/*
 * Copyright (c) 2019 Matthew Dillon <dillon@backplane.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <linux/init.h>
#include <linux/interval_tree.h>
#include <linux/module.h>

typedef struct interval_tree_node itnode_t;

void
interval_tree_insert(struct interval_tree_node *node, struct rb_root *root)
{
        itnode_t *scan;

        scan = (itnode_t *)root->rb_node;
        if (scan) {
                node->next = scan->next;
                node->atroot = 0;
                scan->next = node;
        } else {
                root->rb_node = (void *)node;
                node->atroot = 1;
                node->next = node;
        }
}

void
interval_tree_remove(struct interval_tree_node *node, struct rb_root *root)
{
        itnode_t *scan;

        scan = (itnode_t *)root->rb_node;
        KKASSERT(scan != NULL);
        while (scan->next != node) {
                scan = scan->next;
        }
        scan->next = node->next;
        if (scan == node) {
                /*
                 * Last element is being removed
                 */
                root->rb_node = NULL;
                node->atroot = 0;
        } else if ((itnode_t *)root->rb_node == node) {
                /*
                 * Root pointer is the node being removed, move the root
                 * pointer.
                 */
                node->atroot = 0;
                scan->atroot = 1;
                root->rb_node = (void *)scan;
        }
}

struct interval_tree_node *
interval_tree_iter_first(struct rb_root *root,
                         unsigned long start, unsigned long last)
{
        itnode_t *scan;

        scan = (itnode_t *)root->rb_node;
        if (scan) {
                do {
                        if (start <= scan->last &&
                            last >= scan->start) {
                                return scan;
                        }
                        scan = scan->next;
                } while (scan->atroot == 0);
                scan = NULL;
        }
        return scan;
}

struct interval_tree_node *
interval_tree_iter_next(struct interval_tree_node *node,
                        unsigned long start, unsigned long last)
{
        itnode_t *scan;

        scan = node->next;
        while (scan->atroot == 0) {
                if (start <= scan->last &&
                    last >= scan->start) {
                                return scan;
                }
                scan = scan->next;
        }
        return NULL;
}