From e5c5df5373ab4ad73e5415b63b0e5163c1bc23a7 Mon Sep 17 00:00:00 2001
From: Erki <erki@skullnet.me>
Date: Sat, 3 Jul 2021 12:09:25 +0300
Subject: [PATCH] Utility: add Function and FunctionOwned classes

---
 Tests/CMakeLists.txt             |  2 +-
 Tests/function.cpp               | 84 ++++++++++++++++++++++++++++++++
 Utility/Inc/utility_function.hpp | 72 +++++++++++++++++++++++++++
 3 files changed, 157 insertions(+), 1 deletion(-)
 create mode 100644 Tests/function.cpp
 create mode 100644 Utility/Inc/utility_function.hpp

diff --git a/Tests/CMakeLists.txt b/Tests/CMakeLists.txt
index a654247..cdb718a 100644
--- a/Tests/CMakeLists.txt
+++ b/Tests/CMakeLists.txt
@@ -18,7 +18,7 @@ add_executable(tests
     rand.cpp
     fixedpoint.cpp
     pixelbuffer.cpp
-    pixelbuffer_effects.cpp)
+    pixelbuffer_effects.cpp function.cpp)
 
 target_link_libraries(tests
     PUBLIC
diff --git a/Tests/function.cpp b/Tests/function.cpp
new file mode 100644
index 0000000..a9dbe19
--- /dev/null
+++ b/Tests/function.cpp
@@ -0,0 +1,84 @@
+//
+// Created by erki on 03.07.21.
+//
+
+#include <catch2/catch.hpp>
+
+#include <utility_function.hpp>
+
+TEST_CASE("Function calls function appropriately.", "[utility],[function]")
+{
+  static bool func_called = false;
+
+  auto func_to_call = []() {
+    func_called = true;
+  };
+
+  Utility::Function<void()> function(func_to_call);
+  function();
+
+  REQUIRE(func_called == true);
+}
+
+TEST_CASE("Function passes arguments appropriately.", "[utility],[function]")
+{
+  static int int_to_set = 0;
+  static bool bool_to_set = false;
+
+  auto func_to_call = [](const int i, const bool b) {
+    int_to_set = i;
+    bool_to_set = b;
+  };
+
+  Utility::Function<void(int, bool)> function(func_to_call);
+
+  function(10, true);
+
+  REQUIRE(int_to_set == 10);
+  REQUIRE(bool_to_set == true);
+}
+
+TEST_CASE("FunctionOwned calls function appropriately.", "[utility],[function]")
+{
+  struct S
+  {
+    bool to_set = false;
+
+    void toCall()
+    {
+      to_set = true;
+    }
+  };
+
+  S subject;
+
+  Utility::FunctionOwned<S, void()> function(subject, &S::toCall);
+
+  function();
+
+  REQUIRE(subject.to_set == true);
+}
+
+TEST_CASE("FunctionOwned passes arguments appropriately.", "[utility],[function]")
+{
+  struct S
+  {
+    int int_to_set = 0;
+    bool bool_to_set = true;
+
+    void toCall(const int i, const bool b)
+    {
+      int_to_set = i;
+      bool_to_set = b;
+    }
+  };
+
+  S subject;
+
+  Utility::FunctionOwned<S, void(int, bool)> function(subject, &S::toCall);
+
+  function(10, false);
+
+  REQUIRE(subject.int_to_set == 10);
+  REQUIRE(subject.bool_to_set == false);
+}
diff --git a/Utility/Inc/utility_function.hpp b/Utility/Inc/utility_function.hpp
new file mode 100644
index 0000000..2ea32c8
--- /dev/null
+++ b/Utility/Inc/utility_function.hpp
@@ -0,0 +1,72 @@
+/*
+ * utility_function.hpp
+ *
+ *  Created on: Jun 20, 2021
+ *      Author: erki
+ */
+
+#ifndef SKULLC_UTILITY_FUNCTION_HPP_
+#define SKULLC_UTILITY_FUNCTION_HPP_
+
+namespace Utility
+{
+
+template<class>
+class Function;
+
+template<typename R, typename... Args>
+class Function<R(Args...)>
+{
+public:
+  using result_type = R;
+
+  using signature = R (*)(Args...);
+
+  Function() = delete;
+  explicit Function(signature callable)
+      : callable_(callable)
+  {
+    assert(callable_);
+  }
+
+  result_type operator()(Args&&... args)
+  {
+    return (*callable_)(std::forward<Args>(args)...);
+  }
+
+private:
+  signature callable_ = nullptr;
+};
+
+template<class, class>
+class FunctionOwned;
+
+template<typename H, typename R, typename... Args>
+class FunctionOwned<H, R(Args...)>
+{
+public:
+  using source = H;
+  using result_type = R;
+
+  using signature = R (source::*)(Args...);
+
+  FunctionOwned() = delete;
+  explicit FunctionOwned(source& src, signature callable)
+      : src_(&src), callable_(callable)
+  {
+    assert(callable_);
+  }
+
+  result_type operator()(Args&&... args)
+  {
+    return (src_->*callable_)(std::forward<Args>(args)...);
+  }
+
+private:
+  source* src_ = nullptr;
+  signature callable_ = nullptr;
+};
+
+}// namespace Utility
+
+#endif /* SKULLC_UTILITY_FUNCTION_HPP_ */