/************************************************************************************

Filename    :   OVR_Delegates.h
Content     :   C++ Delegates
Created     :   June 15, 2014
Authors     :   Chris Taylor

Copyright   :   Copyright 2014 Oculus VR, LLC All Rights reserved.

Licensed under the Oculus VR Rift SDK License Version 3.2 (the "License");
you may not use the Oculus VR Rift SDK except in compliance with the License,
which is provided at the time of installation or download, or which
otherwise accompanies this software in either electronic or hard copy form.

You may obtain a copy of the License at

http://www.oculusvr.com/licenses/LICENSE-3.2

Unless required by applicable law or agreed to in writing, the Oculus VR SDK
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

************************************************************************************/

/*
	Based on The Impossibly Fast C++ Delegates by Sergey Ryazanov from
	http://www.codeproject.com/KB/cpp/ImpossiblyFastCppDelegate.aspx (2005)
*/

/*
	Usage:

	Declare a delegate with a void (int) signature, also known as a
	function that returns void and has one parameter that is an int:
		typedef Delegate1<void, int> MyDelegate;
		MyDelegate d;

	Point the delegate to a member function:
		d.SetMember<A, &A::TestFunctionA>(&a);
		d = MyDelegate::FromMember<A, &A::TestFunctionA>(&a);

	Point the delegate to a const member function:
		d.SetConstMember<C, &C::TestFunctionA>(&c);
		d = MyDelegate::FromConstMember<C, &C::TestFunctionA>(&c);

	Point the delegate to a free function:
		d.SetFree<&FreeFunctionX>();
		d = MyDelegate::FromFree<&FreeFunctionX>();

	Invoke the function via the delegate (works for all 3 cases):
		d(1000);

	By default the delegates are uninitialized.
	To clear an array of delegates quickly just zero the memory.

	This implementation is nicer than FastDelegates in my opinion
	because it is simple and easy to read.  It is a little slower
	for virtual functions, but the size of the delegate is small,
	and it will only get better as compilers improve.
*/

#ifndef OVR_Delegates_h
#define OVR_Delegates_h

#include "OVR_Types.h"

namespace OVR {


template <class ret_type>
class Delegate0
{
	typedef ret_type (*StubPointer)(void *);
	typedef Delegate0<ret_type> this_type;

	void *_object;
	StubPointer _stub;

	OVR_FORCE_INLINE Delegate0(void *object, StubPointer stub)
	{
		_object = object;
		_stub = stub;
	}

	// Stubs

	template <ret_type (*F)()>
	static OVR_FORCE_INLINE ret_type FreeStub(void *object)
	{
		return (F)();
	}

	template <class T, ret_type (T::*F)()>
	static OVR_FORCE_INLINE ret_type MemberStub(void *object)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)();
	}

	template <class T, ret_type (T::*F)() const>
	static OVR_FORCE_INLINE ret_type ConstMemberStub(void *object)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)();
	}

public:
	OVR_FORCE_INLINE Delegate0() : _object(0), _stub(0){}

	// Function invocation

	OVR_FORCE_INLINE ret_type operator()() const
	{
		return (*_stub)(_object);
	}

	// Use stub pointer as a validity flag and equality checker

	OVR_FORCE_INLINE bool operator==(const this_type &rhs) const
	{
		return _object == rhs._object && _stub == rhs._stub;
	}

	OVR_FORCE_INLINE bool operator!=(const this_type &rhs) const
	{
		return _object != rhs._object || _stub != rhs._stub;
	}

	OVR_FORCE_INLINE bool IsValid() const
	{
		return _stub != 0;
	}

	OVR_FORCE_INLINE bool operator!() const
	{
		return _stub == 0;
	}

	OVR_FORCE_INLINE void Invalidate()
	{
		_stub = 0;
	}

	// Delegate creation from a function

	template <ret_type (*F)()>
	static OVR_FORCE_INLINE this_type FromFree()
	{
		return this_type(0, &FreeStub<F>);
	}

	template <class T, ret_type (T::*F)()>
	static OVR_FORCE_INLINE this_type FromMember(T *object)
	{
		return this_type(object, &MemberStub<T, F>);
	}

	template <class T, ret_type (T::*F)() const>
	static OVR_FORCE_INLINE this_type FromConstMember(T const *object)
	{
		return this_type(const_cast<T*>( object ), &ConstMemberStub<T, F>);
	}

	// In-place assignment to a different function

	template <ret_type (*F)()>
	OVR_FORCE_INLINE void SetFree()
	{
		*this = FromFree<F>();
	}

	template <class T, ret_type (T::*F)()>
	OVR_FORCE_INLINE void SetMember(T *object)
	{
		*this = FromMember<T, F>(object);
	}

	template <class T, ret_type (T::*F)() const>
	OVR_FORCE_INLINE void SetConstMember(T const *object)
	{
		*this = FromConstMember<T, F>(object);
	}
};


template <class ret_type, class arg1_type>
class Delegate1
{
	typedef ret_type (*StubPointer)(void *, arg1_type);
	typedef Delegate1<ret_type, arg1_type> this_type;

	void *_object;
	StubPointer _stub;

