diff --git a/lib/Index/ProgramImpl.h b/lib/Index/ProgramImpl.h
new file mode 100644
index 0000000..52f153f
--- /dev/null
+++ b/lib/Index/ProgramImpl.h
@@ -0,0 +1,53 @@
+//===--- ProgramImpl.h - Internal Program implementation---------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  Internal implementation for the Program class
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_INDEX_PROGRAMIMPL_H
+#define LLVM_CLANG_INDEX_PROGRAMIMPL_H
+
+#include "clang/Index/Entity.h"
+#include "llvm/ADT/StringSet.h"
+
+namespace clang {
+
+namespace idx {
+  class EntityListener;
+
+class ProgramImpl {
+public:
+  typedef llvm::FoldingSet<Entity> EntitySetTy;
+  typedef llvm::StringMapEntry<char> IdEntryTy;
+  
+private:
+  llvm::FoldingSet<Entity> Entities;
+  llvm::StringSet<> Idents;
+  llvm::BumpPtrAllocator BumpAlloc;
+
+  ProgramImpl(const ProgramImpl&); // do not implement
+  ProgramImpl &operator=(const ProgramImpl &); // do not implement
+  
+public:
+  ProgramImpl() { }
+  
+  llvm::FoldingSet<Entity> &getEntities() { return Entities; }
+  llvm::StringSet<> &getIdents() { return Idents; }
+
+  void *Allocate(unsigned Size, unsigned Align = 8) {
+    return BumpAlloc.Allocate(Size, Align);
+  }
+};
+
+} // namespace idx
+
+} // namespace clang
+
+#endif