.
 */
void g_tree_replace (GTree *tree, gpointer key, gpointer value)
{
    g_return_if_fail (tree != NULL);

    g_tree_insert_internal (tree, key, value, TRUE);

#ifdef G_TREE_DEBUG
    g_tree_node_check (tree->root);
#endif
}

/* internal insert routine */
static void g_tree_insert_internal (GTree *tree, gpointer key, gpointer value, gboolean replace)
{
    GTreeNode *node;
    GTreeNode *path[MAX_GTREE_HEIGHT];
    int idx;

    g_return_if_fail (tree != NULL);

    if (!tree->root)
    {
        tree->root = g_tree_node_new (key, value);
        tree->nnodes++;
        return;
    }

    idx = 0;
    path[idx++] = NULL;
    node = tree->root;

    while (1)
    {
        int cmp = tree->key_compare (key, node->key, tree->key_compare_data);

        if (cmp == 0)
        {
            if (tree->value_destroy_func)
                tree->value_destroy_func (node->value);

            node->value = value;

            if (replace)
            {
                if (tree->key_destroy_func)
                    tree->key_destroy_func (node->key);

                node->key = key;
            }
            else
            {
                /* free the passed key */
                if (tree->key_destroy_func)
                    tree->key_destroy_func (key);
            }

            return;
        }
        else if (cmp < 0)
        {
            if (node->left_child)
            {
                path[idx++] = node;
                node = node->left;
            }
            else
            {
                GTreeNode *child = g_tree_node_new (key, value);

                child->left = node->left;
                child->right = node;
                node->left = child;
                node->left_child = TRUE;
                node->balance -= 1;

                tree->nnodes++;

                break;
            }
        }
        else
        {
            if (node->right_child)
            {
                path[idx++] = node;
                node = node->right;
            }
            else
            {
                GTreeNode *child = g_tree_node_new (key, value);

                child->right = node->right;
                child->left = node;
                node->right = child;
                node->right_child = TRUE;
                node->balance += 1;

                tree->nnodes++;

                break;
            }
        }
    }

    /* Restore balance. This is the goodness of a non-recursive
     * implementation, when we are done with balancing we 'break'
     * the loop and we are done.
     */
    while (1)
    {
        GTreeNode *bparent = path[--idx];
        gboolean left_node = (bparent && node == bparent->left);
        //g_assert (!bparent || bparent->left == node || bparent->right == node);

        if (node->balance < -1 || node->balance > 1)
        {
            node = g_tree_node_balance (node);
            if (bparent == NULL)
                tree->root = node;
            else if (left_node)
                bparent->left = node;
            else
                bparent->right = node;
        }

        if (node->balance == 0 || bparent == NULL)
            break;

        if (left_node)
            bparent->balance -= 1;
        else
            bparent->balance += 1;

        node = bparent;
    }
}

/**
 * g_tree_remove:
 * @tree: a #GTree
 * @key: the key to remove
 * 
 * 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.
 *
 * Returns: %TRUE if the key was found (prior to 2.8, this function
 *     returned nothing)
 */
gboolean g_tree_remove (GTree *tree, gconstpointer  key)
{
    gboolean removed;

    g_return_val_if_fail (tree != NULL, FALSE);

    removed = g_tree_remove_internal (tree, key, FALSE);

#ifdef G_TREE_DEBUG
    g_tree_node_check (tree->root);
#endif

    return removed;
}

/**
 * g_tree_steal:
 * @tree: a #GTree
 * @key: the key to remove
 * 
 * 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.
 *
 * Returns: %TRUE if the key was found (prior to 2.8, this function
 *     returned nothing)
 */
gboolean g_tree_steal (GTree *tree, gconstpointer key)
{
    gboolean removed;

    g_return_val_if_fail (tree != NULL, FALSE);

    removed = g_tree_remove_internal (tree, key, TRUE);

