Implemented a simlpe red-black tree which should give better performance

for certain lookups.

The rb_tree will act as a general purpose key/value storage, and
also give a performance boost in the cases where the other
simple alternative would be to use a linked_list.

On average this should give on average O(log n) lookups, while the linked_list
would be O(n) at worst.

autotest/test_rbtree.tcc

@@ -0,0 +1,144 @@
+#include <uhub.h>
+#include <util/rbtree.h>
+
+#define MAX_NODES 10000
+
+static struct rb_tree* tree = NULL;
+
+int test_tree_compare(const void* a, const void* b)
+{
+	return strcmp((const char*) a, (const char*) b);
+}
+
+
+EXO_TEST(rbtree_create_destroy, {
+	int ok = 0;
+	struct rb_tree* atree;
+	atree = rb_tree_create(test_tree_compare, &hub_malloc, &hub_free);
+	if (atree) ok = 1;
+	rb_tree_destroy(atree);
+	return ok;
+});
+
+EXO_TEST(rbtree_create_1, {
+	tree = rb_tree_create(test_tree_compare, &hub_malloc, &hub_free);
+	return tree != NULL;
+});
+
+EXO_TEST(rbtree_size_0, { return rb_tree_size(tree) == 0; });
+
+EXO_TEST(rbtree_insert_1, {
+	return rb_tree_insert(tree, "one", "1");
+});
+
+EXO_TEST(rbtree_insert_2, {
+	return rb_tree_insert(tree, "two", "2");
+});
+
+EXO_TEST(rbtree_insert_3, {
+	return rb_tree_insert(tree, "three", "3");
+});
+
+EXO_TEST(rbtree_insert_3_again, {
+	return !rb_tree_insert(tree, "three", "3-again");
+});
+
+EXO_TEST(rbtree_size_1, { return rb_tree_size(tree) == 3; });
+
+static int test_check_search(const char* key, const char* expect)
+{
+	const char* value = (const char*) rb_tree_get(tree, key);
+	if (!value) return !expect;
+	if (!expect) return 0;
+	return strcmp(value, expect) == 0;
+}
+
+EXO_TEST(rbtree_search_1, { return test_check_search("one", "1"); });
+EXO_TEST(rbtree_search_2, { return test_check_search("two", "2"); });
+EXO_TEST(rbtree_search_3, { return test_check_search("three", "3"); });
+EXO_TEST(rbtree_search_4, { return test_check_search("four", NULL); });
+
+
+EXO_TEST(rbtree_remove_1, {
+	return rb_tree_remove(tree, "one");
+});
+
+EXO_TEST(rbtree_size_2, { return rb_tree_size(tree) == 2; });
+
+EXO_TEST(rbtree_remove_2, {
+	return rb_tree_remove(tree, "two");
+});
+
+EXO_TEST(rbtree_remove_3, {
+	return rb_tree_remove(tree, "three");
+});
+
+EXO_TEST(rbtree_remove_3_again, {
+	return !rb_tree_remove(tree, "three");
+});
+
+EXO_TEST(rbtree_search_5, { return test_check_search("one", NULL); });
+EXO_TEST(rbtree_search_6, { return test_check_search("two", NULL); });
+EXO_TEST(rbtree_search_7, { return test_check_search("three", NULL); });
+EXO_TEST(rbtree_search_8, { return test_check_search("four", NULL); });
+
+EXO_TEST(rbtree_size_3, { return rb_tree_size(tree) == 0; });
+
+EXO_TEST(rbtree_insert_10000, {
+	int i;
+	for (i = 0; i < MAX_NODES ; i++)
+	{
+		const char* key = strdup(uhub_itoa(i));
+		const char* val = strdup(uhub_itoa(i + 16384));
+		if (!rb_tree_insert(tree, key, val))
+			return 0;
+	}
+	return 1;
+});
+
+EXO_TEST(rbtree_size_4, { return rb_tree_size(tree) == MAX_NODES ; });
+
+EXO_TEST(rbtree_check_10000, {
+	int i;
+	for (i = 0; i < MAX_NODES ; i++)
+	{
+		char* key = strdup(uhub_itoa(i));
+		const char* expect = uhub_itoa(i + 16384);
+		if (!test_check_search(key, expect))
+			return 0;
+		hub_free(key);
+	}
+	return 1;
+});
+
+EXO_TEST(rbtree_iterate_10000, {
+	int i = 0;
+	struct rb_node* n = (struct rb_node*) rb_tree_first(tree);
+	while (n)
+	{
+		struct rb_node* p = n;
+		n = (struct rb_node*) rb_tree_next(tree);
+		i++;
+	}
+	return i == MAX_NODES ;
+});
+
+
+static void free_node(struct rb_node* n)
+{
+	hub_free(n->key);
+	hub_free(n->value);
+}
+
+EXO_TEST(rbtree_remove_5000, {
+	int i = 0;
+	struct rb_node* n = (struct rb_node*) rb_tree_first(tree);
+	for (i = 0; i < MAX_NODES ; i += 2)
+	{
+		const char* key = uhub_itoa(i);
+		rb_tree_remove_node(tree, key, &free_node);
+	}
+	return 1;
+});
+
+