libisofs/src/util_rbtree.c
Vreixo Formoso e6bd1586d6 Replace glibc tsearch() with a custom red-black tree implementation.
The library supplied tree estructure is not enought for our needs, due to its
limited API. Thus, we have implemented a suitable red-black tree.
2007-12-20 00:25:25 +01:00

285 lines
6.8 KiB
C

/*
* Copyright (c) 2007 Vreixo Formoso
*
* This file is part of the libisofs project; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation. See COPYING file for details.
*/
#include "util.h"
#include "error.h"
#include <stdlib.h>
/*
* This implementation of Red-Black tree is based on the public domain
* implementation of Julienne Walker.
*/
struct iso_rbnode {
void *data;
struct iso_rbnode *ch[2];
unsigned int red:1;
};
struct iso_rbtree {
struct iso_rbnode *root;
size_t size;
int (*compare)(const void *a, const void *b);
};
/**
* Create a new binary tree. libisofs binary trees allow you to add any data
* passing it as a pointer. You must provide a function suitable for compare
* two elements.
*
* @param compare
* A function to compare two elements. It takes a pointer to both elements
* and return 0, -1 or 1 if the first element is equal, less or greater
* than the second one.
* @param tree
* Location where the tree structure will be stored.
*/
int
iso_rbtree_new(int (*compare)(const void*, const void*), IsoRBTree **tree)
{
if (compare == NULL || tree == NULL) {
return ISO_NULL_POINTER;
}
*tree = calloc(1, sizeof(IsoRBTree));
if (*tree == NULL) {
return ISO_MEM_ERROR;
}
(*tree)->compare = compare;
return ISO_SUCCESS;
}
static
void rbtree_destroy_aux(struct iso_rbnode *root, void (*free_data)(void *))
{
if (root == NULL) {
return;
}
if (free_data != NULL) {
free_data(root->data);
}
rbtree_destroy_aux(root->ch[0], free_data);
rbtree_destroy_aux(root->ch[1], free_data);
free(root);
}
/**
* Destroy a given tree.
*
* Note that only the structure itself is deleted. To delete the elements, you
* should provide a valid free_data function. It will be called for each
* element of the tree, so you can use it to free any related data.
*/
void
iso_rbtree_destroy(IsoRBTree *tree, void (*free_data)(void *))
{
if (tree == NULL) {
return;
}
rbtree_destroy_aux(tree->root, free_data);
free(tree);
}
static inline
int is_red(struct iso_rbnode *root)
{
return root != NULL && root->red;
}
static
struct iso_rbnode *iso_rbtree_single(struct iso_rbnode *root, int dir)
{
struct iso_rbnode *save = root->ch[!dir];
root->ch[!dir] = save->ch[dir];
save->ch[dir] = root;
root->red = 1;
save->red = 0;
return save;
}
static
struct iso_rbnode *iso_rbtree_double(struct iso_rbnode *root, int dir)
{
root->ch[!dir] = iso_rbtree_single(root->ch[!dir], !dir);
return iso_rbtree_single(root, dir);
}
static
struct iso_rbnode *iso_rbnode_new(void *data)
{
struct iso_rbnode *rn = malloc(sizeof(struct iso_rbnode));
if ( rn != NULL ) {
rn->data = data;
rn->red = 1;
rn->ch[0] = NULL;
rn->ch[1] = NULL;
}
return rn;
}
/**
* Inserts a given element in a Red-Black tree.
*
* @param tree
* the tree where to insert
* @param data
* element to be inserted on the tree. It can't be NULL
* @param item
* if not NULL, it will point to a location where the tree element ptr
* will be stored. If data was inserted, *item == data. If data was
* already on the tree, *item points to the previously inserted object
* that is equal to data.
* @return
* 1 success, 0 element already inserted, < 0 error
*/
int iso_rbtree_insert(IsoRBTree *tree, void *data, void **item)
{
struct iso_rbnode *new;
int added = 0; /* has a new node been added? */
if (tree == NULL || data == NULL) {
return ISO_NULL_POINTER;
}
if (tree->root == NULL) {
/* Empty tree case */
tree->root = iso_rbnode_new(data);
if (tree->root == NULL) {
return ISO_MEM_ERROR;
}
new = data;
added = 1;
} else {
struct iso_rbnode head = {0}; /* False tree root */
struct iso_rbnode *g, *t; /* Grandparent & parent */
struct iso_rbnode *p, *q; /* Iterator & parent */
int dir = 0, last = 0;
int comp;
/* Set up helpers */
t = &head;
g = p = NULL;
q = t->ch[1] = tree->root;
/* Search down the tree */
while (1) {
if (q == NULL) {
/* Insert new node at the bottom */
p->ch[dir] = q = iso_rbnode_new(data);
if (q == NULL) {
return ISO_MEM_ERROR;
}
added = 1;
} else if (is_red(q->ch[0]) && is_red(q->ch[1])) {
/* Color flip */
q->red = 1;
q->ch[0]->red = 0;
q->ch[1]->red = 0;
}
/* Fix red violation */
if (is_red(q) && is_red(p)) {
int dir2 = (t->ch[1] == g);
if (q == p->ch[last]) {
t->ch[dir2] = iso_rbtree_single(g, !last);
} else {
t->ch[dir2] = iso_rbtree_double(g, !last);
}
}
comp = tree->compare(q->data, data);
/* Stop if found */
if (comp == 0) {
new = q->data;
break;
}
last = dir;
dir = (comp < 0);
/* Update helpers */
if (g != NULL)
t = g;
g = p, p = q;
q = q->ch[dir];
}
/* Update root */
tree->root = head.ch[1];
}
/* Make root black */
tree->root->red = 0;
if (item != NULL) {
*item = new;
}
if (added) {
/* a new element has been added */
tree->size++;
return 1;
} else {
return 0;
}
}
/**
* Get the number of elements in a given tree.
*/
size_t iso_rbtree_get_size(IsoRBTree *tree)
{
return tree->size;
}
static
int rbtree_to_array_aux(struct iso_rbnode *root, void **array, size_t pos)
{
if (root == NULL) {
return pos;
}
pos = rbtree_to_array_aux(root->ch[0], array, pos);
array[pos++] = root->data;
pos = rbtree_to_array_aux(root->ch[1], array, pos);
return pos;
}
/**
* Get an array view of the elements of the tree.
*
* @return
* A sorted array with the contents of the tree, or NULL if there is not
* enought memory to allocate the array. You should free(3) the array when
* no more needed. Note that the array is NULL-terminated, and thus it
* has size + 1 length.
*/
void **
iso_rbtree_to_array(IsoRBTree *tree)
{
void **array;
array = malloc((tree->size + 1) * sizeof(void*));
if (array == NULL) {
return NULL;
}
/* fill array */
rbtree_to_array_aux(tree->root, array, 0);
array[tree->size] = NULL;
return array;
}