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@@ -0,0 +1,536 @@
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+/*!
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+ * \file rbtree.c
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+ *
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+ * \brief binary search tree
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+ *
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+ * Generic balanced binary search tree (Red Black Tree) implementation
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+ *
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+ * (C) 2009 by the GRASS Development Team
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+ *
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+ * This program is free software under the GNU General Public License
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+ * (>=v2). Read the file COPYING that comes with GRASS for details.
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+ *
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+ * \author Original author Julienne Walker 2003, 2008
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+ * GRASS implementation Markus Metz, 2009
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+ */
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+
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+/* balanced binary search tree implementation
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+ *
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+ * this one is a Red Black Tree, the bare version, no parent pointers, no threads
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+ * The core code comes from Julienne Walker's tutorials on binary search trees
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+ * original license: public domain
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+ * http://eternallyconfuzzled.com/tuts/datastructures/jsw_tut_rbtree.aspx
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+ * some ideas come from libavl (GPL >= 2)
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+ * I could have used some off-the-shelf solution, but that's boring
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+ *
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+ * Red Black Trees are used to maintain a data structure with
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+ * search, insertion and deletion in O(log N) time
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+ */
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+
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+#include <assert.h>
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+#include <stdlib.h>
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+#include <string.h>
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+#include <grass/gis.h>
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+#include <grass/glocale.h>
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+#include "rbtree.h"
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+
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+/* internal functions */
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+void rbtree_destroy2(struct RB_NODE *);
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+struct RB_NODE *rbtree_single(struct RB_NODE *, int);
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+struct RB_NODE *rbtree_double(struct RB_NODE *, int);
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+void *rbtree_first(struct RB_TRAV *);
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+void *rbtree_next(struct RB_TRAV *);
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+struct RB_NODE *rbtree_make_node(size_t, void *);
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+int is_red(struct RB_NODE *);
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+
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+
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+/* create new tree and initialize
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+ * returns pointer to new tree, NULL for memory allocation error
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+ */
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+struct RB_TREE *rbtree_create(rb_compare_fn *compare, size_t rb_datasize)
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+{
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+ struct RB_TREE *tree = G_malloc(sizeof(*tree));
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+
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+ if (tree == NULL) {
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+ G_warning("RB tree: Out of memory!");
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+ return NULL;
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+ }
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+
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+ assert(compare);
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+
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+ tree->datasize = rb_datasize;
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+ tree->rb_compare = compare;
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+ tree->count = 0;
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+ tree->root = NULL;
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+
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+ return tree;
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+}
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+
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+/* add an item to a tree
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+ * non-recursive top-down insertion
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+ * the algorithm does not allow duplicates and also does not warn about a duplicate
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+ * returns 1 on success, 0 on failure
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+ */
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+int rbtree_insert(struct RB_TREE *tree, void *data)
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+{
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+ assert(tree && data);
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+
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+ if (tree->root == NULL) {
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+ /* create a new root node for tree */
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+ tree->root = rbtree_make_node(tree->datasize, data);
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+ if (tree->root == NULL)
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+ return 0;
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+ }
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+ else {
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+ struct RB_NODE head = {0}; /* False tree root */
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+
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+ struct RB_NODE *g, *t; /* Grandparent & parent */
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+ struct RB_NODE *p, *q; /* Iterator & parent */
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+ int dir = 0, last = 0;
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+
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+ /* Set up helpers */
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+ t = &head;
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+ g = p = NULL;
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+ q = t->link[1] = tree->root;
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+
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+ /* Search down the tree */
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+ for ( ; ; ) {
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+ if (q == NULL) {
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+ /* Insert new node at the bottom */
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+ p->link[dir] = q = rbtree_make_node(tree->datasize, data);
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+ if (q == NULL)
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+ return 0;
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+ }
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+ else if (is_red(q->link[0]) && is_red(q->link[1])) {
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+ /* Color flip */
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+ q->red = 1;
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+ q->link[0]->red = 0;
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+ q->link[1]->red = 0;
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+ }
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+
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+ /* Fix red violation */
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+ if (is_red(q) && is_red(p)) {
