mirror of
https://github.com/matrix-construct/construct
synced 2024-11-26 00:32:35 +01:00
93 lines
3.1 KiB
C++
93 lines
3.1 KiB
C++
/*
|
|
* Copyright (C) 2016 Charybdis Development Team
|
|
* Copyright (C) 2016 Jason Volk <jason@zemos.net>
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice is present in all copies.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
|
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
|
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
|
|
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
|
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
|
|
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
|
|
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
|
|
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
* POSSIBILITY OF SUCH DAMAGE.
|
|
*/
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_LIFE_GUARD_H
|
|
|
|
#ifdef __cplusplus
|
|
namespace ircd {
|
|
|
|
// Tests if type inherits from std::enable_shared_from_this<>
|
|
template<class T>
|
|
constexpr typename std::enable_if<is_complete<T>::value, bool>::type
|
|
is_shared_from_this()
|
|
{
|
|
return std::is_base_of<std::enable_shared_from_this<T>, T>();
|
|
}
|
|
|
|
// Unconditional failure for fwd-declared incomplete types, which
|
|
// obviously don't inherit from std::enable_shared_from_this<>
|
|
template<class T>
|
|
constexpr typename std::enable_if<!is_complete<T>::value, bool>::type
|
|
is_shared_from_this()
|
|
{
|
|
return false;
|
|
}
|
|
|
|
/* Use the life_guard to keep an object alive within a function running in a context.
|
|
*
|
|
* Example:
|
|
*
|
|
void foo(client &c)
|
|
{
|
|
const life_guard<client> lg(c);
|
|
|
|
c.call(); // This call was always safe with or w/o life_guard.
|
|
ctx::wait(); // The context has now yielded and another context might destroy client &c
|
|
c.call(); // The context continues and this would have made a call on a dead c.
|
|
}
|
|
*/
|
|
template<class T>
|
|
struct life_guard
|
|
:std::shared_ptr<T>
|
|
{
|
|
// This constructor is used when the templated type inherits from std::enable_shared_from_this<>
|
|
template<class SFINAE = T>
|
|
life_guard(T &t,
|
|
typename std::enable_if<is_shared_from_this<SFINAE>(), void>::type * = 0)
|
|
:std::shared_ptr<T>(t.shared_from_this())
|
|
{
|
|
}
|
|
|
|
// This constructor uses our convention for forward declaring objects that internally
|
|
// inherit from std::enable_shared_from_this<>. Our convention is to provide:
|
|
//
|
|
// std::shared_ptr<T> shared_from(T &c);
|
|
//
|
|
template<class SFINAE = T>
|
|
life_guard(T &t,
|
|
typename std::enable_if<!is_shared_from_this<SFINAE>(), void>::type * = 0)
|
|
:std::shared_ptr<T>(shared_from(t))
|
|
{
|
|
}
|
|
|
|
// This constructor is used with a weak_ptr of the type. This throws an exception
|
|
// to abort the scope when the object already died before being able to guard at all.
|
|
life_guard(const std::weak_ptr<T> &wp)
|
|
:std::shared_ptr<T>(wp.lock())
|
|
{
|
|
if(wp.expired())
|
|
throw std::bad_weak_ptr();
|
|
}
|
|
};
|
|
|
|
} // namespace ircd
|
|
#endif // __cplusplus
|