#ifdef G_TREE_DEBUG
    g_tree_node_check (tree->root);
#endif

    return removed;
}

/* internal remove routine */
static gboolean g_tree_remove_internal (GTree *tree, gconstpointer key, gboolean steal)
{
    GTreeNode *node, *parent, *balance;
    GTreeNode *path[MAX_GTREE_HEIGHT];
    int idx;
    gboolean left_node;

    g_return_val_if_fail (tree != NULL, FALSE);

    if (!tree->root)
        return FALSE;

    idx = 0;
    path[idx++] = NULL;
    node = tree->root;

    while (1)
    {
        int cmp = tree->key_compare (key, node->key, tree->key_compare_data);

        if (cmp == 0)
            break;
        else if (cmp < 0)
        {
            if (!node->left_child)
                return FALSE;

            path[idx++] = node;
            node = node->left;
        }
        else
        {
            if (!node->right_child)
                return FALSE;

            path[idx++] = node;
            node = node->right;
        }
    }

    /* The following code is almost equal to g_tree_remove_node,
     * except that we do not have to call g_tree_node_parent.
     */
    balance = parent = path[--idx];
    //g_assert (!parent || parent->left == node || parent->right == node);
    left_node = (parent && node == parent->left);

    if (!node->left_child)
    {
        if (!node->right_child)
        {
            if (!parent)
                tree->root = NULL;
            else if (left_node)
            {
                parent->left_child = FALSE;
                parent->left = node->left;
                parent->balance += 1;
            }
            else
            {
                parent->right_child = FALSE;
                parent->right = node->right;
                parent->balance -= 1;
            }
        }
        else /* node has a right child */
        {
            GTreeNode *tmp = g_tree_node_next (node);
            tmp->left = node->left;

            if (!parent)
                tree->root = node->right;
            else if (left_node)
            {
                parent->left = node->right;
                parent->balance += 1;
            }
            else
            {
                parent->right = node->right;
                parent->balance -= 1;
            }
        }
    }
    else /* node has a left child */
    {
        if (!node->right_child)
        {
            GTreeNode *tmp = g_tree_node_previous (node);
            tmp->right = node->right;

            if (parent == NULL)
                tree->root = node->left;
            else if (left_node)
            {
                parent->left = node->left;
                parent->balance += 1;
            }
            else
            {
                parent->right = node->left;
                parent->balance -= 1;
            }
        }
        else /* node has a both children (pant, pant!) */
        {
            GTreeNode *prev = node->left;
            GTreeNode *next = node->right;
            GTreeNode *nextp = node;
            int old_idx = idx + 1;
            idx++;

            /* path[idx] == parent */
            /* find the immediately next node (and its parent) */
            while (next->left_child)
            {
                path[++idx] = nextp = next;
                next = next->left;
            }

            path[old_idx] = next;
            balance = path[idx];

            /* remove 'next' from the tree */
            if (nextp != node)
            {
                if (next->right_child)
                    nextp->left = next->right;
                else
                    nextp->left_child = FALSE;
                nextp->balance += 1;

                next->right_child = TRUE;
                next->right = node->right;
            }
            else
                node->balance -= 1;

            /* set the prev to point to the right place */
            while (prev->right_child)
                prev = prev->right;
            prev->right = next;

            /* prepare 'next' to replace 'node' */
            next->left_child = TRUE;
            next->left = node->left;
            next->balance = node->balance;

            if (!parent)
                tree->root = next;
            else if (left_node)
                parent->left = next;
            else
                parent->right = next;
        }
    }

    /* restore balance */
    if (balance)
        while (1)
        {
            GTreeNode *bparent = path[--idx];
            //g_assert (!bparent || bparent->left == balance || bparent->right == balance);
            left_node = (bparent && balance == bparent->left);

            if(balance->balance < -1 || balance->balance > 1)
            {
                balance = g_tree_node_balance (balance);
                if (!bparent)
                    tree->root = balance;
                else if (left_node)
                    bparent->left = balance;
                else
                    bparent->right = balance;
            }

            if (balance->balance != 0 || !bparent)
                break;

            if (left_node)
                bparent->balance += 1;
            else
                bparent->balance -= 1;

            balance = bparent;
        }

    if (!steal)
    {
        if (tree->key_destroy_func)
            tree->key_destroy_func (node->key);
        if (tree->value_destroy_func)
            tree->value_destroy_func (node->value);
    }

    g_slice_free (GTreeNode, node);

    tree->nnodes--;

    return TRUE;
}

/**
 * g_tree_lookup:
 * @tree: a #GTree
 * @key: the key to look up
 * 
 * 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).
 *
 * Returns: the value corresponding to the key, or %NULL
 *     if the key was not found
 */
gpointer g_tree_lookup (GTree *tree, gconstpointer key)
{
    GTreeNode *node;

