Started implementing btree deletion

sandbox/btree/btree.c

@@ -1,6 +1,7 @@
 #include <socks/btree.h>
 #include <stddef.h>
 #include <stdlib.h>
+#include <stdio.h>
 
 #define MAX(a, b) ((a) > (b) ? (a) : (b))
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
@@ -8,6 +9,13 @@
 #define IS_LEFT_CHILD(p, c) ((p) && (c) && ((p)->b_left == (c)))
 #define IS_RIGHT_CHILD(p, c) ((p) && (c) && ((p)->b_right == (c)))
 
+#define HAS_LEFT_CHILD(x) ((x) && ((x)->b_left))
+#define HAS_RIGHT_CHILD(x) ((x) && ((x)->b_right))
+
+#define HAS_NO_CHILDREN(x) ((x) && (!(x)->b_left) && (!(x)->b_right))
+#define HAS_ONE_CHILD(x) ((HAS_LEFT_CHILD(x) && !HAS_RIGHT_CHILD(x)) || (!HAS_LEFT_CHILD(x) && HAS_RIGHT_CHILD(x)))
+#define HAS_TWO_CHILDREN(x) (HAS_LEFT_CHILD(x) && HAS_RIGHT_CHILD(x))
+
 static void rotate_left(btree_t *tree, btree_node_t *x)
 {
 	btree_node_t *y = x->b_right;
@@ -95,7 +103,7 @@ static void rotate_double_right(btree_t *tree, btree_node_t *z)
 static void insert_fixup(btree_t *tree, btree_node_t *w)
 {
 	btree_node_t *z = NULL, *y = NULL, *x = NULL;
-	
+
 	z = w;
 	while (z) {
 		if (z->b_bfactor >= -1 && z->b_bfactor <= 1) {
@@ -136,7 +144,7 @@ void btree_insert(btree_t *tree, btree_node_t *node)
 	btree_node_t *cur = tree->b_root;
 	while (1) {
 		btree_node_t **nextp = NULL;
-		
+
 		int bfactor_diff = 0;
 		if (node->b_key >= cur->b_key) {
 			nextp = &cur->b_right;
@@ -161,7 +169,100 @@ void btree_insert(btree_t *tree, btree_node_t *node)
 	insert_fixup(tree, node);
 }
 
+static void remove_node_with_no_children(btree_t *tree, btree_node_t *node)
+{
+	printf("remove_node_with_no_children()\n");
+	btree_node_t *p = node->b_parent;
+	node->b_parent = NULL;
+
+	if (!p) {
+		tree->b_root = NULL;
+	} else if (IS_LEFT_CHILD(p, node)) {
+		p->b_left = NULL;
+	} else {
+		p->b_right = NULL;
+	}
+}
+
+static void replace_node_with_one_subtree(btree_t *tree, btree_node_t *node)
+{
+	printf("remove_node_with_one_subtree()\n");
+	btree_node_t *p = node->b_parent;
+	btree_node_t *z = NULL;
+
+	if (HAS_LEFT_CHILD(node)) {
+		z = node->b_left;
+	} else {
+		z = node->b_right;
+	}
+
+	if (IS_LEFT_CHILD(p, node)) {
+		p->b_left = z;
+	} else if (IS_RIGHT_CHILD(p, node)) {
+		p->b_right = z;
+	}
+
+	z->b_parent = p;
+
+	node->b_parent = NULL;
+	node->b_left = node->b_parent = NULL;
+}
+
+static void replace_node_with_two_subtrees(btree_t *tree, btree_node_t *node)
+{
+	printf("remove_node_with_two_subtrees()\n");
+	btree_node_t *cur = node->b_left;
+
+	while (cur->b_right) {
+		cur = cur->b_right;
+	}
+
+	btree_node_t *p = cur->b_parent;
+
+	if (IS_LEFT_CHILD(p, cur)) {
+		p->b_left = NULL;
+		p->b_bfactor++;
+	} else {
+		p->b_right = NULL;
+		p->b_bfactor--;
+	}
+
+	p = node->b_parent;
+
+	if (p) {
+	    if (IS_LEFT_CHILD(p, node)) {
+		    p->b_left = cur;
+	    } else {
+		    p->b_right = cur;
+	    }
+	}
+
+	cur->b_left = node->b_left;
+	cur->b_right = node->b_right;
+	cur->b_bfactor = node->b_bfactor;
+	cur->b_parent = p;
+
+	if (!p) {
+		tree->b_root = cur;
+	}
+}
+
 void btree_delete(btree_t *tree, btree_node_t *node)
 {
-  
+	btree_node_t *x = NULL;
+
+	if (HAS_NO_CHILDREN(node)) {
+		remove_node_with_no_children(tree, node);
+		return;
+	}
+
+	if (HAS_ONE_CHILD(node)) {
+		replace_node_with_one_subtree(tree, node);
+		return;
+	}
+
+	if (HAS_TWO_CHILDREN(node)) {
+		replace_node_with_two_subtrees(tree, node);
+		return;
+	}
 }