scheduler: allow attaching tasks from already running processes (close #845)

TODO

@@ -4,7 +4,8 @@
 * add examples (and credits) from @alanjfs :)
 
 WIP:
-* dense map/set: support uses-allocator construction (single arg, multi-arg, key construction)
+* uses-allocator construction: dense set (review), dense map, compressed pair, any (with allocator support), cache, dispatcher, poly, ...
+* process scheduler: reviews, use free lists internally
 * runtime events (emitter)
 * iterator based try_emplace vs try_insert for perf reasons
 * registry: remove reference to basic_sparse_set<E>

src/entt/process/scheduler.hpp

@@ -42,8 +42,8 @@ template<typename Delta>
 class scheduler {
     struct process_handler {
         using instance_type = std::unique_ptr<void, void (*)(void *)>;
-        using update_fn_type = bool(process_handler &, Delta, void *);
-        using abort_fn_type = void(process_handler &, bool);
+        using update_fn_type = bool(scheduler &, std::size_t, Delta, void *);
+        using abort_fn_type = void(scheduler &, std::size_t, bool);
         using next_type = std::unique_ptr<process_handler>;
 
         instance_type instance;
@@ -75,17 +75,17 @@ class scheduler {
     };
 
     template<typename Proc>
-    [[nodiscard]] static bool update(process_handler &handler, const Delta delta, void *data) {
-        auto *process = static_cast<Proc *>(handler.instance.get());
+    [[nodiscard]] static bool update(scheduler &owner, std::size_t pos, const Delta delta, void *data) {
+        auto *process = static_cast<Proc *>(owner.handlers[pos].instance.get());
         process->tick(delta, data);
 
         if(process->rejected()) {
             return true;
         } else if(process->finished()) {
-            if(handler.next) {
+            if(auto &&handler = owner.handlers[pos]; handler.next) {
                 handler = std::move(*handler.next);
                 // forces the process to exit the uninitialized state
-                return handler.update(handler, {}, nullptr);
+                return handler.update(owner, pos, {}, nullptr);
             }
 
             return true;
@@ -95,8 +95,8 @@ class scheduler {
     }
 
     template<typename Proc>
-    static void abort(process_handler &handler, const bool immediately) {
-        static_cast<Proc *>(handler.instance.get())->abort(immediately);
+    static void abort(scheduler &owner, std::size_t pos, const bool immediately) {
+        static_cast<Proc *>(owner.handlers[pos].instance.get())->abort(immediately);
     }
 
     template<typename Proc>
@@ -172,10 +172,10 @@ public:
     auto attach(Args &&...args) {
         static_assert(std::is_base_of_v<process<Proc, Delta>, Proc>, "Invalid process type");
         auto proc = typename process_handler::instance_type{new Proc{std::forward<Args>(args)...}, &scheduler::deleter<Proc>};
-        process_handler handler{std::move(proc), &scheduler::update<Proc>, &scheduler::abort<Proc>, nullptr};
+        auto &&ref = handlers.emplace_back(process_handler{std::move(proc), &scheduler::update<Proc>, &scheduler::abort<Proc>, nullptr});
         // forces the process to exit the uninitialized state
-        handler.update(handler, {}, nullptr);
-        return continuation{&handlers.emplace_back(std::move(handler))};
+        ref.update(*this, handlers.size() - 1u, {}, nullptr);
+        return continuation{&handlers.back()};
     }
 
     /**
@@ -247,17 +247,14 @@ public:
      * @param data Optional data.
      */
     void update(const Delta delta, void *data = nullptr) {
-        auto sz = handlers.size();
-
         for(auto pos = handlers.size(); pos; --pos) {
-            auto &handler = handlers[pos - 1];
+            const auto curr = pos - 1u;
 
-            if(const auto dead = handler.update(handler, delta, data); dead) {
-                std::swap(handler, handlers[--sz]);
+            if(const auto dead = handlers[curr].update(*this, curr, delta, data); dead) {
+                std::swap(handlers[curr], handlers.back());
+                handlers.pop_back();
             }
         }
-
-        handlers.erase(handlers.begin() + sz, handlers.end());
     }
 