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+ int dir2 = t->link[1] == g;
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+
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+ if (q == p->link[last])
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+ t->link[dir2] = rbtree_single(g, !last);
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+ else
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+ t->link[dir2] = rbtree_double(g, !last);
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+ }
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+
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+ last = dir;
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+ dir = tree->rb_compare(q->data, data);
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+
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+ /* Stop if found. This check also disallows duplicates in the tree */
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+ if (dir == 0)
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+ break;
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+
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+ dir = dir < 0;
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+
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+ /* Move the helpers down */
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+ if (g != NULL)
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+ t = g;
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+
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+ g = p, p = q;
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+ q = q->link[dir];
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+ }
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+
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+ /* Update root */
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+ tree->root = head.link[1];
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+ }
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+
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+ /* Make root black */
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+ tree->root->red = 0;
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+
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+ tree->count++;
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+
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+ return 1;
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+}
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+
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+/* remove an item from a tree that matches given data
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+ * non-recursive top-down removal
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+ * returns 1 on successful removal
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+ * returns 0 if data item was not found
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+ */
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+int rbtree_remove(struct RB_TREE *tree, const void *data)
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+{
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+ struct RB_NODE head = {0}; /* False tree root */
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+ struct RB_NODE *q, *p, *g; /* Helpers */
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+ struct RB_NODE *f = NULL; /* Found item */
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+ int dir = 1, removed = 0;
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+
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+ assert(tree && data);
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+
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+ if (tree->root == NULL) {
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+ return 0; /* empty tree, nothing to remove */
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+ }
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+
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+ /* Set up helpers */
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+ q = &head;
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+ g = p = NULL;
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+ q->link[1] = tree->root;
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+
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+ /* Search and push a red down */
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+ while (q->link[dir] != NULL) {
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+ int last = dir;
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+
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+ /* Update helpers */
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+ g = p, p = q;
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+ q = q->link[dir];
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+ dir = tree->rb_compare(q->data, data);
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+
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+ /* Save found node */
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+ if (dir == 0)
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+ f = q;
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+
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+ dir = dir < 0;
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+
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+ /* Push the red node down */
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+ if (!is_red(q) && !is_red(q->link[dir])) {
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+ if (is_red(q->link[!dir]))
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+ p = p->link[last] = rbtree_single(q, dir);
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+ else if (!is_red(q->link[!dir])) {
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+ struct RB_NODE *s = p->link[!last];
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+
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+ if (s != NULL) {
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+ if (!is_red(s->link[!last]) &&
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+ !is_red(s->link[last])) {
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+ /* Color flip */
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+ p->red = 0;
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+ s->red = 1;
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+ q->red = 1;
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+ }
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+ else {
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+ int dir2 = g->link[1] == p;
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+
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+ if (is_red(s->link[last]))
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+ g->link[dir2] = rbtree_double(p, last);
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+ else if (is_red(s->link[!last]))
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+ g->link[dir2] = rbtree_single(p, last);
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+
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+ /* Ensure correct coloring */
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+ q->red = g->link[dir2]->red = 1;
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+ g->link[dir2]->link[0]->red = 0;
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+ g->link[dir2]->link[1]->red = 0;
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+ }
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+ }
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+ }
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+ }
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+ }
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+
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+ /* Replace and remove if found */
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+ if (f != NULL) {
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+ G_free(f->data);
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+ f->data = q->data;
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+ p->link[p->link[1] == q] = q->link[q->link[0] == NULL];
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+ G_free(q);
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+ tree->count--;
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+ removed = 1;
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+ }
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+ else
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+ G_debug(2, "RB tree: data not found in search tree");
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+
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+ /* Update root and make it black */
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+ tree->root = head.link[1];
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+ if ( tree->root != NULL)
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+ tree->root->red = 0;
