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@@ -0,0 +1,488 @@
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+/****************************************************************************
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+ *
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+ * MODULE: Vector library
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+ *
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+ * AUTHOR(S): Markus Metz
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+ *
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+ * PURPOSE: Lower level functions for reading/writing/manipulating vectors.
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+ *
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+ * COPYRIGHT: (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
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+ * License (>=v2). Read the file COPYING that comes with GRASS
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+ * for details.
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+ *
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+ *****************************************************************************/
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+
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+/* balanced binary search tree implementation
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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
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+ * binary search trees: insert, remove, balance
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+ * support for any kind of data structures comes from libavl (GPL >= 2)
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+ *
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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 that allows
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+ * search, insertion and deletion in O(log N) time
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+ * This is needed for large vectors with many features
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+ */
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+
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+#include <assert.h>
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+#include <stdio.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 <grass/vect/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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+ * return pointer to new tree or NULL for memory allocation error
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+ */
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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 = malloc(sizeof(*tree));
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+
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+ if (tree == NULL) {
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+ G_warning("RB Search Tree: Out of memory!");
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+ return NULL;
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+ }
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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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+ * returns 1 on success, 0 on failure
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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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+ */
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+int rbtree_insert(struct RB_TREE *tree, void *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 */
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+ if (dir == 2)
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+ break;
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+
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+ /* Update helpers */
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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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+/* delete an item from a tree
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+ * returns 1 on successful deletion
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+ * returns 0 if data item was not found
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+ * non-recursive top-down deletion
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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, found = 0;
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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 == 2) {
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+ f = q;
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+ dir = 0;
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+ }
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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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+ p->link[p->link[1] == q] = q->link[q->link[0] == NULL];
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+ free(q->data);
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+ free(q);
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+ tree->count--;
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+ found = 1;
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+ }
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+ else
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+ G_debug(2, "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 found;
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+}
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+
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+/* find data item in tree
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+ * return 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 dir = 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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+ dir = tree->rb_compare(curr_node->data, data);
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+ if (dir == 2)
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+ return curr_node->data;
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+ else {
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+ curr_node = curr_node->link[dir];
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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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+ * return pointer to trav struct or NULL on memory allocation error
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+ */
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+void rbtree_init_trav(struct RB_TRAV *trav, struct RB_TREE *tree)
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+{
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+ int i;
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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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+
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+ for (i = 0; i < RBTREE_MAX_HEIGHT; i++)
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+ trav->up[i] = NULL;
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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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+ * return pointer to data
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+ * struct RB_TRAV *trav needs to be initialized first
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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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+ if (trav->curr_node == NULL) {
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+ if (trav->first)
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+ G_warning("empty tree");
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+ else
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+ G_warning("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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+ trav->first = 0;
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+ return rbtree_first(trav);
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+ }
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+ else
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+ return rbtree_next(trav);
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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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+void *rbtree_first(struct RB_TRAV *trav)
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+{
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+ trav->top = 0;
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+
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+ /* get smallest item */
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+ if (trav->curr_node != NULL) {
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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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+
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+ if (trav->curr_node != NULL) {
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+ return trav->curr_node->data; /* return smallest item */
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+ }
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+ else
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+ return NULL; /* empty tree */
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+}
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+
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+/* continue traversing the tree */
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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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+}
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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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+ free(root->data);
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+ free(root);
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+ }
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+}
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+
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+/*!
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+ * internal funtions used for Red Black Tree maintenance
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+ */
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+
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+/* add a new node to the tree */
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+struct RB_NODE *rbtree_make_node(size_t datasize, void *data)
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+{
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+ struct RB_NODE *new_node = malloc(sizeof(*new_node));
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+
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+ if (new_node != NULL) {
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+ new_node->data = malloc(datasize);
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+ if (new_node->data == NULL)
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+ G_fatal_error("RB Search Tree: Out of memory!");
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+
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+ memcpy(new_node->data, data, datasize);
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+ new_node->red = 1; /* 1 is red, 0 is black */
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+ new_node->link[0] = NULL;
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+ new_node->link[1] = NULL;
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+ }
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+ else
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+ G_fatal_error("RB Search Tree: Out of memory!");
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+
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+ return new_node;
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+}
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+
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+/* check for red violation */
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+int is_red(struct RB_NODE *root)
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+{
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+ if (root)
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+ return root->red == 1;
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+
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+ return 0;
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+}
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+
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+/* single rotation */
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+struct RB_NODE *rbtree_single(struct RB_NODE *root, int dir)
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+{
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+ struct RB_NODE *newroot = root->link[!dir];
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+
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+ root->link[!dir] = newroot->link[dir];
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+ newroot->link[dir] = root;
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+
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+ root->red = 1;
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+ newroot->red = 0;
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+
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+ return newroot;
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+}
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+
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+/* double rotation */
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+struct RB_NODE *rbtree_double(struct RB_NODE *root, int dir)
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+{
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+ root->link[!dir] = rbtree_single(root->link[!dir], !dir);
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+ return rbtree_single(root, dir);
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+}
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+
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+/* only used for debugging */
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+/* check for errors */
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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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+
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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, rcmp;
|
|
|
+
|
|
|
+ /* 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);
|
|
|
+ }
|
|
|
+ else {
|
|
|
+ lcmp = 1;
|
|
|
+ }
|
|
|
+
|
|
|
+ if (rn) {
|
|
|
+ rcmp = tree->rb_compare(rn->data, root->data);
|
|
|
+ }
|
|
|
+ else {
|
|
|
+ rcmp = 1;
|
|
|
+ }
|
|
|
+
|
|
|
+
|
|
|
+ /* Invalid binary search tree */
|
|
|
+ if ((ln != NULL && (lcmp == 0 || lcmp == 2))
|
|
|
+ || (rn != NULL && (rcmp == 1 || rcmp == 2))) {
|
|
|
+ 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;
|
|
|
+ }
|
|
|
+}
|
Markus Metz