Big revelation is that anytime you're doing file I/O you _must_ use std::filesystem. It simplifies so much about working with files.

save.cpp

@@ -3,9 +3,10 @@
 #include "dbc.hpp"
 #include <fmt/core.h>
 #include "config.hpp"
+#include <filesystem>
 
 using namespace components;
-
+using namespace fmt;
 
 template<typename CompT>
 inline void extract(DinkyECS::World &world, std::map<DinkyECS::Entity, CompT> &into) {
@@ -15,7 +16,7 @@ inline void extract(DinkyECS::World &world, std::map<DinkyECS::Entity, CompT> &i
   }
 }
 
-void save::to_file(std::string path, DinkyECS::World &world) {
+void save::to_file(fs::path path, DinkyECS::World &world) {
   SaveData save_data;
   tser::BinaryArchive archive;
 
@@ -40,22 +41,22 @@ inline void inject(DinkyECS::World &world, std::map<DinkyECS::Entity, CompT> &ou
   }
 }
 
-void save::from_file(std::string path, DinkyECS::World &world_out) {
+void save::from_file(fs::path path, DinkyECS::World &world_out) {
   tser::BinaryArchive archive(0);
+  dbc::check(fs::exists(path), format("save file does not exist {}", path.string()));
+  auto size = fs::file_size(path);
 
-  if(std::ifstream in_file{path, std::ios::binary | std::ios::ate}) {
-    auto size = in_file.tellg();
+  if(std::ifstream in_file{path, std::ios::binary}) {
     std::string in_data(size, '\0');
-    in_file.seekg(0);
 
     if(in_file.read(&in_data[0], size)) {
       std::string_view in_view(in_data);
       archive.initialize(in_view);
     } else {
-      dbc::sentinel(fmt::format("wrong size or error reading {}", path));
+      dbc::sentinel(format("wrong size or error reading {}", path.string()));
     }
   } else {
-    dbc::sentinel(fmt::format("failed to load file {}", path));
+    dbc::sentinel(format("failed to load file {}", path.string()));
   }
 
   auto save_data = archive.load<SaveData>();

save.hpp

@@ -3,10 +3,12 @@
 #include "components.hpp"
 #include "dinkyecs.hpp"
 #include "tser.hpp"
+#include <filesystem>
 #include <string>
 #include <map>
 
 namespace save {
+  namespace fs = std::filesystem;
 
   struct Facts {
     components::Player player;
@@ -24,7 +26,7 @@ namespace save {
     DEFINE_SERIALIZABLE(SaveData, facts, position, motion, combat);
   };
 
-  void to_file(std::string path, DinkyECS::World &world);
-  void from_file(std::string path, DinkyECS::World &world_out);
+  void to_file(fs::path path, DinkyECS::World &world);
+  void from_file(fs::path path, DinkyECS::World &world_out);
   void load_configs(DinkyECS::World &world);
 }