pdb: Implement VirtualFunctionTable / VirtualTableShape parsing

Port of getsentry/pdb#141. Implements LF_VTSHAPE (packed 4-bit vtable
shape descriptors) and LF_VFTABLE (owner, base, object offset, and
method name list). Adds VirtualTableShapeDescriptor enum and
VirtualTableShapeType interface. Fixes VirtualFunctionTableType fields
to match the Rust struct (owner, base, objectOffset, names).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kjk

pdb/src/index.ts

@@ -74,6 +74,8 @@ export type {
   BaseClassType,
   VirtualBaseClassType,
   VirtualFunctionTablePointerType,
+  VirtualFunctionTableType,
+  VirtualTableShapeType,
   OverloadedMethodType,
   MethodType,
   EnumerateType,
@@ -95,6 +97,7 @@ export {
   CallingConvention,
   PointerKind,
   PointerMode,
+  VirtualTableShapeDescriptor,
   isStaticMethod,
   isVirtualMethod,
   isPureVirtualMethod,

pdb/src/tpi/parser.ts

@@ -370,6 +370,34 @@ function parseTypeRecord(buf: ParseBuffer, kind: number): TypeData {
       return { kind: "MethodList", methods };
     }
 
+    case C.LF_VTSHAPE: {
+      const count = buf.readU16();
+      const descriptors: number[] = [];
+      for (let i = 0; i < Math.ceil(count / 2); i++) {
+        const byte = buf.readU8();
+        descriptors.push(byte & 0x0f);
+        if (descriptors.length < count) {
+          descriptors.push((byte >> 4) & 0x0f);
+        }
+      }
+      return { kind: "VirtualTableShape", descriptors };
+    }
+
+    case C.LF_VFTABLE: {
+      const owner: TypeIndex = buf.readU32();
+      const base: TypeIndex = buf.readU32();
+      const objectOffset = buf.readVariant().value as number;
+      const namesLength = buf.readVariant().value as number;
+      const names: string[] = [];
+      let bytesRead = 0;
+      while (bytesRead < namesLength) {
+        const name = buf.readCString();
+        bytesRead += name.length + 1;
+        names.push(name);
+      }
+      return { kind: "VirtualFunctionTable", owner, base, objectOffset, names };
+    }
+
     default:
       throw PdbError.unimplementedTypeKind(kind);
   }

pdb/src/tpi/types.ts

@@ -396,11 +396,28 @@ export interface EnumerateType {
   name: string;
 }
 
+/** Virtual table shape descriptor (packed 4-bit values). */
+export enum VirtualTableShapeDescriptor {
+  Near = 0x00,
+  Far = 0x01,
+  Thin = 0x02,
+  Outer = 0x03,
+  Meta = 0x04,
+  Near32 = 0x05,
+  Far32 = 0x06,
+  Unused = 0x07,
+}
+
+export interface VirtualTableShapeType {
+  kind: "VirtualTableShape";
+  descriptors: VirtualTableShapeDescriptor[];
+}
+
 export interface VirtualFunctionTableType {
   kind: "VirtualFunctionTable";
-  completeClass: TypeIndex;
-  overriddenVft: TypeIndex;
-  vftEntries: number;
+  owner: TypeIndex;
+  base: TypeIndex;
+  objectOffset: number;
   names: string[];
 }
 
@@ -426,10 +443,11 @@ export type TypeData =
   | BaseClassType
   | VirtualBaseClassType
   | VirtualFunctionTablePointerType
+  | VirtualFunctionTableType
+  | VirtualTableShapeType
   | OverloadedMethodType
   | MethodType
-  | EnumerateType
-  | VirtualFunctionTableType;
+  | EnumerateType;
 
 // ─── Id Data Types ───