feat: move child resolution to bptree node

src/btree/node.ts

@@ -20,6 +20,8 @@ export class BTreeNode {
   private readonly dataFileResolver: RangeResolver;
   private readonly fileFormat: FileFormat;
   private readonly pageFieldType: FieldType;
+  private readonly tree: RangeResolver;
+  private readonly pageFieldWidth: number;
 
   constructor(
     keys: ReferencedValue[],
@@ -28,13 +30,17 @@ export class BTreeNode {
     dataFileResolver: RangeResolver,
     fileFormat: FileFormat,
     pageFieldType: FieldType,
+    tree: RangeResolver,
+    pageFieldWidth: number,
   ) {
     this.keys = keys;
     this.leafPointers = leafPointers;
     this.internalPointers = internalPointers;
     this.dataFileResolver = dataFileResolver;
     this.fileFormat = fileFormat;
     this.pageFieldType = pageFieldType;
+    this.tree = tree;
+    this.pageFieldWidth = pageFieldWidth;
   }
 
   leaf(): boolean {
@@ -56,6 +62,25 @@ export class BTreeNode {
     return this.internalPointers.length + this.leafPointers.length;
   }
 
+  async child(index: number) {
+    const childPointer = this.pointer(index);
+
+    const { node, bytesRead } = await BTreeNode.fromMemoryPointer(
+      childPointer,
+      this.tree,
+      this.dataFileResolver,
+      this.fileFormat,
+      this.pageFieldType,
+      this.pageFieldWidth,
+    );
+
+    if (!bytesRead) {
+      throw new Error("bytes read do not line up");
+    }
+
+    return node;
+  }
+
   async unmarshalBinary(buffer: ArrayBuffer, pageFieldWidth: number) {
     let dataView = new DataView(buffer);
     let size = dataView.getUint32(0, true);
@@ -226,6 +251,8 @@ export class BTreeNode {
       dataFilePointer,
       fileFormat,
       pageFieldType,
+      resolver,
+      pageFieldWidth,
     );
 
     await node.unmarshalBinary(bufferData, pageFieldWidth);

src/btree/traversal.ts

@@ -59,8 +59,8 @@ export class TraversalIterator {
         return false;
       }
       // propagate the rollover
-      this.records[i].node = await this.tree.readNode(
-        this.records[i + 1].node.pointer(this.records[i + 1].index),
+      this.records[i].node = await this.records[i + 1].node.child(
+        this.records[i + 1].index,
       );
 
       if (rolloverLeft) {