sandbox: btree: deletion fixup bugfix

sandbox/base/main.c

@@ -10,7 +10,7 @@
 #include <socks/memblock.h>
 #include <socks/vm.h>
 
-#define NR_BTREE_NODES 13
+#define NR_BTREE_NODES 32
 
 /* we're working with 512MiB of simulated system RAM */
 #define MEMORY_SIZE_MB 512
@@ -130,10 +130,28 @@ static int memory_test(void)
 
 void btree_print(btree_node_t *node, int depth)
 {
+	if (depth > 10) {
+		for (int i = 0; i < depth; i++) {
+			fputs("    ", stdout);
+		}
+
+		printf("OVERFLOW\n");
+		return;
+	}
+
 	if (!node) {
 		return;
 	}
 
+	if (node->b_parent && node != node->b_parent->b_left && node != node->b_parent->b_right) {
+		for (int i = 0; i < depth; i++) {
+			fputs("    ", stdout);
+		}
+
+		printf("BAD PARENT [%llu]\n", node->b_key);
+		return;
+	}
+
 	if (node) {
 	    btree_print(node->b_right, depth + 1);
 	}
@@ -146,9 +164,12 @@ void btree_print(btree_node_t *node, int depth)
 		if (node->b_parent) {
 			if (node == node->b_parent->b_left) {
 				printf("\\ ");
-			} else {
+			} else if (node == node->b_parent->b_right) {
 				printf("/ ");
+			} else {
+				printf("? ");
 			}
+				
 		}
 
 		printf("%llu (h:%d)\n", node->b_key, node->b_height);
@@ -172,7 +193,7 @@ static int btree_avl_validate(btree_node_t *x)
 	}
 
 	if (!x->b_left && !x->b_right) {
-		return 1;
+		return x->b_height == 1 ? 1 : -1;
 	}
 
 	int left = 0, right = 0;
@@ -241,10 +262,6 @@ static int btree_test(void)
 		printf("deleting node #%d: %llu\n", i, nodes[i].b_key);
 		printf("#######################\n");
 
-		if (nodes[i].b_key == 89) {
-			printf("brk\n");
-		}
-
 		btree_delete(&tree, &nodes[i]);
 		btree_print(tree.b_root, 0);
 

sandbox/btree/btree.c

@@ -222,15 +222,18 @@ static void delete_fixup(btree_t *tree, btree_node_t *w)
 	int nr_rotations = 0;
 
 	while (z) {
+		printf("bf(z)=%d\n", bf(z));
+		printf("bf(z->b_left)=%d\n", bf(z->b_left));
+
 		if (bf(z) > 1) {
-			if (bf(z->b_left) <= 0) {
+			if (bf(z->b_right) >= 0) {
 				rotate_left(tree, z);
 				update_height_to_root(z);
 			} else {
-				rotate_double_left(tree, z);
+				rotate_double_left(tree, z); // <==
 			}
 		} else if (bf(z) < -1) {
-			if (bf(z->b_right) > 0) {
+			if (bf(z->b_left) <= 0) {
 				rotate_right(tree, z);
 				update_height_to_root(z);
 			} else {
@@ -354,62 +357,78 @@ static btree_node_t *replace_node_with_one_subtree(btree_t *tree, btree_node_t *
 	return w;
 }
 
-static btree_node_t *replace_node_with_two_subtrees(btree_t *tree, btree_node_t *node)
+static btree_node_t *replace_node_with_two_subtrees(btree_t *tree, btree_node_t *z)
 {
 	debug_msg("remove_node_with_two_subtrees()\n");
-	btree_node_t *cur = node->b_left;
 
-	while (cur->b_right) {
-		cur = cur->b_right;
+	/* x will replace z */
+	btree_node_t *x = z->b_left;
+
+	while (x->b_right) {
+		x = x->b_right;
 	}
 
-	btree_node_t *p = cur->b_parent;
-	btree_node_t *k = p;
+	/* y is the node that will replace x (if x has a left child) */
+	btree_node_t *y = x->b_left;
 
-	if (IS_LEFT_CHILD(p, cur)) {
-		p->b_left = NULL;
-	} else {
-		p->b_right = NULL;
+	/* w is the starting point for the height update and fixup */
+	btree_node_t *w = x;
+	if (w->b_parent != z) {
+		w = w->b_parent;
 	}
 
-	p = node->b_parent;
-
-	if (p) {
-	    if (IS_LEFT_CHILD(p, node)) {
-		    p->b_left = cur;
-	    } else {
-		    p->b_right = cur;
-	    }
+	if (y) {
+		w = y;
 	}
 
-	cur->b_left = node->b_left;
-	cur->b_right = node->b_right;
-	cur->b_height = node->b_height;
-	cur->b_parent = p;
-	btree_node_t *w = cur;
-
-	if (!p) {
-		tree->b_root = cur;
+	if (IS_LEFT_CHILD(x->b_parent, x)) {
+		x->b_parent->b_left = y;
+	} else if (IS_RIGHT_CHILD(x->b_parent, x)) {
+		x->b_parent->b_right = y;
 	}
 
-	if (tree->b_root->b_left) {
-		tree->b_root->b_left->b_parent = tree->b_root;
+	if (y) {
+	    y->b_parent = x->b_parent;
 	}
 
-	if (tree->b_root->b_right) {
-		tree->b_root->b_right->b_parent = tree->b_root;
+	if (IS_LEFT_CHILD(z->b_parent, z)) {
+		z->b_parent->b_left = x;
+	} else if (IS_RIGHT_CHILD(z->b_parent, z)) {
+		z->b_parent->b_right = x;
 	}
 
+	x->b_parent = z->b_parent;
+	x->b_left = z->b_left;
+	x->b_right = z->b_right;
+
+	if (x->b_left) {
+		x->b_left->b_parent = x;
+	}
+
+	if (x->b_right) {
+		x->b_right->b_parent = x;
+	}
+
+	if (!x->b_parent) {
+		tree->b_root = x;
+	}
+
+	btree_node_t *cur = w;
 	while (cur) {
 		update_height(cur);
 		cur = cur->b_parent;
 	}
 
+	printf("w=%llu, h:%u\n", w->b_key, w->b_height);
 	return w;
 }
 
 void btree_delete(btree_t *tree, btree_node_t *node)
 {
+	if (!node->b_owner) {
+		return;
+	}
+
 	assert(node->b_owner == tree);
 	btree_node_t *w = NULL;
 
@@ -421,6 +440,8 @@ void btree_delete(btree_t *tree, btree_node_t *node)
 		w = replace_node_with_two_subtrees(tree, node);
 	}
 
+	btree_print(tree->b_root, 0);
+
 	if (w) {
 		delete_fixup(tree, w);
 	}