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+
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+ return removed;
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+}
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+
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+/* find data item in tree
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+ * returns pointer to data item if found else NULL
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+ */
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+void *rbtree_find(struct RB_TREE *tree, const void *data)
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+{
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+ struct RB_NODE *curr_node = tree->root;
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+ int cmp = 0;
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+
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+ assert(tree && data);
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+
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+ while (curr_node != NULL) {
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+ cmp = tree->rb_compare(curr_node->data, data);
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+ if (cmp == 0)
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+ return curr_node->data; /* found */
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+ else {
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+ curr_node = curr_node->link[cmp < 0];
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+ }
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+ }
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+ return NULL;
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+}
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+
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+/* initialize tree traversal
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+ * (re-)sets trav structure
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+ * returns 0
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+ */
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+int rbtree_init_trav(struct RB_TRAV *trav, struct RB_TREE *tree)
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+{
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+ assert(trav && tree);
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+
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+ trav->tree = tree;
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+ trav->curr_node = tree->root;
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+ trav->first = 1;
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+ trav->top = 0;
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+
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+ return 0;
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+}
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+
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+/* traverse the tree in ascending order
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+ * useful to get all items in the tree non-recursively
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+ * struct RB_TRAV *trav needs to be initialized first
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+ * returns pointer to data, NULL when finished
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+ */
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+void *rbtree_traverse(struct RB_TRAV *trav)
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+{
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+ assert(trav);
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+
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+ if (trav->curr_node == NULL) {
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+ if (trav->first)
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+ G_debug(1, "RB tree: empty tree");
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+ else
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+ G_debug(1, "RB tree: finished traversing");
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+
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+ return NULL;
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+ }
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+
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+ if (!trav->first)
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+ return rbtree_next(trav);
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+ else {
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+ trav->first = 0;
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+ return rbtree_first(trav);
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+ }
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+}
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+
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+/* find start point to traverse the tree in ascending order
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+ * useful to get a selection of items in the tree
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+ * magnitudes faster than traversing the whole tree
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+ * may return first item that's smaller or first item that's larger
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+ * struct RB_TRAV *trav needs to be initialized first
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+ * returns pointer to data, NULL when finished
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+ */
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+void *rbtree_traverse_start(struct RB_TRAV *trav, const void *data)
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+{
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+ int dir = 0;
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+
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+ assert(trav && data);
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+
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+ if (trav->curr_node == NULL) {
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+ if (trav->first)
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+ G_warning("RB tree: empty tree");
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+ else
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+ G_warning("RB tree: finished traversing");
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+
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+ return NULL;
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+ }
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+
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+ if (!trav->first)
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+ return rbtree_next(trav);
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+
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+ /* else first time, get start node */
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+
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+ trav->first = 0;
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+ trav->top = 0;
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+
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+ while (trav->curr_node != NULL) {
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+ dir = trav->tree->rb_compare(trav->curr_node->data, data);
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+ /* exact match, great! */
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+ if (dir == 0)
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+ return trav->curr_node->data;
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+ else {
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+ dir = dir < 0;
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+ /* end of branch, also reached if
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+ * smallest item is larger than search template or
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+ * largest item is smaller than search template */
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+ if (trav->curr_node->link[dir] == NULL)
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+ return trav->curr_node->data;
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+
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+ trav->up[trav->top++] = trav->curr_node;
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+ trav->curr_node = trav->curr_node->link[dir];
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+ }
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+ }
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+
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+ return NULL; /* should not happen */
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+}
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+
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+/* two functions needed to fully traverse the tree: initialize and continue
