Add the API code to know when the last save was.

docs/dev/Lua API.rst

@@ -771,6 +771,10 @@ arbitrary Lua tables.
   Same semantics as for the ``Site`` functions, but will associated the data
   with the global world context.
 
+* ``dfhack.persistent.getUnsavedSecs()``
+
+  Returns the number of seconds since last save or load of a save
+
 The data is kept in memory, so no I/O occurs when getting or saving keys. It is
 all written to a json file in the game save directory when the game is saved.
 

library/LuaApi.cpp

@@ -353,13 +353,19 @@ static int dfhack_persistent_delete_world_data(lua_State *L) {
     return delete_site_data(L, get_world_data);
 }
 
+static int dfhack_persistent_get_last_save_time(lua_State *L) {
+    lua_pushinteger(L, Persistence::getUnsavedSeconds());
+    return 1;
+}
+
 static const luaL_Reg dfhack_persistent_funcs[] = {
     { "getSiteDataString", dfhack_persistent_get_site_data_string },
     { "saveSiteDataString", dfhack_persistent_save_site_data_string },
     { "deleteSiteData", dfhack_persistent_delete_site_data },
     { "getWorldDataString", dfhack_persistent_get_world_data_string },
     { "saveWorldDataString", dfhack_persistent_save_world_data_string },
     { "deleteWorldData", dfhack_persistent_delete_world_data },
+    { "getUnsavedSeconds", dfhack_persistent_get_last_save_time },
     { NULL, NULL }
 };
 
@@ -1343,6 +1349,7 @@ static string getArchitectureName()
 
 static string getDFVersion() { return Core::getInstance().vinfo->getVersion(); }
 static uint32_t getTickCount() { return Core::getInstance().p->getTickCount(); }
+static uint32_t getCurSaveDur() { return Persistence::getUnsavedSeconds(); }
 
 static string getDFPath() { return Core::getInstance().p->getPath(); }
 static string getHackPath() { return Core::getInstance().getHackPath(); }
@@ -1370,6 +1377,7 @@ static const LuaWrapper::FunctionReg dfhack_module[] = {
     WRAP(getDFVersion),
     WRAP(getDFPath),
     WRAP(getTickCount),
+    WRAP(getCurSaveDur),
     WRAP(getHackPath),
     WRAP(isWorldLoaded),
     WRAP(isMapLoaded),

library/include/modules/Persistence.h

@@ -213,5 +213,7 @@ namespace DFHack
         // Fills the vector with references to each persistent item with a key that is
         // equal to the given key.
         DFHACK_EXPORT void getAllByKey(std::vector<PersistentDataItem> &vec, int entity_id, const std::string &key);
+        // Returns the number of seconds since the current savegame was saved or loaded.
+        DFHACK_EXPORT uint32_t getUnsavedSeconds();
     }
 }

library/modules/Persistence.cpp

@@ -49,6 +49,8 @@ using namespace DFHack;
 static std::unordered_map<int, std::multimap<std::string, std::shared_ptr<Persistence::DataEntry>>> store;
 static std::unordered_map<size_t, std::shared_ptr<Persistence::DataEntry>> entry_cache;
 
+static uint32_t lastLoadSaveTickCount = 0;
+
 size_t next_entry_id = 0;   // goes more positive
 int next_fake_df_id = -101; // goes more negative
 
@@ -237,6 +239,8 @@ void Persistence::Internal::save(color_ostream& out) {
         color_ostream_wrapper wrapper(file);
         Lua::CallLuaModuleFunction(wrapper, "script-manager", "print_timers");
     }
+
+    lastLoadSaveTickCount = Core::getInstance().p->getTickCount();
 }
 
 static bool get_entity_id(const std::string & fname, int & entity_id) {
@@ -306,6 +310,7 @@ void Persistence::Internal::load(color_ostream& out) {
             out.printerr("Cannot load data from: '%s'\n", path.c_str());
     }
 
+    lastLoadSaveTickCount = Core::getInstance().p->getTickCount();
     if (found)
         return;
 
@@ -417,3 +422,8 @@ void Persistence::getAllByKey(std::vector<PersistentDataItem> &vec, int entity_i
     for (auto it = range.first; it != range.second; ++it)
         vec.emplace_back(it->second);
 }
+
+uint32_t Persistence::getUnsavedSeconds() {
+    uint32_t durMS =  Core::getInstance().p->getTickCount() - lastLoadSaveTickCount;
+    return durMS / 1000;
+}