vmap/libs/generic/callback.h

/*
   Copyright (C) 2001-2006, William Joseph.
   All Rights Reserved.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if !defined( INCLUDED_GENERIC_CLOSURE_H )
#define INCLUDED_GENERIC_CLOSURE_H

/// \file
/// \brief Type-safe techniques for binding the first argument of an opaque callback.

#include <cstddef>
#include "functional.h"

namespace detail {

template<typename Thunk_>
class CallbackBase {
void *m_environment;
Thunk_ m_thunk;
public:
typedef Thunk_ Thunk;

CallbackBase(void *environment, Thunk function) : m_environment(environment), m_thunk(function) {
}

void *getEnvironment() const {
	return m_environment;
}

Thunk getThunk() const {
	return m_thunk;
}
};

template<typename Thunk>
inline bool operator==(const CallbackBase<Thunk> &self, const CallbackBase<Thunk> &other) {
	return self.getEnvironment() == other.getEnvironment() && self.getThunk() == other.getThunk();
}

template<typename Thunk>
inline bool operator!=(const CallbackBase<Thunk> &self, const CallbackBase<Thunk> &other) {
	return !(self == other);
}

template<typename Thunk>
inline bool operator<(const CallbackBase<Thunk> &self, const CallbackBase<Thunk> &other) {
	return self.getEnvironment() < other.getEnvironment() ||
	       (!(other.getEnvironment() < self.getEnvironment()) && self.getThunk() < other.getThunk());
}

}

namespace detail {

template<class Type>
struct ConvertFromOpaque {
};

// reference

template<class T>
inline const void *convertToOpaque(const T &t) {
	return &t;
}

template<class T>
struct ConvertFromOpaque<const T &> {
	static T const &apply(void *p) {
		return *static_cast<const T *>(p);
	}
};

template<class T>
inline void *convertToOpaque(T &t) {
	return &t;
}

template<class T>
struct ConvertFromOpaque<T &> {
	static T &apply(void *p) {
		return *static_cast<T *>( p );
	}
};

// pointer

template<class T, class U = typename std::enable_if<!std::is_function<T>::value>::type>
inline const void *convertToOpaque(const T *t) {
	return t;
}

template<class T>
struct ConvertFromOpaque<const T *> {
	static const T *apply(void *p) {
		return static_cast<const T *>(p);
	}
};

template<class T, class U = typename std::enable_if<!std::is_function<T>::value>::type>
inline void *convertToOpaque(T *t) {
	return t;
}

template<class T>
struct ConvertFromOpaque<T *> {
	static T *apply(void *p) {
		return static_cast<T *>(p);
	}
};

// function pointer

template<class R, class... Ts>
inline const void *convertToOpaque(R(*const &t)(Ts ...)) {
	return &t;
}

template<class R, class ... Ts>
struct ConvertFromOpaque<R(*const &)(Ts...)> {
	using Type = R (*)(Ts...);

	static Type const &apply(void *p) {
		return *static_cast<Type *>(p);
	}
};

template<class R, class... Ts>
inline void *convertToOpaque(R(*&t)(Ts ...)) {
	return &t;
}

template<class R, class ... Ts>
struct ConvertFromOpaque<R(*&)(Ts...)> {
	using Type = R (*)(Ts...);

	static Type &apply(void *p) {
		return *static_cast<Type *>(p);
	}
};

template<class Caller, class F>
class BindFirstOpaqueN;

template<class Caller, class R, class FirstBound, class ... Ts>
class BindFirstOpaqueN<Caller, R(FirstBound, Ts...)> {
FirstBound firstBound;
public:
explicit BindFirstOpaqueN(FirstBound firstBound) : firstBound(firstBound) {
}

R operator()(Ts... args) const {
	return Caller::call(firstBound, args ...);
}

FirstBound getBound() const {
	return firstBound;
}

static R thunk(void *environment, Ts... args) {
	return thunk_(detail::ConvertFromOpaque<FirstBound>::apply(environment), args ...);
}

static R thunk_(FirstBound environment, Ts... args) {
	return Caller::call(environment, args ...);
}

void *getEnvironment() const {
	return const_cast<void *>(detail::convertToOpaque(firstBound));
}
};

}

template<class Caller>
using BindFirstOpaque = detail::BindFirstOpaqueN<Caller, get_func<Caller> >;

/// \brief Combines a void pointer with a pointer to a function which operates on a void pointer.
///
/// Use with the callback constructors MemberCaller0, ConstMemberCaller0, ReferenceCaller0, ConstReferenceCaller0, PointerCaller0, ConstPointerCaller0 and FreeCaller0.
template<class F>
class Callback;

template<class R, class ... Ts>
class Callback<R(Ts...)> : public detail::CallbackBase<R (*)(void *, Ts...)> {
using Base = detail::CallbackBase<R (*)(void *, Ts...)>;

static R nullThunk(void *, Ts...) {
}

public:
using func = R(Ts ...);

Callback() : Base(0, nullThunk) {
}

template<typename Caller>
Callback(const BindFirstOpaque<Caller> &caller) : Base(caller.getEnvironment(), BindFirstOpaque<Caller>::thunk) {
}

Callback(void *environment, typename Base::Thunk function) : Base(environment, function) {
}

