373 lines
10 KiB
C
373 lines
10 KiB
C
/* $NetBSD: rb.c,v 1.2 2002/10/08 11:58:54 simonb Exp $ */
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/*-
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* Copyright (c) 2001 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Matt Thomas <matt@3am-software.com>.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/types.h>
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#include <stddef.h>
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#ifndef _KERNEL
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#include <assert.h>
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#define KASSERT(s) assert(s)
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#endif
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#include "rb.h"
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static void rb_tree_rotate(struct rb_tree *, struct rb_node *, int);
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static void rb_tree_insert_rebalance(struct rb_tree *, struct rb_node *);
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static void rb_tree_removal_rebalance(struct rb_tree *, struct rb_node *);
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/*
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* Rather than testing for the NULL everywhere, all terminal leaves are
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* pointed to this node. Note that by setting it to be const, that on
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* some architectures trying to write to it will cause a fault.
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*/
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static const struct rb_node sentinel_node = {
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NULL, NULL, NULL, { NULL, NULL }, 0, 0, 1
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};
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void
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rb_tree_init(struct rb_tree *rbt, rb_compare_nodes_fn compare_nodes,
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rb_compare_key_fn compare_key, rb_print_node_fn print_node)
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{
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TAILQ_INIT(&rbt->rbt_nodes);
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rbt->rbt_count = 0;
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rbt->rbt_compare_nodes = compare_nodes;
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rbt->rbt_compare_key = compare_key;
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rbt->rbt_print_node = print_node;
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*((const struct rb_node **)&rbt->rbt_root) = &sentinel_node;
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}
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/*
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* Rotate the tree between Y and X
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* X c a Y
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* a b b c
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*/
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void
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rb_tree_rotate(struct rb_tree *rbt, struct rb_node *self, int which)
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{
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const int other = which ^ RB_OTHER;
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struct rb_node * const parent = self->rb_parent;
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struct rb_node * const child = self->rb_nodes[other];
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assert(!child->rb_sentinel);
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assert(child->rb_parent == self);
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#if 0
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(*rbt->rbt_print_node)(child, which ? "before-l " : "before-r ");
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#endif
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if ((child->rb_parent = parent) == NULL) {
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assert(rbt->rbt_root == self);
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rbt->rbt_root = child;
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} else {
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parent->rb_nodes[self->rb_position] = child;
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}
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self->rb_nodes[other] = child->rb_nodes[which];
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if (!self->rb_nodes[other]->rb_sentinel)
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self->rb_nodes[other]->rb_parent = self;
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child->rb_nodes[which] = self;
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child->rb_position = self->rb_position;
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self->rb_parent = child;
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self->rb_position = which;
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#if 0
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(*rbt->rbt_print_node)(self, which ? "after-l " : "after-r ");
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#endif
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}
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void
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rb_tree_insert_node(struct rb_tree *rbt, struct rb_node *self)
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{
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struct rb_node *prev, *next, *tmp, *parent;
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struct rb_node **insert_p;
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u_int position;
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prev = NULL;
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next = NULL;
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parent = NULL;
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tmp = rbt->rbt_root;
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/*
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* Find out where to place this new leaf.
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*/
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while (!tmp->rb_sentinel) {
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const int diff = (*rbt->rbt_compare_nodes)(tmp, self);
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parent = tmp;
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assert(diff != 0);
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if (diff < 0) {
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position = RB_LEFT;
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next = parent->rb_left;
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prev = NULL;
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} else {
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position = RB_RIGHT;
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prev = parent->rb_right;
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next = NULL;
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}
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tmp = parent->rb_nodes[position];
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}
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/*
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* Verify our sequential position
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*/
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if (prev != NULL && next == NULL)
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next = TAILQ_NEXT(prev, rb_link);
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if (prev == NULL && next != NULL)
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next = TAILQ_PREV(next, rb_node_qh, rb_link);
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assert(prev == NULL || (*rbt->rbt_compare_nodes)(prev, self) > 0);
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assert(next == NULL || (*rbt->rbt_compare_nodes)(self, next) < 0);
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/*
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* Initialize the node and insert as a leaf into the tree.
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*/
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rbt->rbt_count++;
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self->rb_parent = parent;
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if (parent == NULL) {
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assert(rbt->rbt_root->rb_sentinel);
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self->rb_position = RB_PARENT;
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self->rb_left = rbt->rbt_root;
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self->rb_right = rbt->rbt_root;
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rbt->rbt_root = self;
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} else {
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self->rb_position = position;
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self->rb_left = parent->rb_nodes[position];
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self->rb_right = parent->rb_nodes[position];
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parent->rb_nodes[position] = self;
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}
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assert(self->rb_left == &sentinel_node &&
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self->rb_right == &sentinel_node);
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/*
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* Insert the new node into a sorted list for easy sequential access
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*/
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if (next != NULL) {
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TAILQ_INSERT_BEFORE(next, self, rb_link);
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} else {
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TAILQ_INSERT_TAIL(&rbt->rbt_nodes, self, rb_link);
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}
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/*
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* Rebalance tree after insertation
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*/
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rb_tree_insert_rebalance(rbt, self);
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}
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void
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rb_tree_insert_rebalance(struct rb_tree *rbt, struct rb_node *self)
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{
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self->rb_red = 1;
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while (self != rbt->rbt_root && self->rb_parent->rb_red) {
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const int which =
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(self->rb_parent == self->rb_parent->rb_parent->rb_left
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? RB_LEFT
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: RB_RIGHT);
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const int other = which ^ RB_OTHER;
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struct rb_node *uncle;
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assert(!self->rb_sentinel);
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/*
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* We are red, our are parent is red, and our
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* grandparent is black.
