[GRASS-SVN] r42237 - grass/trunk/raster/r.watershed/ram
svn_grass at osgeo.org
svn_grass at osgeo.org
Wed May 12 05:53:38 EDT 2010
Author: mmetz
Date: 2010-05-12 05:53:37 -0400 (Wed, 12 May 2010)
New Revision: 42237
Added:
grass/trunk/raster/r.watershed/ram/rbtree.c
grass/trunk/raster/r.watershed/ram/rbtree.h
Log:
add search tree
Added: grass/trunk/raster/r.watershed/ram/rbtree.c
===================================================================
--- grass/trunk/raster/r.watershed/ram/rbtree.c (rev 0)
+++ grass/trunk/raster/r.watershed/ram/rbtree.c 2010-05-12 09:53:37 UTC (rev 42237)
@@ -0,0 +1,535 @@
+/*!
+ * \file rbtree.c
+ *
+ * \brief binary search tree
+ *
+ * Generic balanced binary search tree (Red Black Tree) implementation
+ *
+ * (C) 2009 by the GRASS Development Team
+ *
+ * This program is free software under the GNU General Public License
+ * (>=v2). Read the file COPYING that comes with GRASS for details.
+ *
+ * \author Original author Julienne Walker 2003, 2008
+ * GRASS implementation Markus Metz, 2009
+ */
+
+/* balanced binary search tree implementation
+ *
+ * this one is a Red Black Tree, the bare version, no parent pointers, no threads
+ * The core code comes from Julienne Walker's tutorials on binary search trees
+ * original license: public domain
+ * http://eternallyconfuzzled.com/tuts/datastructures/jsw_tut_rbtree.aspx
+ * some ideas come from libavl (GPL >= 2)
+ * I could have used some off-the-shelf solution, but that's boring
+ *
+ * Red Black Trees are used to maintain a data structure with
+ * search, insertion and deletion in O(log N) time
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <grass/gis.h>
+#include <grass/glocale.h>
+#include "rbtree.h"
+
+/* internal functions */
+void rbtree_destroy2(struct RB_NODE *);
+struct RB_NODE *rbtree_single(struct RB_NODE *, int);
+struct RB_NODE *rbtree_double(struct RB_NODE *, int);
+void *rbtree_first(struct RB_TRAV *);
+void *rbtree_next(struct RB_TRAV *);
+struct RB_NODE *rbtree_make_node(size_t, void *);
+int is_red(struct RB_NODE *);
+
+
+/* create new tree and initialize
+ * returns pointer to new tree, NULL for memory allocation error
+ */
+struct RB_TREE *rbtree_create(rb_compare_fn * compare, size_t rb_datasize)
+{
+ struct RB_TREE *tree = G_malloc(sizeof(*tree));
+
+ if (tree == NULL) {
+ G_warning("RB tree: Out of memory!");
+ return NULL;
+ }
+
+ assert(compare);
+
+ tree->datasize = rb_datasize;
+ tree->rb_compare = compare;
+ tree->count = 0;
+ tree->root = NULL;
+
+ return tree;
+}
+
+/* add an item to a tree
+ * non-recursive top-down insertion
+ * the algorithm does not allow duplicates and also does not warn about a duplicate
+ * returns 1 on success, 0 on failure
+ */
+int rbtree_insert(struct RB_TREE *tree, void *data)
+{
+ assert(tree && data);
+
+ if (tree->root == NULL) {
+ /* create a new root node for tree */
+ tree->root = rbtree_make_node(tree->datasize, data);
+ if (tree->root == NULL)
+ return 0;
+ }
+ else {
+ struct RB_NODE head = { 0 }; /* False tree root */
+ struct RB_NODE *g, *t; /* Grandparent & parent */
+ struct RB_NODE *p, *q; /* Iterator & parent */
+ int dir = 0, last = 0;
+
+ /* Set up helpers */
+ t = &head;
+ g = p = NULL;
+ q = t->link[1] = tree->root;
+
+ /* Search down the tree */
+ for (;;) {
+ if (q == NULL) {
+ /* Insert new node at the bottom */
+ p->link[dir] = q = rbtree_make_node(tree->datasize, data);
+ if (q == NULL)
+ return 0;
+ }
+ else if (is_red(q->link[0]) && is_red(q->link[1])) {
+ /* Color flip */
+ q->red = 1;
+ q->link[0]->red = 0;
+ q->link[1]->red = 0;
+ }
+
+ /* Fix red violation */
+ if (is_red(q) && is_red(p)) {
+ int dir2 = t->link[1] == g;
+
+ if (q == p->link[last])
