insert.c

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/**
 * \file
 *
 * \author  Georg Hopp
 *
 * \copyright
 * Copyright © 2012  Georg Hopp
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "tree.h"

void treeRotateLeft(Tree *, Tree);
void treeRotateRight(Tree *, Tree);

void *
treeInsert(Tree * this, const void * search, TreeComp comp)
{
    Tree node     = *this;
    Tree new_node = NULL;

    /*
     * insert the node or return the one in tree if comparison
     * succeeds.
     */
    if (NULL == node) {
        /*
         * if the root is NULL we simple add the element and set
         * node to it.
         */
        *this = node = new_node = new(Tree, search);
    } else {
        /*
         * first search for it and if its found return the data
         * and we are done...
         */
        int  comparison;

        while (NULL != node) {
            comparison = comp(node->data, search);

            if (0 < comparison) {
                if (NULL != TREE_LEFT(node)) {
                    node = TREE_LEFT(node);
                    continue;
                } else {
                    break;
                }
            }

            if (0 > comparison) {
                if (NULL != TREE_RIGHT(node)) {
                    node = TREE_RIGHT(node);
                    continue;
                } else {
                    break;
                }
            }

            if (0 == comparison) {
                return node->data;
            }
        }   

        /*
         * as we have not found it now add a new element.
         */
        if (0 < comparison) {
            node->left = new(Tree, search);
            TREE_LEFT(node)->parent = node;
            node = new_node = TREE_LEFT(node);
        } else {
            node->right = new(Tree, search);
            TREE_RIGHT(node)->parent = node;
            node = new_node = TREE_RIGHT(node);
        }
    }

    /*
     * we expect node not to be NULL and pointing to our
     * new node at this point...now rabalance the tree
     */
    while (1) {
        // case 1
        if (NULL == TREE_PARENT(node)) {
            node->color = rbBlack;
            break;
        }

        // case 2
        if (rbBlack == TREE_PARENT(node)->color) {
            break;
        }

        // case 3
        if (NULL != TREE_UNCLE(node) && rbRed == TREE_UNCLE(node)->color) {
            TREE_PARENT(node)->color      = rbBlack;
            TREE_UNCLE(node)->color       = rbBlack;
            TREE_GRANDPARENT(node)->color = rbRed;

            node = TREE_GRANDPARENT(node);
            continue;
        }

        // case 4
        if (node == TREE_PARENT(node)->right
                && TREE_PARENT(node) == TREE_GRANDPARENT(node)->left) {

            //TREE_ROTATE_LEFT(this, TREE_PARENT(node));
            treeRotateLeft(this, TREE_PARENT(node));
            node = TREE_LEFT(node);

        } else if (node == TREE_PARENT(node)->left
                && TREE_PARENT(node) == TREE_GRANDPARENT(node)->right) {

            //TREE_ROTATE_RIGHT(this, TREE_PARENT(node));
            treeRotateRight(this, TREE_PARENT(node));
            node = TREE_RIGHT(node);

        }

        // case 5
        TREE_PARENT(node)->color      = rbBlack;
        TREE_GRANDPARENT(node)->color = rbRed;

        if (node == TREE_PARENT(node)->left) {
            //TREE_ROTATE_RIGHT(this, TREE_GRANDPARENT(node));
            treeRotateRight(this, TREE_GRANDPARENT(node));
        } else {
            //TREE_ROTATE_LEFT(this, TREE_GRANDPARENT(node));
            treeRotateLeft(this, TREE_GRANDPARENT(node));
        }

        break;
    }

    return new_node->data;
}

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