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//
// Copyright (c) 2016-2019 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_HANDLER_PTR_HPP
#define BOOST_BEAST_HANDLER_PTR_HPP
#include <boost/beast/core/detail/config.hpp>
#include <boost/beast/core/detail/allocator.hpp>
#include <boost/assert.hpp>
#include <boost/config/pragma_message.hpp>
#include <type_traits>
#include <utility>
#ifndef BOOST_BEAST_DOXYGEN
BOOST_PRAGMA_MESSAGE("<boost/beast/core/handler_ptr.hpp> is DEPRECATED and will be removed in a future release.")
namespace boost {
namespace beast {
/** A smart pointer container with associated completion handler.
This is a smart pointer that retains unique ownership of an
object through a pointer. Memory is managed using the allocator
associated with a completion handler stored in the object. The
managed object is destroyed and its memory deallocated when one
of the following occurs:
@li The function @ref invoke is called.
@li The function @ref release_handler is called.
@li The container is destroyed.
Objects of this type are used in the implementation of composed
operations with states that are expensive or impossible to move.
This container manages that non-trivial state on behalf of the
composed operation.
@par Thread Safety
@e Distinct @e objects: Safe.@n
@e Shared @e objects: Unsafe.
@tparam T The type of the owned object. Must be noexcept destructible.
@tparam Handler The type of the completion handler.
*/
template<class T, class Handler>
class handler_ptr
{
#ifndef BOOST_BEAST_ALLOW_DEPRECATED
static_assert(sizeof(T) == 0,
BOOST_BEAST_DEPRECATION_STRING);
#endif
T* t_ = nullptr;
union
{
Handler h_;
};
void clear();
public:
/// The type of element stored
using element_type = T;
/// The type of handler stored
using handler_type = Handler;
/// Default constructor (deleted).
handler_ptr() = delete;
/// Copy assignment (deleted).
handler_ptr& operator=(handler_ptr const&) = delete;
/// Move assignment (deleted).
handler_ptr& operator=(handler_ptr &&) = delete;
/** Destructor
If `*this` owns an object the object is destroyed and
the memory deallocated using the allocator associated
with the handler.
*/
~handler_ptr();
/** Move constructor.
When this call returns, the moved-from container
will have no owned object.
*/
handler_ptr(handler_ptr&& other);
/// Copy constructor (deleted).
handler_ptr(handler_ptr const& other) = delete;
/** Constructor
This creates a new container with an owned object of
type `T`. The allocator associated with the handler will
be used to allocate memory for the owned object. The
constructor for the owned object will be called with the
following equivalent signature:
@code
T::T(Handler const&, Args&&...)
@endcode
@esafe
Strong guarantee.
@param handler The handler to associate with the owned object.
The implementation takes ownership of the handler by performing a decay-copy.
@param args Optional arguments forwarded to
the owned object's constructor.
*/
template<class DeducedHandler, class... Args>
explicit
handler_ptr(DeducedHandler&& handler, Args&&... args);
/// Return a reference to the handler
handler_type const&
handler() const noexcept
{
return h_;
}
/// Return a reference to the handler
handler_type&
handler() noexcept
{
return h_;
}
/// Return `true` if `*this` owns an object
bool
has_value() const noexcept
{
return t_ != nullptr;
}
/** Return a pointer to the owned object.
@par Preconditions:
`has_value() == true`
*/
T*
get() const
{
BOOST_ASSERT(t_);
return t_;
}
/** Return a reference to the owned object.
@par Preconditions:
`has_value() == true`
*/
T&
operator*() const
{
BOOST_ASSERT(t_);
return *t_;
}
/// Return a pointer to the owned object.
T*
operator->() const
{
BOOST_ASSERT(t_);
return t_;
}
/** Returns ownership of the handler
Before this function returns, the owned object is
destroyed, satisfying the deallocation-before-invocation
Asio guarantee.
@return The released handler.
@par Preconditions:
`has_value() == true`
@par Postconditions:
`has_value() == false`
*/
handler_type
release_handler();
/** Invoke the handler in the owned object.
This function invokes the handler in the owned object
with a forwarded argument list. Before the invocation,
the owned object is destroyed, satisfying the
deallocation-before-invocation Asio guarantee.
@par Preconditions:
`has_value() == true`
@par Postconditions:
`has_value() == false`
@note Care must be taken when the arguments are themselves
stored in the owned object. Such arguments must first be
moved to the stack or elsewhere, and then passed, or else
undefined behavior will result.
*/
template<class... Args>
void
invoke(Args&&... args);
};
} // beast
} // boost
#include <boost/beast/core/impl/handler_ptr.hpp>
#endif
#endif
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