+ t->link[dir2] = rbtree_single(g, !last);
+ else
+ t->link[dir2] = rbtree_double(g, !last);
+ }
+
+ last = dir;
+ dir = tree->rb_compare(q->data, data);
+
+ /* Stop if found. This check also disallows duplicates in the tree */
+ if (dir == 0)
+ break;
+
+ dir = dir < 0;
+
+ /* Move the helpers down */
+ if (g != NULL)
+ t = g;
+
+ g = p, p = q;
+ q = q->link[dir];
+ }
+
+ /* Update root */
+ tree->root = head.link[1];
+ }
+
+ /* Make root black */
+ tree->root->red = 0;
+
+ tree->count++;
+
+ return 1;
+}
+
+/* remove an item from a tree that matches given data
+ * non-recursive top-down removal
+ * returns 1 on successful removal
+ * returns 0 if data item was not found
+ */
+int rbtree_remove(struct RB_TREE *tree, const void *data)
+{
+ struct RB_NODE head = { 0 }; /* False tree root */
+ struct RB_NODE *q, *p, *g; /* Helpers */
+ struct RB_NODE *f = NULL; /* Found item */
+ int dir = 1, removed = 0;
+
+ assert(tree && data);
+
+ if (tree->root == NULL) {
+ return 0; /* empty tree, nothing to remove */
+ }
+
+ /* Set up helpers */
+ q = &head;
+ g = p = NULL;
+ q->link[1] = tree->root;
+
+ /* Search and push a red down */
+ while (q->link[dir] != NULL) {
+ int last = dir;
+
+ /* Update helpers */
+ g = p, p = q;
+ q = q->link[dir];
+ dir = tree->rb_compare(q->data, data);
+
+ /* Save found node */
+ if (dir == 0)
+ f = q;
+
+ dir = dir < 0;
+
+ /* Push the red node down */
+ if (!is_red(q) && !is_red(q->link[dir])) {
+ if (is_red(q->link[!dir]))
+ p = p->link[last] = rbtree_single(q, dir);
+ else if (!is_red(q->link[!dir])) {
+ struct RB_NODE *s = p->link[!last];
+
+ if (s != NULL) {
+ if (!is_red(s->link[!last]) && !is_red(s->link[last])) {
+ /* Color flip */
+ p->red = 0;
+ s->red = 1;
+ q->red = 1;
+ }
+ else {
+ int dir2 = g->link[1] == p;
+
+ if (is_red(s->link[last]))
+ g->link[dir2] = rbtree_double(p, last);
+ else if (is_red(s->link[!last]))
+ g->link[dir2] = rbtree_single(p, last);
+
+ /* Ensure correct coloring */
+ q->red = g->link[dir2]->red = 1;
+ g->link[dir2]->link[0]->red = 0;
+ g->link[dir2]->link[1]->red = 0;
+ }
+ }
+ }
+ }
+ }
+
+ /* Replace and remove if found */
+ if (f != NULL) {
+ G_free(f->data);
+ f->data = q->data;
+ p->link[p->link[1] == q] = q->link[q->link[0] == NULL];
+ G_free(q);
+ tree->count--;
+ removed = 1;
+ }
+ else
+ G_debug(2, "RB tree: data not found in search tree");
+
+ /* Update root and make it black */
+ tree->root = head.link[1];
+ if (tree->root != NULL)
+ tree->root->red = 0;
+
+ return removed;
+}
+
+/* find data item in tree
+ * returns pointer to data item if found else NULL
+ */
+void *rbtree_find(struct RB_TREE *tree, const void *data)
+{
+ struct RB_NODE *curr_node = tree->root;
+ int cmp;
+
+ assert(tree && data);
+
+ while (curr_node != NULL) {
+ cmp = tree->rb_compare(curr_node->data, data);
+ if (cmp == 0)
+ return curr_node->data; /* found */
+
+ curr_node = curr_node->link[cmp < 0];
+ }
+ return NULL;
+}
+
+/* initialize tree traversal
+ * (re-)sets trav structure
+ * returns 0
+ */
+int rbtree_init_trav(struct RB_TRAV *trav, struct RB_TREE *tree)
+{
+ assert(trav && tree);
+
+ trav->tree = tree;
+ trav->curr_node = tree->root;
+ trav->first = 1;
+ trav->top = 0;
+
+ return 0;
+}
+
+/* traverse the tree in ascending order
+ * useful to get all items in the tree non-recursively
+ * struct RB_TRAV *trav needs to be initialized first
+ * returns pointer to data, NULL when finished
+ */
+void *rbtree_traverse(struct RB_TRAV *trav)
+{
+ assert(trav);
+
+ if (trav->curr_node == NULL) {
+ if (trav->first)
+ G_debug(1, "RB tree: empty tree");
+ else
+ G_debug(1, "RB tree: finished traversing");
+
+ return NULL;
+ }
+
+ if (!trav->first)
