boost/spirit/home/support/action_dispatch.hpp
/*=============================================================================
Copyright (c) 2001-2011 Joel de Guzman
Copyright (c) 2001-2011 Hartmut Kaiser
http://spirit.sourceforge.net/
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#if !defined(BOOST_SPIRIT_ACTION_DISPATCH_APRIL_18_2008_0720AM)
#define BOOST_SPIRIT_ACTION_DISPATCH_APRIL_18_2008_0720AM
#if defined(_MSC_VER)
#pragma once
#endif
#include<boost/config.hpp>
#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_NO_CXX11_LAMBDAS) && \
!defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE)
#include <utility>
#include <type_traits>
#endif
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/home/support/attributes.hpp>
namespace boost { namespace spirit { namespace traits
{
template <typename Component>
struct action_dispatch
{
#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && !defined(BOOST_NO_CXX11_LAMBDAS) && \
!defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && !defined(BOOST_NO_CXX11_DECLTYPE)
// omit function parameters without specializing for each possible
// type of callable entity
// many thanks to Eelis/##iso-c++ for this contribution
private:
// this will be used to pass around POD types which are safe
// to go through the ellipsis operator (if ever used)
template <typename>
struct fwd_tag {};
// the first parameter is a placeholder to obtain SFINAE when
// doing overload resolution, the second one is the actual
// forwarder, where we can apply our implementation
template <typename, typename T>
struct fwd_storage { typedef T type; };
// gcc should accept fake<T>() but it prints a sorry, needs
// a check once the bug is sorted out, use a FAKE_CALL macro for now
template <typename T>
T fake_call();
#define BOOST_SPIRIT_FAKE_CALL(T) (*(T*)0)
// the forwarders, here we could tweak the implementation of
// how parameters are passed to the functions, if needed
struct fwd_none
{
template<typename F, typename... Rest>
auto operator()(F && f, Rest&&...) -> decltype(f())
{
return f();
}
};
struct fwd_attrib
{
template<typename F, typename A, typename... Rest>
auto operator()(F && f, A && a, Rest&&...) -> decltype(f(a))
{
return f(a);
}
};
struct fwd_attrib_context
{
template<typename F, typename A, typename B, typename... Rest>
auto operator()(F && f, A && a, B && b, Rest&&...)
-> decltype(f(a, b))
{
return f(a, b);
}
};
struct fwd_attrib_context_pass
{
template<typename F, typename A, typename B, typename C
, typename... Rest>
auto operator()(F && f, A && a, B && b, C && c, Rest&&...)
-> decltype(f(a, b, c))
{
return f(a, b, c);
}
};
// SFINAE for our calling syntax, the forwarders are stored based
// on what function call gives a proper result
// this code can probably be more generic once implementations are
// steady
template <typename F>
static auto do_call(F && f, ...)
-> typename fwd_storage<decltype(f()), fwd_none>::type
{
return {};
}
template <typename F, typename A>
static auto do_call(F && f, fwd_tag<A>, ...)
-> typename fwd_storage<decltype(f(BOOST_SPIRIT_FAKE_CALL(A)))
, fwd_attrib>::type
{
return {};
}
template <typename F, typename A, typename B>
static auto do_call(F && f, fwd_tag<A>, fwd_tag<B>, ...)
-> typename fwd_storage<
decltype(f(BOOST_SPIRIT_FAKE_CALL(A), BOOST_SPIRIT_FAKE_CALL(B)))
, fwd_attrib_context>::type
{
return {};
}
template <typename F, typename A, typename B, typename C>
static auto do_call(F && f, fwd_tag<A>, fwd_tag<B>, fwd_tag<C>, ...)
-> typename fwd_storage<
decltype(f(BOOST_SPIRIT_FAKE_CALL(A), BOOST_SPIRIT_FAKE_CALL(B)
, BOOST_SPIRIT_FAKE_CALL(C)))
, fwd_attrib_context_pass>::type
{
return {};
}
// this function calls the forwarder and is responsible for
// stripping the tail of the parameters
template <typename F, typename... A>
static void caller(F && f, A && ... a)
{
do_call(f, fwd_tag<typename std::remove_reference<A>::type>()...)
(std::forward<F>(f), std::forward<A>(a)...);
}
#undef BOOST_SPIRIT_FAKE_CALL
public:
template <typename F, typename Attribute, typename Context>
bool operator()(F const& f, Attribute& attr, Context& context)
{
bool pass = true;
caller(f, attr, context, pass);
return pass;
}
#else
// general handler for everything not explicitly specialized below
template <typename F, typename Attribute, typename Context>
bool operator()(F const& f, Attribute& attr, Context& context)
{
bool pass = true;
f(attr, context, pass);
return pass;
}
#endif
// handler for phoenix actors
// If the component this action has to be invoked for is a tuple, we
// wrap any non-fusion tuple into a fusion tuple (done by pass_attribute)
// and pass through any fusion tuple.
template <typename Eval, typename Attribute, typename Context>
bool operator()(phoenix::actor<Eval> const& f
, Attribute& attr, Context& context)
{
bool pass = true;
typename pass_attribute<Component, Attribute>::type attr_wrap(attr);
f(attr_wrap, context, pass);
return pass;
}
// specializations for plain function pointers taking different number of
// arguments
template <typename RT, typename A0, typename A1, typename A2
, typename Attribute, typename Context>
bool operator()(RT(*f)(A0, A1, A2), Attribute& attr, Context& context)
{
bool pass = true;
f(attr, context, pass);
return pass;
}
template <typename RT, typename A0, typename A1
, typename Attribute, typename Context>
bool operator()(RT(*f)(A0, A1), Attribute& attr, Context& context)
{
f(attr, context);
return true;
}
template <typename RT, typename A0, typename Attribute, typename Context>
bool operator()(RT(*f)(A0), Attribute& attr, Context&)
{
f(attr);
return true;
}
template <typename RT, typename Attribute, typename Context>
bool operator()(RT(*f)(), Attribute&, Context&)
{
f();
return true;
}
};
}}}
#endif
