✨ conservative saving

include/bank.h

@@ -1,7 +1,8 @@
 #pragma once
+#include <iostream> //temporary
 #include <fstream>
-#include <iostream>
 #include <shared_mutex>
+#include <atomic>
 #include "error_responses.hpp"
 #include "parallel-hashmap/parallel_hashmap/phmap.h"
 #include "user.h"
@@ -18,6 +19,16 @@ private:
         std::mutex>
         users;
 
+#if CONSERVATIVE_DISK_SAVE
+    std::atomic<bool> change_flag = false; //if true changes have been made
+
+    void ChangesMade() noexcept;  //called after making changes
+    void ChangesSaved() noexcept; //called after saving
+#elif
+#define ChangesMade() ;
+#define ChangesSaved() ;
+#endif
+
     /**
      * @brief size_l should be grabbed if the operation MODIFIES the size (shared), this is so that when save claims unique
      * 

src/bank.cpp

@@ -1,11 +1,27 @@
 #include "bank.h"
 
+#if CONSERVATIVE_DISK_SAVE
+void Bank::ChangesMade() noexcept
+{
+    while (change_flag.exchange(true, std::memory_order_relaxed))
+        ;
+    std::atomic_thread_fence(std::memory_order_acquire);
+}
+
+void Bank::ChangesSaved() noexcept
+{
+    std::atomic_thread_fence(std::memory_order_release);
+    change_flag.store(false, std::memory_order_relaxed);
+}
+#endif
+
 int_fast8_t Bank::AddUser(const std::string &name, const std::string &init_pass) noexcept
 {
     if (name.size() > max_name_size)
     {
         return ErrorResponse::NameTooLong;
     }
+    //replace with string find
     for (char c : name)
     {
         if (c == ' ')