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+ * useful to get all items in the tree non-recursively
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+ * this one here uses a stack
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+ * parent pointers or threads would also be possible
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+ * but these would need to be added to RB_NODE
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+ * -> more memory needed for standard operations
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+ */
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+
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+/* start traversing the tree
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+ * returns pointer to smallest data item
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+ */
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+void *rbtree_first(struct RB_TRAV *trav)
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+{
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+ /* get smallest item */
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+ while (trav->curr_node->link[0] != NULL) {
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+ trav->up[trav->top++] = trav->curr_node;
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+ trav->curr_node = trav->curr_node->link[0];
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+ }
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+
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+ return trav->curr_node->data; /* return smallest item */
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+}
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+
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+/* continue traversing the tree in ascending order
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+ * returns pointer to data item, NULL when finished
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+ */
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+void *rbtree_next(struct RB_TRAV *trav)
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+{
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+ if (trav->curr_node->link[1] != NULL) {
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+ /* something on the right side: larger item */
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+ trav->up[trav->top++] = trav->curr_node;
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+ trav->curr_node = trav->curr_node->link[1];
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+
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+ /* go down, find smallest item in this branch */
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+ while (trav->curr_node->link[0] != NULL) {
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+ trav->up[trav->top++] = trav->curr_node;
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+ trav->curr_node = trav->curr_node->link[0];
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+ }
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+ }
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+ else {
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+ /* at smallest item in this branch, go back up */
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+ struct RB_NODE *last;
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+ do {
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+ if (trav->top == 0) {
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+ trav->curr_node = NULL;
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+ break;
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+ }
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+ last = trav->curr_node;
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+ trav->curr_node = trav->up[--trav->top];
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+ } while (last == trav->curr_node->link[1]);
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+ }
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+
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+ if (trav->curr_node != NULL) {
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+ return trav->curr_node->data;
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+ }
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+ else
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+ return NULL; /* finished traversing */
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+}
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+
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+/* destroy the tree */
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+void rbtree_destroy(struct RB_TREE *tree) {
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+ rbtree_destroy2(tree->root);
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+ G_free(tree);
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+}
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+
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+void rbtree_destroy2(struct RB_NODE *root)
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+{
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+ if (root != NULL) {
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+ rbtree_destroy2(root->link[0]);
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+ rbtree_destroy2(root->link[1]);
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+ G_free(root->data);
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+ G_free(root);
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+ }
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+}
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+
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+/* used for debugging: check for errors in tree structure */
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+int rbtree_debug(struct RB_TREE *tree, struct RB_NODE *root)
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+{
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+ int lh, rh;
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|
+
|
|
|
+ if (root == NULL)
|
|
|
+ return 1;
|
|
|
+ else {
|
|
|
+ struct RB_NODE *ln = root->link[0];
|
|
|
+ struct RB_NODE *rn = root->link[1];
|
|
|
+ int lcmp = 0, rcmp = 0;
|
|
|
+
|
|
|
+ /* Consecutive red links */
|
|
|
+ if (is_red(root)) {
|
|
|
+ if (is_red(ln) || is_red(rn)) {
|
|
|
+ G_warning("Red Black Tree debugging: Red violation");
|
|
|
+ return 0;
|
|
|
+ }
|
|
|
+ }
|
|
|
+
|
|
|
+ lh = rbtree_debug(tree, ln);
|
|
|
+ rh = rbtree_debug(tree, rn);
|
|
|
+
|
|
|
+ if (ln) {
|
|
|
+ lcmp = tree->rb_compare(ln->data, root->data);
|
|
|
+ }
|
|
|
+
|
|
|
+ if (rn) {
|
|
|
+ rcmp = tree->rb_compare(rn->data, root->data);
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Invalid binary search tree:
|
|
|
+ * left node >= parent or right node <= parent */
|
|
|
+ if ((ln != NULL && lcmp > -1)
|
|
|
+ || (rn != NULL && rcmp < 1)) {
|
|
|
+ G_warning("Red Black Tree debugging: Binary tree violation" );
|
|
|
+ return 0;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Black height mismatch */
|
|
|
+ if (lh != 0 && rh != 0 && lh != rh) {
|
|
|
+ G_warning("Red Black Tree debugging: Black violation");
|
|
|
+ return 0;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Only count black links */
|
|
|
+ if (lh != 0 && rh != 0)
|
|
|
+ return is_red(root) ? lh : lh + 1;
|
|
|
+ else
|
|
|
+ return 0;
|
|
|
+ }
|
|
|
+}
|
|
|
+
|
|
|
+/*******************************************************
|
|
|
+ * *
|
|
|
+ * internal functions for Red Black Tree maintenance *
|
|
|
+ * *
|
|
|
+ *******************************************************/
|
|
|
+
|
|
|
+/* add a new node to the tree */
|
|
|
+struct RB_NODE *rbtree_make_node(size_t datasize, void *data)
|
|
|
+{
|
|
|
+ struct RB_NODE *new_node = G_malloc(sizeof(*new_node));
|
|
|
+
|
|
|
+ if (new_node == NULL)
|
|
|
+ G_fatal_error("RB Search Tree: Out of memory!");
|
|
|
+
|
|
|
+ new_node->data = G_malloc(datasize);
|
|
|
+ if (new_node->data == NULL)
|
|
|
+ G_fatal_error("RB Search Tree: Out of memory!");
|
|
|
+
|
|
|
+ memcpy(new_node->data, data, datasize);
|
|
|
+ new_node->red = 1; /* 1 is red, 0 is black */
|
|
|
+ new_node->link[0] = NULL;
|
|
|
+ new_node->link[1] = NULL;
|
|
|
+
|
|
|
+ return new_node;
|
|
|
+}
|
|
|
+
|
|
|
+/* check for red violation */
|
|
|
+int is_red(struct RB_NODE *root)
|
|
|
+{
|
|
|
+ if (root)
|
|
|
+ return root->red == 1;
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/* single rotation */
|
|
|
+struct RB_NODE *rbtree_single(struct RB_NODE *root, int dir)
|
|
|
+{
|
|
|
+ struct RB_NODE *newroot = root->link[!dir];
|
|
|
+
|
|
|
+ root->link[!dir] = newroot->link[dir];
|
|
|
+ newroot->link[dir] = root;
|
|
|
+
|
|
|
+ root->red = 1;
|
|
|
+ newroot->red = 0;
|
|
|
+
|
|
|
+ return newroot;
|
|
|
+}
|
|
|
+
|
|
|
+/* double rotation */
|
|
|
+struct RB_NODE *rbtree_double(struct RB_NODE *root, int dir)
|
|
|
+{
|
|
|
+ root->link[!dir] = rbtree_single(root->link[!dir], !dir);
|
|
|
+ return rbtree_single(root, dir);
|
|
|
+}
|
Markus Metz