+ return rbtree_next(trav);
+ else {
+ trav->first = 0;
+ return rbtree_first(trav);
+ }
+}
+
+/* find start point to traverse the tree in ascending order
+ * useful to get a selection of items in the tree
+ * magnitudes faster than traversing the whole tree
+ * may return first item that's smaller or first item that's larger
+ * struct RB_TRAV *trav needs to be initialized first
+ * returns pointer to data, NULL when finished
+ */
+void *rbtree_traverse_start(struct RB_TRAV *trav, const void *data)
+{
+ int dir = 0;
+
+ assert(trav && data);
+
+ if (trav->curr_node == NULL) {
+ if (trav->first)
+ G_warning("RB tree: empty tree");
+ else
+ G_warning("RB tree: finished traversing");
+
+ return NULL;
+ }
+
+ if (!trav->first)
+ return rbtree_next(trav);
+
+ /* else first time, get start node */
+
+ trav->first = 0;
+ trav->top = 0;
+
+ while (trav->curr_node != NULL) {
+ dir = trav->tree->rb_compare(trav->curr_node->data, data);
+ /* exact match, great! */
+ if (dir == 0)
+ return trav->curr_node->data;
+ else {
+ dir = dir < 0;
+ /* end of branch, also reached if
+ * smallest item is larger than search template or
+ * largest item is smaller than search template */
+ if (trav->curr_node->link[dir] == NULL)
+ return trav->curr_node->data;
+
+ trav->up[trav->top++] = trav->curr_node;
+ trav->curr_node = trav->curr_node->link[dir];
+ }
+ }
+
+ return NULL; /* should not happen */
+}
+
+/* two functions needed to fully traverse the tree: initialize and continue
+ * useful to get all items in the tree non-recursively
+ * this one here uses a stack
+ * parent pointers or threads would also be possible
+ * but these would need to be added to RB_NODE
+ * -> more memory needed for standard operations
+ */
+
+/* start traversing the tree
+ * returns pointer to smallest data item
+ */
+void *rbtree_first(struct RB_TRAV *trav)
+{
+ /* get smallest item */
+ while (trav->curr_node->link[0] != NULL) {
+ trav->up[trav->top++] = trav->curr_node;
+ trav->curr_node = trav->curr_node->link[0];
+ }
+
+ return trav->curr_node->data; /* return smallest item */
+}
+
+/* continue traversing the tree in ascending order
+ * returns pointer to data item, NULL when finished
+ */
+void *rbtree_next(struct RB_TRAV *trav)
+{
+ if (trav->curr_node->link[1] != NULL) {
+ /* something on the right side: larger item */
+ trav->up[trav->top++] = trav->curr_node;
+ trav->curr_node = trav->curr_node->link[1];
+
+ /* go down, find smallest item in this branch */
+ while (trav->curr_node->link[0] != NULL) {
+ trav->up[trav->top++] = trav->curr_node;
+ trav->curr_node = trav->curr_node->link[0];
+ }
+ }
+ else {
+ /* at smallest item in this branch, go back up */
+ struct RB_NODE *last;
+
+ do {
+ if (trav->top == 0) {
+ trav->curr_node = NULL;
+ break;
+ }
+ last = trav->curr_node;
+ trav->curr_node = trav->up[--trav->top];
+ } while (last == trav->curr_node->link[1]);
+ }
+
+ if (trav->curr_node != NULL) {
+ return trav->curr_node->data;
+ }
+ else
+ return NULL; /* finished traversing */
+}
+
+/* destroy the tree */
+void rbtree_destroy(struct RB_TREE *tree)
+{
+ rbtree_destroy2(tree->root);
+ G_free(tree);
+}
+
+void rbtree_destroy2(struct RB_NODE *root)
+{
+ if (root != NULL) {
+ rbtree_destroy2(root->link[0]);
+ rbtree_destroy2(root->link[1]);
+ G_free(root->data);
+ G_free(root);
+ }
+}
+
+/* used for debugging: check for errors in tree structure */
+int rbtree_debug(struct RB_TREE *tree, struct RB_NODE *root)
+{
+ int lh, rh;
+
+ 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);
+}
Added: grass/trunk/raster/r.watershed/ram/rbtree.h
===================================================================
--- grass/trunk/raster/r.watershed/ram/rbtree.h (rev 0)