    g_return_val_if_fail (tree != NULL, NULL);

    node = g_tree_find_node (tree, key);

    return node ? node->value : NULL;
}

/**
 * g_tree_lookup_extended:
 * @tree: a #GTree
 * @lookup_key: the key to look up
 * @orig_key: (out) (optional) (nullable): returns the original key
 * @value: (out) (optional) (nullable): returns the value associated with the key
 * 
 * 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().
 * 
 * Returns: %TRUE if the key was found in the #GTree
 */
gboolean g_tree_lookup_extended (GTree *tree,
        gconstpointer  lookup_key,
        gpointer      *orig_key,
        gpointer      *value)
{
    GTreeNode *node;

    g_return_val_if_fail (tree != NULL, FALSE);

    node = g_tree_find_node (tree, lookup_key);

    if (node)
    {
        if (orig_key)
            *orig_key = node->key;
        if (value)
            *value = node->value;
        return TRUE;
    }
    else
        return FALSE;
}

/**
 * g_tree_foreach:
 * @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
 *
 * 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.
 */
void g_tree_foreach (GTree *tree, GTraverseFunc func, gpointer user_data)
{
    GTreeNode *node;

    g_return_if_fail (tree != NULL);

    if (!tree->root)
        return;

    node = g_tree_first_node (tree);

    while (node)
    {
        if ((*func) (node->key, node->value, user_data))
            break;

        node = g_tree_node_next (node);
    }
}

/**
 * g_tree_traverse:
 * @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
 * 
 * Calls the given function for each node in the #GTree. 
 *
 * Deprecated:2.2: 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][glib-N-ary-Trees].
 */
/**
 * GTraverseFunc:
 * @key: a key of a #GTree node
 * @value: the value corresponding to the key
 * @data: user data passed to g_tree_traverse()
 *
 * 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.
 *
 * Returns: %TRUE to stop the traversal
 */
void g_tree_traverse (GTree *tree,
        GTraverseFunc  traverse_func,
        GTraverseType  traverse_type,
        gpointer       user_data)
{
    g_return_if_fail (tree != NULL);

    if (!tree->root)
        return;

    switch (traverse_type)
    {
        case G_PRE_ORDER:
            g_tree_node_pre_order (tree->root, traverse_func, user_data);
            break;

        case G_IN_ORDER:
            g_tree_node_in_order (tree->root, traverse_func, user_data);
            break;

        case G_POST_ORDER:
            g_tree_node_post_order (tree->root, traverse_func, user_data);
            break;

        case G_LEVEL_ORDER:
            //g_warning ("g_tree_traverse(): traverse type G_LEVEL_ORDER isn't implemented.");
            break;
    }
}

/**
 * g_tree_search:
 * @tree: a #GTree
 * @search_func: a function used to search the #GTree
 * @user_data: the data passed as the second argument to @search_func
 *
 * 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.
 *
 * Returns: the value corresponding to the found key, or %NULL
 *     if the key was not found
 */
gpointer g_tree_search (GTree *tree,
        GCompareFunc   search_func,
        gconstpointer  user_data)
{
    g_return_val_if_fail (tree != NULL, NULL);

    if (tree->root)
        return g_tree_node_search (tree->root, search_func, user_data);
    else
        return NULL;
}

/**
 * g_tree_height:
 * @tree: a #GTree
 * 
 * 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.
 * 
 * Returns: the height of @tree
 */
gint g_tree_height (GTree *tree)
{
    GTreeNode *node;
    gint height;

    g_return_val_if_fail (tree != NULL, 0);

    if (!tree->root)
        return 0;

    height = 0;
    node = tree->root;

    while (1)
    {
        height += 1 + MAX(node->balance, 0);

        if (!node->left_child)
            return height;

        node = node->left;
    }
}

/**
 * g_tree_nnodes:
 * @tree: a #GTree
 * 
 * Gets the number of nodes in a #GTree.
 * 
 * Returns: the number of nodes in @tree
 */
gint g_tree_nnodes (GTree *tree)
{
    g_return_val_if_fail (tree != NULL, 0);

    return tree->nnodes;
}

static GTreeNode *g_tree_node_balance (GTreeNode *node)
{
    if (node->balance < -1)
    {
        if (node->left->balance > 0)
            node->left = g_tree_node_rotate_left (node->left);
        node = g_tree_node_rotate_right (node);
    }
    else if (node->balance > 1)
    {
        if (node->right->balance < 0)
            node->right = g_tree_node_rotate_right (node->right);
        node = g_tree_node_rotate_left (node);
    }

