Add back parent pointer

cstack · cstack · commit 0ed745f3f683 · 2017-11-25T10:15:53.000-08:00
diff --git a/_parts/part12.md b/_parts/part12.md
@@ -257,33 +257,6 @@ Executed.
 db >
 ```
 
-Whew! One bug after another, but we're making progress. Now that we've got the sibling pointer, I don't think we actually need a parent pointer. I added it preemptively, but we never actually used it.
-
-```diff
- const uint32_t NODE_TYPE_OFFSET = 0;
- const uint32_t IS_ROOT_SIZE = sizeof(uint8_t);
- const uint32_t IS_ROOT_OFFSET = NODE_TYPE_SIZE;
--const uint32_t PARENT_POINTER_SIZE = sizeof(uint32_t);
--const uint32_t PARENT_POINTER_OFFSET = IS_ROOT_OFFSET + IS_ROOT_SIZE;
- const uint8_t COMMON_NODE_HEADER_SIZE =
--    NODE_TYPE_SIZE + IS_ROOT_SIZE + PARENT_POINTER_SIZE;
-+    NODE_TYPE_SIZE + IS_ROOT_SIZE;
-```
-
-```diff
-     expect(result).to eq([
-       "db > Constants:",
-       "ROW_SIZE: 293",
--      "COMMON_NODE_HEADER_SIZE: 6",
--      "LEAF_NODE_HEADER_SIZE: 14",
-+      "COMMON_NODE_HEADER_SIZE: 2",
-+      "LEAF_NODE_HEADER_SIZE: 10",
-       "LEAF_NODE_CELL_SIZE: 297",
--      "LEAF_NODE_SPACE_FOR_CELLS: 4082",
-+      "LEAF_NODE_SPACE_FOR_CELLS: 4086",
-       "LEAF_NODE_MAX_CELLS: 13",
-       "db > ",
-     ])
-```
+Whew! One bug after another, but we're making progress.
 
 Until next time.
diff --git a/db.c b/db.c
@@ -102,8 +102,10 @@ const uint32_t NODE_TYPE_SIZE = sizeof(uint8_t);
 const uint32_t NODE_TYPE_OFFSET = 0;
 const uint32_t IS_ROOT_SIZE = sizeof(uint8_t);
 const uint32_t IS_ROOT_OFFSET = NODE_TYPE_SIZE;
+const uint32_t PARENT_POINTER_SIZE = sizeof(uint32_t);
+const uint32_t PARENT_POINTER_OFFSET = IS_ROOT_OFFSET + IS_ROOT_SIZE;
 const uint8_t COMMON_NODE_HEADER_SIZE =
-    NODE_TYPE_SIZE + IS_ROOT_SIZE;
+    NODE_TYPE_SIZE + IS_ROOT_SIZE + PARENT_POINTER_SIZE;
 
 /*
  * Internal Node Header Layout
diff --git a/spec/main_spec.rb b/spec/main_spec.rb
@@ -198,10 +198,10 @@ def run_script(commands)
     expect(result).to eq([
       "db > Constants:",
       "ROW_SIZE: 293",
-      "COMMON_NODE_HEADER_SIZE: 2",
-      "LEAF_NODE_HEADER_SIZE: 10",
+      "COMMON_NODE_HEADER_SIZE: 6",
+      "LEAF_NODE_HEADER_SIZE: 14",
       "LEAF_NODE_CELL_SIZE: 297",
-      "LEAF_NODE_SPACE_FOR_CELLS: 4086",
+      "LEAF_NODE_SPACE_FOR_CELLS: 4082",
       "LEAF_NODE_MAX_CELLS: 13",
       "db > ",
     ])
