Add ref_target attribute to primitive field references

library/LuaTypes.cpp

@@ -536,6 +536,7 @@ static void field_reference(lua_State *state, const struct_field_info *field, vo
         case struct_field_info::PRIMITIVE:
         case struct_field_info::SUBSTRUCT:
             push_object_internal(state, field->type, ptr);
+            get_object_ref_header(state, -1)->field_info = field;
             return;
 
         case struct_field_info::POINTER:
@@ -706,6 +707,16 @@ static type_identity *find_primitive_field(lua_State *state, int field, const ch
  */
 static int meta_primitive_index(lua_State *state)
 {
+    const char *attr = lua_tostring(state, -1);
+    if (attr == std::string("ref_target")) {
+        const struct_field_info *field_info = get_object_ref_header(state, 1)->field_info;
+        if (field_info && field_info->extra && field_info->extra->ref_target) {
+            LookupInTable(state, field_info->extra->ref_target, &DFHACK_TYPEID_TABLE_TOKEN);
+        } else {
+            lua_pushnil(state);
+        }
+        return 1;
+    }
     uint8_t *ptr = get_object_addr(state, 1, 2, "read");
     auto type = find_primitive_field(state, 2, "read", &ptr);
     if (!type)

library/LuaWrapper.cpp

@@ -170,18 +170,24 @@ void LuaWrapper::push_object_ref(lua_State *state, void *ptr)
     // stack: [metatable]
     auto ref = (DFRefHeader*)lua_newuserdata(state, sizeof(DFRefHeader));
     ref->ptr = ptr;
+    ref->field_info = NULL;
 
     lua_swap(state);
     lua_setmetatable(state, -2);
     // stack: [userdata]
 }
 
-void *LuaWrapper::get_object_ref(lua_State *state, int val_index)
+DFRefHeader *LuaWrapper::get_object_ref_header(lua_State *state, int val_index)
 {
     assert(!lua_islightuserdata(state, val_index));
 
     auto ref = (DFRefHeader*)lua_touserdata(state, val_index);
-    return ref->ptr;
+    return ref;
+}
+
+void *LuaWrapper::get_object_ref(lua_State *state, int val_index)
+{
+    return get_object_ref_header(state, val_index)->ptr;
 }
 
 /**

library/include/LuaWrapper.h

@@ -126,6 +126,7 @@ namespace LuaWrapper {
      */
     struct DFRefHeader {
         void *ptr;
+        const struct_field_info *field_info;
     };
 
     /**
@@ -133,15 +134,7 @@ namespace LuaWrapper {
      */
     void push_object_ref(lua_State *state, void *ptr);
     DFHACK_EXPORT void *get_object_ref(lua_State *state, int val_index);
-
-    /*
-     * The system might be extended to carry some simple
-     * objects inline inside the reference buffer.
-     */
-    inline bool is_self_contained(DFRefHeader *ptr) {
-        void **pp = &ptr->ptr;
-        return **(void****)pp == (pp + 1);
-    }
+    DFHACK_EXPORT DFRefHeader *get_object_ref_header(lua_State *state, int val_index);
 
     /**
     * Report an error while accessing a field (index = field name).