     /**
@@ -271,15 +268,10 @@ public:
      * @param immediately Requests an immediate operation.
      */
     void abort(const bool immediately = false) {
-        decltype(handlers) exec;
-        exec.swap(handlers);
-
-        for(auto &&handler: exec) {
-            handler.abort(handler, immediately);
+        for(auto pos = handlers.size(); pos; --pos) {
+            const auto curr = pos - 1u;
+            handlers[curr].abort(*this, curr, immediately);
         }
-
-        std::move(handlers.begin(), handlers.end(), std::back_inserter(exec));
-        handlers.swap(exec);
     }
 
 private:

test/entt/process/scheduler.cpp

@@ -22,29 +22,30 @@ struct foo_process: entt::process<foo_process, int> {
 
 struct succeeded_process: entt::process<succeeded_process, int> {
     void update(delta_type, void *) {
-        ASSERT_FALSE(updated);
-        updated = true;
         ++invoked;
         succeed();
     }
 
-    static unsigned int invoked;
-    bool updated = false;
+    static inline unsigned int invoked;
 };
 
-unsigned int succeeded_process::invoked = 0;
-
 struct failed_process: entt::process<failed_process, int> {
     void update(delta_type, void *) {
-        ASSERT_FALSE(updated);
-        updated = true;
+        ++invoked;
         fail();
     }
 
-    bool updated = false;
+    static inline unsigned int invoked;
 };
 
-TEST(Scheduler, Functionalities) {
+struct Scheduler: ::testing::Test {
+    void SetUp() override {
+        succeeded_process::invoked = 0u;
+        failed_process::invoked = 0u;
+    }
+};
+
+TEST_F(Scheduler, Functionalities) {
     entt::scheduler<int> scheduler{};
 
     bool updated = false;
@@ -75,7 +76,7 @@ TEST(Scheduler, Functionalities) {
     ASSERT_TRUE(scheduler.empty());
 }
 
-TEST(Scheduler, Then) {
+TEST_F(Scheduler, Then) {
     entt::scheduler<int> scheduler;
 
     // failing process with successor
@@ -93,15 +94,18 @@ TEST(Scheduler, Then) {
     scheduler.attach<succeeded_process>()
         .then<succeeded_process>();
 
-    for(auto i = 0; i < 8; ++i) {
+    ASSERT_EQ(succeeded_process::invoked, 0u);
+    ASSERT_EQ(failed_process::invoked, 0u);
+
+    while(!scheduler.empty()) {
         scheduler.update(0);
     }
 
     ASSERT_EQ(succeeded_process::invoked, 6u);
-    ASSERT_TRUE(scheduler.empty());
+    ASSERT_EQ(failed_process::invoked, 2u);
 }
 
-TEST(Scheduler, Functor) {
+TEST_F(Scheduler, Functor) {
     entt::scheduler<int> scheduler;
 
     bool first_functor = false;
@@ -121,7 +125,7 @@ TEST(Scheduler, Functor) {
 
     scheduler.attach(std::move(attach)).then(std::move(then)).then([](auto...) { FAIL(); });
 
-    for(auto i = 0; i < 8; ++i) {
+    while(!scheduler.empty()) {
         scheduler.update(0);
     }
 
@@ -129,3 +133,22 @@ TEST(Scheduler, Functor) {
     ASSERT_TRUE(second_functor);
     ASSERT_TRUE(scheduler.empty());
 }
+
+TEST_F(Scheduler, SpawningProcess) {
+    entt::scheduler<int> scheduler;
+
+    scheduler.attach([&scheduler](auto, void *, auto resolve, auto) {
+        scheduler.attach<succeeded_process>().then<failed_process>();
+        resolve();
+    });
+
+    ASSERT_EQ(succeeded_process::invoked, 0u);
+    ASSERT_EQ(failed_process::invoked, 0u);
+
+    while(!scheduler.empty()) {
+        scheduler.update(0);
+    }
+
+    ASSERT_EQ(succeeded_process::invoked, 1u);
+    ASSERT_EQ(failed_process::invoked, 1u);
+}