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//
// impl/use_future.hpp
// ~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2014 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// 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)
//
#ifndef BOOST_ASIO_IMPL_USE_FUTURE_HPP
#define BOOST_ASIO_IMPL_USE_FUTURE_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/config.hpp>
#include <future>
#include <boost/asio/async_result.hpp>
#include <boost/system/error_code.hpp>
#include <boost/asio/handler_type.hpp>
#include <boost/system/system_error.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
// Completion handler to adapt a promise as a completion handler.
template <typename T>
class promise_handler
{
public:
// Construct from use_future special value.
template <typename Allocator>
promise_handler(use_future_t<Allocator> uf)
: promise_(std::allocate_shared<std::promise<T> >(
uf.get_allocator(), std::allocator_arg, uf.get_allocator()))
{
}
void operator()(T t)
{
promise_->set_value(t);
}
void operator()(const boost::system::error_code& ec, T t)
{
if (ec)
promise_->set_exception(
std::make_exception_ptr(
boost::system::system_error(ec)));
else
promise_->set_value(t);
}
//private:
std::shared_ptr<std::promise<T> > promise_;
};
// Completion handler to adapt a void promise as a completion handler.
template <>
class promise_handler<void>
{
public:
// Construct from use_future special value. Used during rebinding.
template <typename Allocator>
promise_handler(use_future_t<Allocator> uf)
: promise_(std::allocate_shared<std::promise<void> >(
uf.get_allocator(), std::allocator_arg, uf.get_allocator()))
{
}
void operator()()
{
promise_->set_value();
}
void operator()(const boost::system::error_code& ec)
{
if (ec)
promise_->set_exception(
std::make_exception_ptr(
boost::system::system_error(ec)));
else
promise_->set_value();
}
//private:
std::shared_ptr<std::promise<void> > promise_;
};
// Ensure any exceptions thrown from the handler are propagated back to the
// caller via the future.
template <typename Function, typename T>
void asio_handler_invoke(Function f, promise_handler<T>* h)
{
std::shared_ptr<std::promise<T> > p(h->promise_);
try
{
f();
}
catch (...)
{
p->set_exception(std::current_exception());
}
}
} // namespace detail
#if !defined(GENERATING_DOCUMENTATION)
// Handler traits specialisation for promise_handler.
template <typename T>
class async_result<detail::promise_handler<T> >
{
public:
// The initiating function will return a future.
typedef std::future<T> type;
// Constructor creates a new promise for the async operation, and obtains the
// corresponding future.
explicit async_result(detail::promise_handler<T>& h)
{
value_ = h.promise_->get_future();
}
// Obtain the future to be returned from the initiating function.
type get() { return std::move(value_); }
private:
type value_;
};
// Handler type specialisation for use_future.
template <typename Allocator, typename ReturnType>
struct handler_type<use_future_t<Allocator>, ReturnType()>
{
typedef detail::promise_handler<void> type;
};
// Handler type specialisation for use_future.
template <typename Allocator, typename ReturnType, typename Arg1>
struct handler_type<use_future_t<Allocator>, ReturnType(Arg1)>
{
typedef detail::promise_handler<Arg1> type;
};
// Handler type specialisation for use_future.
template <typename Allocator, typename ReturnType>
struct handler_type<use_future_t<Allocator>,
ReturnType(boost::system::error_code)>
{
typedef detail::promise_handler<void> type;
};
// Handler type specialisation for use_future.
template <typename Allocator, typename ReturnType, typename Arg2>
struct handler_type<use_future_t<Allocator>,
ReturnType(boost::system::error_code, Arg2)>
{
typedef detail::promise_handler<Arg2> type;
};
#endif // !defined(GENERATING_DOCUMENTATION)
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_IMPL_USE_FUTURE_HPP
|
