621 lines
16 KiB
C
621 lines
16 KiB
C
/*
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* rbtree.c -- generic red black tree
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*
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* Copyright (c) 2001-2007, NLnet Labs. All rights reserved.
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*
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* This software is open source.
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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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*
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* Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of the NLNET LABS nor the names of its contributors may
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* be used to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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/**
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* \file
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* Implementation of a redblack tree.
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*/
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#include "config.h"
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#include "log.h"
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#include "fptr_wlist.h"
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#include "util/rbtree.h"
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/** Node colour black */
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#define BLACK 0
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/** Node colour red */
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#define RED 1
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/** the NULL node, global alloc */
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rbnode_t rbtree_null_node = {
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RBTREE_NULL, /* Parent. */
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RBTREE_NULL, /* Left. */
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RBTREE_NULL, /* Right. */
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NULL, /* Key. */
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BLACK /* Color. */
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};
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/** rotate subtree left (to preserve redblack property) */
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static void rbtree_rotate_left(rbtree_t *rbtree, rbnode_t *node);
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/** rotate subtree right (to preserve redblack property) */
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static void rbtree_rotate_right(rbtree_t *rbtree, rbnode_t *node);
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/** Fixup node colours when insert happened */
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static void rbtree_insert_fixup(rbtree_t *rbtree, rbnode_t *node);
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/** Fixup node colours when delete happened */
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static void rbtree_delete_fixup(rbtree_t* rbtree, rbnode_t* child, rbnode_t* child_parent);
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/*
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* Creates a new red black tree, initializes and returns a pointer to it.
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*
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* Return NULL on failure.
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*
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*/
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rbtree_t *
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rbtree_create (int (*cmpf)(const void *, const void *))
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{
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rbtree_t *rbtree;
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/* Allocate memory for it */
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rbtree = (rbtree_t *) malloc(sizeof(rbtree_t));
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if (!rbtree) {
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return NULL;
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}
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/* Initialize it */
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rbtree_init(rbtree, cmpf);
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return rbtree;
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}
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void
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rbtree_init(rbtree_t *rbtree, int (*cmpf)(const void *, const void *))
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{
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/* Initialize it */
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rbtree->root = RBTREE_NULL;
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rbtree->count = 0;
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rbtree->cmp = cmpf;
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}
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/*
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* Rotates the node to the left.
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*
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*/
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static void
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rbtree_rotate_left(rbtree_t *rbtree, rbnode_t *node)
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{
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rbnode_t *right = node->right;
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node->right = right->left;
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if (right->left != RBTREE_NULL)
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right->left->parent = node;
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right->parent = node->parent;
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if (node->parent != RBTREE_NULL) {
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if (node == node->parent->left) {
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node->parent->left = right;
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} else {
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node->parent->right = right;
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}
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} else {
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rbtree->root = right;
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}
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right->left = node;
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node->parent = right;
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}
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/*
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* Rotates the node to the right.
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*
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*/
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static void
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rbtree_rotate_right(rbtree_t *rbtree, rbnode_t *node)
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{
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rbnode_t *left = node->left;
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node->left = left->right;
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if (left->right != RBTREE_NULL)
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left->right->parent = node;
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left->parent = node->parent;
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if (node->parent != RBTREE_NULL) {
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if (node == node->parent->right) {
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node->parent->right = left;
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} else {
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node->parent->left = left;
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}
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} else {
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rbtree->root = left;
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}
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left->right = node;
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node->parent = left;
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}
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static void
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rbtree_insert_fixup(rbtree_t *rbtree, rbnode_t *node)
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{
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rbnode_t *uncle;
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/* While not at the root and need fixing... */
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while (node != rbtree->root && node->parent->color == RED) {
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/* If our parent is left child of our grandparent... */
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if (node->parent == node->parent->parent->left) {
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uncle = node->parent->parent->right;
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/* If our uncle is red... */
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if (uncle->color == RED) {
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/* Paint the parent and the uncle black... */
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node->parent->color = BLACK;
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uncle->color = BLACK;
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/* And the grandparent red... */
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node->parent->parent->color = RED;
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/* And continue fixing the grandparent */
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node = node->parent->parent;
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} else { /* Our uncle is black... */
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/* Are we the right child? */
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if (node == node->parent->right) {
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node = node->parent;
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rbtree_rotate_left(rbtree, node);
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}
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/* Now we're the left child, repaint and rotate... */
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node->parent->color = BLACK;
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node->parent->parent->color = RED;
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rbtree_rotate_right(rbtree, node->parent->parent);
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}
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} else {
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uncle = node->parent->parent->left;
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/* If our uncle is red... */
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if (uncle->color == RED) {
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/* Paint the parent and the uncle black... */
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node->parent->color = BLACK;
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uncle->color = BLACK;
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/* And the grandparent red... */
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node->parent->parent->color = RED;
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/* And continue fixing the grandparent */
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node = node->parent->parent;
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} else { /* Our uncle is black... */
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/* Are we the right child? */
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if (node == node->parent->left) {
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node = node->parent;
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rbtree_rotate_right(rbtree, node);
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}
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/* Now we're the right child, repaint and rotate... */
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node->parent->color = BLACK;
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node->parent->parent->color = RED;
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rbtree_rotate_left(rbtree, node->parent->parent);
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}
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}
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}
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rbtree->root->color = BLACK;
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}
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/*
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* Inserts a node into a red black tree.