+++ grass/trunk/raster/r.watershed/ram/rbtree.h 2010-05-12 09:53:37 UTC (rev 42237)
@@ -0,0 +1,112 @@
+/*************************************************************
+ * USAGE *
+ *************************************************************
+ *
+ * NOTE: duplicates are not supported
+ *
+ * custom compare function
+ * extern int my_compare_fn(const void *, const void *);
+ * int my_compare_fn(const void *a, const void *b) {
+ * if ((mydatastruct *) a < (mydatastruct *) b)
+ * return -1;
+ * else if ((mydatastruct *) a > (mydatastruct *) b)
+ * return 1;
+ * else if ((mydatastruct *) a == (mydatastruct *) b)
+ * return 0;
+ * }
+ *
+ * create and initialize tree:
+ * struct RB_TREE *mytree = rbtree_create(my_compare_fn, item_size);
+ *
+ * insert items to tree:
+ * struct mydatastruct data = <some data>;
+ * if (rbtree_insert(mytree, &data) == 0)
+ * G_warning("could not insert data");
+ *
+ * find item in tree:
+ * struct mydatastruct data = <some data>;
+ * if (rbtree_find(mytree, &data) == 0)
+ * G_message("data not found");
+ *
+ * delete item from tree:
+ * struct mydatastruct data = <some data>;
+ * if (rbtree_remove(mytree, &data) == 0)
+ * G_warning("could not find data in tree");
+ *
+ * traverse tree (get all items in tree in ascending order):
+ * struct RB_TRAV trav;
+ * rbtree_init_trav(&trav, tree);
+ * while ((data = rbtree_traverse(&trav)) != NULL) {
+ * if (my_compare_fn(data, threshold_data) == 0) break;
+ * <do something with data>;
+ * }
+ *
+ * get a selection of items: all data > data1 and < data2
+ * start in tree where data is last smaller or first larger compared to data1
+ * struct RB_TRAV trav;
+ * rbtree_init_trav(&trav, tree);
+ * data = rbtree_traverse_start(&trav, &data1);
+ * <do something with data>;
+ * while ((data = rbtree_traverse(&trav)) != NULL) {
+ * if (data > data2) break;
+ * <do something with data>;
+ * }
+ *
+ * destroy tree:
+ * rbtree_destroy(mytree);
+ *
+ * debug the whole tree with
+ * rbtree_debug(mytree, mytree->root);
+ *
+ *************************************************************/
+
+#include <stddef.h>
+
+/* maximum RB Tree height */
+#define RBTREE_MAX_HEIGHT 64 /* should be more than enough */
+
+/* routine to compare data items
+ * return -1 if rb_a < rb_b
+ * return 0 if rb_a == rb_b
+ * return 1 if rb_a > rb_b
+ */
+typedef int rb_compare_fn(const void *rb_a, const void *rb_b);
+
+struct RB_NODE
+{
+ unsigned char red; /* 0 = black, 1 = red */
+ void *data; /* any kind of data */
+ struct RB_NODE *link[2]; /* link to children: link[0] for smaller, link[1] for larger */
+};
+
+struct RB_TREE
+{
+ struct RB_NODE *root; /* root node */
+ size_t datasize; /* item size */
+ size_t count; /* number of items in tree. */
+ rb_compare_fn *rb_compare; /* function to compare data */
+};
+
+struct RB_TRAV
+{
+ struct RB_TREE *tree; /* tree being traversed */
+ struct RB_NODE *curr_node; /* current node */
+ struct RB_NODE *up[RBTREE_MAX_HEIGHT]; /* stack of parent nodes */
+ int top; /* index for stack */
+ int first; /* little helper flag */
+};
+
+/* tree functions */
+struct RB_TREE *rbtree_create(rb_compare_fn *, size_t);
+void rbtree_destroy(struct RB_TREE *);
+int rbtree_insert(struct RB_TREE *, void *);
+int rbtree_remove(struct RB_TREE *, const void *);
+void *rbtree_find(struct RB_TREE *, const void *);
+
+/* tree traversal functions */
+int rbtree_init_trav(struct RB_TRAV *, struct RB_TREE *);
+void* rbtree_traverse(struct RB_TRAV *);
+void *rbtree_traverse_start(struct RB_TRAV *, const void *);
+
+/* debug tree from given node downwards */
+int rbtree_debug(struct RB_TREE *, struct RB_NODE *);
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