From 277a8acdced9f7b2d26f2080481e80b1362644d7 Mon Sep 17 00:00:00 2001
From: "Dr. Patrick Urbanke" <patrick@getml.com>
Date: Sun, 19 Jan 2025 20:54:37 +0100
Subject: [PATCH] Added calc_vtable_offset

---
 include/rfl/flatbuf/Reader.hpp             | 10 ++++------
 include/rfl/flatbuf/Writer.hpp             |  6 +++---
 include/rfl/flatbuf/calc_vtable_offset.hpp | 17 +++++++++++++++++
 include/rfl/parsing/ViewReader.hpp         |  3 +++
 4 files changed, 27 insertions(+), 9 deletions(-)
 create mode 100644 include/rfl/flatbuf/calc_vtable_offset.hpp

diff --git a/include/rfl/flatbuf/Reader.hpp b/include/rfl/flatbuf/Reader.hpp
index 4ec1398d..9ba619b3 100644
--- a/include/rfl/flatbuf/Reader.hpp
+++ b/include/rfl/flatbuf/Reader.hpp
@@ -16,6 +16,7 @@
 #include "../always_false.hpp"
 #include "../internal/is_literal.hpp"
 #include "../internal/ptr_cast.hpp"
+#include "calc_vtable_offset.hpp"
 
 namespace rfl::flatbuf {
 
@@ -124,13 +125,10 @@ class Reader {
   template <class ObjectReader>
   std::optional<Error> read_object(const ObjectReader& _object_reader,
                                    const InputObjectType& _obj) const noexcept {
-    // TODO
-    // constexpr auto offset_array =
-    //    offset_array<typename ObjectReader::ViewType>;
-    for (size_t i = 0; i < 0 /*TODO offset_array.size()*/; ++i) {
+    constexpr size_t size = ObjectReader::size();
+    for (size_t i = 0; i < size; ++i) {
       _object_reader.read(
-          i,
-          InputVarType{_obj.val_->GetAddressOf(0 /* TODO offset_array[i]*/)});
+          i, InputVarType{_obj.val_->GetAddressOf(calc_vtable_offset(i))});
     }
   }
 
diff --git a/include/rfl/flatbuf/Writer.hpp b/include/rfl/flatbuf/Writer.hpp
index 5f2ad043..791e0acd 100644
--- a/include/rfl/flatbuf/Writer.hpp
+++ b/include/rfl/flatbuf/Writer.hpp
@@ -23,6 +23,7 @@
 #include "../always_false.hpp"
 #include "../internal/is_literal.hpp"
 #include "../internal/ptr_cast.hpp"
+#include "calc_vtable_offset.hpp"
 
 namespace rfl::flatbuf {
 
@@ -39,7 +40,6 @@ class Writer {
   };
 
   struct FlatbufOutputObject {
-    flatbuffers::voffset_t* field_offsets_ = nullptr;
     flatbuffers::uoffset_t offset_ = 0;
     size_t ix_ = 0;
   };
@@ -179,7 +179,7 @@ class Writer {
                                     OutputObjectType* _parent) const noexcept {
     if constexpr (std::is_same<std::remove_cvref_t<T>, std::string>()) {
       const auto str = fbb_->CreateString(_var.c_str(), _var.size());
-      fbb_->AddOffset(_parent->field_offsets_[_parent->ix_++], str);
+      fbb_->AddOffset(calc_vtable_offset(_parent->ix_++), str);
 
       // TODO
       // } else if constexpr (std::is_same<std::remove_cvref_t<T>,
@@ -188,7 +188,7 @@ class Writer {
     } else if constexpr (std::is_floating_point<std::remove_cvref_t<T>>() ||
                          std::is_same<std::remove_cvref_t<T>, bool>() ||
                          std::is_integral<std::remove_cvref_t<T>>()) {
-      fbb_->AddElement<T>(_parent->field_offsets_[_parent->ix_++], _var);
+      fbb_->AddElement<T>(calc_vtable_offset(_parent->ix_++), _var);
 
       // TODO
       //} else if constexpr (internal::is_literal_v<T>) {
diff --git a/include/rfl/flatbuf/calc_vtable_offset.hpp b/include/rfl/flatbuf/calc_vtable_offset.hpp
new file mode 100644
index 00000000..a8a6b704
--- /dev/null
+++ b/include/rfl/flatbuf/calc_vtable_offset.hpp
@@ -0,0 +1,17 @@
+#ifndef RFL_FLATBUF_CALCVTABLEOFFSET_HPP_
+#define RFL_FLATBUF_CALCVTABLEOFFSET_HPP_
+
+#include <flatbuffers/flatbuffers.h>
+
+namespace rfl::flatbuf {
+
+inline flatbuffers::voffset_t calc_vtable_offset(const size_t _i) {
+  return 2 * sizeof(flatbuffers::voffset_t) +
+         static_cast<flatbuffers::voffset_t>(_i) *
+             sizeof(flatbuffers::voffset_t);
+}
+
+}  // namespace rfl::flatbuf
+
+#endif
+
diff --git a/include/rfl/parsing/ViewReader.hpp b/include/rfl/parsing/ViewReader.hpp
index a9d97c82..198b7048 100644
--- a/include/rfl/parsing/ViewReader.hpp
+++ b/include/rfl/parsing/ViewReader.hpp
@@ -44,6 +44,9 @@ class ViewReader {
                              std::make_integer_sequence<int, size_>());
   }
 
+  /// Returns the size of the underlying view.
+  static constexpr size_t size() { return size_; }
+
  private:
   template <int i, class FieldType>
   static bool is_matching(const int _current_index) {