Template based fsm. Initial commit.

2026-02-28 19:09:37 -05:00
parent f8681441e2
commit 0285bc402e
4 changed files with 527 additions and 0 deletions
--- a/templatefsm/main.cpp
+++ b/templatefsm/main.cpp
@@ -0,0 +1,148 @@
+#include "fsm.h"
+#include <cstdint>
+
+/** States */
+struct Idle  { };
+struct Active {
+  std::uint32_t session_id = 0;
+};
+
+/** Events */
+struct EvStart {
+  std::uint32_t requested_session = 0;
+};
+struct EvStop  { };
+
+/** Context */
+struct Context {
+  std::uint32_t starts = 0;
+};
+
+/** Names (optional) */
+template <> struct name_of<Idle>    {
+  static constexpr const char *value = "Idle";
+};
+template <> struct name_of<Active>  {
+  static constexpr const char *value = "Active";
+};
+template <> struct name_of<EvStart> {
+  static constexpr const char *value = "EvStart";
+};
+template <> struct name_of<EvStop>  {
+  static constexpr const char *value = "EvStop";
+};
+
+/** Logger */
+struct MyLogger {
+  void ignored_transition (const char *from_state, const char *event) noexcept {
+    (void)from_state;
+    (void)event;
+    // printf("FSM ignored: %s + %s\n", from_state, event);
+  }
+
+  void unhandled_transition (const char *from_state, const char *event) noexcept {
+    (void)from_state;
+    (void)event;
+    // printf("FSM UNHANDLED: %s + %s\n", from_state, event);
+  }
+
+  void guard_blocked (const char *from_state, const char *event) noexcept {
+    (void)from_state;
+    (void)event;
+    // printf("FSM guard blocked: %s + %s\n", from_state, event);
+  }
+};
+
+/** Guard */
+struct GuardStartAllowed {
+  bool operator() (Context &ctx, const Idle &, const EvStart &) const noexcept {
+    return ctx.starts < 10U;
+  }
+};
+
+/** Action */
+struct ActionOnStart {
+  void operator() (Context &ctx, const Idle &, const Active &, const EvStart &) const noexcept {
+    ++ctx.starts;
+  }
+};
+
+/** Factory specialization (NOTE: now includes Context in template parameters) */
+template <>
+struct state_factory<Context, Idle, EvStart, Active> {
+  static Active make (Context &, const Idle &, const EvStart &ev) {
+    Active a{};
+    a.session_id = ev.requested_session;
+    return a;
+  }
+};
+
+/** Hooks (optional) */
+template <>
+struct on_entry_state<Active> {
+  static void call (Context &, const Active &) noexcept {
+    // start timers, etc.
+  }
+};
+
+template <>
+struct on_exit_state<Active> {
+  static void call (Context &, const Active &) noexcept {
+    // stop timers, etc.
+  }
+};
+
+template <>
+struct on_entry_event<Active, EvStart> {
+  static void call (Context &, const Active &, const EvStart &) noexcept {
+    // entered Active due to EvStart
+  }
+};
+
+/** Transitions */
+template <>
+struct transition<Idle, EvStart> {
+  using type = transition_to<Active, GuardStartAllowed, ActionOnStart>;
+};
+
+template <>
+struct transition<Active, EvStop> {
+  using type = transition_to<Idle>;
+};
+
+/**
+ * "Adult strictness": mark only required pairs strict.
+ * Everything else is ignore by default.
+ */
+template <>
+struct missing_transition<Idle, EvStart> {
+  static constexpr missing_transition_policy policy = missing_transition_policy::strict;
+};
+
+template <>
+struct missing_transition<Active, EvStop> {
+  static constexpr missing_transition_policy policy = missing_transition_policy::strict;
+};
+
+/** FSM type */
+using MyFsm = fsm<Context, MyLogger, Idle, Active>;
+
+static constexpr void validate_fsm_contract() {
+  MyFsm::validate_events<EvStart, EvStop>();
+}
+
+int main() {
+  validate_fsm_contract();
+
+  Context ctx{};
+  MyFsm f (ctx, Idle{}, MyLogger{});
+
+  f.dispatch (EvStart{42}); // Idle -> Active
+  f.dispatch (EvStop{});   // Active -> Idle
+
+  // Not required by strict contract => default ignore (logged via ignored_transition)
+  f.dispatch (EvStop{});   // Idle + EvStop => ignored
+  f.dispatch (EvStart{7}); // (if currently Active) Active + EvStart => ignored
+
+  return 0;
+}