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*/
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uncle = self->rb_parent->rb_parent->rb_nodes[other];
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if (uncle->rb_red) {
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/*
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* Case 1: our uncle is red
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* Simply invert the colors of our parent and
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* uncle and make our grandparent red. And
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* then solve the problem up at his level.
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*/
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uncle->rb_red = 0;
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self->rb_parent->rb_red = 0;
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self->rb_parent->rb_parent->rb_red = 1;
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self = self->rb_parent->rb_parent;
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} else {
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/*
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* Case 2&3: our uncle is black.
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*/
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if (self == self->rb_parent->rb_nodes[other]) {
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/*
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* Case 2: we are on the same side as our uncle
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* Rotate parent away from uncle so this
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* case becomes case 3
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*/
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self = self->rb_parent;
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rb_tree_rotate(rbt, self, which);
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}
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/*
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* Case 3: we are opposite a child of a black uncle.
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* Change parent to black and grandparent to
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* red. Rotate grandparent away from ourself.
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*/
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self->rb_parent->rb_red = 0;
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self->rb_parent->rb_parent->rb_red = 1;
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rb_tree_rotate(rbt, self->rb_parent->rb_parent, other);
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}
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}
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/*
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* Final step: Set the root to black.
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*/
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rbt->rbt_root->rb_red = 0;
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}
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struct rb_node *
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rb_tree_lookup(struct rb_tree *rbt, void *key)
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{
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struct rb_node *parent = rbt->rbt_root;
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while (!parent->rb_sentinel) {
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const int diff = (*rbt->rbt_compare_key)(parent, key);
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if (diff == 0)
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return parent;
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parent = parent->rb_nodes[diff > 0];
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}
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return NULL;
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}
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void
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rb_tree_remove_node(struct rb_tree *rbt, struct rb_node *self)
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{
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struct rb_node *child;
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/*
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* Easy case, one or more children is NULL (leaf node or parent of
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* leaf node).
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*/
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if (self->rb_left->rb_sentinel || self->rb_left->rb_sentinel) {
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const int which = (!self->rb_left->rb_sentinel ? RB_LEFT : RB_RIGHT);
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child = self->rb_nodes[which];
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if (self->rb_parent == NULL) {
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rbt->rbt_root = child;
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} else {
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self->rb_parent->rb_nodes[self->rb_position] = child;
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}
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if (child->rb_sentinel)
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child = self->rb_parent;
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else
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child->rb_parent = self->rb_parent;
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} else {
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struct rb_node *new_self;
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child = self->rb_right;
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while (!child->rb_left->rb_sentinel)
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child = child->rb_left;
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new_self = child;
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assert(new_self == TAILQ_NEXT(self, rb_link));
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/*
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* Take new_self out of the tree (its only subnode can be on the
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* right since we know the left subnode is NULL).
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*/
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child->rb_parent->rb_left = child->rb_right;
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if (!child->rb_right->rb_sentinel) {
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child->rb_right->rb_parent = child->rb_parent;
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child->rb_right->rb_position = RB_LEFT;
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}
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/*
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* Take self out of the tree and insert new_self into its place.
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*/
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new_self->rb_right = self->rb_right;
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new_self->rb_left = self->rb_left;
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if (!new_self->rb_right->rb_sentinel)
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new_self->rb_right->rb_parent = new_self;
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if (!new_self->rb_left->rb_sentinel)
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new_self->rb_left->rb_parent = new_self;
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new_self->rb_red = self->rb_red;
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new_self->rb_parent = self->rb_parent;
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/*
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* Update parent
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*/
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if (new_self->rb_parent == NULL) {
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rbt->rbt_root = new_self;
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} else {
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new_self->rb_parent->rb_nodes[self->rb_position] = new_self;
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}
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}
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TAILQ_REMOVE(&rbt->rbt_nodes, self, rb_link);
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rbt->rbt_count--;
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if (child != NULL) {
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assert(!child->rb_sentinel);
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#if 0
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(*rbt->rbt_print_node)(child, "before ");
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#endif
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rb_tree_removal_rebalance(rbt, child);
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#if 0
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(*rbt->rbt_print_node)(child, "after ");
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#endif
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}
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}
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void
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rb_tree_removal_rebalance(struct rb_tree *rbt, struct rb_node *self)
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{
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assert(!self->rb_sentinel);
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while (self->rb_parent != NULL && !self->rb_red) {
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struct rb_node *parent = self->rb_parent;
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int which = (self == parent->rb_left) ? RB_LEFT : RB_RIGHT;
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int other = which ^ RB_OTHER;
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struct rb_node *sibling = parent->rb_nodes[other];
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if (sibling->rb_red) {
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sibling->rb_red = 0;
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parent->rb_red = 1;
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rb_tree_rotate(rbt, parent, which);
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parent = self->rb_parent;
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sibling = parent->rb_nodes[other];
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}
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if (sibling->rb_sentinel ||
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(!sibling->rb_left->rb_red && !sibling->rb_right->rb_red)) {
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sibling->rb_red = 1;
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self = parent;
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continue;
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}
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if (!sibling->rb_nodes[other]->rb_red) {
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sibling->rb_nodes[which]->rb_red = 0;
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sibling->rb_red = 1;
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rb_tree_rotate(rbt, sibling, other);
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parent = self->rb_parent;
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sibling = parent->rb_nodes[other];
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}
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sibling->rb_red = parent->rb_red;
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parent->rb_red = 0;
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sibling->rb_nodes[other]->rb_red = 0;
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rb_tree_rotate(rbt, parent, which);
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break;
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}
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}
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