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*
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* Returns NULL on failure or the pointer to the newly added node
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* otherwise.
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*/
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rbnode_t *
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rbtree_insert (rbtree_t *rbtree, rbnode_t *data)
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{
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/* XXX Not necessary, but keeps compiler quiet... */
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int r = 0;
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/* We start at the root of the tree */
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rbnode_t *node = rbtree->root;
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rbnode_t *parent = RBTREE_NULL;
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fptr_ok(fptr_whitelist_rbtree_cmp(rbtree->cmp));
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/* Lets find the new parent... */
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while (node != RBTREE_NULL) {
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/* Compare two keys, do we have a duplicate? */
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if ((r = rbtree->cmp(data->key, node->key)) == 0) {
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return NULL;
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}
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parent = node;
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if (r < 0) {
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node = node->left;
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} else {
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node = node->right;
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}
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}
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/* Initialize the new node */
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data->parent = parent;
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data->left = data->right = RBTREE_NULL;
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data->color = RED;
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rbtree->count++;
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/* Insert it into the tree... */
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if (parent != RBTREE_NULL) {
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if (r < 0) {
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parent->left = data;
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} else {
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parent->right = data;
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}
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} else {
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rbtree->root = data;
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}
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/* Fix up the red-black properties... */
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rbtree_insert_fixup(rbtree, data);
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return data;
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}
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/*
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* Searches the red black tree, returns the data if key is found or NULL otherwise.
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*
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*/
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rbnode_t *
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rbtree_search (rbtree_t *rbtree, const void *key)
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{
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rbnode_t *node;
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if (rbtree_find_less_equal(rbtree, key, &node)) {
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return node;
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} else {
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return NULL;
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}
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}
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/** helpers for delete: swap node colours */
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static void swap_int8(uint8_t* x, uint8_t* y)
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{
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uint8_t t = *x; *x = *y; *y = t;
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}
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/** helpers for delete: swap node pointers */
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static void swap_np(rbnode_t** x, rbnode_t** y)
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{
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rbnode_t* t = *x; *x = *y; *y = t;
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}
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/** Update parent pointers of child trees of 'parent' */
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static void change_parent_ptr(rbtree_t* rbtree, rbnode_t* parent, rbnode_t* old, rbnode_t* new)
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{
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if(parent == RBTREE_NULL)
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{
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log_assert(rbtree->root == old);
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if(rbtree->root == old) rbtree->root = new;
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return;
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}
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log_assert(parent->left == old || parent->right == old
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|| parent->left == new || parent->right == new);
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if(parent->left == old) parent->left = new;
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if(parent->right == old) parent->right = new;
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}
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/** Update parent pointer of a node 'child' */
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static void change_child_ptr(rbnode_t* child, rbnode_t* old, rbnode_t* new)
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{
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if(child == RBTREE_NULL) return;
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log_assert(child->parent == old || child->parent == new);
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if(child->parent == old) child->parent = new;
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}
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rbnode_t*
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rbtree_delete(rbtree_t *rbtree, const void *key)
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{
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rbnode_t *to_delete;
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rbnode_t *child;
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if((to_delete = rbtree_search(rbtree, key)) == 0) return 0;
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rbtree->count--;
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/* make sure we have at most one non-leaf child */
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if(to_delete->left != RBTREE_NULL && to_delete->right != RBTREE_NULL)
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{
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/* swap with smallest from right subtree (or largest from left) */