	OVR_FORCE_INLINE Delegate1(void *object, StubPointer stub)
	{
		_object = object;
		_stub = stub;
	}

	// Stubs

	template <ret_type (*F)(arg1_type)>
	static OVR_FORCE_INLINE ret_type FreeStub(void *object, arg1_type a1)
	{
		return (F)(a1);
	}

	template <class T, ret_type (T::*F)(arg1_type)>
	static OVR_FORCE_INLINE ret_type MemberStub(void *object, arg1_type a1)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)(a1);
	}

	template <class T, ret_type (T::*F)(arg1_type) const>
	static OVR_FORCE_INLINE ret_type ConstMemberStub(void *object, arg1_type a1)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)(a1);
	}

public:
	OVR_FORCE_INLINE Delegate1() : _object(0), _stub(0){}

	// Function invocation

	OVR_FORCE_INLINE ret_type operator()(arg1_type a1) const
	{
		return (*_stub)(_object, a1);
	}

	// Use stub pointer as a validity flag and equality checker

	OVR_FORCE_INLINE bool operator==(const this_type &rhs) const
	{
		return _object == rhs._object && _stub == rhs._stub;
	}

	OVR_FORCE_INLINE bool operator!=(const this_type &rhs) const
	{
		return _object != rhs._object || _stub != rhs._stub;
	}

	OVR_FORCE_INLINE bool IsValid() const
	{
		return _stub != 0;
	}

	OVR_FORCE_INLINE bool operator!() const
	{
		return _stub == 0;
	}

	OVR_FORCE_INLINE void Invalidate()
	{
		_stub = 0;
	}

	// Delegate creation from a function

	template <ret_type (*F)(arg1_type)>
	static OVR_FORCE_INLINE this_type FromFree()
	{
		return this_type(0, &FreeStub<F>);
	}

	template <class T, ret_type (T::*F)(arg1_type)>
	static OVR_FORCE_INLINE this_type FromMember(T *object)
	{
		return this_type(object, &MemberStub<T, F>);
	}

	template <class T, ret_type (T::*F)(arg1_type) const>
	static OVR_FORCE_INLINE this_type FromConstMember(T const *object)
	{
		return this_type(const_cast<T*>( object ), &ConstMemberStub<T, F>);
	}

	// In-place assignment to a different function

	template <ret_type (*F)(arg1_type)>
	OVR_FORCE_INLINE void SetFree()
	{
		*this = FromFree<F>();
	}

	template <class T, ret_type (T::*F)(arg1_type)>
	OVR_FORCE_INLINE void SetMember(T *object)
	{
		*this = FromMember<T, F>(object);
	}

	template <class T, ret_type (T::*F)(arg1_type) const>
	OVR_FORCE_INLINE void SetConstMember(T const *object)
	{
		*this = FromConstMember<T, F>(object);
	}
};


template <class ret_type, class arg1_type, class arg2_type>
class Delegate2
{
	typedef ret_type (*StubPointer)(void *, arg1_type, arg2_type);
	typedef Delegate2<ret_type, arg1_type, arg2_type> this_type;

	void *_object;
	StubPointer _stub;

	OVR_FORCE_INLINE Delegate2(void *object, StubPointer stub)
	{
		_object = object;
		_stub = stub;
	}

	// Stubs

	template <ret_type (*F)(arg1_type, arg2_type)>
	static OVR_FORCE_INLINE ret_type FreeStub(void *object, arg1_type a1, arg2_type a2)
	{
		return (F)(a1, a2);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type)>
	static OVR_FORCE_INLINE ret_type MemberStub(void *object, arg1_type a1, arg2_type a2)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)(a1, a2);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type) const>
	static OVR_FORCE_INLINE ret_type ConstMemberStub(void *object, arg1_type a1, arg2_type a2)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)(a1, a2);
	}

public:
	OVR_FORCE_INLINE Delegate2() : _object(0), _stub(0){}

	// Function invocation

	OVR_FORCE_INLINE ret_type operator()(arg1_type a1, arg2_type a2) const
	{
		return (*_stub)(_object, a1, a2);
	}

	// Use stub pointer as a validity flag and equality checker

	OVR_FORCE_INLINE bool operator==(const this_type &rhs) const
	{
		return _object == rhs._object && _stub == rhs._stub;
	}

	OVR_FORCE_INLINE bool operator!=(const this_type &rhs) const
	{
		return _object != rhs._object || _stub != rhs._stub;
	}

