repos/CallbackTest_02/CallbackTest_02.cpp

/* printf example */
#include <stdio.h>
#include <cstdio>

#include <iostream>
#include <functional>               // std::function
#include <stdint.h>                 // uint64_t
#include <unordered_map>            // std::unordered_map
#include <utility>                  // std::move    
#include <vector>                   // std::vector
using namespace std;

#if 1

//
// https://manderc.com/types/functionpointertype/index.php
//


void globalfunction(void * pthis, int i) {
	printf("Global globalfunction (%i)\n", i); 
}

static void staticglobalfunction(void * pthis,int i) {
	printf("Static Global (%i)\n", i);
}

namespace Name_Space {
	void namespacefunc(void * pthis, int i) {
		printf("Namespace (%i)\n", i);
	}
}

#if 0
void (*returnfunction(const char* str))(int) {
	printf("Return \"%s\":\n", str);
	return &globalfunction;
}
#endif 

class ExternClass {
public:

	void externClassfunction(void * pthis, int i) {
		printf("externClassfunction (%i)\n", i);
	}
	static void staticExternClassfunction(void * pthis, int i) {
		printf("staticExternClassfunction (%i)\n", i);
	}
};


class Test {
private:
	void (*funcptr1)(void*, int i) = &globalfunction;
	unsigned int myTestVar = 10; 

public:

	void (*funcptr2)(void* pthis, int i) = nullptr;
	void (*funcptr3)(void* pthis, int i) = nullptr;
	void (*funcptr4)(void* pthis, int i) = nullptr;
	void (Test::* funcptr5)(int i);

	void classfunction(int i) {
		printf("Test Class local classfunction (%i)\n", i);
	}

	void callglobal(int i) {
		funcptr1 = &globalfunction;
	}
	void callclass(int i) {
		funcptr5 = &Test::classfunction;
	}

	void run(int i) {
		(*funcptr1)(this, i);
		(*funcptr2)(this, i);
		(*funcptr3)(this, i);
		(*funcptr4)(this, i);
//		(this->*funcptr5)(this, i);
	}
};

int main() {
	Test test;
	ExternClass extClass; 


	// Global function with class-function-ptr outside class
	test.funcptr2 = &globalfunction;


	// Function in namespace with local function pointer
	test.funcptr3 = &Name_Space::namespacefunc;

	// Class function with class-function-ptr outside class
	test.funcptr4 = &ExternClass::staticExternClassfunction;

	// Class function with class-function-ptr outside class
	test.funcptr5 = &Test::classfunction;

	// Class function with local function-ptr
	void (Test:: * classfunc)(int i) = &Test::classfunction;

	test.run(10); 

	// (*returnfunction("global"))(10);
	// printf("Using typedef:\n");
#if 0
	typedef void (*functiontype)(int);
	functiontype typefuncptr = &globalfunction;
	(*typefuncptr)(11);
#endif 
	return 0;
}
#endif 


#if 0

template<typename R, typename P1, typename P2>
class Callback
{
public:
	typedef R(*FuncType)(void*, P1, P2);
	Callback() : func(0), obj(0) {}
	Callback(FuncType f, void* o) : func(f), obj(o) {}
	R operator()(P1 a1, P2 a2)
	{
		return (*func)(obj, a1, a2);
	}

private:
	FuncType func;
	void* obj;
};

template<typename R, class T, typename P1, typename P2, R(T::* Func)(P1, P2)>
R Wrapper(void* o, P1 a1, P2 a2)
{
	return (static_cast<T*>(o)->*Func)(a1, a2);
}

class Foo
{
public:
	float Average(int n1, int n2)
	{
		return (n1 + n2) / 2.0f;
	}
};

float Calculate(int n1, int n2, Callback<float, int, int> callback)
{
	return callback(n1, n2);
}

int main()
{
	Foo f;
	Callback<float, int, int> cb
	(&Wrapper<float, Foo, int, int, &Foo::Average>, &f);
	float result = Calculate(50, 100, cb);
	// result == 75.0f
	return 0;
}

#endif


#if 0

namespace my
{
	using Callback = function<void()>;
	template< class Key, class Value > using Map_ = unordered_map<Key, Value>;

	class Subject
	{
	public:
		enum Id : uint64_t {};

	private:
		Map_<uint64_t, Callback> m_callbacks;

		static auto id_value()
			-> uint64_t&
		{
			static uint64_t the_id;
			return the_id;
		}

	public:
		auto add_listener(Callback cb)
			-> Id
		{
			const auto id = Id(++id_value());
			m_callbacks.emplace(id, move(cb));
			return id;
		}

		auto remove_listener(const Id id)
			-> bool
		{
			const auto it = m_callbacks.find(id);
			if (it == m_callbacks.end())
			{
				return false;
			}
			m_callbacks.erase(it);
			return true;
		}

		void notify_all() const
		{
			for (const auto& pair : m_callbacks)
			{
				pair.second();
			}
		}
	};
}

struct Observer_1
{
	void notify() { cout << "Observer_1::notify() called." << endl; }
};

struct Observer_2
{
	void notify() { cout << "Observer_2::notify() called." << endl; }
};

auto main()
-> int
{
	my::Subject     subject;
	Observer_1      one;
	Observer_2      two;

	using Id = my::Subject::Id;
	const Id listener_id_1 = subject.add_listener([&] { one.notify(); });
	const Id listener_id_2 = subject.add_listener([&] { two.notify(); });

	cout << "After adding two listeners:" << endl;
	subject.notify_all();
	cout << endl;

	subject.remove_listener(listener_id_1)
		and (cout << "Removed listener 1." << endl)
		or (cout << "Did not find registration of listener 1." << endl);
	cout << endl;
	cout << "After removing or attempting to remove listener 1:" << endl;
	subject.notify_all();
}

#endif

#if 0

class A
{
public:
	std::function<void(int, const std::string&)> m_CbFunc = nullptr;
	void foo()
	{
		if (m_CbFunc)
		{
			m_CbFunc(100, "event fired");
		}
	}

};

class B
{
public:
	unsigned int TestVariable = 10; 

	B()
	{
		auto aFunc = std::bind(&B::eventHandler, this, std::placeholders::_1, std::placeholders::_2);
		anObjA.m_CbFunc = aFunc;
	}
	void eventHandler(int i, const std::string& s)
	{
		std::cout << s << ": " << i << std::endl;
	}

	void DoSomethingOnA()
	{
		anObjA.foo();
	}

	A anObjA;
};

int main(int argc, char* argv[])
{
	B anObjB;
	anObjB.DoSomethingOnA();
}
#endif