R operator()(Ts... args) const {
	return Base::getThunk()(Base::getEnvironment(), args ...);
}
};

namespace detail {
template<class F>
struct Arglist;

template<class R, class Head, class ... Ts>
struct Arglist<R(Head, Ts...)> {
	using type = R(Head, Ts ...);

	template <class Unshift>
	using unshift = Arglist<R(Unshift, Head, Ts...)>;

	using shift = Arglist<R(Ts...)>;
};

template<class R, class ... Ts>
struct Arglist<R(Ts...)> {
	using type = R(Ts ...);

	template <class Unshift>
	using unshift = Arglist<R(Unshift, Ts...)>;
};

template<class F>
using ArgShift = typename detail::Arglist<F>::shift::type;

template<class F, class T>
using ArgUnshift = typename detail::Arglist<F>::template unshift<T>::type;
}

template<typename Caller>
inline Callback<detail::ArgShift<get_func<Caller> > > makeCallback(const Caller &caller, get_argument<Caller, 0> callee) {
	return BindFirstOpaque<Caller>(callee);
}

template<class Caller, class F>
class CallerShiftFirst;

template<class Caller, class R, class FirstArgument, class ... Ts>
class CallerShiftFirst<Caller, R(FirstArgument, Ts...)> {
public:
using func = R(FirstArgument, Ts ...);

static R call(FirstArgument, Ts... args) {
	return Caller::call(args ...);
}
};

template<typename Caller>
inline Callback<get_func<Caller> > makeStatelessCallback(const Caller &caller) {
	return makeCallback(CallerShiftFirst<Caller, detail::ArgUnshift<get_func<Caller>, void *> >(), nullptr);
}

/// \brief Forms a Callback from a non-const Environment reference and a non-const Environment member-function.
template<class Environment, class F, MemberFunction<Environment, F> member>
using MemberCaller = BindFirstOpaque<Member<Environment, F, member> >;

/// \brief  Constructs a Callback1 from a non-const \p functor
///
/// \param Functor Must define \c first_argument_type and \c operator()(first_argument_type).
template<typename Functor>
inline Callback<get_func<Functor> > makeCallback(Functor &functor) {
	return MemberCaller<Functor, get_func<Functor>, &Functor::operator()>(functor);
}

/// \brief Forms a Callback from a const Environment reference and a const Environment member-function.
template<class Environment, class F, ConstMemberFunction<Environment, F> member>
using ConstMemberCaller = BindFirstOpaque<ConstMember<Environment, F, member> >;

/// \brief  Constructs a Callback1 from a const \p functor
///
/// \param Functor Must define \c first_argument_type and const \c operator()(first_argument_type).
template<typename Functor>
inline Callback<get_func<Functor> > makeCallback(const Functor &functor) {
	return ConstMemberCaller<Functor, get_func<Functor>, &Functor::operator()>(functor);
}

/// \brief Forms a Callback from a non-const Environment reference and a free function which operates on a non-const Environment reference.
template<class Environment, class F, detail::ArgUnshift<F, Environment &> *func>
using ReferenceCaller = BindFirstOpaque<Function<detail::ArgUnshift<F, Environment &>, func> >;

/// \brief Forms a Callback from a const Environment reference and a free function which operates on a const Environment reference.
template<class Environment, class F, detail::ArgUnshift<F, const Environment &> *func>
using ConstReferenceCaller = BindFirstOpaque<Function<detail::ArgUnshift<F, const Environment &>, func> >;

/// \brief Forms a Callback from a non-const Environment pointer and a free function which operates on a non-const Environment pointer.
template<class Environment, class F, detail::ArgUnshift<F, Environment *> *func>
using PointerCaller = BindFirstOpaque<Function<detail::ArgUnshift<F, Environment *>, func> >;

/// \brief Forms a Callback from a const Environment pointer and a free function which operates on a const Environment pointer.
template<class Environment, class F, detail::ArgUnshift<F, const Environment *> *func>
using ConstPointerCaller = BindFirstOpaque<Function<detail::ArgUnshift<F, const Environment *>, func> >;

namespace detail {
template<class Caller, class F>
class FreeCaller : public BindFirstOpaque<CallerShiftFirst<Caller, detail::ArgUnshift<F, void *> > > {
public:
FreeCaller() : BindFirstOpaque<CallerShiftFirst<Caller, detail::ArgUnshift<F, void *> > >(nullptr) {
}
};

template<class F>
struct FreeCallerWrapper;

template<class R, class ... Ts>
struct FreeCallerWrapper<R(Ts...)> {
	using func = R(void *, Ts ...);

	static R call(void *f, Ts... args) {
		// ideally, we'd get the implementation of the function type directly. Instead, it's passed in
		return reinterpret_cast<R (*)(Ts...)>(f)(args ...);
	}
};
}

/// \brief Forms a Callback from a free function
template<class F, F *func>
using FreeCaller = detail::FreeCaller<Function<F, func>, F>;

template<class R, class ... Ts>
inline Callback<R(Ts...)> makeCallbackF(R (*func)(Ts...)) {
	void *pVoid = reinterpret_cast<void *>(func);
	return BindFirstOpaque<detail::FreeCallerWrapper<R(Ts...)> >(pVoid);
}

#endif