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rbnode_t *smright = to_delete->right;
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while(smright->left != RBTREE_NULL)
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smright = smright->left;
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/* swap the smright and to_delete elements in the tree,
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* but the rbnode_t is first part of user data struct
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* so cannot just swap the keys and data pointers. Instead
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* readjust the pointers left,right,parent */
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/* swap colors - colors are tied to the position in the tree */
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swap_int8(&to_delete->color, &smright->color);
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/* swap child pointers in parents of smright/to_delete */
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change_parent_ptr(rbtree, to_delete->parent, to_delete, smright);
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if(to_delete->right != smright)
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change_parent_ptr(rbtree, smright->parent, smright, to_delete);
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/* swap parent pointers in children of smright/to_delete */
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change_child_ptr(smright->left, smright, to_delete);
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change_child_ptr(smright->left, smright, to_delete);
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change_child_ptr(smright->right, smright, to_delete);
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change_child_ptr(smright->right, smright, to_delete);
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change_child_ptr(to_delete->left, to_delete, smright);
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if(to_delete->right != smright)
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change_child_ptr(to_delete->right, to_delete, smright);
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if(to_delete->right == smright)
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{
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/* set up so after swap they work */
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to_delete->right = to_delete;
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smright->parent = smright;
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}
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/* swap pointers in to_delete/smright nodes */
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swap_np(&to_delete->parent, &smright->parent);
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swap_np(&to_delete->left, &smright->left);
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swap_np(&to_delete->right, &smright->right);
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/* now delete to_delete (which is at the location where the smright previously was) */
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}
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log_assert(to_delete->left == RBTREE_NULL || to_delete->right == RBTREE_NULL);
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if(to_delete->left != RBTREE_NULL) child = to_delete->left;
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else child = to_delete->right;
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/* unlink to_delete from the tree, replace to_delete with child */
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change_parent_ptr(rbtree, to_delete->parent, to_delete, child);
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change_child_ptr(child, to_delete, to_delete->parent);
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if(to_delete->color == RED)
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{
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/* if node is red then the child (black) can be swapped in */
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}
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else if(child->color == RED)
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{
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/* change child to BLACK, removing a RED node is no problem */
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if(child!=RBTREE_NULL) child->color = BLACK;
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}
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else rbtree_delete_fixup(rbtree, child, to_delete->parent);
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/* unlink completely */
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to_delete->parent = RBTREE_NULL;
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to_delete->left = RBTREE_NULL;
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to_delete->right = RBTREE_NULL;
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to_delete->color = BLACK;
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return to_delete;
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}
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static void rbtree_delete_fixup(rbtree_t* rbtree, rbnode_t* child, rbnode_t* child_parent)
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{
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rbnode_t* sibling;
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int go_up = 1;
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/* determine sibling to the node that is one-black short */
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if(child_parent->right == child) sibling = child_parent->left;
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else sibling = child_parent->right;
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while(go_up)
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{
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if(child_parent == RBTREE_NULL)
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{
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/* removed parent==black from root, every path, so ok */
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return;
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}
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if(sibling->color == RED)
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{ /* rotate to get a black sibling */
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child_parent->color = RED;
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sibling->color = BLACK;
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if(child_parent->right == child)
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rbtree_rotate_right(rbtree, child_parent);
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else rbtree_rotate_left(rbtree, child_parent);
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/* new sibling after rotation */
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if(child_parent->right == child) sibling = child_parent->left;
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else sibling = child_parent->right;
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}
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if(child_parent->color == BLACK
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&& sibling->color == BLACK
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&& sibling->left->color == BLACK
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&& sibling->right->color == BLACK)
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{ /* fixup local with recolor of sibling */
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if(sibling != RBTREE_NULL)
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sibling->color = RED;
