auto: overkill logging

multun · Jul 10, 2018 · 68bf686 · 68bf686
1 parent bcd4462
commit 68bf686
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Showing 2 changed files with 59 additions and 21 deletions.
diff --git a/auto.hh b/auto.hh
@@ -11,13 +11,22 @@
 
 #include "type_utils.hxx"
 
+template<class Auto>
+struct NoopAutoLogger {
+    template<template<class> class NewState,
+             template<class> class OldState>
+    void log() {
+    }
+};
+
 template<template<class> class PInterface,
          class AllowedTransitions,
-         template<class> class ...States>
+         class States,
+	 template<class> class Logger = NoopAutoLogger>
 class Auto {
-    using self_t = Auto<PInterface, AllowedTransitions, States...>;
+    using self_t = Auto<PInterface, AllowedTransitions, States, Logger>;
     using intf_t = PInterface<self_t>;
-    using ttlist = TTList<States...>;
+    using ttlist = States;
 
     template<template<class> class State>
     struct Automaker {
@@ -53,6 +62,8 @@ class Auto {
     StateData data_[2];
     bool data_pos_;
 
+    Logger<self_t> logger;
+
     StateData &cur_data() {
         return data_[data_pos_];
     }
@@ -63,6 +74,9 @@ class Auto {
 
     Auto() : data_pos_(0) {}
 
+    Auto(Logger<self_t> &&log)
+      : data_pos_(0), logger(log) {}
+
 public:
     auto &get_state() {
         return *cur_data().template get_data<intf_t>();
@@ -80,6 +94,14 @@ public:
 	return res;
     }
 
+    template<template<class> class InitialState, class ...Args>
+    static Auto init(Logger<self_t> &&logger, Args&& ...args) {
+        auto res = Auto{std::move(logger)};
+        res.cur_data().template enter<InitialState, Args...>(
+            std::forward<Args>(args)...);
+	return res;
+    }
+
     template<template<class> class NewState, class ...Args>
     void enter(Args&& ...args) {
         other_data().template enter<NewState, Args...>(
@@ -88,14 +110,6 @@ public:
         data_pos_ = !data_pos_;
     }
 
-    template<template<class> class NewState,
-             template<class> class OldState,
-             class Auto>
-    static void default_logger(Auto) {
-        std::clog << "transition from " << typeid(OldState<Auto>).name() << " to "
-	          << typeid(NewState<Auto>).name() << std::endl;
-    }
-
     template<template<class> class NewState,
              template<class> class OldState,
              class ...Args>
@@ -108,13 +122,7 @@ public:
         /* traits on variadic templates would be mandatory,
            which is too annoying to be worth it */
 
-#ifdef DEFAULT_LOG_TRANSITIONS
-# define LOG_TRANSITIONS default_logger
-#endif
-
-#ifdef LOG_TRANSITIONS
-	LOG_TRANSITIONS<NewState, OldState>(this);
-#endif
+        logger.template log<NewState, OldState>();
 
         enter<NewState, Args...>(std::forward<Args>(args)...);
     }

diff --git a/test.cc b/test.cc
@@ -44,11 +44,41 @@ struct StateB : ExInterface<Auto> {
 };
 
 
-using trans = TList<TPair<StateB, StateA>>;
-using MyAuto = Auto<ExInterface, trans, StateA, StateB>;
+template<class Auto>
+struct OverkillLogger {
+    size_t log_count = 0;
 
-int main() {
+    OverkillLogger(size_t msg_id)
+        : log_count{msg_id} {}
+
+    template<template<class> class NewState,
+             template<class> class OldState>
+    void log() {
+        std::clog << log_count++ << " transition from "
+                  << typeid(OldState<Auto>).name() << " to "
+	          << typeid(NewState<Auto>).name() << std::endl;
+    }
+};
+
+using Transitions = TList<TTPair<StateB, StateA>>;
+using States = TTList<StateA, StateB>;
+using MyAuto = Auto<ExInterface, Transitions, States>;
+using MyLoggingAuto = Auto<ExInterface, Transitions, States, OverkillLogger>;
+
+void logging_example() {
+    auto logger = OverkillLogger<MyLoggingAuto>{42};
+    auto a = MyLoggingAuto::template init<StateB>(std::move(logger), 1);
+    a.get_state().callback(a);
+    a.get_state().callback(a);
+}
+
+void silent_example() {
     auto a = MyAuto::template init<StateB>(1);
     a.get_state().callback(a);
     a.get_state().callback(a);
 }
+
+int main() {
+    logging_example();
+    silent_example();
+}