	OVR_FORCE_INLINE bool IsValid() const
	{
		return _stub != 0;
	}

	OVR_FORCE_INLINE bool operator!() const
	{
		return _stub == 0;
	}

	OVR_FORCE_INLINE void Invalidate()
	{
		_stub = 0;
	}

	// Delegate creation from a function

	template <ret_type (*F)(arg1_type, arg2_type)>
	static OVR_FORCE_INLINE this_type FromFree()
	{
		return this_type(0, &FreeStub<F>);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type)>
	static OVR_FORCE_INLINE this_type FromMember(T *object)
	{
		return this_type(object, &MemberStub<T, F>);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type) const>
	static OVR_FORCE_INLINE this_type FromConstMember(T const *object)
	{
		return this_type(const_cast<T*>( object ), &ConstMemberStub<T, F>);
	}

	// In-place assignment to a different function

	template <ret_type (*F)(arg1_type, arg2_type)>
	OVR_FORCE_INLINE void SetFree()
	{
		*this = FromFree<F>();
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type)>
	OVR_FORCE_INLINE void SetMember(T *object)
	{
		*this = FromMember<T, F>(object);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type) const>
	OVR_FORCE_INLINE void SetConstMember(T const *object)
	{
		*this = FromConstMember<T, F>(object);
	}
};


template <class ret_type, class arg1_type, class arg2_type, class arg3_type>
class Delegate3
{
	typedef ret_type (*StubPointer)(void *, arg1_type, arg2_type, arg3_type);
	typedef Delegate3<ret_type, arg1_type, arg2_type, arg3_type> this_type;

	void *_object;
	StubPointer _stub;

	OVR_FORCE_INLINE Delegate3(void *object, StubPointer stub)
	{
		_object = object;
		_stub = stub;
	}

	// Stubs

	template <ret_type (*F)(arg1_type, arg2_type, arg3_type)>
	static OVR_FORCE_INLINE ret_type FreeStub(void *object, arg1_type a1, arg2_type a2, arg3_type a3)
	{
		return (F)(a1, a2, a3);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type, arg3_type)>
	static OVR_FORCE_INLINE ret_type MemberStub(void *object, arg1_type a1, arg2_type a2, arg3_type a3)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)(a1, a2, a3);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type, arg3_type) const>
	static OVR_FORCE_INLINE ret_type ConstMemberStub(void *object, arg1_type a1, arg2_type a2, arg3_type a3)
	{
		T *p = static_cast<T*>(object);
		return (p->*F)(a1, a2, a3);
	}

public:
	OVR_FORCE_INLINE Delegate3() : _object(0), _stub(0){}

	// Function invocation

	OVR_FORCE_INLINE ret_type operator()(arg1_type a1, arg2_type a2, arg3_type a3) const
	{
		return (*_stub)(_object, a1, a2, a3);
	}

	// Use stub pointer as a validity flag and equality checker

	OVR_FORCE_INLINE bool operator==(const this_type &rhs) const
	{
		return _object == rhs._object && _stub == rhs._stub;
	}

	OVR_FORCE_INLINE bool operator!=(const this_type &rhs) const
	{
		return _object != rhs._object || _stub != rhs._stub;
	}

	OVR_FORCE_INLINE bool IsValid() const
	{
		return _stub != 0;
	}

	OVR_FORCE_INLINE bool operator!() const
	{
		return _stub == 0;
	}

	OVR_FORCE_INLINE void Invalidate()
	{
		_stub = 0;
	}

	// Delegate creation from a function

	template <ret_type (*F)(arg1_type, arg2_type, arg3_type)>
	static OVR_FORCE_INLINE this_type FromFree()
	{
		return this_type(0, &FreeStub<F>);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type, arg3_type)>
	static OVR_FORCE_INLINE this_type FromMember(T *object)
	{
		return this_type(object, &MemberStub<T, F>);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type, arg3_type) const>
	static OVR_FORCE_INLINE this_type FromConstMember(T const *object)
	{
		return this_type(const_cast<T*>( object ), &ConstMemberStub<T, F>);
	}

	// In-place assignment to a different function

	template <ret_type (*F)(arg1_type, arg2_type, arg3_type)>
	OVR_FORCE_INLINE void SetFree()
	{
		*this = FromFree<F>();
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type, arg3_type)>
	OVR_FORCE_INLINE void SetMember(T *object)
	{
		*this = FromMember<T, F>(object);
	}

	template <class T, ret_type (T::*F)(arg1_type, arg2_type, arg3_type) const>
	OVR_FORCE_INLINE void SetConstMember(T const *object)
	{
		*this = FromConstMember<T, F>(object);
	}
};

// Add more here if needed, but keep in mind that a short, simple interface
// is rewarded by making the delegates faster...


} // namespace OVR

#endif // OVR_Delegates_h