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child = child_parent;
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child_parent = child_parent->parent;
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/* prepare to go up, new sibling */
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if(child_parent->right == child) sibling = child_parent->left;
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else sibling = child_parent->right;
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}
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else go_up = 0;
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}
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if(child_parent->color == RED
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&& sibling->color == BLACK
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&& sibling->left->color == BLACK
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&& sibling->right->color == BLACK)
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{
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/* move red to sibling to rebalance */
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if(sibling != RBTREE_NULL)
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sibling->color = RED;
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child_parent->color = BLACK;
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return;
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}
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log_assert(sibling != RBTREE_NULL);
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/* get a new sibling, by rotating at sibling. See which child
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of sibling is red */
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if(child_parent->right == child
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&& sibling->color == BLACK
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&& sibling->right->color == RED
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&& sibling->left->color == BLACK)
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{
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sibling->color = RED;
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sibling->right->color = BLACK;
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rbtree_rotate_left(rbtree, sibling);
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/* new sibling after rotation */
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if(child_parent->right == child) sibling = child_parent->left;
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else sibling = child_parent->right;
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}
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else if(child_parent->left == child
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&& sibling->color == BLACK
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&& sibling->left->color == RED
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&& sibling->right->color == BLACK)
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{
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sibling->color = RED;
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sibling->left->color = BLACK;
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rbtree_rotate_right(rbtree, sibling);
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/* new sibling after rotation */
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if(child_parent->right == child) sibling = child_parent->left;
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else sibling = child_parent->right;
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}
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/* now we have a black sibling with a red child. rotate and exchange colors. */
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sibling->color = child_parent->color;
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child_parent->color = BLACK;
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if(child_parent->right == child)
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{
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log_assert(sibling->left->color == RED);
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sibling->left->color = BLACK;
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rbtree_rotate_right(rbtree, child_parent);
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}
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else
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{
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log_assert(sibling->right->color == RED);
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sibling->right->color = BLACK;
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rbtree_rotate_left(rbtree, child_parent);
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}
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}
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int
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rbtree_find_less_equal(rbtree_t *rbtree, const void *key, rbnode_t **result)
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{
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int r;
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rbnode_t *node;
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log_assert(result);
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/* We start at root... */
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node = rbtree->root;
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*result = NULL;
|
|
fptr_ok(fptr_whitelist_rbtree_cmp(rbtree->cmp));
|
|
|
|
/* While there are children... */
|
|
while (node != RBTREE_NULL) {
|
|
r = rbtree->cmp(key, node->key);
|
|
if (r == 0) {
|
|
/* Exact match */
|
|
*result = node;
|
|
return 1;
|
|
}
|
|
if (r < 0) {
|
|
node = node->left;
|
|
} else {
|
|
/* Temporary match */
|
|
*result = node;
|
|
node = node->right;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Finds the first element in the red black tree
|
|
*
|
|
*/
|
|
rbnode_t *
|
|
rbtree_first (rbtree_t *rbtree)
|
|
{
|
|
rbnode_t *node;
|
|
|
|
for (node = rbtree->root; node->left != RBTREE_NULL; node = node->left);
|
|
return node;
|
|
}
|
|
|
|
rbnode_t *
|
|
rbtree_last (rbtree_t *rbtree)
|
|
{
|
|
rbnode_t *node;
|
|
|
|
for (node = rbtree->root; node->right != RBTREE_NULL; node = node->right);
|
|
return node;
|
|
}
|
|
|
|
/*
|
|
* Returns the next node...
|
|
*
|
|
*/
|
|
rbnode_t *
|
|
rbtree_next (rbnode_t *node)
|
|
{
|
|
rbnode_t *parent;
|
|
|
|
if (node->right != RBTREE_NULL) {
|
|
/* One right, then keep on going left... */
|
|
for (node = node->right; node->left != RBTREE_NULL; node = node->left);
|
|
} else {
|
|
parent = node->parent;
|
|
while (parent != RBTREE_NULL && node == parent->right) {
|
|
node = parent;
|
|
parent = parent->parent;
|
|
}
|
|
node = parent;
|
|
}
|
|
return node;
|
|
}
|
|
|
|
rbnode_t *
|
|
rbtree_previous(rbnode_t *node)
|
|
{
|
|
rbnode_t *parent;
|
|
|
|
if (node->left != RBTREE_NULL) {
|
|
/* One left, then keep on going right... */
|
|
for (node = node->left; node->right != RBTREE_NULL; node = node->right);
|
|
} else {
|
|
parent = node->parent;
|
|
while (parent != RBTREE_NULL && node == parent->left) {
|
|
node = parent;
|
|
parent = parent->parent;
|
|
}
|
|
node = parent;
|
|
}
|
|
return node;
|
|
}
|
|
|
|
/** recursive descent traverse */
|
|
static void
|
|
traverse_post(void (*func)(rbnode_t*, void*), void* arg, rbnode_t* node)
|
|
{
|
|
if(!node || node == RBTREE_NULL)
|
|
return;
|
|
/* recurse */
|
|
traverse_post(func, arg, node->left);
|
|
traverse_post(func, arg, node->right);
|
|
/* call user func */
|
|
(*func)(node, arg);
|
|
}
|
|
|
|
void
|
|
traverse_postorder(rbtree_t* tree, void (*func)(rbnode_t*, void*), void* arg)
|
|
{
|
|
traverse_post(func, arg, tree->root);
|
|
}
|