boost/beast/websocket/detail/pausation.hpp
//
// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail 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)
//
// Official repository: https://github.com/boostorg/beast
//
#ifndef BOOST_BEAST_WEBSOCKET_DETAIL_PAUSATION_HPP
#define BOOST_BEAST_WEBSOCKET_DETAIL_PAUSATION_HPP
#include <boost/beast/core/detail/allocator.hpp>
#include <boost/asio/associated_allocator.hpp>
#include <boost/assert.hpp>
#include <memory>
#include <utility>
namespace boost {
namespace beast {
namespace websocket {
namespace detail {
// A container that holds a suspended, asynchronous composed
// operation. The contained object may be invoked later to
// resume the operation, or the container may be destroyed.
//
class pausation
{
struct handler
{
handler() = default;
handler(handler &&) = delete;
handler(handler const&) = delete;
virtual ~handler() = default;
virtual void destroy() = 0;
virtual void invoke() = 0;
};
template<class Handler>
class impl : public handler
{
Handler h_;
public:
template<class DeducedHandler>
impl(DeducedHandler&& h)
: h_(std::forward<DeducedHandler>(h))
{
}
void
destroy() override
{
Handler h(std::move(h_));
typename beast::detail::allocator_traits<
boost::asio::associated_allocator_t<
Handler>>::template rebind_alloc<impl> alloc{
boost::asio::get_associated_allocator(h)};
beast::detail::allocator_traits<
decltype(alloc)>::destroy(alloc, this);
beast::detail::allocator_traits<
decltype(alloc)>::deallocate(alloc, this, 1);
}
void
invoke() override
{
Handler h(std::move(h_));
typename beast::detail::allocator_traits<
boost::asio::associated_allocator_t<
Handler>>::template rebind_alloc<impl> alloc{
boost::asio::get_associated_allocator(h)};
beast::detail::allocator_traits<
decltype(alloc)>::destroy(alloc, this);
beast::detail::allocator_traits<
decltype(alloc)>::deallocate(alloc, this, 1);
h();
}
};
handler* h_ = nullptr;
public:
pausation() = default;
pausation(pausation const&) = delete;
pausation& operator=(pausation const&) = delete;
~pausation()
{
if(h_)
h_->destroy();
}
pausation(pausation&& other)
{
boost::ignore_unused(other);
BOOST_ASSERT(! other.h_);
}
pausation&
operator=(pausation&& other)
{
boost::ignore_unused(other);
BOOST_ASSERT(! h_);
BOOST_ASSERT(! other.h_);
return *this;
}
template<class CompletionHandler>
void
emplace(CompletionHandler&& handler);
explicit
operator bool() const
{
return h_ != nullptr;
}
bool
maybe_invoke()
{
if(h_)
{
auto const h = h_;
h_ = nullptr;
h->invoke();
return true;
}
return false;
}
};
template<class CompletionHandler>
void
pausation::emplace(CompletionHandler&& handler)
{
BOOST_ASSERT(! h_);
typename beast::detail::allocator_traits<
boost::asio::associated_allocator_t<
CompletionHandler>>::template rebind_alloc<
impl<CompletionHandler>> alloc{
boost::asio::get_associated_allocator(handler)};
using A = decltype(alloc);
auto const d =
[&alloc](impl<CompletionHandler>* p)
{
beast::detail::allocator_traits<A>::deallocate(alloc, p, 1);
};
std::unique_ptr<impl<CompletionHandler>, decltype(d)> p{
beast::detail::allocator_traits<A>::allocate(alloc, 1), d};
beast::detail::allocator_traits<A>::construct(
alloc, p.get(), std::forward<CompletionHandler>(handler));
h_ = p.release();
}
} // detail
} // websocket
} // beast
} // boost
#endif