    return node;
}

static GTreeNode *g_tree_find_node (GTree *tree, gconstpointer key)
{
    GTreeNode *node;
    gint cmp;

    node = tree->root;
    if (!node)
        return NULL;

    while (1)
    {
        cmp = tree->key_compare (key, node->key, tree->key_compare_data);
        if (cmp == 0)
            return node;
        else if (cmp < 0)
        {
            if (!node->left_child)
                return NULL;

            node = node->left;
        }
        else
        {
            if (!node->right_child)
                return NULL;

            node = node->right;
        }
    }
}

static gint g_tree_node_pre_order (GTreeNode *node, GTraverseFunc traverse_func, gpointer data)
{
    if ((*traverse_func) (node->key, node->value, data))
        return TRUE;

    if (node->left_child)
    {
        if (g_tree_node_pre_order (node->left, traverse_func, data))
            return TRUE;
    }

    if (node->right_child)
    {
        if (g_tree_node_pre_order (node->right, traverse_func, data))
            return TRUE;
    }

    return FALSE;
}

static gint g_tree_node_in_order (GTreeNode *node, GTraverseFunc  traverse_func, gpointer data)
{
    if (node->left_child)
    {
        if (g_tree_node_in_order (node->left, traverse_func, data))
            return TRUE;
    }

    if ((*traverse_func) (node->key, node->value, data))
        return TRUE;

    if (node->right_child)
    {
        if (g_tree_node_in_order (node->right, traverse_func, data))
            return TRUE;
    }

    return FALSE;
}

static gint g_tree_node_post_order (GTreeNode *node,
        GTraverseFunc  traverse_func,
        gpointer       data)
{
    if (node->left_child)
    {
        if (g_tree_node_post_order (node->left, traverse_func, data))
            return TRUE;
    }

    if (node->right_child)
    {
        if (g_tree_node_post_order (node->right, traverse_func, data))
            return TRUE;
    }

    if ((*traverse_func) (node->key, node->value, data))
        return TRUE;

    return FALSE;
}

static gpointer g_tree_node_search (GTreeNode     *node,
        GCompareFunc   search_func,
        gconstpointer  data)
{
    gint dir;

    if (!node)
        return NULL;

    while (1) 
    {
        dir = (* search_func) (node->key, data);
        if (dir == 0)
            return node->value;
        else if (dir < 0) 
        {
            if (!node->left_child)
                return NULL;

            node = node->left;
        }
        else
        {
            if (!node->right_child)
                return NULL;

            node = node->right;
        }
    }
}

static GTreeNode *g_tree_node_rotate_left (GTreeNode *node)
{
    GTreeNode *right;
    gint a_bal;
    gint b_bal;

    right = node->right;

    if (right->left_child)
        node->right = right->left;
    else
    {
        node->right_child = FALSE;
        right->left_child = TRUE;
    }
    right->left = node;

    a_bal = node->balance;
    b_bal = right->balance;

    if (b_bal <= 0)
    {
        if (a_bal >= 1)
            right->balance = b_bal - 1;
        else
            right->balance = a_bal + b_bal - 2;
        node->balance = a_bal - 1;
    }
    else
    {
        if (a_bal <= b_bal)
            right->balance = a_bal - 2;
        else
            right->balance = b_bal - 1;
        node->balance = a_bal - b_bal - 1;
    }

    return right;
}

static GTreeNode *g_tree_node_rotate_right (GTreeNode *node)
{
    GTreeNode *left;
    gint a_bal;
    gint b_bal;

    left = node->left;

    if (left->right_child)
        node->left = left->right;
    else
    {
        node->left_child = FALSE;
        left->right_child = TRUE;
    }
    left->right = node;

    a_bal = node->balance;
    b_bal = left->balance;

    if (b_bal <= 0)
    {
        if (b_bal > a_bal)
            left->balance = b_bal + 1;
        else
            left->balance = a_bal + 2;
        node->balance = a_bal - b_bal + 1;
    }
    else
    {
        if (a_bal <= -1)
            left->balance = b_bal + 1;
        else
            left->balance = a_bal + b_bal + 2;
        node->balance = a_bal + 1;
    }

    return left;
}